,view west toward ,grand ,teton on skyline4 ,hedrick's ,pond surrounded by 8knob and kettle0 topography is in foreground1 tree-covered ,burned ,ridge moraine is in middle distance1 and extending from it to foot of mountains is gray flat treeless glacial outwash plain4 ,national ,park ,service photo by ,w4 ,e4 ,dilley4 ,illustration3 ,view west up ,cascade ,canyon1 with north face of ,mt4 ,owen in center4 ,national ,park ,service photo by ,h4 ,d4 ,pownall4 ,to ,fritiof ,m4 ,fryxell1 geologist1 teacher1 writer1 mountaineer1 and the first ranger-naturalist in ,grand ,teton ,national ,park4 ,all who love and strive to understand the ,teton landscape follow in his footsteps4 ,,creation ,,of ,,the ,,teton ,,landscape ,the ,geologic ,story of ,grand ,teton ,national ,park ,by ,j4 ,d4 ,,love ,,and ,,john ,c4 ,,reed1 ,,jr4 ,u4,s4 ,geological ,survey ,library of ,congress ,catalogue ,card ,no43 #fh-bjfbh ,,isbn ,o-#icahie-jh-a #ast ,edition #aifh #ast ,revised ,edition #aiga ,reprinted #aigi ,reprinted #aihd ,reprinted #aihi ,grand ,teton ,natural ,history ,association ,moose1 ,wyoming #hcjab ,,contents ,foreword #f ,,the ,,story ,,begins #h ,first questions1 brief answers #i ,an extraordinary story #aj ,an astronaut's view #ab ,a pilot's view #ad ,a motorist's view #ae ,view north #ae ,view west #ah ,view south #ai ,a mountaineer's view #bj ,,carving ,,the ,,rugged ,,peaks #bd ,steep mountain slopes--the perpetual battleground #bd ,rock disintegration and gravitational movement #bd ,running water cuts and carries #bf ,glaciers scour and transport #bh ,effects on ,jackson ,hole #cj ,,mountain ,,uplift #cf ,kinds of mountains #cf ,anatomy of faults #ch ,time and rate of uplift #dj ,why are mountains here8 #da ,the restless land #dc ,,enormous ,,time ,,and ,,dynamic ,,earth #de ,framework of time #de ,rocks and relative age #de ,fossils and geologic time #df ,radioactive clocks #dg ,the yardstick of geologic time #dh ,,precambrian ,,rocks--,,the ,,core ,,of ,,the ,,tetons #ea ,ancient gneisses and schists #ea ,granite and pegmatite #ee ,black dikes #eh ,quartzite #fc ,a backward glance #fd ,the close of the ,precambrian--end of the beginning #fd ,,the ,,paleozoic ,,era--,,time ,,of ,,long-,,vanished ,,seas ,,and ,,the ,,development ,,of ,,life #ff ,the ,paleozoic sequence #ff ,alaska ,basin--site of an outstanding rock and fossil record #ff ,advance and retreat of ,cambrian seas2 an example #fi ,younger ,paleozoic formations #gd ,,the ,,mesozoic--,,era ,,of ,,transition #gi ,colorful first ,mesozoic strata #gi ,drab ,cretaceous strata #ha ,birth of the ,rocky ,mountains #hb ,,tertiary--,,time ,,of ,,mammals1 ,,mountains1 ,,lakes1 ,,and ,,volcanoes #hf ,rise and burial of mountains #hh ,the first big lake #ib ,development of mammals #ie ,volcanoes #ih ,,quaternary--,,time ,,of ,,ice1 ,,more ,,lakes1 ,,and ,,continued ,,crustal ,,disturbance #ajb ,hoback normal fault #ajc ,volcanic activity #ajc ,preglacial lakes #ajd ,the ,ice ,age #aje ,modern glaciers #aab ,,the ,,present ,,and ,,the ,,future #aac ,,appendix #aae ,acknowledgements #aae ,selected references--if you wish to read further #aaf ,about the authors #aag ,index of selected terms and features #aah ,,foreword ,geology is the science of the ,earth--the study of the forces1 processes1 and past life that not only shape our land but influence our daily lives and our ,nation's welfare4 ,this booklet1 prepared by two members of the ,u4,s4 ,geological ,survey1 discusses how geologic phenomena are responsible for the magnificent scenery of the ,teton region4 ,recognition of the complex geologic history of our ,earth is vital to the enjoyment and appreciation of beautiful landscapes and other natural wonders1 to the planning of our cities and highway systems1 to the wise use of our water supplies1 to the study of earthquake and landslide areas1 to the never-ending search for new mineral deposits1 and to the conservation and development of our known natural resources4 ,who can say1 in the long run1 which of the many uses of this knowledge is the most compelling reason to seek an understanding of the ,earth8 ,illustration3 ,signature ,w4 ,t4 ,pecora1 ,director ,u4,s4 ,geological ,survey ,this booklet is based on geologic investigations by the ,u4 ,s4 ,geological ,survey in cooperation with the ,national ,park ,service1 ,u4 ,s4 ,department of ,interior4 8,something hidden4 ,go and find it4 ,go and look behind the ,ranges-- ,something lost behind the ,ranges4 ,lost and waiting for you4 ,go40 ,,kipling--,,the ,,explorer ,,the ,,story ,,begins ,the ,teton ,range is one of the most magnificent mountain ranges on the ,north ,american ,continent4 ,others are longer1 wider1 and higher1 but few can rival the breath-taking alpine grandeur of the eastern front of the ,tetons4 ,ridge after jagged ridge of naked rock soar upward into the western sky1 culminating in the towering cluster of peaks to which the early ,french voyageurs gave the name 8les ,trois ,tetons0 7the three breasts74 ,the range hangs like a great stone wave poised to break across the valley at its base4 ,to the south and east are lesser mountains1 interesting and scenic but lacking the magic appeal of the ,tetons4 ,this is a range of many moods and colors3 stark and austere in morning sun1 but gold and purple and black in the softly lengthening shadows of afternoon2 somber and foreboding when the peaks wrap themselves in the tattered clouds of an approaching storm1 but tranquil and ethereal blue and silver beneath a full moon4 ,these great peaks and much of the floor of the valley to the east1 ,jackson ,hole 7a hole was the term used by pioneer explorers and mountain men to describe any open valley encircled by mountains71 lie within ,grand ,teton ,national ,park1 protected and preserved for the enjoyment of present and future generations4 ,each year more than #c million visitors come to the park4 ,many pause briefly and pass on4 ,others stay to explore its trails1 fish its streams1 study the plants and wildlife that abound within its borders1 or to savor the colorful human history of this area4 ,most visitors1 whatever their interests and activities1 are probably first attracted to the park by its unsurpassed mountain scenery4 ,the jagged panorama of the ,tetons is the backdrop to which they may turn again and again1 asking questions1 seeking answers4 ,how did the mountains form8 ,how long have they towered into the clouds1 washed by rain1 riven by frost1 swept by wind and snow8 ,what enormous forces brought them forth and raised them skyward8 ,what stories are chronicled in their rocks1 what epics chiseled in the craggy visage of this mountain landscape8 ,why are the ,tetons different from other mountains8 ,first questions1 brief answers ,how did the ,tetons and ,jackson ,hole form8 ,they are both tilted blocks of the earth's crust that behaved like two adjoining giant trapdoors hinged so that they would swing in opposite directions4 ,the block on the west1 which forms the ,teton ,range1 was hinged along the ,idaho-,wyoming ,state line2 the eastern edge was uplifted along a fault 7a fracture along which displacement has occurred74 ,this is why the highest peaks and steepest faces are near the east margin of the range4 ,the hinge line of the eastern block1 which forms ,jackson ,hole1 was in the highlands to the east4 ,the western edge of the block is downdropped along the fault at the base of the ,teton ,range4 ,as a consequence1 the floor of ,jackson ,hole tilts westward toward the ,tetons 7see cross section inside back cover74 ,when did the ,tetons and ,jackson ,hole develop the spectacular scenery we see today8 ,the ,tetons are the youngest of all the mountain ranges in the ,rocky ,mountain chain4 ,most other mountains in the region are at least #ej million years old but the ,tetons are less than #aj million and are still rising4 ,jackson ,hole is of the same age and is still sinking4 ,the ,teton landscape is the product of many earth processes1 the most recent of which is cutting by water and ice4 ,within the last #ae1jjj years1 ice sculpturing of peaks and canyons and impounding of glacial lakes have added finishing touches to the scenic beauty4 ,why did the ,tetons rise and ,jackson ,hole sink8 ,for thousands of years men have wondered about the origin of mountains and their speculations have filled many books4 ,two of the more popular theories are3 7#a7 continental drift 7such as ,south ,america moving away from ,africa71 with the upper lighter layer of the earth's crust moving over the lower denser layer and wrinkling along belts of weakness2 and 7#b7 convection currents within the earth1 caused by heat transfer1 resulting in linear zones of wrinkling1 uplift1 and collapse4 ,these concepts were developed to explain the origin of mountainous areas hundreds or thousands of miles long but they do not answer directly the question of why the ,tetons rose and ,jackson ,hole sank4 ,as is discussed in the chapter on mountains1 it is probable that semifluid rock far below the surface of ,jackson ,hole flowed north into the ,yellowstone ,volcanic ,plateau-,absaroka ,range volcanic area1 perhaps taking the place of the enormous amount of ash and lava blown out of volcanoes during the last #ej million years4 ,the origin of the line of weakness that marks the ,teton fault along the east face of the ,teton ,range may go back to some unknown inequality in the earth's composition several billion years ago4 ,why it suddenly became active late in the earth's history is an unanswered question4 ,the ultimate source of heat and energy that caused the mountains and basins to form probably is disintegration of radioactive materials deep within the earth4 ,the ,tetons are a spectacular demonstration that the enormous energy necessary to create mountains is not declining1 even though our planet is several billion years old4 ,an extraordinary story ,visitors whose curiosity is whetted by this unusual and varied panorama are not satisfied with only a few questions and answers4 ,they sense that here for the asking is an extraordinary geologic 7geo--earth2 logic--science7 story4 ,with a little direction1 many subtle features become evident--features that otherwise might escape notice4 ,here1 for example1 is a valley with an odd ,u-shape4 ,there is a sheer face crisscrossed with light- and dark-colored rocks4 ,on the valley floor is a tuft of pine trees that seem to be confined to one particular kind of rock4 ,on the rolling hills is a layer of peculiar white soil--the only soil in which coyote dens are common4 ,all these are geologically controlled phenomena4 ,in short1 with a bit of initial guidance1 the viewer gains an ability to observe and to understand so much that the panorama takes on new depth1 vividness1 and excitement4 ,it changes from a flat1 two-dimensional picture to a colorful multi-dimensional exhibit of the earth's history4 ,illustration3 ,figure #a4 ,the ,tetons from afar--an astronaut's view of the range and adjacent mountains1 basins1 and plateaus4 ,width of area shown in photo is about #ajj miles4 ,stippled pattern marks boundary of ,grand ,teton ,national ,park4 ,illustration3 ,figure #b4 ,sketch of the ,teton ,range and ,jackson ,hole1 southwest view4 ,drawing by ,j4 ,r4 ,stacy4 ,,block ,,diagram ,,view ,,southwest ,,showing ,,the ,,teton ,,range ,,and ,,jackson ,,hole ,an astronaut's view ,the ,tetons are a short1 narrow1 and high mountain range1 distinctive in the midst of the great chain of the ,rocky ,mountains1 the backbone of western ,north ,america4 ,figure #a shows how the ,tetons and their surroundings might appear if you viewed them from a satellite at an altitude of perhaps a hundred miles4 ,the ,u4 ,s4 ,geological ,survey topographic map of ,grand ,teton ,national ,park shows the names of many features not indicated on figure #a or on the geologic map inside the back cover4 ,the ,teton ,range is a rectangular mountain block about #dj miles long and #aj-ae miles wide4 ,it is flanked on the east and west by flat-floored valleys4 ,jackson ,hole is the eastern one and ,teton ,basin 7called ,pierre's ,hole by the early trappers7 is the western4 ,the ,teton ,range is not symmetrical4 ,the highest peaks lie near the eastern edge of the mountain block1 rather than along its center1 as is true in conventional mountains1 and the western slopes are broad and gentle in contrast to the precipitous eastern slopes4 ,the northern end of the range disappears under enormous lava flows that form the ,yellowstone ,volcanic ,plateau4 ,even from this altitude the outlines of some of these flows can be seen4 ,on the south the ,teton ,range abuts almost at right angles against a northwest-trending area of lower and less rugged mountains 7the ,snake ,river1 ,wyoming1 and ,hoback ,ranges74 ,these mountains appear altogether different from the ,tetons4 ,they consist of a series of long parallel ridges cut or separated by valleys and canyons4 ,this pattern is characteristic of mountains composed of crumpled1 steeply tilted rock layers--erosion wears away the softer layers1 leaving the harder ones standing as ridges4 ,on the east and northeast1 ,jackson ,hole is bounded by the ,gros ,ventre and ,washakie ,ranges1 which are composed chiefly of folded hard and soft sedimentary rocks4 ,in contrast1 between these mountains and the deepest part of ,jackson ,hole to the west1 thick layers of soft nearly flat-lying sedimentary rocks have been sculptured by streams and ice into randomly oriented knife-edge ridges and rolling hills separated by broad valleys4 ,the hills east of the park are called the ,mount ,leidy ,highlands and those northeast are the ,pinyon ,peak ,highlands4 ,a pilot's view ,if you descend from #ajj miles to about #e miles above the ,teton region1 the asymmetry of the range1 the extraordinary variety of landscapes1 and the vivid colors of rocks become more pronounced4 ,figure #b shows a panorama of the ,teton ,range and ,jackson ,hole from a vantage point over the ,pinyon ,peak ,highlands4 ,the rough steep slopes and jagged ridges along the east front of the range contrast with smoother slopes and more rounded ridges on the western side4 ,nestled at the foot of the mountains and extending out onto the floor of ,jackson ,hole are tree-rimmed sparkling lakes of many sizes and shapes4 ,still others lie in steep-sided rocky amphitheaters near the mountain crests4 ,one of the most colorful flight routes into ,jackson ,hole is from the east1 along the north flank of the ,gros ,ventre ,mountains4 ,for #dj miles this mountain range is bounded by broad parallel stripes of bright-red1 pink1 purple1 gray1 and brown rocks4 ,some crop out as cliffs or ridges1 and others are badlands 7bare unvegetated hills and valleys with steep slopes and abundant dry stream channels74 ,in places the soft beds have broken loose and flowed down slopes like giant varicolored masses of taffy4 ,these are mudflows and landslides4 ,the colorful rocks are bounded on the south by gray and yellow tilted layers forming snowcapped peaks of the ,gros ,ventre ,mountains4 ,these landscapes are the product of many natural forces acting on a variety of rock types during long or short intervals of geologic time4 ,each group of rocks records a chapter in the geologic story of the region4 ,other chapters can be read from the tilting1 folding1 and breaking of the rocks4 ,the latest episodes are written on the face of the land itself4 ,a motorist's view ,most park visitors first see the ,teton peaks from the highway4 ,whether they drive in from the south1 east1 or north1 there is one point on the route at which a spectacular panorama of the ,tetons and ,jackson ,hole suddenly appears4 ,part of the thrill of these three views is that they are so unexpected and so different4 ,the geologic history is responsible for these differences4 ,view north4-- ,throughout the first #d miles north of the town of ,jackson1 the view of the ,tetons from ,u4 ,s4 #bf-hi is blocked by ,east ,gros ,ventre ,butte4 ,at the north end of the butte1 the highway climbs onto a flat upland at the south boundary of ,grand ,teton ,national ,park4 ,without any advance warning1 the motorist sees the whole east front of the ,teton ,range rising steeply from the amazingly flat floor of ,jackson ,hole4 ,from the park boundary turnout no lakes or rivers are visible to the north but the nearest line of trees in the direction of the highest ,teton peaks marks the approximate position of the ,gros ,ventre ,river4 ,the elevation of this river is surprising1 for the route has just come up a #aej-;foot hill1 out of the flat valley of a much smaller stream1 yet here at eye-level is a major river perched on an upland plain4 ,the reason for these strange relations is that the hill is a fault scarp 7see fig4 #af;,a for a diagram7 and the valley in which the town of ,jackson is located was dropped #aej feet or more in the last #ae1jjj years4 ,on the skyline directly west of the turnout are horizontal and inclined layers of rocks4 ,these once extended over the tops of the highest peaks but were worn away from some parts as the mountains rose4 ,all along the range1 trees grow only up to treeline 7also called timberline--a general elevation above which trees do not grow7 which here is about #aj1ejj feet above the sea4 ,to the southeast and east1 beyond the sage-covered floor of ,jackson ,hole1 are rolling partly forested slopes marking the west end of the ,gros ,ventre ,mountains4 ,they do not look at all like the ,tetons because they were formed in a very different manner4 ,the ,gros ,ventres are folded mountains that have foothills2 the ,tetons are faulted mountains that do not4 ,figure #c4 ,the ,teton landscape as seen from ,signal ,mountain4 ,illustration3 ,a4 ,view west across ,jackson ,lake4 ,major peaks1 canyons1 and outcrops of sedimentary rocks are indicated by 8s40 ,illustration3 ,b4 ,view northeast2 a study in contrast with the panorama above4 ,three steepsided hills called buttes rise out of the flat floor of ,jackson ,hole4 ,they are tilted and faulted masses of hard1 layered rock that have been shaped by southward-moving glaciers4 ,six miles north of the boundary turnout is ,blacktail ,butte1 on the flanks of which are west-dipping white beds4 ,southwest of the turnout is ,east ,gros ,ventre ,butte1 composed largely of layered rocks that are exposed along the road from ,jackson almost to the turnout4 ,these are capped by very young lava that forms the brown cliff overlooking the highway at the north end of the butte4 ,to the southwest is ,west ,gros ,ventre ,butte1 composed of similar rocks4 ,view west4-- ,the motorist traveling west along ,u4 ,s4 #bf-bhg is treated to two magnificent views of the ,teton ,range4 ,the first is #h miles and the second #ac miles west of ,togwotee ,pass4 ,at these vantage points1 between #bj and #cj miles from the mountains1 the great peaks seem half suspended between earth and sky--too close1 almost1 to believe1 but too distant to comprehend4 ,only from closer range can the motorist begin to appreciate the size and steepness of the mountains and to discern the details of their architecture4 ,the many roads on the floor of ,jackson ,hole furnish ever-changing vistas1 and signs provided by the ,national ,park ,service at numerous turnouts and scenic overlooks help the visitor to identify quickly the major peaks and canyons and the principal features of the valley floor4 ,of all these roadside vantage points1 the top of ,signal ,mountain1 an isolated hill rising nearly #a1jjj feet out of the east margin of ,jackson ,lake1 probably offers the best overall perspective 7fig4 #c74 ,to the west1 across the shimmering blue waters of ,jackson ,lake1 the whole long parade of rugged peaks stretches from the north horizon to the south1 many of the higher ones wearing the tattered remnants of winter snow4 ,from here1 only #h miles away1 the towering pinnacles1 saw-toothed ridges1 and deep ,u-shaped canyons are clearly visible4 ,unlike most other great mountain ranges1 the ,tetons rise steeply from the flat valley floor in a straight unbroken line4 ,the high central peaks tower more than a mile above the valley1 but northward and southward the peaks diminish in height and lose their jagged character1 gradually giving way to lower ridges and rounded hills4 ,some of the details of the mountain rock can be seen--gnarled gray rocks of the high peaks threaded by a fine white lacework of dikes1 the dark band that cleaves through ,mount ,moran from base to summit1 and the light brown and gray layers on the northern and southern parts of the range4 ,at first glance the floor of ,jackson ,hole south of ,signal ,mountain seems flat1 smooth1 and featureless1 except for the ,snake ,river that cuts diagonally across it4 ,nevertheless1 even the flats show a variety of land forms4 ,the broad sage-covered areas1 low isolated hills1 and hummocky tree-studded ridges that form the foreground are all parts of the ,teton landscape1 and give us clues to the natural processes that shaped it4 ,a critical look to the south discloses more strange things4 ,we take for granted the fact that the sides of normal valleys slope inward toward a central major stream4 ,south of ,signal ,mountain1 however1 the visitor can see that the ,snake ,river ,valley does not fit this description4 ,the broad flat west of the river should slope east but it does not4 ,instead1 it has been tilted westward by downward movement along the ,teton fault at the base of the mountains4 ,view south4-- ,about a million motorists drive south from ,yellowstone to ,grand ,teton ,national ,park each year4 ,as they wind along the crooked highway on the west brink of ,lewis ,river ,canyon 7fig4 #a71 the view south is everywhere blocked by dense forest4 ,then1 abruptly the road leaves the canyon1 straightens out1 and one can look south down a #c-mile sloping avenue cut through the trees4 ,there1 #bj to #cj miles away1 framed by the roadway1 are the snow-capped ,tetons1 with ,jackson ,lake1 luminous in reflected light1 nestled against the east face4 ,this is one of the loveliest and most unusual views of the mountains that is available to the motorist1 partly because he is #hjj feet above the level of ,jackson ,lake and partly because this is the only place on a main highway where he can see clearly the third dimension 7width7 of the ,tetons4 ,the high peaks are on the east edge2 they rise #g1jjj feet above the lake but other peaks and precipitous ridges1 progressively diminishing in height1 extend on to the west for a dozen miles 7fig4 #ad74 ,giant1 relatively young lava flows1 into which the ,lewis ,river ,canyon was cut1 poured southward all the way to the shore of ,jackson ,lake and buried the north end of the ,teton ,range 7figs4 #ac and #ec74 ,south of ,yellowstone ,park these flows were later tilted and broken by the dropping of ,jackson ,hole and the rise of the mountains4 ,a mountaineer's view ,as in many pursuits in life1 the greatest rewards of a visit to the ,tetons come to those who expend a real effort to earn them4 ,only by leaving the teeming valley and going up into the mountains to hike the trails and climb the peaks can the visitor come to know the ,tetons in all their moods and changes and view close at hand the details of this magnificent mountain edifice4 ,even a short hike to ,hidden ,falls and ,inspiration ,point affords an opportunity for a more intimate view of the mountains4 ,along the trail the hiker can examine outcrops of sugary white granite1 glittering mica-studded dikes1 and dark intricately layered rocks4 ,nearby are great piles of broken fragments that have fallen from the cliffs above1 and the visitor can begin to appreciate how vulnerable are the towering crags to the relentless onslaught of frost and snow4 ,the roar of the foaming stream and the thunder of the falls are constant reminders of the patient work of running water in wearing away the 8everlasting hills40 ,running his hand across one of the smoothly polished rock faces below ,inspiration ,point1 the hiker gains an unforgettable concept of the power of glacial ice and its importance in shaping this majestic landscape4 ,looking back across ,jenny ,lake at the encircling ridge of glacial debris1 he can easily comprehend the size of the ancient glacier that once flowed down ,cascade ,canyon and emerged onto the floor of ,jackson ,hole4 ,the more ambitious hiker or mountaineer can seek out the inner recesses of the range and explore other facets of its geology4 ,he can visit the jewel-like mountain lakes--,solitude1 ,holly1 and ,amphitheater are just a few--cradled in high remote basins left by the ,ice ,age glaciers4 ,he can get a closeup view of the ,teton ,glacier above ,amphitheater ,lake1 or explore the ,schoolroom ,glacier1 the tiny ice body below ,hurricane ,pass4 ,he may follow the trail into ,garnet ,canyon to see the crystals from which the canyon takes its name and to examine the soaring ribbonlike black dike near the end of the trail4 ,in ,alaska ,basin he can study the gently tilted layers of sandstone1 limestone1 and shale that once blanketed the entire ,teton ,range and can search for the fossils that help determine their age and decipher their history4 ,from ,hurricane ,pass he can see how these even layers of sedimentary rock have been broken and displaced and how the older harder rocks that form the highest ,teton peaks have been raised far above them along the ,buck ,mountain fault4 ,of all those who explore the high country1 it is the mountaineer who has perhaps the greatest opportunity to appreciate its geologic story4 ,indeed1 the success of his climb and his very life may depend on an intuitive grasp of the mountain geology and the processes that shaped the peaks4 ,he observes the most intimate details--the inclination of the joints and fractures1 which gullies are swept by falling rocks1 which projecting knobs are firm1 and which cracks will safely take a piton4 ,to many climbers the ascent of a peak is a challenge to technical competence1 endurance1 and courage1 but to those endowed with curiosity and a sharp eye it can be much more4 ,as he stands shoulder to shoulder with the clouds on some windswept peak1 such as the ,grand ,teton1 with the awesome panorama dropping away on all sides1 he can hardly avoid asking how this came to be4 ,what does the mountaineer see that inspires this curiosity8 ,from the very first glance1 it is apparent that the scenes to the north1 south1 east1 and west are startlingly different4 ,looking west from the rough1 narrow1 weather-ravaged granite summit of the ,grand ,teton1 one sees far below him the layered gray cliffs of marine sedimentary rocks 7solidified sediment originally deposited in a shallow arm of the ocean7 overlapping the granite and dipping gently west1 finally disappearing under the checkerboard farmland of ,teton ,basin4 ,still farther west are the rolling timbered slopes of the ,big ,hole ,range in ,idaho4 ,a glance at the foreground1 #c1jjj feet below1 shows some unusual relations of the streams to the mountains4 ,the watershed divide of the ,teton ,range is not marked by the highest peaks as one would expect4 ,streams in ,cascade ,canyon and in other canyons to the north and south begin west of the peaks1 bend around them1 then flow eastward in deep narrow gorges cut through the highest part of the range1 and emerge onto the flat floor of ,jackson ,hole4 ,in the view north along the crest of the ,teton ,range1 the asymmetry of the mountains is most apparent4 ,the steep east face culminating in the highest peaks contrasts with the lower more gentle west flank of the uplift4 ,from the ,grand ,teton it is not possible to see the actual place where the mountains disappear under the lavas of ,yellowstone ,park1 but the heavily timbered broad gentle surface of the lava plain is visible beyond the peaks and extends across the entire north panorama4 ,still farther north1 #ge to #ajj miles away1 rise the snowcapped peaks 7from northwest to northeast7 of the ,madison1 ,gallatin1 and ,beartooth ,mountains4 ,the view east presents the greatest contrasts in the shortest distances--the flat floor of ,jackson ,hole is #c miles away and #g1jjj feet below the top of the ,grand ,teton4 ,along the junction of the mountains and valley floor are blue glacial lakes strung out like irregular beads in a necklace4 ,they are conspicuously rimmed by black-appearing margins of pine trees that grow only on the surrounding glacial moraines4 ,beyond these are the broad treeless boulder-strewn plains of ,jackson ,hole4 ,fifty miles to the east and northeast1 on the horizon beyond the rolling hills of the ,pinyon ,peak ,highlands1 are the horizontally layered volcanic rocks of the ,absaroka ,range4 ,southeast is the colorful red1 purple1 green1 and gray ,gros ,ventre ,river ,valley1 with the fresh giant scar of the ,lower ,gros ,ventre ,slide near its mouth4 ,bounding the south side of this valley are the peaks of the ,gros ,ventre ,mountains1 whose tilted slabby gray cliff-forming layers resemble 7and are the same as7 those on the west flank of the ,teton ,range4 ,seventy miles away1 in the southeast distance1 beyond the ,gros ,ventre ,mountains are the shining snowcapped peaks of the ,wind ,river ,range1 the highest peak of which 7,gannett ,peak7 is about #bj feet higher than the ,grand ,teton4 ,conspicuous on the eastern and southeastern skyline are high-level 7#aa1jjj-ab1jjj feet7 flat-topped surfaces on both the ,wind ,river and ,absaroka ,ranges4 ,these are remnants that mark the upper limit of sedimentary fill of the basins adjacent to the mountains4 ,a plain once connected these surfaces and extended westward at least as far as the conspicuous flat on the mountain south of ,lower ,gros ,ventre ,slide4 ,it is difficult to imagine the amount of rock that has been washed away from between these remnants in comparatively recent geologic time1 during and after the rise of the ,teton ,range4 ,from this vantage point the mountaineer also gets a concept of the magnitude of the first and largest glaciers that scoured the landscape4 ,ice flowed southwestward in an essentially unbroken stream from the ,beartooth ,mountains1 #ajj miles away1 westward from the ,absaroka ,range1 and northwestward from the ,wind ,river ,range 7fig4 #eg74 ,ice lapped up to treeline on the ,teton ,range and extended across ,jackson ,hole nearly to the top of the ,lower ,gros ,ventre ,slide4 ,the ,pinyon ,peak and ,mount ,leidy ,highlands were almost buried4 ,all these glaciers came together in ,jackson ,hole and flowed south within the ever-narrowing ,snake ,river ,valley4 ,the view south presents a great variety of contrasts4 ,conspicuous1 as in the view north1 is the asymmetry of the range4 ,south of the high peaks of crystalline rocks1 gray layered cliffs of limestone extend in places all the way to the steep east face of the ,teton ,range where they are abruptly cut off by the great ,teton fault4 ,the flat treeless floor of ,jackson ,hole narrows southward4 ,rising out of the middle are the previously described steepsided ice-scoured rocky buttes4 ,beginning near the town of ,jackson1 part of which is visible1 and extending as far south as the eye can see are row upon row of sharp ridges and snowcapped peaks that converge at various angles4 ,these are the ,hoback1 ,wyoming1 ,salt ,river1 and ,snake ,river ,ranges4 ,,carving ,,the ,,rugged ,,peaks ,the rugged grandeur of the ,tetons is a product of four geologic factors3 the tough hard rocks in the core1 the amount of vertical uplift1 the recency of the mountain-making movement1 and the dynamic forces of destruction4 ,many other mountains in ,wyoming have just as hard rocks in their cores and an equally great amount of vertical uplift1 but they rose #ej to #fj million years ago and have been worn down by erosion from that time on4 ,the ,tetons1 on the other hand1 are the youngest range in ,wyoming1 less than #aj million years old1 and have not had time to be so deeply eroded4 ,steep mountain slopes--the perpetual battleground ,any steep slope or cliff is especially vulnerable to nature's methods of destruction4 ,in the ,tetons we see the never-ending struggle between two conflicting factors4 ,the first is the extreme toughness of the rocks and their consequent resistance to erosion4 ,the second is the presence of efficient transporting agencies that move out and away from the mountains all rock debris that might otherwise bury the lower slopes4 ,the rocks making up most of the ,teton ,range are among the hardest1 toughest1 and least porous known4 ,therefore1 they resist mechanical disintegration by temperature changes1 ice1 and water4 ,they consist predominantly of minerals that are subject to very little chemical decay in the cold climate of the ,tetons4 ,absence of weak layers prevents breaking of the tough rock masses under their own weight4 ,all these conditions1 then1 are favorable for preservation of steep walls and high rock pinnacles4 ,nevertheless1 they do break down4 ,great piles of broken rock 7talus7 that festoon the slopes of all the higher peaks bear witness to the unrelenting assault by the process of erosion upon the mountain citadels 7figs4 #d and #ca74 ,rock disintegration and gravitational movement ,a great variation in both daily and annual temperatures results in minute amounts of contraction and expansion of rock particles4 ,repeated changes in volume produce stress and strain4 ,although the rocks in the ,tetons are very dense1 they eventually yield2 a crack forms4 ,water which seeps in along this surface of weakness freezes1 either overnight or during long cold spells1 and expands1 thereby prying a slab of rock away from the mountain wall4 ,repeated frost wedging1 as the process is called1 results eventually in tipping the slab so that it falls4 ,illustration3 ,figure #d4 ,talus at the foot of the jagged frost-riven peaks around ,ice ,floe ,lake in the south fork of ,cascade ,canyon4 ,photo by ,philip ,hyde4 ,what happens to the rock slab8 ,it may fall and roll several hundred or thousand feet1 depending on the steepness of the mountain surface4 ,pieces are broken off as it encounters obstacles4 ,all the fragments find their way to a valley floor or slope1 where they momentarily come to rest4 ,thus1 rock debris is moved significant and easily observed distances by gravity4 ,none of this debris is stationary4 ,if it is mixed with snow or saturated with water1 the whole mass may slowly flow in the same manner as a glacier4 ,these are called rock glaciers2 some can be seen on the south side of ,granite ,canyon and one1 nearly a mile long1 is in the valley north of ,eagles ,rest ,peak4 ,the countless snow avalanches that thunder down the mountain flanks after heavy winter snowfalls play their part1 too1 in gravitational transport4 ,loose rocks and debris are incorporated with the moving snow and borne down the mountainsides to the talus piles below4 ,trees1 bushes1 and soil are swept from the sites of the slides1 leaving conspicuous scars down the slopes and exposing new rock surfaces to the attack of water and frost4 ,battered1 broken1 and uprooted trees along many of the canyon trails bear silent witness to the awesome power of snowslides4 ,these are some of the methods used by ,nature in making debris and then1 by means of gravity1 clearing it from the mountain slopes4 ,there are other ways1 too4 ,a weak layer of rock 7usually one with a lot of clay in it71 parallel to and underlying a mountain slope1 may occur between two hard layers4 ,an extended rainy spell may result in saturation of the weak zone so that it is well lubricated2 then an earthquake or perhaps merely the weight of the overlying rock sends the now unstable mass cascading down the slope to the valley below4 ,the famous ,lower ,gros ,ventre ,slide 7fig4 #e7 was formed in this way on ,june #bc1 #aibe4 ,running water cuts and carries ,running water is another effective agent that transports rock debris and has helped dissect the ,teton ,range4 ,the damage a broken water main can wreak on a roadbed is well known1 as is the havoc of destructive floods4 ,the spring floods of streams in the ,tetons1 swollen by melting snow and ice 7annual precipitation1 mostly snow1 in the high parts would average a layer of water #e feet thick71 move some rock debris onto the adjoining floor of ,jackson ,hole4 ,illustration3 ,figure #e4 ,the ,lower ,gros ,ventre slide1 air oblique view south4 ,the top of the scar is #b1jjj feet above the river2 the slide is more than a mile long and one-half mile wide4 ,it dammed the ,gros ,ventre ,river in the foreground1 impounding a lake about #bjj feet deep and #e miles long4 ,gros ,ventre ,mountains are in the distance4 ,photo by ,p4 ,e4 ,millward4 ,now and then the range is deluged by summer cloudbursts4 ,water funnels down the maze of gullies on the mountainsides1 quickly gathering volume and power1 and plunges on to the talus slopes below1 as if from gigantic hoses4 ,the sudden onslaught of these torrents of water on the saturated unstable talus may trigger enormous rock and mudflows that carry vast quantities of material down into the canyons4 ,during the summer of #aida more than #ajj of these flows occurred in the park4 ,wherever water moves1 it carries rock fragments varying in size from boulders to sand grains and on down to minute clay particles4 ,erosion 7wearing away7 by streams is conspicuous wherever the water is muddy1 as it always is each spring in the ,snake1 ,buffalo ,fork1 and ,gros ,ventre ,rivers4 ,clear mountain streams likewise can erode4 ,although the volume of material moved and the amount of downcutting of the stream bottom may not seem great in a single stream1 the cumulative effect of many streams in an area1 year after year and century after century1 is enormous4 ,streams not only transport rocks brought to them by gravitational movement but also continually widen and deepen their valleys1 thereby increasing the volume of transported debris4 ,the effectiveness of streams as transporting agents in the ,tetons is enhanced by steep gradients 7slopes72 these increase water velocity which in turn expands the capability of the streams to carry larger and larger rock fragments4 ,glaciers scour and transport ,mountain landscapes shaped by frost action1 gravitational transport1 and stream erosion alone generally have rounded summits1 smooth slopes1 and ,v-shaped valleys4 ,the jagged ridges1 sharply pointed peaks1 and deep ,u-shaped valleys of the ,tetons show that glaciers have played an important role in their sculpture4 ,the small present-day glaciers still cradled in shaded recesses among the higher peaks 7fig4 #f7 are but miniature replicas of great ice streams that occupied the region during the ,ice ,age4 ,evidence both here and in other parts of the world confirms that glaciers were once far more extensive than they are today4 ,glaciers form wherever more snow accumulates during the winter than is melted during the summer4 ,gradually the piles of snow solidify to form ice1 which begins to flow under its own weight4 ,rocks that have fallen from the surrounding ridges or have been picked up from the underlying bedrock are incorporated in the moving ice mass and carried along4 ,the ability of ice to transport huge volumes of rock is easily observed even in the small present-day glaciers in the ,tetons1 all of which carry abundant rock fragments both on and within the ice4 ,illustration3 ,figure #f4 ,the ,teton ,glacier on the north side of ,grand ,teton1 air oblique view west4 ,photo by ,a4 ,s4 ,post1 ,august #ai1 #aifc4 ,recent measurements show that the ice in the present ,teton ,glacier 7fig4 #f7 moves nearly #cj feet per year4 ,the ancient glaciers1 which were much wider and deeper1 may have moved as much as several hundred feet a year1 like some of the large glaciers in ,alaska4 ,as the glacier moves down a valley1 it scours the valley bottom and walls4 ,the efficiency of ice in this process is greatly increased by the presence of rock fragments which act as abrasives4 ,the valley bottom is plowed1 quarried1 and swept clean of soil and loose rocks4 ,fragments of many sizes and shapes are dragged along the bottom of the moving ice and the hard ones scratch long parallel grooves in the underlying tough bedrock 7fig4 #g74 ,such grooves 7glacial striae7 record the direction of ice movement4 ,the effectiveness of glaciers in cutting a ,u-shaped valley is particularly striking in ,glacier ,gulch and ,cascade ,canyon 7figs4 #b and #h74 ,the rock-walled amphitheater at the head of a glaciated valley is called a cirque 7a good example is at the upper edge of the ,teton ,glacier1 fig4 #f74 ,the steep cirque walls develop by frost action and by quarrying and abrasive action of the glacier ice where it is near its maximum thickness4 ,commonly the glacier scoops out a shallow basin in the floor of the cirque4 ,amphitheater ,lake1 ,lake ,solitude1 ,holly ,lake1 and many of the other small lakes high in the ,teton ,range are located in such basins4 ,the sharp peaks and the jagged knife-edge ridges so characteristic of the ,tetons are divides left between cirques and valleys carved by the ancient glaciers4 ,effects on ,jackson ,hole ,rock debris is carried toward the end of the glacier or along the margins where it is released as the ice melts4 ,the semicircular ridge of rock fragments that marks the downhill margin of the glacier is called a terminal moraine2 that along the sides is a lateral moraine 7figs4 #i and #aj74 ,these are formed by the slow accumulation of material in the same manner as that at the end of a conveyor belt4 ,they are not built by material pushed up ahead of the ice as if by a bulldozer4 ,large boulders carried by ice are called erratics2 many of these are scattered on the floor of ,jackson ,hole and on the flanks of the surrounding mountains 7fig4 #aa74 ,illustration3 ,figure #g4 ,rock surface polished and grooved by ice on the floor of ,glacier ,gulch4 ,great volumes of water pour from melting ice near the lower end of a glacier4 ,these streams1 heavily laden with rock flour produced by the grinding action of the glacier and with debris liberated from the melting ice1 cut channels through the terminal moraine and spread a broad apron of gravel1 sand1 and silt down-valley from the glacier terminus 7end74 ,material deposited by streams issuing from a glacier is called outwash2 the sheet of outwash in front of the glacier is called an outwash plain4 ,if the terminus is retreating1 masses of old stagnant ice commonly are buried beneath the outwash2 when these melt1 the space they once occupied becomes a deep circular or irregular depression called a kettle 7fig4 #ab72 many of these now contain small lakes or swamps4 ,as a glacier retreats1 it may build a series of terminal moraines1 marking pauses in the recession of the ice front4 ,streams issuing from the ice behind each new terminal moraine are incised more and more deeply into the older moraines and their outwash plains4 ,thus1 new and younger layers of bouldery debris are spread at successively lower and lower levels4 ,these surfaces are called outwash terraces4 ,illustration3 ,figure #h4 ,east face of the ,teton ,range showing some of the glacial features1 air oblique view4 ,cascade ,canyon1 the ,u-shaped valley1 was cut by ice4 ,the glacier flowed toward the flats1 occupied the area of ,jenny ,lake 7foreground71 and left an encircling ring of morainal debris1 now covered with trees4 ,the flat bare outwash plain in foreground was deposited by meltwater from the glacier4 ,the lake occupies a depression that was left when the ice melted away4 ,national ,park ,service photo by ,bryan ,harry4 ,illustration3 ,figure #i4 ,cutaway view of a typical valley glacier4 ,illustration3 ,figure #aj4 ,recently-built terminal moraine of the ,schoolroom ,glacier1 a small ice mass near the head of the south fork of ,cascade ,canyon4 ,the present glacier lies to the right just out