,illustration3 ,,denver1 ,,colorado ,but from these immense prairies may arise one great advantage to the ,united ,states1 viz41 the restriction of our population to some certain limits1 and thereby a continuation of the union4 ,our citizens being so prone to rambling1 and extending themselves on the frontiers1 will1 through necessity1 be constrained to limit their extent on the west to the borders of the ,missouri and the ,mississippi1 while they leave the prairies1 incapable of cultivation1 to the wandering and uncivilized ,aborigines of the country4 ,zebulon ,pike ,exploratory ,travels ,through ,the ,western ,territories of ,north ,america comprising a voyage from ,st4 ,louis1 on the ,mississippi1 to the source of that river1 and a journey through the interior of ,louisiana and the north-eastern provinces of ,new ,spain4 ,performed in the years #ahje1 #ahjf1 and #ahjg1 by order of the ,government of the ,united ,states4 ,by ,zebulon ,montgomery ,pike4 ,published by ,paternoster-,row1 ,london1 #ahaa3 ,w4 ,h4 ,lawrence and ,company1 ,denver1 #ahhi4 ,quotation from pages #bcj-bca1 #ahhi edition4 ,the ,,geologic ,,story of ,the ,,great ,,plains ,by ,,donald ,e4 ,,trimble ,a nontechnical description of the origin and evolution of the landscape of the ,great ,plains ,,geological ,,survey ,,bulletin #adic ,,united ,,states ,,department ,,of ,,the ,,interior ,,cecil ,d4 ,,andrus1 ,secretary ,,geological ,,survey ,h4 ,william ,menard1 ,director ,illustration3 ,u4 ,s4 ,,department ,,of ,,the ,,interior ,march #c1 #ahdi ,,united ,,states ,,government ,,printing ,,office1 ,,washington3 #aihj ,library of ,congress ,cataloging in ,publication ,data ,trimble1 ,donald ,e4 ,the geologic story of the ,great ,plains4 7,u4,s4 ,geological ,survey ,bulletin #adic7 ,bibliography3 p4 #ej ,includes index4 ,supt4 of ,docs4 no43 ,i #ai4c3 #adic ,i4 ,geology--,great ,plains4 ,i4 ,title4 ,,ii4 ,series3 ,united ,states ,geological ,survey ,bulletin #adic4 ,,qe#ge4;,b#i no4 #adic ,,qe#ga #eeg4cs #eeg4h #hj-fjgjbb ,for sale by the ,superintendent of ,documents1 ,u4,s4 ,government ,printing ,office ,washington1 ,d4,c4 #bjdjb ,,contents ,introduction #a ,what is the ,great ,plains8 #e ,the ,great ,plains--its parts #g ,early history #aj ,warping and stream deposition #aa ,sculpturing the land #ah ,landforms of today--,the surface features of the ,great ,plains #ai ,black ,hills #bj ,central ,texas ,uplift #bb ,raton ,section #bc ,high ,plains #be ,missouri ,plateau #cb ,preglacial ,drainage #cc ,glaciated ,missouri ,plateau #cc ,unglaciated ,missouri ,plateau #cf ,the ,colorado ,piedmont #db ,pecos ,valley #de ,edwards ,plateau #df ,plains ,border ,section #dh ,epilogue #di ,acknowledgments #di ,some source references #ej ,,figures ,,frontispiece4 ,aerial photograph of ,denver4 #a4 ,index map #c #b-c4 ,maps showing3 #b4 ,physical divisions of the ,united ,states and maximum extent of the continental ice sheets #f #c4 ,the ,great ,plains province and its sections #h #d4 ,photograph of ,mescalero escarpment and southern ,high ,plains #i #e4 ,geologic time chart #ab #f-h4 ,maps showing3 #f4 ,paleogeography of ,u4,s4 in ,late ,cretaceous #ad #g4 ,structural setting of the ,great ,plains #ad #h4 ,progressive southward expansion of areas of deposition #ag #i4 ,photograph of ,big ,horn strip mine at ,acme1 ,wyo4 #ah #aj4 ,black ,hills diagram #ba #aa-af4 ,photographs showing3 #aa4 ,weathering of granite at ,sylvan ,lake in the ,black ,hills #bb #ab4 ,capulin ,mountain ,national ,monument1 ,n4 ,mex4 #bd #ac4 ,mesa de ,maya1 ,colo4 #be #ad4 ,spanish ,peaks1 ,colo4 #bf #ae4 8,the ,gangplank10 ,wyo4 #bg #af4 ,scotts ,bluff ,national ,monument1 ,nebr4 #bh #ag4 ,aerial photograph of the ,nebraska ,sand ,hills #cj #ah4 ,map of the ,nebraska ,sand ,hills #ca #ai-cj4 ,photographs showing3 #ai4 ,loess plain in ,nebraska #cb #bj4 ,ground moraine on the ,coteau du ,missouri in ,north ,dakota #cd #ba4 ,slump blocks in ,north ,unit of ,theodore ,roosevelt ,national ,memorial ,park1 ,n4 ,dak4 #cf #bb4 ,highwood ,mountains1 ,mont4 #cg #bc4 ,devils ,tower ,national ,monument1 ,wyo4 #ch #bd4 ,glaciated valley in ,crazy ,mountains1 ,mont4 #ci #be4 ,powder ,river ,basin in vicinity of ,tongue ,river #dj #bf4 ,badlands ,national ,monument1 ,s4 ,dak4 #da #bg4 ,badlands of ,little ,missouri ,river in ,south ,unit of ,theodore ,roosevelt ,national ,memorial ,park1 ,n4 ,dak4 #db #bh4 ,hogback ridges along the ,front ,range1 ,colo4 #dc #bi4 ,pawnee ,buttes1 ,colo4 #dd #cj4 ,edwards ,plateau1 ,tex4 #dg ,,table #a4 ,generalized chart of rocks of the ,great ,plains #ae ,the ,,geologic ,,story of ,the ,,great ,,plains ,by ,donald ,e4 ,trimble ,,introduction ,the ,great ,plains6 ,the words alone create a sense of space and a feeling of destiny--a challenge4 ,but what exactly is this special part of ,western ,america that contains so much of our history8 ,how did it come to be8 ,why is it different8 ,geographically1 the ,great ,plains is an immense sweep of country2 it reaches from ,mexico far north into ,canada and spreads out east of the ,rocky ,mountains like a huge welcome mat4 ,so often maligned as a drab1 featureless area1 the ,great ,plains is in fact a land of marked contrasts and limitless variety3 canyons carved into solid rock of an arid land by the waters of the ,pecos and the ,rio ,grande2 the seemingly endless grainfields