of the field of view4 ,the moraine marks a former position of the ice terminus2 the lake 7frozen over in this picture7 occupies the depression left when the glacier wasted back from the moraine to its present position4 ,crest of the moraine stands about #ej feet above the lake level4 ,many of the lakes along the foot of the ,teton ,range occupy similar depressions behind older moraines4 ,photo by ,philip ,hyde4 ,illustration3 ,figure #aa4 ,large ice-transported boulder of coarse-grained pegmatite and granite resting on ,cretaceous shale near ,mosquito ,creek1 on the southwest margin of ,jackson ,hole4 ,many boulders at this locality are composed of pegmatite rock characteristic of the middle part of the ,teton ,range4 ,this occurrence demonstrates that boulders #dj feet in diameter were carried southward #be miles and left along the west edge of the ice stream1 #a1ejj feet above the base of the glacier on the floor of ,jackson ,hole4 ,just as the jagged ridges1 ,u-shaped valleys1 and ice-polished rocks of the ,teton ,range attest the importance of glaciers in carving the mountain landscape1 the flat gravel outwash plains and hummocky moraines on the floor of ,jackson ,hole demonstrate their efficiency in transporting debris from the mountains and shaping the scenery of the valley4 ,glaciers sculptured all sides of ,jackson ,hole and filled it with ice to an elevation between #a1jjj and #b1jjj feet above the present valley floor4 ,the visitor who looks eastward from the south entrance to the park can see clearly glacial scour lines that superficially resemble a series of terraces on the bare lower slopes of the ,gros ,ventre ,mountains4 ,southward-moving ice cut these features in hard rocks4 ,elsewhere around the margins of ,jackson ,hole1 especially where the rocks are soft1 evidence that the landscape was shaped by ice has been partly or completely obliterated by later events4 ,rising #a1jjj feet above the floor of ,jackson ,hole are several steepsided buttes 7figs4 #ac and #ee7 described previously1 that represent 8islands0 of hard rock overridden and abraded by the ice4 ,after the ice melted1 these buttes were surrounded and partly buried by outwash debris4 ,illustration3 ,figure #ab4 8,the ,potholes10 knob and kettle topography caused by melting of stagnant ice partly buried by outwash gravel4 ,air oblique view north from over ,burned ,ridge moraine 7see fig4 #fa for orientation74 ,photo by ,w4 ,b4 ,hall and ,j4 ,m4 ,hill4 ,the story of the glaciers and their place in the geologic history of the ,teton region is discussed in more detail later in this booklet4 ,illustration3 ,figure #ac4 ,radar image of part of ,tetons and ,jackson ,hole4 ,distance shown between left and right margins is #ce miles4 ,lakes from left to right3 ,phelps1 ,taggart1 ,bradley1 ,jenny1 ,leigh1 ,jackson4 ,blacktail ,butte is at lower left4 ,channel of ,snake ,river and outwash terraces are at lower left4 ,burned ,ridge and ,jackson ,lake moraines are in center4 ,lava flows at upper right engulf north end of ,tetons4 ,striated surfaces at lower right are glacial scour lines made by ice moving south from ,yellowstone ,national ,park4 ,image courtesy of ,national ,aeronautics and ,space ,administration4 ,,mountain ,,uplift ,mountains appear ageless1 but as with people1 they pass through the stages of birth1 youth1 maturity1 and old age1 and eventually disappear4 ,the ,tetons are youthful and steep and are1 therefore1 extremely vulnerable to destructive processes that are constantly sculpturing the rugged features and carrying away the debris4 ,the mountains are being destroyed4 ,although the processes of destruction may seem slow to us1 we know they have been operating for millions of years--so why have the mountains not been leveled8 ,how did they form in the first place8 ,kinds of mountains ,there are many kinds of mountains4 ,some are piles of lava and debris erupted from a volcano4 ,others are formed by the bowing up of the earth's crust in the shape of a giant dome or elongated arch4 ,still others are remnants of accumulated sedimentary rocks that once filled a basin between preexisting mountains and which are now partially worn away4 ,an example of this type is the ,absaroka ,range #dj miles northeast of the ,tetons 7figs4 #a and #eb74 ,the ,tetons are a still different kind--a fault block mountain range carved from a segment of the earth's crust that has been uplifted along a fault4 ,the ,teton fault is approximately at the break in slope where the eastern foot of the range joins the flats at the west edge of ,jackson ,hole 7see map inside back cover71 but in most places is concealed beneath glacial deposits and debris shed from the adjacent steep slopes4 ,the shape of the range and its relation to ,jackson ,hole have already been described4 ,clues as to the presence of the fault are3 7#a7 the straight and deep east face of the ,teton ,range1 7#b7 absence of foothills1 7#c7 asymmetry of the range 7fig4 #ad71 and 7#d7 small fault scarps 7cliffs or steep slopes formed by faulting7 along the mountain front 7fig4 #ae74 ,illustration3 ,figure #ad4 ,air oblique view south showing the width and asymmetry of ,teton ,range4 ,grand ,teton is left of center and ,mt4 ,moran is the broad humpy peak still farther left4 ,photo taken ,october #a1 #aife4 ,recent geophysical surveys of ,jackson ,hole combined with data from deep wells drilled in search of oil and gas east of the park also yield valuable clues4 ,by measuring variations in the earth's magnetic field and in the pull of gravity and by studying the speed of shock waves generated by small dynamite explosions1 ,dr4 ,john ,c4 ,behrendt of the ,u4 ,s4 ,geological ,survey has determined the depth and tilt of rock layers buried beneath the veneer of glacial debris and stream-laid sand and gravel on the valley floor4 ,this information was used in constructing the geologic cross section in the back of the booklet4 ,the same rock layers that cap the summit of ,mount ,moran 7fig4 #bg7 are buried at depths of nearly #bd1jjj feet beneath the nearby floor of ,jackson ,hole but are cut off by the ,teton fault at the west edge of the valley4 ,thus the approximate amount of movement along the fault here would be about #cj1jjj feet4 ,anatomy of faults ,the preceding discussion shows that the ,tetons are an upfaulted mountain block4 ,why is this significant8 ,the extreme youth of the ,teton fault1 its large amount of displacement1 and the fact that the newly upfaulted angular mountain block was subjected to intense glaciation are among the prime factors responsible for the development of the magnificent alpine scenery of the ,teton ,range4 ,an understanding of the anatomy of faults is1 therefore1 pertinent4 ,illustration3 ,figure #ae4 ,recent fault scarp 7arrows indicate base7 offsetting alluvial fan at foot of ,rockchuck ,peak4 ,view west from ,cathedral ,group scenic turnout4 ,national ,park ,service photo by ,w4 ,e4 ,dilley and ,r4 ,a4 ,mebane4 ,a fault is a plane or zone in the earth's crust along which the rocks on one side have moved in relation to the rocks on the other4 ,there are various kinds of faults just as there are various types of mountains4 ,three principal types of faults are present in the ,teton region3 normal faults1 reverse faults1 and thrust faults4 ,a normal fault 7fig4 #af;,a7 is a steeply dipping 7steeply inclined7 fault along which rocks above the fault have moved down relative to those beneath it4 ,a reverse fault 7fig4 #af;,b7 is a steeply inclined fault along which the rocks above the fault have moved up relative to those below it4 ,a thrust fault 7fig4 #af;,c7 is a gently inclined fault along which the principal movement has been more nearly horizontal than vertical4 ,normal faults may be the result of tension or pulling apart of the earth's crust or they may be caused by adjustment of the rigid crust to the flow of semi-fluid material below4 ,the crust sags or collapses in areas from which the subcrustal material has flowed and is bowed up and stretched in areas where excess subcrustal material has accumulated4 ,in both areas the adjustments may result in normal faults4 ,reverse faults are generally caused by compression of a rigid block of the crust1 but some may also be due to lateral flow of subcrustal material4 ,thrust faults are commonly associated with tightly bent or folded rocks4 ,many of them are apparently caused by severe compression of part of the crust1 but some are thought to have formed at the base of slides of large rock masses that moved from high areas into adjacent low areas under the influence of gravity4 ,the ,teton fault 7see cross section inside back cover7 is a normal fault2 the ,buck ,mountain fault1 which lies west of the main peaks of the ,teton ,range1 is a reverse fault4 ,no thrust faults have been recognized in the ,teton ,range1 but the mountains south and southwest of the ,tetons 7fig4 #a7 display several enormous thrust faults along which masses of rocks many miles in extent have moved tens of miles eastward and northeastward4 ,time and rate of uplift ,when did the ,tetons rise8 ,a study of the youngest sedimentary rocks on the floor of ,jackson ,hole shows that the ,teton ,range began to rise rapidly and take its present shape less than #i million years ago4 ,the towering peaks themselves are direct evidence that the rate of uplift far exceeded the rate at which the rising block was worn away by erosion4 ,the mountains are still rising1 and comparatively rapidly1 as is indicated by small faults cutting the youngest deposits 7fig4 #ae74 ,how rapidly8 ,can the rate be measured8 ,we know that in less than #i million years 7and probably in less than #g million years7 there has been #be1jjj to #cj1jjj feet of displacement on the ,teton fault4 ,this is an average of about #a foot in #cjj-djj years4 ,the movement probably was not continuous but came as a series of jerks accompanied by violent earthquakes4 ,one fault on the floor of ,jackson ,hole near the southern boundary of the park moved #aej feet in the last #ae1jjj years1 an average of #a foot per #ajj years4 ,in view of this evidence of recent crustal unrest1 it is not surprising that small earthquakes are frequent in the ,teton region4 ,more violent ones can probably be expected from time to time4 ,figure #af4 ,types of faults4 ,illustration3 ,a4--,normal fault 7tensional7 ,illustration3 ,b4--,reverse fault 7compressional7 ,illustration3 ,c4--,thrust fault 7compressional7 ,why are mountains here8 ,why did the ,tetons form where they are8 ,at the beginning of this booklet we discussed briefly the two most common theories of origin of mountains3 continental drift and convection currents4 ,the question of why mountains are where they are and more specifically why the ,tetons are here remains a continuing scientific challenge regardless of the wealth of data already accumulated in our storehouse of knowledge4 ,the mobility of the earth's crust is an established fact4 ,despite its apparent rigidity1 laboratory experiments demonstrate that rocks flow when subjected to extremely high pressures and temperatures4 ,if the stress exceeds the strength at a given pressure and temperature1 the rock breaks4 ,flowing and fracturing are two of the ways by which rocks adjust to the changing environments at various levels in the earth's crust4 ,these acquired characteristics1 some of which can be duplicated in the laboratory1 are guides by which we interpret the geologic history of rocks that once were deep within the earth4 ,the site of the ,teton block no doubt reflects hidden inequalities at depth4 ,we cannot see these1 nor in this area can we drill below the outer layer of the earth2 nevertheless1 measurements of gravity and of the earth's magnetic field clearly show that they exist4 ,we know that the ,tetons rose at the time ,jackson ,hole collapsed but the volume of the uplifted block is considerably less than that of the downdropped block4 ,this1 then1 was not just a simple case in which all the subcrustal material displaced by the sinking block was squeezed under the rising block 7the way a hydraulic jack works74 ,what happened to the rest of the material that once was under ,jackson ,hole8 ,it could not be compressed so it had to go somewhere4 ,as you look northward from the top of the ,grand ,teton or ,mount ,moran1 or from the main highway at the north edge of ,grand ,teton ,national ,park1 you see the great smooth sweep of the volcanic plateau in ,yellowstone ,national ,park4 ,farther off to the northeast are the strikingly layered volcanic rocks of the ,absaroka ,range 7fig4 #eb74 ,for these two areas1 an estimate of the volume of volcanic rock that reached the surface and flowed out1 or was blown out and spread far and wide by wind and water1 is considerably in excess of #aj1jjj cubic miles4 ,on the other hand1 this volume is many times more than that displaced by the sagging and downfaulting of ,jackson ,hole4 ,where did the rest of the volcanic material come from8 ,is it pertinent to our story8 ,teton ,basin1 on the west side of the ,teton ,range1 and the broad ,snake ,river downwarp farther to the northwest 7fig4 #a7 are sufficiently large to have furnished the remainder of the volcanic debris4 ,as it was blown out of vents in the ,yellowstone-,absaroka area1 its place could have been taken deep underground by material that moved laterally from below all three downdropped areas4 ,the movement may have been caused by slow convection currents within the earth1 or perhaps by some other1 as yet unknown1 force4 ,the sagging of the earth's crust on both sides of the ,teton ,range as well as the long-continued volcanism are certainly directly related to the geologic history of the park4 ,in summary1 we theorize as to how the ,tetons rose and ,jackson ,hole sank but are not sure why the range is located at this particular place1 why it trends north1 why it rose so high1 or why this one1 of all the mountain ranges surrounding the ,yellowstone-,absaroka volcanic area1 had such a unique history of uplift4 ,these are problems to challenge the minds of generations of earth scientists yet to come4 ,the restless land ,among the greatest of the park's many attractions is the solitude one can savor in the midst of magnificent scenery4 ,only a short walk separates us from the highway1 torrents of cars1 noise1 and tension4 ,away from these1 everything seems restful4 ,quiescent it may seem1 yet the landscape is not static but dynamic4 ,this is one of the many exciting ideas that geology has contributed to society4 ,the concept of the 8everlasting hills0 is a myth4 ,all the features around us are actually rather short-lived in terms of geologic time4 ,the discerning eye detects again and again the restlessness of the land4 ,we have discussed many bits of evidence that show how the landscape and the earth's crust beneath it are constantly being carved1 pushed up1 dropped down1 folded1 tilted1 and faulted4 ,the ,teton landscape is a battleground1 the scene of a continuing unresolved struggle between the forces that deform the earth's crust and raise the mountains and the slow processes of erosion that strive to level the uplands1 fill the hollows1 and reduce the landscape to an ultimate featureless plain4 ,the remainder of this booklet is devoted to tracing the seesaw conflict between these inexorable antagonists through more than #b4e billion years as they shaped the present landscape--and the battle still goes on4 ,evidence of the struggle is all around us4 ,even though to some observers it may detract from the restfulness of the scene1 perhaps it conveys to all of us a new appreciation of the tremendous dynamic forces responsible for the magnificence of the ,teton ,range4 ,the battle is indicated by the small faults that displace both the land surface and young deposits at the east base of ,mount ,teewinot1 ,rockchuck ,peak 7fig4 #ae71 and other places along the foot of the ,tetons4 ,jackson ,hole continues to drop and tilt4 ,the gravel-covered surfaces that originally sloped southward are now tilted westward toward the mountains4 ,the ,snake ,river1 although the major stream1 is not in the lowest part of ,jackson ,hole2 ,fish ,creek1 a lesser tributary near the town of ,wilson1 is #ae feet lower4 ,for #aj miles this creek flows southward parallel to the ,snake ,river but with a gentler gradient1 thus permitting the two streams to join near the south end of ,jackson ,hole4 ,as tilting continues1 the ,snake ,river west of ,jackson tries to move westward but is prevented from doing so by long flood-control levees built south of the park4 ,recent faults also break the valley floor between the ,gros ,ventre ,river and the town of ,jackson4 ,the ever-changing piles of rock debris that mantle the slopes adjacent to the higher peaks1 the creeping advance of rock glaciers1 the devastating snow avalanches1 and the thundering rockfalls are specific reminders that the land surface is restless4 ,jackson ,hole contains more landslides and rock mudflows than almost any other part of the ,rocky ,mountain region4 ,they constantly plague road builders 7fig4 #ag7 and add to the cost of other types of construction4 ,all of these examples of the relentless battle between constructive and destructive processes modifying the ,teton landscape are but minor skirmishes4 ,the bending and breaking of rocks at the surface are small reflections of enormous stresses and strains deep within the earth where the major conflict is being waged4 ,it is revealed every now and then by a convulsion such as the #aiei earthquake in and west of ,yellowstone ,park4 ,events of this type release much more energy than all the nuclear devices thus far exploded by man4 ,illustration3 ,figure #ag4 ,slide blocking main highway in northern part of ,grand ,teton ,national ,park4 ,national ,park ,service photo by ,eliot ,davis1 ,may #aieb4 ,,enormous ,,time ,,and ,,dynamic ,,earth ,framework of time ,one of geology's greatest philosophical contributions has been the demonstration of the enormity of geologic time4 ,astronomers deal with distances so great that they are almost beyond understanding2 nuclear physicists study objects so small that we can hardly imagine them4 ,similarly1 the geologist is concerned with spans of time so immense that they are scarcely comprehensible4 ,geology is a science of time as well as rocks1 and in our geologic story of the ,teton region we must refer frequently to the geologic time scale1 the yardstick by which we measure the vast reaches of time in earth history4 ,rocks and relative age ,very early in the science of geology it was recognized that in many places one can tell the comparative ages of rocks by their relations to one another4 ,for example1 most sedimentary rocks are consolidated accumulations of large or small rock fragments and were deposited as nearly horizontal layers of gravel1 sand1 or mud4 ,in an undisturbed sequence of sedimentary rocks1 the layer on the bottom was deposited first and the layer on top was deposited last4 ,all of these must1 of course1 be younger than any previously formed rock fragments incorporated in them4 ,igneous rocks are those formed by solidification of molten material1 either as lava flows on the earth's surface 7extrusive igneous rocks7 or at depth within the earth 7intrusive igneous rocks74 ,the relative ages of extrusive igneous rocks can often be determined in much the same way as those of sedimentary strata4 ,a lava flow is younger than the rocks on which it rests1 but older than those that rest on top of it4 ,an intrusive igneous rock must be younger than the rocks that enclosed it at the time it solidified4 ,it may contain pieces of the enclosing rocks that broke off the walls and fell into the liquid4 ,pebbles of the igneous rock that are incorporated in nearby sedimentary layers indicate that the sediments must be somewhat younger4 ,all of these criteria tell us only that one rock is older or younger than another4 ,they tell us little about the absolute age of the rocks or about how much older one is than the other4 ,fossils and geologic time ,fossils provide important clues to the ages of the rocks in which they are found4 ,the slow evolution of living things through geologic time can be traced by a systematic study of fossils4 ,the fossils are then used to determine the relative ages of the rocks that contain them and to establish a geologic time scale that can be applied to fossil-bearing rocks throughout the world4 ,figure #ah shows the major subdivisions of the last #fjj million years of geologic time and some forms of life that dominated the scene during each of these intervals4 ,strata containing closely related fossils are grouped into systems2 the time interval during which the strata comprising a particular system were deposited is termed a period4 ,the periods are subdivisions of larger time units called eras and some are split into smaller time units called epochs4 ,strata deposited during an epoch comprise a series4 ,series are in turn subdivided into rock units called groups and formations4 ,expressed in tabular form these divisions are3 ,subdivisions of ,time-rock units ,rock units geologic time ,era ,period ,system ,epoch ,series ,group ,formation ,the time scale based on the study of fossil-bearing sedimentary rocks is called the stratigraphic time scale2 it is given in table #a4 ,the subdivisions are arranged in the same order in which they were deposited1 with the oldest at the bottom and the youngest at the top4 ,all rocks older than ,cambrian 7the first period in the ,paleozoic ,era7 are classed as ,precambrian4 ,these rocks are so old that fossils are rare and therefore cannot be conveniently used as a basis for subdivision4 ,the stratigraphic time scale is extremely useful1 but it has serious drawbacks4 ,it can be applied only to fossil-bearing strata or to rocks whose ages are determined by their relation to those containing fossils4 ,it cannot be used directly for rocks that lack fossils1 such as igneous rocks1 or metamorphic rocks in which fossils have been destroyed by heat or pressure4 ,it is used to establish the relative ages of sedimentary strata throughout the world1 but it gives no information as to how long ago a particular layer was deposited or how many years a given period or era lasted4 ,radioactive clocks ,the measurement of geologic time in terms of years was not possible until the discovery of natural radioactivity4 ,it was found that certain atoms of a few elements spontaneously throw off particles from their nuclei and break down to form atoms of other elements4 ,these decay processes take place at constant rates1 unaffected by heat1 pressure1 or chemical conditions4 ,if we know the rate at which a particular radioactive element decays1 the length of time that has passed since a mineral crystal containing the elements formed can be calculated by comparing the amount of the radioactive element remaining in the crystal with the amount of disintegration products present4 ,illustration3 ,figure #ah4 ,major subdivisions of the last #fjj million years of geologic time and some of the dominant forms of life4 ,,millions ,,of ,,years ,,ago #j ,man #j-fj ,,cenozoic ,,quaternary and ,,tertiary ,mammals #fj-acj ,,mesozoic ,,cretaceous #acj-ahj ,,jurassic ,dinosaurs #ahj-bbj ,,triassic #bbj-bfj ,,paleozoic ,,permian ,reptiles #bfj-cej ,,pennsylvanian1 ,amphibians ,,mississippian #cej-djj ,,devonian ,fishes #djj-ddj ,,silurian ,sea scorpions #ddj-ejj ,,ordovician ,nautiloids #ejj-ecj ,,cambrian ,trilobites #ecj- ,,precambrian ,soft-bodied creatures ,three principal radioactive clocks now in use are based on the decay of uranium to lead1 rubidium to strontium1 and potassium to argon4 ,they are effective in dating minerals millions or billions of years old4 ,another clock1 based on the decay of one type of carbon 7,carbon-#ad7 to nitrogen1 dates organic material1 but only if it is less than about #dj1jjj years old4 ,the uranium1 rubidium1 and potassium clocks are especially useful in dating igneous rocks4 ,by determining the absolute ages of igneous rocks whose stratigraphic relations to fossil-bearing strata are known1 it is possible to estimate the number of years represented by the various subdivisions of the stratigraphic time scale4 ,the yardstick of geologic time ,recent estimates suggest that the earth was formed at least #d4e billion years ago4 ,to visualize the length of geologic time and the relations between the stratigraphic and absolute time scales1 let us imagine a yardstick as representing the length of time from the origin of the earth to the present 7fig4 #ai74 ,on one side of the yardstick we plot time in years2 on the other1 we plot the divisions of the stratigraphic time scale according to the most reliable absolute age determinations4 ,illustration3 ,table #a4 ,the stratigraphic time scale4 ,era ,system or period ,series or epoch ,cenozoic ,quaternary ,recent ,pleistocene ,tertiary ,pliocene ,miocene ,oligocene ,eocene ,paleocene ,mesozoic ,cretaceous ,jurassic ,triassic ,paleozoic ,permian ,pennsylvanian ,mississippian ,devonian ,silurian#a ,ordovician ,cambrian -- ,precambrian #a,the ,silurian is the only major subdivision of the stratigraphic time scale not represented in ,grand ,teton ,national ,park4 ,we are immediately struck by the fact that all of the subdivisions of the stratigraphic time scale since the beginning of the ,paleozoic are compressed into the last #e inches of our yardstick6 ,all of the other #ca inches represent ,precambrian time4 ,we also see that subdivisions of the stratigraphic time scale do not represent equal numbers of years4 ,we use smaller and smaller subdivisions as we approach the present4 7,notice the subdivisions of the ,tertiary and ,quaternary in table #a that are too small to show even in the enlarged part of figure #ai74 ,this is because the record of earth history is more vague and incomplete the farther back in time we go4 ,in effect1 we are very nearsighted in our view of time4 ,this 8geological myopia0 becomes increasingly evident throughout the remainder of this booklet4 ,illustration3 ,figure #ai4 ,the geologic time scale--our yardstick in time4 ,,absolute ,,time 7,years ago7 ,,inches ,,stratigraphic ,,time ,,scale ,first man #j ,,cenozoic #a ,,mesozoic ,first dinosaurs #b ,,paleozoic #c #ejj million #d ,first abundant fossils #e ,,precambrian #f #g #a billion #h #i #aj #aa #ab #ac #ad ,oldest known fossils #ae #b billion #af #ag #ah #ai #bj #ba #bb #bc #c billion #bd #be #bf #bg ,oldest dated rocks #bh #bi #cj #ca #d billion #cb #cc #cd #ce ,minimum age of the earth #cf ,,enlargement ,,of ,,the ,,last ,,six ,,inches ,,absolute ,,time ,,inches ,,stratigraphic ,,time ,,scale 7,years ,ago7 #j #j ,,cenozoic ,,quaternary ,,tertiary ,,mesozoic ,,cretaceous #a ,,jurassic ,,triassic #b ,,paleozoic ,,permian ,,pennsylvanian ,,mississippian #c ,,devonian ,,silurian ,,ordovician #ejj million #d ,,cambrian #e ,,precambrian #f ,,precambrian ,,rocks--,,the ,,core ,,of ,,the ,,tetons ,the visitor who looks at the high1 rugged peaks of the ,teton ,range is seeing rocks that record about seven-eighths of all geologic time4 ,these ,precambrian rocks are part of the very foundation of the continent and are therefore commonly referred to by geologists as basement rocks4 ,in attempting to decipher their origin and history we peer backward through the dim mists of time1 piecing together scattered clues to events that occurred billions of years ago1 perhaps during the very birth of the ,north ,american ,continent4 ,to cite an oft-quoted example1 it is as though we were attempting to read the history of an ancient and long-forgotten civilization from the scattered unnumbered pages of a torn manuscript1 written in a language that we only partially understand4 ,ancient gneisses and schists ,the oldest ,precambrian rocks in the ,teton ,range are layered gneisses and schists exposed over wide areas in the northern and southern parts of the range and as scattered isolated masses in the younger granite that forms the high peaks in the central parts4 ,the layered gneisses may be seen easily along the trails in the lower parts of ,indian ,paintbrush and ,death ,canyons1 and near ,static ,peak4 ,the layered gneisses are composed principally of quartz1 feldspar1 biotite 7black mica71 and hornblende 7a very dark-green or black mineral commonly forming rodlike crystals74 ,distinct layers1 a few inches to several feet thick1 contain different proportions of these minerals and account for the banded appearance4 ,layers composed almost entirely of quartz and feldspar are light-gray or white1 whereas darker gray layers contain higher proportions of biotite and hornblende4 ,some layers are dark-green to black amphibolite1 composed principally of hornblende but with a little feldspar and quartz4 ,in many places the gneisses include layers of schist1 a flaky rock1 much of which is mica4 ,at several places on the east slopes of ,mount ,moran thin layers of impure gray marble are found interleaved with the gneisses4 ,west of ,static ,peak along the ,alaska ,basin ,trail a heavy dark rock with large amounts of magnetite 7strongly magnetic black iron oxide7 occurs as layers in the gneiss4 ,in some places the gneiss contains dark-reddish crystals of garnet as much as an inch in diameter4 ,commonly the garnet crystals are surrounded by white 8halos0 which lack biotite or hornblende1 probably because the constituents necessary to form these minerals were absorbed by the garnet crystals4 ,in ,death ,canyon and on the slopes of ,static ,peak some layers of gray gneiss contain egg-shaped masses of magnetite as much as one-half inch in diameter 7fig4 #bj74 ,these masses are likewise surrounded by elliptical white halos and have the startling appearance of small eyes peering from the rock4 ,appropriately1 this rock has been called the 8bright-eyed0 gneiss by ,prof4 ,charles ,c4 ,bradley in his published study 7,wyoming ,geological ,association1 #aief7 of this area4 ,what were the ancient rocks from which the gneisses of the ,teton ,range were formed8 ,most of the evidence has been obliterated but a few remaining clues enable us to draw some general conclusions4 ,the banded appearance of many of the gneisses suggests that they were formed from sedimentary and volcanic rocks that accumulated on the sea floor near a chain of volcanic islands--perhaps somewhat similar to the modern ,aleutians or the islands of ,indonesia4 ,when these deposits were buried deep in the earth's crust the chemical composition of some layers may have undergone radical changes4 ,other layers1 however1 still have compositions resembling those of younger rocks elsewhere whose origins are better known4 ,for example1 the layers of impure marble were probably once beds of sandy limestone1 and the lighter colored gneiss may have been muddy sandstone1 possibly containing volcanic ash4 ,some dark amphibolite layers could represent altered lava flows or beds of volcanic ash2 others may have resulted from the addition of silica to muddy magnesium-rich limestone during metamorphism4 ,the magnetite-rich gneiss probably was originally a sedimentary iron ore4 ,illustration3 ,figure #bj4 8,bright-eyed0 gneiss from ,death ,canyon4 ,the dark magnetite spots are about inch in diameter4 ,the surrounding gneiss is composed of quartz1 feldspar1 and biotite1 but biotite is missing in the white halos around the magnetite4 ,minerals that were most easily altered at depth reacted with one another to form new minerals more 8at home0 under the high temperature and pressure in this environment just as the ingredients in a cake react when heated in an oven4 ,rocks formed by such processes are called metamorphic rocks2 careful studies of the minerals that they contain suggest that the layered gneisses developed at temperatures as high as #ajjj;,f at depths of #e to #aj miles4 ,under these conditions the rocks must have behaved somewhat like soft taffy as is shown by layers that have been folded nearly double without being broken 7fig4 #ba74 ,folds such as these range from fractions of an inch to thousands of feet across and are found in gneisses throughout the ,teton ,range4 ,in a few places folds are superimposed in such a way as to indicate that the rocks were involved in several episodes of deformation in response to different sets of stress during metamorphism4 ,when did these gneisses form8 ,age determinations of minerals containing radioactive elements show that granite which was intruded into them after they were metamorphosed and folded is more than #b4e billion years old4 ,they must1 therefore1 be older than that4 ,thus1 they probably are at least a billion years older than rocks containing the first faint traces of life on earth and #b billion years older than the oldest rocks containing abundant fossils4 ,how much older is not known1 but the gneisses are certainly among the oldest rocks in ,north ,america and record some of the earliest events in the building of this continent4 ,figure #ba4 ,folds in layered gneisses4 ,illustration3 ,a4 ,north face of the ridge west of ,eagles ,rest ,peak4 ,the face is about #gjj feet high4 ,notice the extreme contortion of the gneiss layers4 ,illustration3 ,b4 ,closeup view of some of the folds near the bottom of the face in figure ,a4 ,the light-colored layers are composed principally of quartz and feldspar4 ,the darker layers are rich in hornblende4 ,irregular bodies of granite gneiss are interleaved with the layered gneisses in the northern part of the ,teton ,range4 ,the granite gneiss is relatively coarse grained1 streaky gray or pink1 and composed principally of quartz1 feldspar1 biotite1 and hornblende4 ,it differs from enclosing layered gneisses in its coarser texture1 lack of layering1 and more uniform appearance4 ,the dark minerals 7biotite and hornblende7 are concentrated in thin discontinuous wisps that give the rock its streaky appearance4 ,the largest body of granite gneiss is exposed in a belt #a to #b miles wide and #aj miles long extending northeastward from near the head of ,moran ,canyon1 across the upper part of ,moose ,basin1 and into the lower reaches of ,webb ,canyon4 ,this gneiss may have been formed from granite that invaded the ancient sedimentary and volcanic rocks before they were metamorphosed1 or it may have been formed during metamorphism from some of the sediments and volcanics themselves4 ,at several places in ,snowshoe1 ,waterfalls1 and ,colter ,canyons the layered gneisses contain discontinuous masses a few tens or hundreds of feet in diameter of heavy dark-green or black serpentine4 ,this rock is frequently called 8soapstone0 because the surface feels smooth and soapy to the touch4 ,indians carved bowls 7fig4 #bb7 from similar material obtained from the west side of the ,tetons and from the ,gros ,ventre ,mountains to the southeast4 ,pebbles of serpentine along streams draining the west side of the ,tetons have been cut and polished for jewelry and sold as 8,teton jade02 it is much softer and less lustrous than real jade4 ,the serpentine was formed by metamorphism of dark-colored igneous rocks lacking quartz and feldspar4 ,granite and pegmatite ,contrary to popular belief1 granite 7crystalline igneous rock composed principally of quartz and feldspar7 forms only a part of the ,teton ,range4 ,the ,grand ,teton 7fig4 #f7 and most surrounding subsidiary peaks are sculptured from an irregular mass of granite exposed continuously along the backbone of the range from ,buck ,mountain northward toward upper ,leigh ,canyon4 ,the rock is commonly fine grained1 white or light-gray1 and is largely composed of crystals of gray quartz and white feldspar about the size and texture of the grains in very coarse lump sugar4 ,flakes of black or dark-brown mica 7biotite7 and silvery white mica 7muscovite7 about the size of grains of pepper are scattered through the rock4 ,from the floor of ,jackson ,hole the granite cliffs and buttresses of the high peaks appear nearly white in contrast to the more somber grays and browns of surrounding gneisses and schists4 ,these dark rocks are laced by a network of irregular light-colored granite dikes ranging in thickness from fractions of an inch to tens of feet 7fig4 #bc74 ,illustration3 ,figure #bb4 ,indian bowls carved from soapstone1 probably from the ,teton ,range4 ,mouth of the unbroken bowl is about #d inches in diameter4 ,the largest masses of granite contain abundant unoriented angular blocks and slabs of the older gneisses4 ,these inclusions range from a few inches in diameter 7fig4 #bd7 to slabs hundreds of feet thick and thousands of feet long4 ,dikes or irregular intrusions of pegmatite are found in almost every exposure of granite4 ,pegmatite contains the same minerals as granite but the individual mineral crystals are several inches or even as much as a foot in diameter4 ,some pegmatites contain silvery plates or tabular crystals of muscovite mica as much as #f inches across that can be split into transparent sheets with a pocket knife4 ,others have dark-brown biotite mica in crystals about the size and shape of the blade of a table knife4 ,a few pegmatites contain scattered red-brown crystals of garnet ranging in size from that of a ,,bb shot to a small marble2 a few in ,garnet ,canyon and ,glacier ,gulch are larger than baseballs 7fig4 #be74 ,the garnets are fractured and many are partly altered to chlorite 7a dull-green micaceous mineral7 so they are of no value as gems4 ,figure #bc4 ,dikes of granite and pegmatite4 ,illustration3 ,a4 ,network of light-colored granite dikes on the northeast face of the ,west ,horn on ,mt4 ,moran4 ,the dikes cut through gneiss in which the layers slant steeply downward to the left4 ,the face is about #gjj feet high4 ,snowfield in the foreground is at the edge of the ,falling ,ice ,glacier4 ,illustration3 ,b4 ,irregular dike of granite and pegmatite cutting through dark layered gneisses near ,wilderness ,falls in ,waterfalls ,canyon4 ,the cliff face is about #hj feet high4 ,contacts of the dike are sharp and angular and cut across the layers in the enclosing gneiss4 ,pegmatite dikes 7tabular bodies of rock that1 while still molten1 were forced along fractures in older rocks7 commonly cut across granite dikes1 but in many places the reverse is true4 ,some dikes are composed of layers of pegmatite alternating with layers of granite 7fig4 #bf71 showing that the pegmatite and granite are nearly contemporaneous4 ,prof4 ,bruno ,giletti and his coworkers at ,brown ,university1 using the rubidium-strontium radioactive clock1 determined that the granite and pegmatite in the ,teton ,range are about #b4e billion years old4 ,illustration3 ,figure #bd4 ,angular blocks of old streaky granite gneiss in fine-grained granite northwest of ,lake ,solitude4 ,the difference in orientation of the streaks in the gneiss blocks indicates that the blocks have been rotated with respect to one another and that the fine-grained granite must therefore have been liquid at the time of intrusion4 ,a small light-colored dike in the upper left-hand block of gneiss ends at the edge of the block2 it intruded the gneiss before the block was broken off and incorporated in the granite4 ,a small dike of pegmatite cuts diagonally through the granite just to the left of the hammer and extends into the blocks of gneiss at both ends4 ,this dike was intruded after the granite had solidified4 ,thus1 in this one small exposure we can recognize four ages of rocks3 the streaky granite gneiss1 the light-colored dike1 the fine-grained granite1 and the small pegmatite dike4 ,black dikes ,even the most casual visitor to the ,teton ,range notices the remarkable black band that extends down the east face of ,mount ,moran 7figs4 #bg and #bh7 from the summit and disappears into the trees north of ,leigh ,lake4 ,this is the outcropping edge of a steeply inclined dike composed of diabase1 a nearly black igneous rock very similar to basalt4 ,thinner diabase dikes are visible on the east face of ,middle ,teton1 on the south side of the ,grand ,teton1 and in several other places in the range 7see geologic map inside back cover74 ,illustration3 ,figure #be4 ,garnet crystal in pegmatite4 ,the crystal is about #f inches in diameter4 ,other minerals are feldspar 7white7 and clusters of white mica flakes4 ,the mica crystals appear dark in the photograph because they are wet4 ,the diabase is a heavy dark-greenish-gray to black rock that turns rust brown on faces that have been exposed to the weather4 ,it is studded with small lath-shaped crystals of feldspar that are greenish gray in the fresh rock and milk white on weathered surfaces4 ,the black dikes formed from molten rock that welled up into nearly vertical fissures in the older ,precambrian rocks4 ,toward the edges of the dikes the feldspar laths in the diabase become smaller and smaller 7fig4 #bi71 indicating that the wall rocks were relatively cool when the magma or melted rock was intruded4 ,rapid chilling at the edges prevented growth of large crystals4 ,in many places hot solutions from the dike permeated the wall rocks1 staining them rosy red4 ,illustration3 ,figure #bf4 ,a small dike of pegmatite and granite cutting through folded layered gneiss in ,death ,canyon4 ,coarse-grained pegmatite forms most of the dike1 but fine-grained granite is found near the center4 ,small offshoots of the dike penetrate into the wall rocks4 ,the dike cuts straight across folds in the enclosing gneisses and must therefore have been intruded after development of the folds4 ,the white ruler is about #f inches long4 ,the black dike on ,mount ,moran is about #aej feet thick near the summit of the peak4 ,this dike has been traced westward for more than #g miles4 ,where it passes out of the park south of ,green ,lakes ,mountain it is #ajj feet thick4 ,the amount of molten material needed to form the exposed segment of this single dike could fill ,jenny ,lake three times over4 ,the other dikes are thinner and not as long3 the dike on ,middle ,teton is #bj to #dj feet thick1 and the dike on ,grand ,teton is #dj to #fj feet thick4 ,illustration3 ,figure #bg4 ,air oblique view of the east face of ,mt4 ,moran1 showing the great black dike4 ,main mass of the mountain is layered gneiss and streaky granite gneiss4 ,white lines are dikes of granite and pegmatite2 light-gray mound on the summit is about #ej feet of ,cambrian sedimentary rock 7,flathead ,sandstone74 ,notice that the black dike cuts across the dikes of granite and pegmatite but that its upper edge is covered by the much younger layer of sandstone4 ,falling ,ice ,glacier is in the left center2 ,skillet ,glacier is in the lower right center4 ,photo by ,a4 ,s4 ,post4 ,university of ,washington1 ,august #ai1 #aifc4 ,illustration3 ,figure #bh4 ,the great black dike on the east face of ,mt4 ,moran4 ,the dike is about #aej feet thick and its vertical extent in the picture is about #c1jjj feet4 ,the fractures in the dike perpendicular to its walls are cracks formed as the liquified rock cooled and crystallized4 ,falling ,ice ,glacier is in the center4 ,national ,park ,service photo by ,h4 ,d4 ,pownall4 ,illustration3 ,figure #bi4 ,closeup view of the edge of the ,middle ,teton black dike exposed on the north wall of ,garnet ,canyon near the west end of the trail4 ,dike rock 7diabase7 is on the right2 wall rock 7gneiss7 is on the left4 ,match shows scale4 ,the black dikes must be the youngest of the ,precambrian units because they cut across all other ,precambrian rocks4 ,the dikes must have been intruded before the beginning of ,cambrian deposition inasmuch as they do not cut the oldest ,cambrian beds4 ,gneiss adjacent to the dike on ,mount ,moran contains biotite that was heated and altered about #a4c billion years ago according to ,professor ,giletti4 ,the alteration is believed to have occurred when the dike was emplaced2 therefore this and similar dikes elsewhere in the range are probably about #a4c billion years old4 ,quartzite ,at about the same time as the dikes were being intruded in the ,tetons1 many thousands of feet of sedimentary rocks1 chiefly sandstone1 were deposited in western ,montana1 #bjj miles northwest of ,grand ,teton ,national ,park4 ,the sandstone was later recrystallized and recemented and became a very dense hard rock called quartzite4 ,similar quartzite1 possibly part of the same deposit1 was laid down west of the north end of the ,teton ,range1 within the area now called the ,snake ,river downwarp 7fig4 #a74 ,the visitor who hikes or camps anywhere on the floor of ,jackson ,hole becomes painfully aware of the thousands upon thousands of remarkably rounded hard quartzite boulders4 ,he wonders where they came from because nowhere in the adjacent mountains is this rock type exposed4 ,the answer is that the quartzites were derived from a long-vanished uplift 7figs4 #db and #df71 carried eastward by powerful rivers past the north end of the ,teton ,range1 and then were deposited in a vast sheet of gravel that covered much of ,jackson ,hole #fj to #hj million years ago4 ,since then1 these virtually indestructible boulders have been re-worked many times by streams and ice1 yet still retain the characteristics of the original ancient sediments4 ,a backward glance ,so far we have seen that the ,precambrian basement exposed in the ,teton ,range contains a complex array of rocks of diverse origins and various ages4 ,before passing on to the younger rocks1 reference to our yardstick may help to place the ,precambrian events in their proper perspective4 ,in all of ,precambrian time1 which encompasses more than #he percent of the history of the earth 7#ca of the #cf inches of our yardstick71 only two events are dated in the ,teton ,range3 the intrusion of granite and pegmatite about #b4e billion years ago1 and the emplacement of the black dikes about #a4c billion years ago4 ,these dates are indicated by heavy arrows on the time scale 7fig4 #cj74 ,the ancient gneisses and schists were formed sometime before #b4e billion years ago1 and probably are no older than #c4e billion years1 the age of the oldest rocks dated anywhere in the world4 ,the close of the ,precambrian--end of the beginning ,more than #gjj million years elapsed between intrusion of the black dikes and deposition of the first ,paleozic sedimentary rocks--a longer period of time than has elapsed since the beginning of the ,paleozic ,era4 ,during this enormous interval the ,precambrian rocks were uplifted1 exposed to erosion1 and gradually worn to a nearly featureless plain1 perhaps somewhat resembling the vast flat areas in which similar ,precambrian rocks are now exposed in central and eastern ,canada4 ,at the close of ,precambrian time1 about #fjj million years ago1 the plain slowly floundered and the site of the future ,teton ,range disappeared beneath shallow seas that were to wash across it intermittently for the next #ejj million years4 ,it is to the sediments deposited in these seas that we turn to read the next chapter in the geologic story of the ,teton ,range4 ,illustration3 ,figure #cj4 ,a glance at the yardstick4 ,the geologic time scale shows positions of principal events recorded in the ,precambrian rocks of the ,tetons4 ,,absolute ,,time 7,years ago7 ,,inches ,beginning of the ,paleozoic4 ,first abundant fossils #d #a billion #h ,maximum age of black dikes #aj ,oldest known fossils #ae #b billion #af ,old granite and pegmatite #bj #c billion #bd ,gneisses and schists formed sometime in this interval #bj-bg ,oldest dated rocks #bh #d billion #cb ,minimum age of the earth #cf ,,the ,,paleozoic ,,era--,,time ,,of ,,long-,,vanished ,,seas ,,and ,,the ,,development ,,of ,,life ,the ,paleozoic sequence ,north1 west1 and south of the highest ,teton peaks the soaring spires and knife-edge ridges of ,precambrian rock give way to rounded spurs and lower flat-topped summits1 whose slopes are palisaded by continuous gray cliffs that resemble the battlements of some ancient and long-abandoned fortress 7fig4 #ca74 ,as mentioned previously1 the cliffs are the projecting edges of layers of sedimentary rocks of ,paleozoic age that accumulated in or along the margins of shallow seas4 ,at one time the layers formed a thick unbroken1 nearly horizontal blanket across the ,precambrian basement rocks1 but subsequent uplift of the eastern edge of the ,teton fault block tilted them westward4 ,they were then stripped from the highest peaks4 ,the ,paleozoic and younger sedimentary rocks in the ,teton region are subdivided into formations1 each of which is named4 ,a formation is composed of rock layers which1 because of their similar physical characteristics1 can be distinguished from overlying and underlying layers4 ,they must be thick enough to be shown on a geologic map4 ,table #b lists the various ,paleozoic formations present in and adjacent to ,grand ,teton ,national ,park and gives their thicknesses and characteristics4 ,these sedimentary rocks are of special interest1 for they not only record an important chapter of geologic history but elsewhere in the region they contain petroleum and other mineral deposits4 ,the ,paleozoic rocks can be viewed close at hand from the top of the ,teton ,village tram 7fig4 #cb7 on the south boundary of the park4 ,a less accessible but equally spectacular exposure of ,paleozoic rocks is in ,alaska ,basin1 along the west margin of the park1 where they are stacked like even layers in a gigantic cake 7fig4 #cc74 ,alaska ,basin--site of an outstanding rock and fossil record ,strata in ,alaska ,basin record with unusual clarity the opening chapters in the chronicle of seas that flowed and ebbed across the future site of the ,teton ,range during most of the ,paleozoic ,era4 ,in the various rock layers are inscribed stories of the slow advance and retreat of ancient shorelines1 of the storm waves breaking on long-vanished beaches1 and of the slow and intricate evolution of the myriads of sea creatures that inhabited these restless waters4 ,illustration3 ,figure #ca4 ,paleozoic rocks on the west flank of the ,teton ,range1 air oblique view west4 ,ragged peaks in the foreground 7,buck ,mountain on the left center1 ,mt4 ,wister1 with top outlined by snow patch on the extreme right71 are carved in ,precambrian rocks4 ,banded cliffs in the background are sedimentary rocks4 ,alaska ,basin is at upper right4 ,teton ,basin1 a broad1 extensively farmed valley in eastern ,idaho1 is at top4 ,photo by ,a4 ,s4 ,post1 ,university of ,washington1 #aifc4 ,careful study of the fossils allows us to determine the age of each formation 7table #c74 ,even more revealing1 the fossils themselves are tangible evidence of the orderly parade of life that crossed the ,teton landscape during more than #bej million years4 ,here is a record of ,nature's experiments with life1 the triumphs1 failures1 the bizarre1 the beautiful4 ,illustration3 ,table #b4--,paleozoic sedimentary rocks exposed in the ,teton region4 ,age ,formation ,thickness ,description ,where exposed 7feet7 ,permian ,phosphoria #aej-bej ,dolomite1 gray1 ,north and west ,formation cherty1 sandy1 flanks of ,teton black shale and ,range1 north phosphate beds2 flank of ,gros marine4 ,ventre ,mountains1 southern ,jackson ,hole4 ,pennsylvanian ,tensleep #fjj-a1ejj ,tensleep ,sandstone1 ,north and west and ,amsden light-gray1 hard1 flanks of ,teton ,formations underlain by ,range1 north ,amsden ,formation1 flank of ,gros a domolite and red ,ventre ,mountains1 shale with a basal southern ,jackson red sandstone2 ,hole4 marine4 ,mississippian ,madison #a1jjj-a1bjj ,limestone1 ,north and west ,limestone blue-gray1 hard1 flanks of ,teton fossiliferous2 ,range1 north thin red shale in flank of ,gros places near top2 ,ventre ,mountains1 marine4 southern ,jackson ,hole4 ,devonian ,darby #bjj-ejj ,dolomite1 dark-gray ,north and west ,formation to brown1 fetid1 flanks of ,teton hard1 and brown1 ,range1 north black1 and yellow flank of ,gros shale2 marine4 ,ventre ,mountains1 southern ,jackson ,hole4 ,ordovician ,bighorn #cjj-ejj ,dolomite1 ,north and west ,dolomite light-gray1 flanks of ,teton siliceous1 very ,range1 north and hard2 white dense west flanks of very fine-grained ,gros ,ventre dolomite at top2 ,mountains1 marine4 southern ,jackson ,hole4 ,cambrian ,gallatin #ahj-cjj ,limestone1 blue ,north and west ,limestone gray1 hard1 flanks of ,teton thin-bedded2 ,range and ,gros marine4 ,ventre ,mountains4 ,gros ,ventre #fjj-hjj ,shale1 green1 ,north and west ,formation flaky1 with ,death flanks of ,teton ,canyon ,limestone ,range and ,gros ,member composed of ,ventre ,mountains4 about #cjj feet of hard cliff-forming limestone in middle2 marine4 ,flathead #age-bjj ,sandstone1 ,north and west ,sandstone reddish-brown1 flanks of ,teton very hard1 ,range and ,gros brittle2 partly ,ventre ,mountains4 marine4 ,the regularity and parallel relations of the layers in well-exposed sections such as the one in ,alaska ,basin suggest that all these rocks were deposited in a single uninterrupted sequence4 ,however1 the fossils and regional distribution of the rock units show that this is not really the case4 ,the incomplete nature of this record becomes apparent if we plot the ages of the various formations on the absolute geologic time scale 7fig4 #cd74 ,the length of time from the beginning of the ,cambrian ,period to the end of the ,mississippian ,period is about #bhe million years4 ,the strata in ,alaska ,basin are a record of approximately #abj million years4 ,more than half of the pages in the geologic story are missing even though1 compared with most other areas1 the book as a whole is remarkably complete6 ,during these unrecorded intervals of time either no sediments were deposited in the area of the ,teton ,range or1 if deposited1 they were removed by erosion4 ,illustration3 ,figure #cb4 ,paleozoic marine sedimentary rocks near south boundary of ,grand ,teton ,national ,park4 ,view is south from top of ,teton ,village tram4 ,national ,park ,service photo by ,w4 ,e4 ,dilley and ,r4 ,a4 ,mebane4 ,madison ,limestone ,darby ,formation ,bighorn ,dolomite ,gallatin ,limestone ,advance and retreat of ,cambrian seas3 an example ,the first invasion and retreat of the ,paleozoic sea are sketched on figure #ce4 ,early in ,cambrian time a shallow seaway1 called the ,cordilleran trough1 extended from southern ,california northeastward across ,nevada into ,utah and ,idaho 7fig4 #ce;,a74 ,the vast gently rolling plain on ,precambrian rocks to the east was drained by sluggish westward-flowing rivers that carried sand and mud into the sea4 ,slow subsidence of the land caused the sea to spread gradually eastward4 ,sand accumulated along the beaches just as it does today4 ,as the sea moved still farther east1 mud was deposited on the now-submerged beach sand4 ,in the ,teton area1 the oldest sand deposit is called the ,flathead ,sandstone 7fig4 #cf74 ,the mud laid down on top of the ,flathead ,sandstone as the shoreline advanced eastward across the ,teton area is now called the ,wolsey ,shale ,member of the ,gros ,ventre ,formation4 ,some shale shows patterns of cracks that formed when the accumulating mud was briefly exposed to the air along tidal flats4 ,small phosphatic-shelled animals called brachiopods inhabited these lonely tidal flats 7fig4 #cg;,a and #cg;,b7 but as far as is known1 nothing lived on land4 ,many shale beds are marked with faint trails and borings of wormlike creatures1 and a few contain the remains of tiny very intricately developed creatures with head1 eyes1 segmented body1 and tail4 ,these are known as trilobites 7fig4 #cg;,c and #cg;,d74 ,descendants of these lived in various seas that crossed the site of the dormant ,teton ,range for the next #bej million years4 ,illustration3 ,figure #cc4 ,view southwest across ,alaska ,basin1 showing tilted layers of ,paleozoic sedimentary rocks on the west flank of the ,teton ,range4 ,national ,park ,service photo4 ,mount ,meek ,madison ,limestone ,bighorn ,dolomite ,death ,canyon ,limestone ,member ,flathead ,sandstone ,precambrian ,rock ,as the shoreline moved eastward1 the ,death ,canyon ,limestone ,member of the ,gros ,ventre ,formation 7fig4 #cc7 was deposited in clear water farther from shore4 ,following this the sea retreated to the west for a short time4 ,in the shallow muddy water resulting from this retreat the ,park ,shale ,member of the ,gros ,ventre ,formation was deposited4 ,in places underwater 8meadows0 of algae flourished on the sea bottom and built extensive reefs 7fig4 #ch;,a74 ,from time to time shoal areas were hit by violent storm waves that tore loose platy fragments of recently solidified limestone and swept them into nearby channels where they were buried and cemented into thin beds of jumbled fragments 7fig4 #ch;,b7 called 8edgewise0 conglomerate4 ,these are widespread in the shale and in overlying and underlying limestones4 ,illustration3 ,table #c4 ,formations exposed in ,alaska ,basin4 ,,age 7,numbers ,,formation 7,thickness7 ,,rocks ,,and ,,fossils show age in millions of years7 7#caj7 ,,mississippian ,,madison ,,limestone ,uniform thin beds of 7,total about #a1ajj blue-gray limestone and feet1 but only lower sparse very thin layers of #cjj feet preserved in shale4 ,brachiopods1 corals1 this section7 and other fossils abundant4 7#cde7 ,,late ,,and ,,darby ,,formation 7,about ,thin beds of gray and buff ,,middle ,,devonian #cej feet7 dolomite interbedded with layers of gray1 yellow1 and black shale4 ,a few fossil brachiopods1 corals1 and bryozoans4 7#cij7 7#dbe7 ,,late ,,and ,,bighorn ,,dolomite 7,about ,thick to very thin beds of ,,middle #dej feet2 ,leigh blue-gray or brown dolomite1 ,,ordovician ,dolomite ,member about white on weathered surfaces4 #dj feet thick at top7 ,a few broken fossil brachiopods1 bryozoans1 and horn corals4 ,thin beds of white fine-grained dolomite at top are the ,leigh ,member4 7#ddj7 7#ejj7 ,,late ,,cambrian ,,gallatin ,,limestone 7#ahj ,blue-gray limestone mottled feet7 with irregular rusty or yellow patches4 ,trilobites and brachiopods4 7#ecj7 ,,middle ,,cambrian ,,gros ,,ventre ,,formation ,,park ,,shale ,,member ,gray-green shale containing 7#bbj feet7 beds of platy limestone conglomerate4 ,trilobites1 brachiopods1 and fossil algal heads4 ,,death ,,canyon ,two thick beds of ,,limestone ,,member dark-blue-gray limestone 7#bhe feet7 separated by #ae to #bj feet of shale that locally contains abundant fossil brachiopods and trilobites4 ,,wolsey ,,shale ,,member ,soft greenish-gray shale 7#ajj feet7 containing beds of purple and green sandstone near base4 ,a few fossil brachiopods4 ,,flathead ,,limestone 7#age ,brown1 maroon1 and white feet7 sandstone1 locally containing many rounded pebbles of quartz and feldspar4 ,some beds of green shale at top4 7#egj7 ,,precambrian ,granite1 gneiss1 and pegmatite4 ,illustration3 ,figure #cd4 ,absolute ages of the formations in ,alaska ,basin4 ,shaded parts of the scale show intervals for which there is no record4 ,,stratigraphic ,,scale ,,absolute ,,enlarged ,,piece ,,of ,,time 7,years ,,yardstick ,,shown ,,on ago7 ,,figure #ai #b ,,palezoic ,,pennsylvanian 8 #cjj million ,,mississippian ,,madison ,,devonian ,,darby #c #djj million ,,silurian ,,ordovician ,,bighorn #ejj million #d ,,cambrian ,,gallatin ,,gros ,,ventre ,,flathead #fjj million ,,precambrian #e ,figure #ce4 ,the first invasions of the ,paleozoic sea4 ,illustration3 ,a4 ,in ,early ,cambrian time an arm of the ,pacific ,ocean occupied a deep trough in ,idaho1 ,nevada1 and part of ,utah4 ,the land to the east was a broad gently rolling plain of ,precambrian rocks drained by sluggish westward-flowing streams4 ,the site of the ,teton ,range was part of this plain4 ,slow subsidence of the land caused the sea to move eastward during ,middle ,cambrian time flooding the ,precambrian plain4 ,illustration3 ,b4 ,by ,late ,cambrian time the sea had drowned all of ,montana and most of ,wyoming4 ,the ,flathead ,sandstone and ,gros ,ventre ,formation were deposited as the sea advanced4 ,the ,gallatin ,limestone was being deposited when the shoreline was in about the position shown in this drawing4 ,illustration3 ,c4 ,in ,early ,ordovician time uplift of the land caused the sea to retreat back into the trough1 exposing the ,cambrian deposits to erosion4 ,cambrian deposits were partly stripped off of some areas4 ,the ,bighorn ,dolomite was deposited during the next advance of the sea in ,middle and ,late ,ordovician time4 ,illustration3 ,figure #cf4 ,conglomeratic basal bed of ,flathead ,sandstone and underlying ,precambrian granite gneiss2 contact is indicated by a dark horizontal line about #a foot below hammer4 ,this contact is all that is left to mark a #b-;billion year gap in the rock record of earth history4 ,the locality is on the crest of the ,teton ,range #a mile northwest of ,lake ,solitude4 ,once again the shoreline crept eastward1 the seas cleared1 and the ,gallatin ,limestone was deposited4 ,the ,gallatin1 like the ,death ,canyon ,limestone ,member1 was laid down for the most part in quiet1 clear water1 probably at depths of #ajj to #bjj feet4 ,however1 a few beds of 8edgewise0 conglomerate indicate the occurrence of sporadic storms4 ,at this time1 the sea covered all of ,idaho and ,montana and most of ,wyoming 7fig4 #ce;,b7 and extended eastward across the ,dakotas to connect with shallow seas that covered the eastern ,united ,states4 ,soon after this maximum stage was reached slow uplift caused the sea to retreat gradually westward4 ,the site of the ,teton ,range emerged above the waves1 where1 as far as is now known1 it may have been exposed to erosion for nearly #gj million years 7fig4 #ce;,c74 ,the above historical summary of geologic events in ,cambrian time is recorded in the ,cambrian formations4 ,this is an example of the reconstructions1 based on the sedimentary rock record1 that have been made of the ,paleozoic systems in this area4 ,figure #cg4 ,cambrian fossils in ,grand ,teton ,national ,park4 ,a-,b4 ,phosphatic-shelled brachiopods1 the oldest fossils found in the park4 ,actual width of specimens is about inch4 ,c-,d4 ,trilobites4 ,width of ,c is inch1 ,d is inch4 ,national ,park ,service photos by ,w4 ,e4 ,dilley and ,r4 ,a4 ,mebane4 ,illustration3 ,a4 ,illustration3 ,b4 ,illustration3 ,c4 ,illustration3 ,d4 ,younger ,paleozoic formations ,formations of the remaining ,paleozoic systems are likewise of interest because of the ways in which they differ from those already described4 ,figure #ch4 ,distinctive features of ,cambrian rocks4 ,illustration3 ,a4 ,algal heads in the ,park ,shale ,member of the ,gros ,ventre ,formation4 ,these calcareous mounds were built by algae growing in a shallow sea in ,cambrian time4 ,they are now exposed on the divide between ,north and ,south ,leigh ,creeks1 nearly #b miles above sea level6 ,illustration3 ,b4 ,bed of 8edgewise0 conglomerate in the ,gallatin ,limestone4 ,angular plates of solidified lime-ooze were torn from the sea bottom by storm waves1 swept into depressions1 and then buried in lime mud4 ,these fragments1 seen in cross section1 make the strange design on the rock4 ,thin limestone beds below are undisturbed4 ,national ,park ,service photo by ,w4 ,e4 ,dilley4 ,the ,bighorn ,dolomite of ,ordovician age forms ragged hard massive light-gray to white cliffs #ajj to #bjj feet high 7figs4 #cb and #cc74 ,dolomite is a calcium-magnesium carbonate1 but the original sediment probably was a calcium carbonate mud that was altered by magnesium-rich sea water shortly after deposition4 ,corals and other marine animals were abundant in the clear warm seas at this time4 ,dolomite in the ,darby ,formation of ,devonian age differs greatly from the ,bighorn ,dolomite2 that in the ,darby is dark-brown to almost black1 has an oily smell1 and contains layers of black1 pink1 and yellow mudstone and thin sandstone4 ,the sea bottom during deposition of these rocks was foul and frequently the water was turbid4 ,abundant fossil fragments indicate fishes were common for the first time4 ,exposures of the ,darby ,formation are recognizable by their distinctive dull-yellow thin-layered slopes between the prominent gray massive cliffs of formations below and above4 ,the ,madison ,limestone of ,mississippian age is #a1jjj feet thick and is exposed in spectacular vertical cliffs along canyons in the north1 west1 and south parts of the ,tetons4 ,it is noted for the abundant remains of beautifully preserved marine organisms 7fig4 #ci74 ,the fossils and the relatively pure blue-gray limestone in which they are embedded indicate deposition in warm tranquil seas4 ,the beautiful ,ice ,cave on the west side of the ,tetons and all other major caves in the region were dissolved out of this rock by underground water4 ,the ,pennsylvanian ,system is represented by the ,amsden ,formation and the ,tensleep ,sandstone4 ,cliffs of the ,tensleep ,sandstone can be seen along the ,gros ,ventre ,river at the east edge of the park4 ,the ,amsden1 below the ,tensleep1 consists of red and green shale1 sandstone1 and thin limestone4 ,the shale is especially weak and slippery when exposed to weathering and saturated with water4 ,these are the strata that make up the glide plane of the ,lower ,gros ,ventre ,slide 7fig4 #e7 east of the park4 ,the ,phosphoria ,formation and its equivalents of ,permian age are unlike any other ,paleozoic rocks because of their extraordinary content of uncommon elements4 ,the formation consists of sandy dolomite1 widespread black phosphate beds and black shale that is unusually rich not only in phosphorus1 but also in vanadium1 uranium1 chromium1 zinc1 selenium1 molybdenum1 cobalt1 and silver4 ,the formation is mined extensively in nearby parts of ,idaho and in ,wyoming for phosphatic fertilizer1 for the chemical element phosphorus1 and for some of the metals that can be derived from the rocks as byproducts4 ,these elements and compounds are not everywhere concentrated enough to be of economic interest1 but their dollar value is1 in a regional sense1 comparable to that of some of the world's greatest mineral deposits4 ,figure #ci4 ,a glimpse of the sea floor during deposition of the ,madison ,limestone #ccj million years ago1 showing the remains of brachiopods1 corals1 and other forms of life that inhabited the shallow warm water4 ,illustration3 ,a4 ,slab in which fossils are somewhat broken and scattered4 ,scale slightly reduced4 ,national ,park ,service photo by ,w4 ,e4 ,dilley and ,r4 ,a4 ,mebane4 ,illustration3 ,b4 ,slab in which fossils are remarkably complete4 ,silver dollar gives scale4 ,specimen is in ,university of ,wyoming ,geological ,museum4 ,,the ,,mesozoic--,,era ,,of ,,transition ,the ,mesozoic ,era in the ,teton region was a time of alternating marine1 transitional1 and continental environments4 ,moreover1 the highly diversified forms of life1 ranging from marine mollusks to tremendous1 land-living dinosaurs1 confirm and reinforce the story of the rocks4 ,living things1 too1 were in transition1 for as environment changed1 many forms moved from the sea to land in order to survive4 ,it was the time when some of the most spectacularly colored rock strata of the region were deposited4 ,colorful first ,mesozoic strata ,bright-red soft ,triassic rocks more than #a1jjj feet thick1 known as the ,chugwater ,formation1 comprise most of the basal part of the ,mesozoic sequence 7table #d74 ,they form colorful hills east and south of the park4 ,the red color is caused by a minor amount of iron oxide4 ,mud cracks and the presence of fossil reptiles and amphibians indicate deposition in a tidal flat environment1 with the sea lying several miles southwest of ,jackson ,hole4 ,a few beds of white gypsum 7calcium sulfate7 are present2 they were apparently deposited during evaporation of shallow bodies of salt water cut off from the open sea4 ,as the ,triassic ,period gave way to the ,jurassic1 salmon-red windblown sand 7,nugget ,sandstone7 spread across the older red beds and in turn was buried by thin red shale and thick gypsum deposits of the ,gypsum ,spring ,formation4 ,then down from ,alaska and spreading across most of ,wyoming came the ,sundance ,sea1 a warm1 muddy1 shallow body of water that teemed with marine mollusks4 ,in it more than #ejj feet of highly fossiliferous soft gray shale and thin limestones and sandstones were deposited4 ,the sea withdrew and the ,morrison and ,cloverly ,formations 7,jurassic and ,lower ,cretaceous7 were deposited on low-lying tropical humid flood plains4 ,these rocks are colorful1 consisting of red1 pink1 purple1 and green badland-forming claystones and mudstones1 and yellow to buff sandstones4 ,vegetation was abundant and large and small dinosaurs roamed the countryside or inhabited the swamps4 ,illustration3 ,table #d4--,mesozoic sedimentary rocks exposed in the ,teton region4 ,age ,formation ,thickness ,description ,where exposed 7feet7 ,,cretaceous ,harebell #j-e1jjj ,sandstone1 olive ,eastern and ,formation drab1 silty1 drab northeastern parts siltstone1 and of ,jackson ,hole4 dark-gray shale2 thick beds of quartzite pebble conglomerate in upper part4 ,meeteetse #j-gjj ,sandstone1 gray to ,spread ,creek area4 ,formation chalky white1 blue-green to gray siltstone1 thin coal1 and green to yellow bentonite4 ,mesaverde #j-a1jjj ,sandstone1 white1 ,eastern ,jackson ,formation massive1 soft1 thin ,hole4 gray shale1 sparse coal4 ,unnamed #c1ejj ,sandstone and ,eastern ,jackson sequence of shale1 gray to ,hole and eastern lenticular brown2 abundant margin of the park4 sandstone1 coal in lower #b1jjj shale1 and feet4 coal4 ,bacon ,ridge #ijj-a1bjj ,sandstone1 light ,eastern ,jackson ,sandstone gray1 massive1 ,hole and eastern marine1 gray shale1 margin of the park4 many coal beds4 ,cody ,shale #a1cjj-b1bjj ,shale1 gray1 soft2 ,eastern and thin green northern parts of sandstone1 some ,jackson ,hole4 bentonite2 marine4 ,frontier #a1jjj ,sandstone1 gray1 ,eastern and ,formation and black to gray northern parts and shale1 marine2 many south-western persistent white margin of ,jackson bentonite beds in ,hole4 lower part4 ,mowry ,shale #gjj ,shale1 ,gros ,ventre ,river silvery-gray1 hard1 ,valley1 northern siliceous1 with margin of the park1 many fish scales2 and southern part thin bentonite of ,jackson ,hole4 beds2 marine4 ,thermopolis #aej-bjj ,shale1 black1 soft1 ,gros ,ventre ,river ,shale fissile1 with ,valley1 northern persistent margin of the park1 sandstone at top2 and southern part marine4 of ,jackson ,hole4 ,cloverly and #fej ,sandstone1 light ,north end of ,teton ,morrison787 gray1 sparkly1 ,range and ,gros ,formations rusty near top1 ,ventre ,river ,valley4 underlain by variegated soft claystone2 basal part is silty dully-variegated sandstone and claystone4 ,,jurassic ,sundance #ejj-gjj ,sandstone1 green1 ,north end of ,teton ,formation underlain by soft ,range1 ,blacktail gray shale and thin ,butte1 ,gros ,ventre highly ,river ,valley4 fossiliferous limestones2 marine4 ,gypsum ,spring #ge-ajj ,gypsum1 white1 ,north end of ,teton ,formation interbedded with ,range1 ,blacktail red shale and gray ,butte1 ,gros ,ventre dolomite2 partly ,river ,valley4 marine4 ,nugget #j-cej ,sandstone1 ,north flank of ,gros ,sandstone salmon-red1 hard4 ,ventre ,mountains1 southern ,jackson ,hole4 ,,triassic ,chugwater #a1jjj-a1ejj ,siltstone and ,north flank of ,gros ,formation shale1 red1 ,ventre ,mountains1 thin-bedded2 one north end of ,teton thin marine ,range1 southernmost limestone in upper ,jackson ,hole4 third4 ,dinwoody #bjj-djj ,siltstone1 brown1 ,north flank of ,gros ,formation hard1 thin-bedded2 ,ventre ,mountains1 marine4 north end of ,teton ,range1 southernmost ,jackson ,hole4 ,drab ,cretaceous strata ,the youngest division of the ,mesozoic ,era is the ,cretaceous ,period4 ,near the beginning of this period1 brightly colored rocks continued to be deposited4 ,then1 the ,teton region1 as well as most of ,wyoming1 was partly1 and at times completely1 submerged by shallow muddy seas4 ,as a result1 the brightly variegated strata were covered by #aj1jjj feet of generally drab-colored sand1 silt1 and clay containing some coal beds1 volcanic ash layers1 and minor amounts of gravel4 ,the ,cretaceous sea finally retreated eastward from the ,teton region about #he million years ago1 following the deposition of the ,bacon ,ridge ,sandstone 7fig4 #dj74 ,as it withdrew1 extensive coal swamps developed along the sea coast4 ,the record of these swamps is preserved in coal beds #e to #aj feet thick in the ,upper ,cretaceous deposits4 ,the coal beds are now visible in abandoned mines along the east margin of the park4 ,coal is formed from compacted plant debris2 about #e feet of this material is needed to form #a inch of coal4 ,thus1 lush vegetation must have flourished for long periods of time1 probably in a hot wet climate similar to that now prevailing in the ,florida ,everglades4 ,sporadically throughout ,cretaceous time fine-grained ash was blown out of volcanoes to the west and northwest and deposited in quiet shallow water4 ,subsequently the ash was altered to a type of clay called bentonite that is used in the foundry industry and in oil well drilling muds4 ,in ,jackson ,hole1 the elk and deer lick bentonite exposures to get a bitter salt and1 where the beds are water-saturated1 enjoy 8stomping0 on them4 ,bentonite swells when wet and causes many landslides along access roads into ,jackson ,hole 7fig4 #ag74 ,the ,cretaceous rocks in the ,teton region are part of an enormous east-thinning wedge that here is nearly #b miles thick4 ,most of the debris was derived from slowly rising mountains to the west4 ,cretaceous sedimentary rocks are much more than of just scientific interest2 they contain mineral deposits important to the economy of ,wyoming and of the nation4 ,wyoming leads the ,states in production of bentonite1 all of it from ,cretaceous rocks4 ,these strata have yielded far more oil and gas than any other geologic system in the ,state and the production is geographically widespread4 ,they also contain enormous coal reserves1 some in beds between #ej and #ajj feet thick4 ,the energy resources alone of the ,cretaceous ,system in ,wyoming make it invaluable to our industrialized society4 ,illustration3 ,figure #dj4 ,the yardstick and the sea4 ,the shaded part of the yardstick shows the #ejj-million-year interval during which ,paleozoic and ,mesozoic seas swept intermittently across the future site of the ,tetons4 ,when they finally withdrew about #he million years ago1 a little more than #e_/h of an inch of the yardstick remained to be accounted for4 ,,absolute ,,time 7,millions of years ago7 ,,inches submerged #he-ehe -#d ,,cenozoic #j-hj #j- ,,mesozoic #hj-ahj - ,,paleozoic #ahj-egj -#d ,,precambrian #egj- #d- ,as the end of the ,cretaceous ,period approached1 slightly more than #hj million years ago1 the flat monotonous landscape 7fig4 #da7 which had prevailed during most of ,late ,cretaceous time gave little hint that the stage was set for one of the most exciting and important chapters in the geologic history of ,north ,america4 ,birth of the ,rocky ,mountains ,the episode of mountain building that resulted in formation of the ancestral ,rocky ,mountains has long been known as the ,laramide ,revolution4 ,west and southwest of ,wyoming1 mountains had already formed1 the older ones as far away as ,nevada and as far back in time as ,jurassic1 the younger ones rising progressively farther east1 like giant waves moving toward a coast4 ,the first crustal movement in the ,teton area began in latest ,cretaceous time when a broad low northwest-trending arch developed in the approximate area of the present ,teton ,range and ,gros ,ventre ,mountains4 ,however1 this uplift bore no resemblance to the ,tetons as we know them today for the present range formed #gj million years later4 ,illustration3 ,figure #da4 ,grand ,teton ,national ,park region slightly more than #hj million years ago1 just before onset of ,laramide ,revolution4 ,the last ,cretaceous sea still lingered in central ,wyoming4 ,one bit of evidence 7there are others7 of the first ,laramide mountain building west of the ,tetons is a tremendous deposit of quartzite boulder debris 7several hundred cubic miles in volume7 derived from the ,targhee uplift 7fig4 #db74 ,nowhere is the uplift now exposed1 but from the size1 composition1 and distribution of rock fragments that came from it1 we know that it was north and west of the northern end of the present-day ,teton ,range4 ,powerful streams carried boulders1 sand1 and clay eastward and southeastward across the future site of ,jackson ,hole and deposited them in the ,harebell ,formation 7table #d74 ,mingled with this sediment were tiny flakes of gold and a small amount of mercury4 ,fine-grained debris was carried still farther east and southeast into two enormous depositional troughs in central and southern ,wyoming4 ,most of the large rock fragments were derived from ,precambrian and possibly lower ,paleozoic quartzites4 ,this means that at least #ae1jjj feet of overlying ,paleozoic and ,mesozoic strata must first have been stripped away from the ,targhee uplift before the quartzites were exposed to erosion4 ,illustration3 ,figure #db4 ,teton region at the end of ,cretaceous time about #fe million years ago4 ,the ancestral ,teton-,gros ,ventre uplift had risen and prominent southeastward drainage from the ,targhee uplift was well established4 ,see figure #da for ,state lines and location map4 ,remains of four-legged horned ceratopsian dinosaurs1 possibly ,triceratops 7fig4 #dc71 reflecting the last population explosion of these reptiles1 have been found in pebbly sandstone of the ,harebell ,formation in highway cuts on the ,togwotee ,pass road #h miles east of the park4 ,illustration3 ,figure #dc4 ,triceratops1 a horned dinosaur of the type that inhabited ,jackson ,hole about #fe million years ago4 ,sketch by ,s4 ,h4 ,knight4 ,near the end of ,cretaceous time1 broad gentle uplifts also began to stir at the sites of future mountain ranges in many parts of ,wyoming4 ,the ancestral ,teton-,gros ,ventre arch continued to grow4 ,associated with and parallel to it was a series of sharp steepsided elongated northwest-trending upfolds 7anticlines74 ,one of these can be seen where it crosses the highway at the ,lava ,creek ,campground near the eastern margin of ,grand ,teton ,national ,park4 ,during these episodes of mountain building1 erosion1 and deposition1 the dinosaurs became extinct all over the world4 ,the 8,age of ,mammals0 was about to begin4 ,,tertiary--,,time ,,of ,,mammals1 ,,mountains1 ,,lakes1 ,,and ,,volcanoes ,illustration3 ,figure #dd4 ,the last inch of the yardstick1 enlarged to show subdivisions of the ,cenozoic ,era4 ,,stratigraphic ,,scale ,,the ,,last ,,inch ,,of ,,absolute ,,time 7million ,,the ,,yardstick years ago7 ,,cenozoic ,,quaternary ,recent and #j #j ,pleistocene ,,tertiary ,pliocene #j #j ,miocene #ab ,oligocene #be ,eocene #dj ,paleocene _/ #ee ,,mesozoic ,,cretaceous #fe ,the ,cenozoic 7table #a71 last and shortest of the geologic eras1 comprises the ,tertiary and ,quaternary ,periods4 ,it began about #fe million years ago and is represented by only the final one-half inch of our imaginary yardstick of time 7fig4 #ai74 ,nevertheless1 it is the era during which the ,tetons rose in their present form and the landscape was sculptured into the panorama of beauty that we now see4 ,in order to show the many ,tertiary and ,quaternary events in the ,teton region1 it is necessary to enlarge greatly the last part of the yardstick 7fig4 #dd74 ,there are two reasons for the extraordinarily clear and complete record4 ,first1 the ,teton region was a relatively active part of the earth's crust1 characterized by many downdropped blocks4 ,the number of events is great and their records are preserved in sediments trapped in the subsiding basins4 ,second1 the geologically recent past is much easier to see than the far dimmer1 distant past2 the rocks that record later events are fresher1 less altered1 more complete1 and more easily interpreted than are those that tell us of older events4 ,illustration3 ,table #e4--;,cenozoic sedimentary rocks and unconsolidated deposits in the ,teton region4 ,age ,formation ,thickness ,description ,where exposed 7feet7 ,,quaternary ,recent ,modern #j-bjj ,sand1 gravel1 and ,floor of ,jackson stream1 silt along present ,hole and in canyons landslide1 streams2 jumbled and on glacial and broken rock in mountainsides talus deposits landslides and on throughout the talus slopes2 region4 debris around existing glaciers4 ,pleistocene ,glacial #j-bjj ,gravel1 sand1 silt1 ,floor of ,jackson deposits and and glacial debris4 ,hole4 loess ,unnamed upper #j-ejj ,shale1 brown-gray1 ,gros ,ventre ,river lake sequence sandstone1 and ,valley4 conglomerate4 ,unnamed lower #j-bjj ,shale1 siltstone1 ,national ,elk ,refuge4 lake sequence and sandstone1 gray1 green1 and red4 8 ,pleistocene or ,pliocene ,bivouac #j-a1jjj ,conglomerate1 with ,signal ,mountain and ,formation purplish-gray ,west ,gros ,ventre welded tuff in ,butte4 upper part4 ,,tertiary ,pliocene ,teewinot #j-f1jjj ,limestone1 tuff1 ,national ,elk ,formation and claystone1 ,refuge1 ,blacktail white1 soft4 ,butte1 and eastern margin of ,antelope ,flat4 ,camp ,davis #j-e1ejj ,conglomerate1 red ,southernmost tip of ,formation and gray1 with ,jackson ,hole4 white tuff1 diatomite1 and red and white claystone4 ,miocene ,colter #j-g1jjj ,volcanic ,pilgrim and ,ditch ,formation conglomerate1 tuff1 ,creeks1 and north and sandstone1 end of ,teton ,range4 white to green-brown1 with locally-derived basalt and andesite rock fragments4 ,oligocene ,wiggins #j-c1jjj ,volcanic ,eastern margin of ,formation conglomerate1 gray ,jackson ,hole4 to brown1 with white tuff layers4 ,eocene ,unnamed upper #j-a1jjj ,tuff1 conglomerate1 ,eastern margin of and middle sandstone1 and ,jackson ,hole4 ,eocene claystone1 green1 sequence underlain by variegated claystone and quartzite pebble conglomerate4 ,wind ,river #b1jjj-c1jjj ,claystone and ,eastern margin of and ,indian sandstone1 ,jackson ,hole4 ,meadows variegated1 and ,formations locally-derived conglomerate2 persistent coal and gray shale zone in middle4 ,paleocene ,unnamed #a1jjj-b1jjj ,sandstone and ,eastern margin of greenish-gray claystone1 ,jackson ,hole4 and brown greenish-gray and sandstone and brown1 claystone intertonguing at sequence base with quartzite pebble conglomerate4 ,pinyon #ejj-e1jjj ,conglomerate1 ,eastern part of ,conglomerate brown1 chiefly of ,jackson ,hole1 ,mt4 rounded quartzite2 ,leidy and ,pinyon coal and claystone ,peak ,highlands1 and locally at base4 north end of ,teton ,range4 ,illustration3 ,figure #de4 ,pinyon ,conglomerate of ,paleocene age1 along the northwest margin of the ,teton ,range4 ,during the early part of the ,tertiary ,period1 mountain building and basin subsidence were the dominant types of crustal movement4 ,seas retreated southward down the ,mississippi ,valley and never again invaded the ,teton area4 ,environments on the recently uplifted land were diverse and favorable for the development of new forms of plants and animals4 ,rise and burial of mountains ,the enormous section of ,tertiary sedimentary rocks in the ,jackson ,hole area 7table #e7 is one of the most impressive in ,north ,america4 ,if the maximum thicknesses of all formations were added1 they would total more than #f miles1 but nowhere did this amount of rock accumulate in a single unbroken sequence4 ,no other region in the ,united ,states contains a thicker or more complete nonmarine ,tertiary record2 many areas have little or none4 ,the accumulation in ,jackson ,hole reflects active uplifts of nearby mountains that supplied abundant rock debris1 concurrent sinking of nearby basins in which the sediments could be preserved1 and proximity to the great ,yellowstone-,absaroka volcanic area1 one of the most active continental volcanic fields in the ,united ,states4 ,the volume and composition of the ,tertiary strata are1 therefore1 clear evidence of crustal and subcrustal instability4 ,illustration3 ,figure #df4 ,teton region near end of deposition of ,paleocene rocks1 slightly less than #fj million years ago4 ,the ancestral ,teton-,gros ,ventre uplift formed a partial barrier between the ,jackson ,hole and ,green ,river depositional basins2 major drainages from the ,targhee uplift spread an enormous sheet of gravel for #ajj miles to the east4 ,see figure #da for ,state lines and location map4 ,the many thick layers of conglomerate are evidence of rapid erosion of nearby highlands4 ,the ,pinyon ,conglomerate 7fig4 #de71 for example1 contains zones as much as #b1ejj feet thick of remarkably well-rounded pebbles1 cobbles1 and boulders1 chiefly of quartzite identical with that in the underlying ,harebell ,formation and derived from the same source1 the ,targhee uplift4 ,like the ,harebell the matrix contains small amounts of gold and mercury4 ,rock fragments increase in size northwestward toward the source area 7fig4 #df7 and most show percussion scars1 evidence of ferocious pounding that occurred during transport by powerful1 swift rivers and steep gradients4 ,illustration3 ,figure #dg4 ,teton region at climax of ,laramide ,revolution1 between #ej and #ee million years ago4 ,see figure #da for ,state lines and location map4 ,conglomerates such as the ,pinyon are not the only clue to the time of mountain building4 ,another type of evidence--faults--is demonstrated in figure #af4 ,the youngest rocks cut by a fault are always older than the fault4 ,many faults and the rocks on each side are covered by still younger unbroken sediments4 ,these must1 therefore1 have been deposited after fault movement ceased4 ,by dating both the faulted and the overlying unbroken sediments1 the time of fault movement can be bracketed4 ,observations of this type in western ,wyoming indicate that the ,laramide ,revolution reached a climax during earliest ,eocene time1 #ej to #ee million years ago4 ,mountain-producing upwarps formed during this episode were commonly bounded on one side by either reverse or thrust faults 7fig4 #af;,b and #af;,c7 and intervening blocks were downfolded into large1 very deep basins4 ,the amount of movement of the mountain blocks over the basins ranged from tens of miles in the ,snake ,river1 ,salt ,river1 ,wyoming1 and ,hoback ,ranges directly south of the ,tetons to less than #e miles on the east margin of ,jackson ,hole 7the west flank of the ,washakie ,range shown in figure #a74 ,the ancestral ,teton-,gros ,ventre uplift continued to rise but remained one of the less conspicuous mountain ranges in the region 7fig4 #dg74 ,the ,buck ,mountain fault1 the great reverse fault which lies just west of the highest ,teton peaks 7see geologic map and cross section71 was formed either at this time or during a later episode of movement that also involved the southwest margin of the ,gros ,ventre ,mountains4 ,the ,buck ,mountain fault is of special importance because it raised a segment of ,precambrian rocks several thousand feet4 ,later1 when the entire range as we now know it was uplifted by movement along the ,teton fault1 the hard basement rocks in this previously upfaulted segment continued to stand much higher than those in adjacent parts of the range4 ,all of the major peaks in the ,tetons are carved from this doubly uplifted block4 ,the brightly colored sandstone1 mudstone1 and claystone in the ,indian ,meadows and ,wind ,river ,formations 7lower ,eocene7 in the eastern part of ,jackson ,hole were derived from variegated ,triassic1 ,jurassic1 and ,lower ,cretaceous rocks exposed on the adjacent mountain flanks4 ,fossils in these ,eocene ,formations show that it took less than #aj million years for the uplifts to be deeply eroded and partially buried in their own debris4 ,the ,laramide ,revolution in the area of ,grand ,teton ,national ,park ended during ,eocene time between #de and #ej million years ago1 and as the mountains and basins became stabilized a new element was added4 ,volcanoes broke through to the surface in many parts of the ,yellowstone-,absaroka area and the constantly increasing volume of their eruptive debris was a major factor in the speed of filling of basins and burial of mountains throughout ,wyoming4 ,this entire process only took about #bj million years1 and along the east margin of ,jackson ,hole it was largely completed during ,oligocene time 7fig4 #dh74 ,however1 east and northeast of ,jackson ,lake a ,miocene downwarp subsequently formed and in it accumulated at least #g1jjj feet of locally derived sediments of volcanic origin4 ,illustration3 ,figure #dh4 ,teton region near the close of ,oligocene deposition1 between #be and #cj million years ago1 showing areas of major volcanoes and lava flows4 ,see figure #da for ,state lines and location map4 ,the ,first ,big ,lake ,teewinot ,lake 7fig4 #di71 the first big freshwater lake in ,jackson ,hole1 was formed during ,pliocene time1 about #aj million years ago1 and in it the ,teewinot ,formation was deposited4 ,these lake strata consist of more than #e1jjj feet of white limestone1 thin-bedded claystone1 and tuff 7solidified ash made up of tiny fragments of volcanic rock and splinters of volcanic glass74 ,the claystones contain fossil snails1 clams1 beaver bones and teeth1 aquatic mice1 suckers1 and other fossils that indicate deposition in a shallow freshwater lake environment4 ,these beds underlie ,jackson ,lake ,lodge1 the ,national ,elk ,refuge1 part of ,blacktail ,butte1 and are conspicuously exposed in white outcrops that look like snowbanks on the upper slopes along the east margin of the park across the valley from the ,grand ,teton4 ,illustration3 ,figure #di4 ,teton region near close of middle ,pliocene time1 about #e million years ago1 showing areas of major volcanoes and lava flows4 ,see figure #da for ,state lines and location map4 ,teewinot ,lake was formed on a down-faulted block and was dammed behind 7north of7 a fault that trends east across the floor of ,jackson ,hole at the south boundary of the park4 ,lakes are among the most short-lived of earth features because the forces of nature soon conspire to fill them up or empty them4 ,this lake existed for perhaps #e million years during middle ,pliocene time2 it was shallow1 and remained so despite the pouring in of a mile-thick layer of sediment4 ,this indicates that downdropping of the lake floor just about kept pace with deposition4 ,illustration3 ,figure #ej4 ,restoration of a middle ,eocene landscape showing some of the more abundant types of mammals4 ,mural painting by ,jay ,h4 ,matterness2 photo courtesy of the ,smithsonian ,institution4 ,uintatherium #f-;horned1 saber-toothed plant eater ,stylinodon gnawing-toothed mammal ,palaeosyops early titanothere ,helaletes primitive tapir ,sciuravus squirrel-like rodent ,smilodectes lemurlike monkey ,trogosus gnawing-toothed mammal ,hyrachyus fleet-footed rhinoceros ,ischyrotomus marmotlike rodent ,homacodon even-toed hoofed animal ,orohippus ancestral horse ,patriofelis large flesh eater ,mesonyx hyenalike mammal ,helohyus even-toed hoofed mammal ,metacheiromys armadillolike edentate ,machaeroides saber-toothed mammal ,hyopsodus clawed1 plant-eating mammal ,saniwa monitorlike lizard ,crocodilus crocodile ,echmatemys turtle ,other lakes formed in response to similar crustal movements in nearby places4 ,one such lake1 ,grand ,valley ,lake 7fig4 #di71 formed about #be miles southwest of ,teewinot ,lake2 both contained sediments with nearly the same thickness1 composition1 appearance1 age1 and fossils4 ,although these two lakes are on opposite sides of the ,snake ,river ,range1 the ancestral ,snake ,river apparently flowed through a canyon previously cut across the range and provided a direct connection between them4 ,development of mammals ,the ,cenozoic ,era is known as the 8,age of ,mammals40 ,small mammals had already existed1 though quite inconspicuously1 in ,wyoming for about #ij million years before ,paleocene time4 ,then about #fe million years ago their proliferation began as a result of the extinction of dinosaurs1 obliteration of seaways that were barriers to distribution1 and the development of new and varied types of environment4 ,these new environments included savannah plains1 low hills and high mountains1 freshwater lakes and swamps1 and extensive river systems4 ,the mammals increased in size and1 for the first time1 became abundant in numbers of both species and individuals4 ,the development and widespread distribution of grasses and other forage on which many of the animals depended were highly significant4 ,successful adaptation of herbivores 7vegetation-eating animals7 led1 in turn1 to increased varieties and numbers of predatory carnivores 7meat-eating animals74 ,during early ,eocene time1 coal swamps formed in eastern ,jackson ,hole and persisted for thousands of years1 as is shown by #fj feet of coal in a single bed at one locality4 ,continuing on into middle ,eocene time1 the climate was subtropical and humid1 and the terrain was near sea level4 ,tropical breadfruits1 figs1 and magnolias flourished along with a more temperate flora of redwood1 hickory1 maple1 and oak4 ,horses the size of a dog and many other small mammals were abundant4 ,primates1 thriving in an ideal forest habitat1 were numerous4 ,streams contained gar fish and crocodiles 7fig4 #ej74 ,illustration3 ,figure #ea4 ,a typical ,oligocene landscape showing some of the more abundant types of mammals4 ,mural painting by ,jay ,h4 ,matterness2 photo courtesy of ,smithsonian ,institution4 ,trigonias early rhinoceros ,perchoerus early peccary ,mesohippus #c-toed horse ,aepinacodon remote relative of hippopotamus ,archaeotherium giant piglike mammal ,protoceras bizarre horned ruminant ,hesperocyon ancestral dog ,hyracodon small fleet-footed rhinoceros ,pobrotherium ancestral camel ,hypisodus very small chevrotainlike ruminant ,ictops small insect-eating mammal ,brontotherium titanothere ,protapirus ancestral tapir ,glyptosaurus extinct lizard ,hoplophoneus saber-toothed cat ,subhyracodon early rhinoceros ,merycoidodon sheeplike grazing mammal ,hyaenodon archaic hyenalike mammal ,hypertragulus chevrotainlike ruminant ,early in the ,oligocene ,epoch1 between #cj and #ce million years ago1 the climate in ,jackson ,hole became cooler and drier1 and the subtropical plants gave way to the warm temperate flora of oak1 beech1 maple1 alder1 and ash4 ,the general land surface rose higher above sea level1 perhaps by accumulation of several thousand feet of ,oligocene volcanic rocks 7fig4 #eb7 rather than by continental uplift4 ,titanotheres 7large four-legged mammals with the general size and shape of a rhinoceros7 flourished in great numbers for a few million years and then abruptly vanished4 ,horses by now were about the size of a very small modern colt4 ,rabbits1 rodents1 carnivores1 tiny camels1 and other mammals were abundant in ,jackson ,hole1 and the fauna1 surprisingly1 was essentially the same as that #ejj miles to the east1 at a much lower elevation1 on the plains of ,nebraska and ,south ,dakota 7fig4 #ea74 ,the ,miocene ,epoch 7#ae to #be million years ago7 was the time of such intense volcanic activity in the ,teton region that animals must have found survival very difficult4 ,a few skeletons and fragmentary parts of camels about the size of a small horse and other piglike animals called oreodonts comprise our only record of mammals2 nothing is known of the plants4 ,farther east the climate fluctuated from subtropical to warm temperate1 gradually becoming cooler toward the end of the epoch4 ,fossils in the ,pliocene lake deposits 7#h to #aj million years old2 see description of ,teewinot ,formation7 include shallow-water types of snails1 clams1 diatoms1 and ostracodes1 as well as beavers1 mice1 suckers1 and frogs4 ,pollen in these beds show that adjacent upland areas supported fir1 spruce1 pine1 juniper1 sage1 and other trees and shrubs common to the area today4 ,therefore1 the climate must have been much cooler than in ,miocene time4 ,no large mammals of ,pliocene age have been found in ,jackson ,hole4 ,the record of life during ,quaternary time is discussed later4 ,illustration3 ,figure #eb4 ,layers of volcanic conglomerate separated by thin white tuff beds in ,wiggins ,formation4 ,these cliffs1 on the north side of ,togwotee ,pass1 are about #a1ajj feet high and represent a cross section of part of the enormous blanket of waterlaid debris that spread south and east from the ,yellowstone-,absaroka volcanic area4 ,these and younger deposits from the same general source filled the basins and almost completely buried the mountains in this part of ,wyoming4 ,volcanoes ,volcanoes are one of the most interesting parts of the geologic story of the ,teton region4 ,although ash from distant volcanoes had settled in northwestern ,wyoming at least as far back in time as ,jurassic1 the first nearby active volcanoes 7since the ,precambrian7 erupted in the ,yellowstone-,absaroka region during the early ,eocene1 about #ej million years ago4 ,from then on1 the volcanic area grew in size and the violence of eruptions and volume of debris increased until ,pliocene time4 ,this debris had a profound influence on the color and composition of the sediments and on the environment and types of plants and animals4 ,the color of the volcanic rocks and the sediments derived from them varies significantly from one epoch to another4 ,for example1 the middle ,eocene rocks are white to light-green1 red1 and purple1 upper ,eocene are dark-green1 ,oligocene are light-gray1 white1 and brown1 ,miocene are dark-green1 brown1 and gray1 and ,pliocene are white to red-brown4 ,illustration3 ,figure #ec4 ,air oblique view south1 showing the north end of the ,teton ,range disappearing beneath ,pleistocene lava flows4 ,light-colored bare area at lower left is vertical ,paleozoic limestone surrounded on three sides by nearly horizontal rhyolite lava flows4 ,bare slope at lower right is west-dipping ,pinyon ,conglomerate1 also overlapped by lava4 ,grand ,teton is on right skyline and ,mt4 ,moran is rounded summit on middle skyline4 ,as mentioned earlier1 it is probable that the vast outpouring of volcanic rocks during late ,tertiary time in the ,teton region and to the north and northeast is directly related to the subsidence of ,jackson ,hole and the rise of the ,tetons4 ,the spectacular banded cliffs of the ,wiggins ,formation on both sides of ,togwotee ,pass 7fig4 #eb7 and farther north in the ,absaroka ,range are remnants of ,oligocene volcanic conglomerate and tuff that once spread as a blanket several thousand feet thick across eastern ,jackson ,hole and partially or completely buried the nearby older folded mountain ranges4 ,illustration3 ,figure #ed4 ,obsidian1 a volcanic glass less than #aj million years old1 especially prized by ,indians who used it for spear and arrow points and for tools4 ,about #be million years ago1 with the start of the ,miocene ,epoch1 volcanic vents opened up within1 and along the borders of1 ,grand ,teton ,national ,park4 ,major centers of eruption were at the north end of the ,teton ,range1 east of ,jackson ,lake1 and south of ,spread ,creek4 ,they emitted a prodigious amount of volcanic ash and fragments of congealed lava4 ,for example1 adjacent to one vent a mile in diameter1 about #d miles north-northeast of ,jackson ,lake ,lodge1 is a continuous section1 #g1jjj feet thick1 of waterlaid strata derived in large part from this volcanic source4 ,these sedimentary rocks comprise the ,colter ,formation which is darker colored and contains more iron and magnesium than the ,wiggins ,formation4 ,the site of deposition at this locality was a north-trending trough that represented an early stage in the downwarping of ,jackson ,hole4 ,pliocene volcanoes erupted in southern and central ,yellowstone ,park4 ,the volcanoes emitted viscous1 frothy1 pinkish-gray and brown lava called rhyolite4 ,this is an extrusive igneous rock that has the same composition as granite1 but is much finer grained4 ,in several places1 lava apparently flowed into the north end of ,teewinot ,lake1 chilled suddenly1 and solidified into a black volcanic glass called obsidian4 ,because it chips easily into thin flakes having a smooth surface1 obsidian was prized by the ,indians1 who used it for spear and arrow points 7fig4 #ed74 ,some of this obsidian has a potassium-argon date of #i million years4 ,illustration3 ,figure #ee4 ,east face of ,signal ,mountain showing ,bivouac ,formation 7upper ,pliocene or ,pleistocene74 ,tilted ledge is rhyolitic welded tuff #b4e million years old1 and slopes above and below it are conglomerate4 ,national ,park ,service photo by ,w4 ,e4 ,dilley4 ,after ,teewinot ,lake was filled with sediment1 the floor of ,jackson ,hole became a flat boulder-covered surface4 ,nearby vents erupted heavy fiery clouds of gaseous molten rock that rolled across this plain and then congealed into hard layers with the general appearance of lava flows4 ,under a microscope1 however1 the rock is seen to be made up of compressed fragments of glass that matted down and solidified when the clouds stopped moving4 ,this kind of rock is called a welded tuff4 ,one of these forms the conspicuous ledge in the ,bivouac ,formation on the north and east sides of ,signal ,mountain 7fig4 #ee71 and is especially important because it has a potassium-argon date of #b4e million years4 ,more of this welded tuff flowed southward from ,yellowstone ,national ,park1 engulfed the north end of the ,teton ,range 7fig4 #ec71 and continued southward along the west side of the mountains for #ce miles and along the east side for #be miles4 ,illustration3 ,figure #ef4 ,the final #c million years on our yardstick of time1 enlarged to show approximate dates of major events4 ,,the ,,last ,,hundredths ,,absolute ,,time ,,important ,,events ,,of ,,an ,,inch ,,of ,,the 7,years ago7 ,,yardstick #j #j ,last glaciation followed by faulting _/ #ejjjj ,second glaciation _/ #ajjjjj 8--,first glaciation _/ #gjjjjj 8--,second ,quaternary lake _/ #a million 8--,tilting and faulting of southern part of ,jackson ,hole _/ #a4c million 8--,first ,quaternary lake _/ #a4e million ,complex series of volcanic eruptions in southern ,jackson ,hole _/ #a4i million _/ #b million 8--,development of ,hoback normal fault _/ #b4e million ,eruption of welded tuff in ,bivouac ,formation _/ #c million ,,quaternary--,,time ,,of ,,ice1 ,,more ,,lakes1 ,,and ,,continued ,,crustal ,,disturbance ,the ,quaternary ,period is represented by less than #ae-thousandths of the last inch on our yardstick of time 7fig4 #ef7 and the entire ,ice ,age takes up less than #b-thousandths of an inch 7less than the thickness of this page74 ,nevertheless1 the spectacular effects of various forces of nature on the ,teton landscape during this short interval of time are of such significance that they warrant a separate discussion4 ,the role of glaciers in carving the rugged ,teton peaks and shaping the adjacent valleys was mentioned in the first part of this booklet1 but is discussed in more detail here4 ,the magnitude and complexity of crustal movements increased during the final #b million years of time--so much so that the beginning of ,quaternary time has not yet been identified with any single event4 ,figure #ef shows the major events described below4 ,hoback normal fault ,the ,hoback normal fault1 #cj miles long1 with a mile or more displacement1 developed in the southernmost part of ,jackson ,hole about #b million years ago4 ,this fault is on the east side of the valley4 ,thus1 the valley block was downdropped between this fault and the ,teton fault that borders the west side4 ,volcanic activity ,during or shortly after major movement on the ,hoback fault1 and perhaps related to it1 there was a complex series of volcanic eruptions west and north of the town of ,jackson1 along the south boundary of the park4 ,in rapid succession1 lavas of many types1 with a combined thickness of more than #a1jjj feet1 were extruded and volcanic plugs intruded into the near-surface sedimentary rocks4 ,these volcanic rocks can be seen on the ,east and ,west ,gros ,ventre ,buttes4 ,there are no active volcanoes in the ,teton region today and no postglacial lava flows or cinder cones4 ,five miles north of ,grand ,teton ,national ,park are boiling springs 7,flagg ,ranch hot springs7 that are associated with the youngest 7late ,quaternary7 lavas in southern ,yellowstone ,park4 ,elsewhere in ,jackson ,hole are a number of lukewarm springs but their relation to volcanic rocks has not been determined4 ,what happened to the vast thicknesses of volcanic debris8 ,we know they existed because sections of them have been measured on the eroded edges of uptilted folds and fault blocks4 ,many cubic miles of these rocks are now buried beneath the floor of ,jackson ,hole1 but a much greater volume was carried completely out of the region by water1 ice1 and wind during the final chapter of geologic history4 ,preglacial lakes ,remnants of two sets of lake deposits in ,jackson ,hole record preglacial events in ,quaternary time4 ,downdropping of southern ,jackson ,hole along the ,hoback and ,teton faults blocked the southwestward drainage of the ,snake ,river1 and a new lake formed overlapping and extending south of the site of the long-vanished ,teewinot ,lake4 ,incorporated in the lake sediments are fragments of lava like that in nearby ,quaternary flows4 ,from this we know that the lake formed after at least some of the lava was emplaced4 ,apparently subsidence was more rapid than filling1 for a time1 at least1 because this new lake was deep4 ,fossil snails preserved in olive-drab to gray fine-grained claystone overlying lava flows at the north end of ,east ,gros ,ventre ,butte are the kind now living at depths of #abj to #cjj feet in ,lake ,tahoe1 ,california-,nevada4 ,near the margins of the lake1 pink and green claystone and soft sandstone were deposited4 ,the duration of this lake is not known but it lasted long enough for #bjj feet of beds to accumulate4 ,subsequent faulting and warping destroyed the lake1 left tilted remnants of the beds perched #a1jjj feet up on the east side of ,jackson ,hole1 and permitted the ,snake ,river to reestablish its course across the mountains to the southwest4 ,later downdropping of ,jackson ,hole impounded a second preglacial lake4 ,little is known about its extent because nearly everywhere the soft brown and gray shale1 claystone1 and sandstone deposited in it were scooped out and washed away during subsequent glaciations4 ,a few remnants of the lake deposits are preserved in protected places1 however2 two are within the ,gros ,ventre ,river ,valley--one downstream from ,lower ,slide ,lake about a mile east of the park and the other #d miles farther east4 ,the latter remnant is nearly #ejj feet thick and the upper half is largely very fine grained shale and claystone4 ,this fine texture suggests that the lake existed for a good many thousand years1 for such deposits commonly accumulate more slowly than coarser grained debris4 ,illustration3 ,figure #eg4 ,map showing extent and direction of movement of first and largest ice sheet4 ,see figure #da for ,state lines and location map4 ,the ,ice ,age ,with the uplift of the ,teton ,range and the formation of ,jackson ,hole late in ,cenozoic time the landscape gradually began to assume the general outlines that we see today4 ,rain1 wind1 snow1 and frost shaped the first crude approximations of the present ridges and peaks4 ,streams cut into the rising ,teton fault block1 eroding the ancestral canyons deeper and deeper as the uplift continued4 ,the most recent great chapter in the story of the ,teton landscape1 however1 remained to be written by the glaciers of the ,ice ,age4 ,the reasons for the climatic changes that caused the ,ice ,age are still a matter of much scientific debate4 ,various theories have been advanced that attribute them to changes in solar radiation1 changes in the earth's orbit and inclination to the sun1 variations in the amount of carbon dioxide in the atmosphere1 shifts in the positions of the continents or the poles1 and to many other factors1 but none has met with universal acceptance4 ,no doubt the explanation lies in some unusual combination of circumstances1 for widespread glaciation occurred only twice before in the earth's history--once in the late ,precambrian and once during the ,permian4 ,it is quite clear1 however1 that the glaciers did not form in response to any local cause such as the uplift of the ,teton ,range1 for concurrent climatic changes and ice advance took place throughout many parts of the world4 ,at least three times in the last #bej1jjj years glaciers from the surrounding highlands invaded ,jackson ,hole4 ,the oldest and most widespread glaciation probably took place about #bjj1jjj years ago2 it was called the ,buffalo ,glaciation by ,prof4 ,eliot ,blackwelder in #aiae 7see selected references74 ,the age estimate is based on measurements of the thickness of the decomposed layer on the surface of obsidian pebbles in the glacial debris4 ,major sources of ice were the ,beartooth ,mountains 7fig4 #a71 the ,absaroka ,range1 and the ,wind ,river ,range4 ,the ,gros ,ventre ,mountains and ,teton ,range furnished lesser amounts of ice4 ,the ice from the ,beartooth and ,absaroka centers of ice accumulation converged in the northeastern part of ,grand ,teton ,national ,park and flowed south along the face of the ,teton ,range in a giant stream that in many places was #b1jjj feet thick 7fig4 #eg74 ,all but the highest parts of the ,pinyon ,peak and ,mount ,leidy ,highlands were buried and scoured4 ,signal ,mountain1 ,blacktail ,butte1 and the ,gros ,ventres ,buttes were overridden and shaped by ice at this time4 ,another glacier1 this one from the ,wind ,river ,range1 flowed northwest along the ,continental ,divide1 then down the ,gros ,ventre ,river ,valley1 and merged with the southward-moving main ice stream west of ,lower ,slide ,lake4 ,where ,jackson ,hole narrows southward1 the glacier became more and more confined1 but nevertheless flowed all the way through the ,snake ,river ,canyon and on into ,idaho4 ,illustration3 ,figure #eh4 ,glacial deposits1 outwash1 and loess exposed along ,boyle ,ditch in ,jackson ,hole ,national ,elk ,refuge4 ,indicated are middle ,pliocene ,teewinot formation 7,a71 oldest till 7,b71 ,bull ,lake outwash gravel 7,c71 and post-,bull ,lake loess 7,d71 which here contains snail shells dated by ,carbon-#ad as #ae1jjj years old4 ,height of cliff is about #cj feet4 ,the volume of this great ice mass was probably considerably more than #a1jjj cubic miles4 ,when it melted1 nearly all the previously accumulated soil in ,jackson ,hole was washed away and a pavement of quartzite boulders mantled much of the glaciated surface4 ,in areas not subsequently glaciated1 the lack of soil and abundance of quartzite boulders drastically influenced the topography1 later drainage1 distribution of all types of vegetation1 especially conifers and grass1 and the pattern of human settlement and industry4 ,illustration3 ,figure #ei4 ,view west from the ,snake ,river overlook showing at upper right the ,burned ,ridge moraine 7with trees7 merging southward with the highest 7oldest7 ,pinedale outwash plain4 ,the next lower surface is composed of outwash from the ,jackson ,lake moraine which lies to the right1 out of the picture4 ,at the bottom is ,deadman's ,bar1 a gravel deposit at the present river level4 ,photo by ,h4 ,d4 ,pownall4 ,the second glaciation1 named ,bull ,lake1 was less than half as extensive as the first4 ,a large tongue of ice from the ,absaroka center of accumulation flowed down the ,buffalo ,river ,valley and joined ice from the ,tetons on the floor of ,jackson ,hole4 ,an enormous outwash fan of quartzite boulders extended from near ,blacktail ,butte southward throughout most of southern ,jackson ,hole4 ,glaciers in the ,gros ,ventre ,mountains did not advance beyond the east margin of the valley floor4 ,carbon-#ad ages and data from weathered obsidian pebbles suggest that this glaciation took place between #ce1jjj and #hj1jjj years ago4 ,bull ,lake moraines and outwash deposits are overlain directly in the southern part of ,jackson ,hole by fine silt1 rather than by deposits of the third glaciation 7fig4 #eh74 ,this silt1 of windblown origin1 is called loess and contains fossil shells dated by ,carbon-#ad as between #ac1jjj and #ai1jjj years old4 ,wherever the loess occurs1 it is marked by abundant modern coyote dens and badger burrows4 ,illustration3 ,figure #fj4 ,air oblique view west toward the ,teton ,range1 showing effects of ,pinedale ,glaciation on the landscape4 ,mt4 ,moran is at top left2 the mountain front is broken by ,u-shaped valleys from which ice emerged into the area now occupied by ,jackson ,lake4 ,the timbered area bordering ,jackson ,lake is the ,jackson ,lake moraine4 ,one of the braided outlet channels breaching the ,jackson ,lake moraine can be seen crossing the outwash plain at the left center4 ,lakes at lower right occupy 8potholes0 near where the #i1jjj-year-old snail shells occur4 ,snake ,river is in foreground4 ,photo by ,r4 ,l4 ,casebeer4 ,the third and last glaciation1 named the ,pinedale1 was even less extensive than the others4 ,nevertheless it was of great importance for it added the final touches to the present landscape4 ,the jagged intricately ice-carved peaks 7fig4 #d7 and the glittering lakes and broad gravelly plains are vivid reminders of this recent chapter in geologic history4 ,pinedale glaciers advanced down ,cascade1 ,garnet1 ,avalanche1 and ,death ,canyons and spilled out onto the floor of ,jackson ,hole1 where they built the outermost loops of the conspicuous terminal moraines that now encircle ,jenny1 ,bradley1 ,taggart1 and ,phelps ,lakes 7fig4 #ac74 ,ice streams from ,glacier ,gulch and ,open ,canyon also left prominent moraines on the valley floor1 but these do not contain lakes4 ,ice from ,leigh ,canyon and all of the eastward-draining valleys to the north combined to form a large glacier in roughly the present position of ,jackson ,lake4 ,this ice entirely surrounded ,signal ,mountain1 leaving only the upper few hundred feet projecting as an island or nunatak4 ,illustration3 ,figure #fa4 ,the ,pinedale ,glaciers in the central part of ,jackson ,hole as they might have appeared at the time the ,jackson ,lake moraine was built4 ,solid color areas are lakes2 dark irregular pattern shows areas of moraine deposited during the maximum advance of the ,pinedale ,glaciers4 ,pattern of open circles shows older ,pinedale outwash plains2 pattern of fine dots shows outwash plains built at the time the glaciers were in the positions shown in the drawing4 ,coarser dots near the margins of the glaciers represent concentrations of rock debris in the ice4 ,the southernmost major advance of ,pinedale ice from ,jackson ,lake is marked by a series of densely timbered moraines that cross the ,snake ,river ,valley4 ,this series is collectively named the ,burned ,ridge moraine 7fig4 #fa74 ,extending southward for #aj miles from this moraine is a remarkably flat surfaced gravelly outwash deposit4 ,it was spread by streams that poured from the glacier at the time the moraine was being built 7fig4 #ei74 ,east of the ,snake ,river1 the main highway from a point just north of ,blacktail ,butte to the ,snake ,river overlook is built on this flat untimbered surface4 ,we assume that the outwash is younger than #ae1jjj years because it apparently overlies loess of that age4 ,the glacier withdrew rapidly northward from the ,burned ,ridge moraine1 leaving behind many large irregular masses of stagnant1 debris-covered ice4 ,the sites of these became kettles1 locally known as 8,the ,potholes0 7fig4 #ab74 ,the main glacier retreated to a position marked by the loop of moraines just south of ,jackson ,lake 7fig4 #fj74 ,figure #fa is a sketch map showing how the glaciers in this part of ,jackson ,hole might have appeared at the time the ,jackson ,lake moraine was built4 ,abundant snail shells have been found in lake sediments in the bottoms of the kettles north of the ,burned ,ridge moraine 7fig4 #fj7 as well as on low ridges between them4 ,carbon-#ad age determinations indicate that the snails lived about #i1jjj years ago1 either in a lake already present before the ,pinedale ice advanced and formed the ,burned ,ridge moraine or in ponds that filled kettles left as the ice melted behind this moraine4 ,in either case1 the shells indicate that the ,pinedale glaciers probably existed on the floor of ,jackson ,hole as recently as #i1jjj years ago1 at a time when ,indians were already living in the area4 ,we can easily imagine the fascination with which these primitive peoples may have watched as year after year the glaciers wasted away1 slowly retreating back into the canyons1 then withdrawing into the sheltered recesses of the high mountains1 eventually to dwindle and disappear4 ,many bits of evidence1 both from ,north ,america and ,europe1 indicate that there was a period called the climatic optimum about #f1jjj years ago when the climate was significantly warmer and drier than at present4 ,we suspect1 though there is as yet no direct proof1 that the ,pinedale glaciers wasted away entirely during this interval4 ,the modern pattern of vegetation in ,jackson ,hole is strongly influenced by the distribution of ,pinedale glacial moraines and outwash deposits4 ,almost without exception the moraines are heavily forested1 whereas the nearby outwash deposits are covered only by a sparse growth of sagebrush4 ,this is probably because the moraines contain large amounts of clay and silt produced by the grinding action of the glaciers4 ,material of this type retains water much better and1 because of the greater variety of chemical elements1 is more fertile than the porous quartzite gravel and sand on the outwash plains4 ,modern glaciers ,about a dozen small rapidly dwindling glaciers exist today in shaded reentrants high in the ,teton ,range4 ,they are probably vestiges of ice masses built up since the climatic optimum1 during the so-called 8,little ,ice ,age40 ,these glaciers1 while insignificant compared to those still present in many other mountain ranges1 are fascinating working models of the great ice streams that shaped the ,tetons during ,pleistocene time4 ,the ,teton ,glacier 7fig4 #f7 is one of the best known4 ,it is an ice body about #c1ejj feet long and #a1ajj feet wide that lies at the head of ,glacier ,gulch1 shaded by the encircling ridges of the ,grand ,teton1 ,mount ,owen1 and ,mount ,teewinot4 ,ice in the central part is moving at a rate of more than #cj feet a year4 ,,the ,,present ,,and ,,the ,,future ,the geologic story of the ,teton country from the time the earth was new to the present day has been summarized4 ,what can we learn from it8 ,we become aware that events recorded in the rocks are not a chaotic jumble of random accidents but came in an orderly1 logical succession4 ,we see the majestic parade of life evolving from simple to complex types1 overcoming all natural disasters1 and adapting to ever-changing environments4 ,we can only speculate as to the motivating force that launched this fascinating geologic and biologic venture and what the ultimate goal may be4 ,new facts and new ideas are added to the story each year1 but many unknown chapters remain to be studied2 these offer an irresistible1 continuing challenge to inquisitive minds1 strong bodies1 and restless1 adventurous spirits4 ,most geologic processes that developed the ,teton landscape have been beneficial to man2 a few have interfered with his activities1 cost him money1 time1 effort1 and on occasion1 his life4 ,postglacial faulting and tilting along the southern margin of ,grand ,teton ,national ,park diverted drainage systems 7such as ,flat ,creek1 southwest of the ,flat ,creek fault on the south edge of the geologic map71 raised hills1 dropped valleys1 and made steep slopes unstable4 ,flood-control engineers wage a never-ending struggle to keep the ,snake ,river from shifting to the west side of ,jackson ,hole as the valley tilts westward in response to movement along the ,teton fault4 ,each highway into ,jackson ,hole has been blocked by a landslide at one time or another and maintenance of roads across slide areas requires much ingenuity4 ,we see one slide 7the ,gros ,ventre7 that blocked a river2 larger slides have occurred in the past1 and more can be expected4 ,abundant fresh fault scarps are a constant reminder that public buildings1 campgrounds1 dams1 and roads need to be designed to withstand the effects of earthquakes4 ,some of these problems have geologic solutions2 others can be avoided or minimized as further study increases our understanding of this region4 ,man appeared during the last one-fiftieth of an inch on our yardstick of time gone by4 ,in this short span he has had more impact on the earth and its inhabitants than any other form of life4 ,will he use wisely the lessons of the past as a guide while he writes his record on the yardstick of the future8 ,,appendix ,acknowledgements ,this booklet could not have been prepared without the cooperation and assistance of many individuals and organizations4 ,we are indebted to the ,national ,park ,service for the use of facilities1 equipment1 and photographs1 and for the enthusiasm and interest of all of the park staff4 ,we especially appreciate the cooperation1 advice1 and assistance rendered by the late ,fred ,c4 ,fagergren1 former superintendent of ,grand ,teton ,national ,park2 ,willard ,e4 ,dilley1 former chief park naturalist2 and ,r4 ,alan ,mebane1 former assistant chief park naturalist4 ,profs4 ,charles ,c4 ,bradley and ,john ,montagne of ,montana ,state ,university and ,bruno ,j4 ,giletti of ,brown ,university generously provided us with unpublished data4 ,cooperators during the years of background research were the late ,dr4 ,h4 ,d4 ,thomas1 ,state ,geologist of ,wyoming1 and ,dr4 ,d4 ,l4 ,blackstone1 ,jr41 ,chairman1 ,department of ,geology1 ,university of ,wyoming4 ,helpful suggestions were made by many of our colleagues with the ,u4 ,s4 ,geological ,survey2 ,s4 ,s4 ,oriel1 in particular1 gave unstintingly of his time and talents in the review and revision of an early version of the manuscript4 ,a later version had the further benefit of critical review by three other people1 all experienced in presenting various types of scientific data to public groups3 ,john ,m4 ,good1 former chief park naturalist of ,yellowstone ,national ,park2 ,bryan ,harry1 former assistant chief park naturalist of ,grand ,teton ,national ,park2 and ,richard ,klinck1 8#aife ,national ,teacher of the ,year40 ,we are indebted to ,ann ,c4 ,christiansen1 ,geologic ,map ,editor1 for advice and guidance on the illustrations and to ,r4 ,c4 ,fuhrmann and his staff for preparation of many of the line drawings4 ,block diagrams and photo artwork were prepared by ,j4 ,r4 ,stacy and ,r4 ,a4 ,reilly4 ,all photographs without specific credit lines are by the authors4 ,from the beginning of the ,teton field study to editing and proofing of the final manuscript1 our wives1 ,jane ,m4 ,love and ,linda ,h4 ,reed1 have been enthusiastic and indispensable participants4 ,selected references--if you wish to read further ,blackwelder1 ,eliot1 #aiae1 ,post-,cretaceous history of the mountains of central western ,wyoming3 ,jour4 ,geology1 v4 #bc1 p4 #ig-aag1 #aic-bag1 #cjg-cdj4 ,bradley1 ,f4 ,h41 #ahgc1 ,report on the geology of the ,snake ,river district3 ,u4,s4 ,geol4 ,survey ,terr4 #fth ,ann4 ,rept4 7,hayden71 p4 #aij-bga4 ,edmund1 ,r4 ,w41 #aiea1 ,structural geology and physiography of the northern end of the ,teton ,range1 ,wyoming3 ,augustana ,library ,pub4 #bc1 #hb p4 ,fryxell1 ,f4 ,m41 #aicj1 ,glacial features of ,jackson ,hole1 ,wyoming3 ,augustana ,library ,pub4 #ac1 #abi p4 ----1 #aich1 ,the ,tetons1 interpretations of a mountain landscape3 ,univ4 ,california ,press1 ,berkeley1 ,calif41 #gg p4 ,hague1 ,arnold1 #aijd1 ,atlas to accompany ,u4,s4 ,geol4 ,survey ,monograph #cb on the geology of ,yellowstone ,national ,park4 ----1 ,iddings1 ,j4 ,p41 ,weed1 ,w4 ,h41 and others1 #ahii1 ,geology of the ,yellowstone ,national ,park3 ,u4,s4 ,geol4 ,survey ,monograph #cb1 ,pt4 #b1 #hic p4 ,harry1 ,bryan1 #aifc1 ,teton trails1 a guide to the trails of ,grand ,teton ,national ,park3 ,grand ,teton ,natural ,history ,association1 ,moose1 ,wyo41 #ef p4 ,horberg1 ,leland1 #aich1 ,the structural geology and physiography of the ,teton ,pass area1 ,wyoming3 ,augustana ,library ,pub4 #af1 #hf p4 ,hurley1 ,p4 ,m41 #aiei1 ,how old is the earth83 ,anchor ,books1 ,garden ,city1 ,n4 ,y41 #afj p4 ,ortenburger1 ,leigh1 #aife1 ,a climber's guide to the ,teton ,range3 ,sierra ,club1 ,san ,francisco1 #ccf p4 ,st4 ,john1 ,o4 ,h41 #ahhc1 ,report on the geology of the ,wind ,river district3 ,u4,s4 ,geol4 ,geog4 ,survey ,terr4 #abth ,ann4 ,rept4 7,hayden71 ,pt4 #a1 p4 #agc-bgj4 ,wyoming ,geological ,association1 #aief1 ,guidebook1 #aath annual field conf41 ,jackson ,hole1 ,wyoming1 #aief1 ,casper1 ,wyo41 #bef p41 incl4 sketch maps1 diagrams1 tables1 and illus41 also geol4 map1 sections1 and charts4 ,composed of a series of individual papers by various authors4 ,about the authors ,j4 ,d4 ,love1 a native of ,wyoming1 received his bachelor and master of arts degrees from the ,university of ,wyoming and his doctor of philosophy degree from ,yale ,university4 ,his first field season in the ,teton country1 in #aicc1 was financed by the ,geological ,survey of ,wyoming4 ,after #ab years of geologic work ranging from ,new ,england to ,utah and ,michigan to ,mississippi1 he returned to the ,teton region4 ,beginning in #aide1 he spent parts or all of #bj field seasons in and near the ,tetons4 ,he compiled the first geologic map of ,teton ,county4 ,he is the senior author of the geologic map of ,wyoming1 and author or co-author of more than #gj other published maps and papers on the geology of ,wyoming4 ,in #aifa1 the ,university of ,wyoming awarded him an honorary doctor of laws degree for his work on uranium deposits that 8led to the development of the uranium industry in ,wyoming40 ,the ,wyoming ,geological ,association made him an honorary life member and gave him a special award for his geologic studies of the ,teton area4 ,he is a ,fellow of the ,geological ,society of ,america and is active in various other geological organizations1 as well as having been president of the ,wyoming ,chapters of ,sigma ,xi 7scientific honorary7 and ,phi ,beta ,kappa 7scholastic honorary7 societies4 ,john ,c4 ,reed1 ,jr41 joined the ,u4,s4 ,geological ,survey in #aiec after receiving his doctor of philosophy degree from the ,john ,hopkins ,university4 ,his principal geologic work before coming to the ,teton region was in ,alaska and in the southern ,appalachians4 ,beginning in #aifa1 he spent five field seasons studying and mapping the ,precambrian rocks in ,grand ,teton ,national ,park1 including all the high peaks in the ,teton ,range4 ,he is a noted mountaineer1 a ,fellow of the ,geological ,society of ,america1 a member of the ,arctic ,institute of ,north ,america1 and the ,american ,alpine ,club4 ,his numerous publications1 in addition to those on the ,tetons1 describe the geology of mountainous areas in ,alaska1 the ,appalachians1 and ,utah4 ,index of selected terms and features ,term ,defined or described on page ,a amphibolite #ea anticlines #he ,b badlands #ad bentonite #ha biotite #ea brachiopods #gj ,buffalo ,glaciation #ajf ,bull ,lake ,glaciation #ajh ,burned ,ridge moraine #aaa buttes #ah ,c ,carbon-#ad #dh carnivores #ie chlorite #ef cirque #cj climatic optimum #aab ,cordilleran trough #fi ,d diabase #ei dikes #ef dipping #ci dolomite #ge ,e 8edgewise0 conglomerate #gc epochs #df eras #df erosion #bg erratics #ca extrusive igneous rocks #df ,f fault #i fault block mountain range #cg fault scarps #cg formations #ff frost wedging #be ,g geologic #aj glacial striae #cj gradients #bh ,grand ,valley ,lake #ie granite #ee granite gneiss #ed groups #dg gypsum #gi ,h herbivores #ie ,hoback normal fault #ajc hole #h hornblende #ea ,i ,ice ,age #aje igneous rocks #df intrusive igneous rocks #df ,j ,jackson ,hole #h jade #ee ,k kettle #ca ,l ,laramide ,revolution #hb lateral moraine #cj layered gneisses #ea ,little ,ice ,age #aab loess #ajh ,m magma #fj magnetite #eb marine sedimentary rocks #ba metamorphic rocks #ec muscovite #ee ,n normal fault #ci nunatak #aaa ,o obsidian #aja oreodonts #ig outwash #ca outwash plain #ca outwash terraces #cd ,p pegmatite #ef period #df ,pinedale ,glaciation #aji ,q quartzite #fc ,r reverse fault #ci rhyolite #ajj rock glaciers #bf ,s schist #ea sedimentary rocks #de series #dg serpentine #ee 8soapstone0 #ee ,sundance ,sea #gi systems #df ,t talus #bd ,targhee uplift #hc ,teewinot ,lake #ib terminal moraine #cj ,tetons #h ,teton fault #cg thrust fault #ci timberline #ae titanothere #ig treeline #ae ,triceratops #he trilobites #gj tuff #ib ,w welded tuff #aja ,the ,,grand ,,teton ,,natural ,,history ,,association ,the ,grand ,teton ,natural ,history ,association assists the ,national ,park ,service in the development of a broad public understanding of the geology1 plant and animal life1 history1 and related subjects pertaining to ,grand ,teton ,national ,park4 ,it aids in the development of museums and wayside exhibits1 offers for sale publications on natural and human history1 and cooperates with the ,government in the interest of ,grand ,teton ,national ,park4 ,mail orders3 ,for a publication list1 write the ,grand ,teton ,natural ,history ,association1 ,moose1 ,wyoming #hcjab4 ,creative ,director3 ,century ,,iii ,advertising4 ,inc4 ,designer3 ,les ,hays ,studios1 ,inc4 ,color ,separations--,assembly--,plates3 ,orent ,graphic ,arts1 ,inc4 ,type3 ,bodoni and ,gothic ,printer3 ,omaha ,printing ,co4 ,printing3 ,offset ,lithography4 ,six ,colors on ,covers ,two ,colors on ,body ,illustration3 ,,geologic ,,map ,,of ,,grand ,,teton ,,national ,,park ,illustration3 ,,explanation ,,cenozoic ,,quaternary ,sand1 gravel1 and talus ,includes glacial outwash and materials deposited by present streams ,landslide deposits ,moraine deposits of ,pinedale glaciers ,moraine deposits of ,bull ,lake and older glaciers ,,tertiary ,volcanic rocks ,lava flows and volcanic ash ,conglomerate1 sandstone1 shale1 claystone1 marl1 and pumice ,deposited on land or in shallow lakes ,,mesozoic ,conglomerate1 sandstone1 shale1 and coal ,deposited on land ,shale1 sandstone1 and limestone ,mostly deposited in shallow seas ,,paleozoic ,limestone1 shale1 and sandstone ,deposited in shallow seas ,,precambrian ,diabase dikes ,granite1 gneiss1 and schist ,fault ,dashed where approximately located2 dotted where concealed beneath unfaulted younger deposits4 ,u is on the side that moved up2 ,d1 on the side that moved down ,geologic contact ,illustration3 ,view southwest from ,lake ,solitude toward the ,grand ,teton 7right71 ,mt4 ,owen1 and ,mt4 ,teewinot4 ,wyoming ,travel ,commission photo by ,j4 ,r4 ,simon4 ,illustration3 ,grand ,teton1 ,mt4 ,owen1 and ,mt4 ,teewinot from ,jenny ,lake ,flat4 ,national ,park ,service photo by ,w4 ,e4 ,dilley4 ,transcriber's ,notes --,retained publication information from the printed edition3 this e,book is public-domain in the country of publication4 --,corrected a few palpable typos4 --,re-arranged text in captions closer to the corresponding image4 --,expanded ambiguous references to illustrations1 e4g4 8,figure ,d0 to 8,figure #af;,d0 --,added one section heading1 8,the ,first ,big ,lake0 to match the table of contents4 --,included a transcription of the text within some images1 with estimated scale readings from charts4 --,in the text versions only1 text in italics is delimited by underscores4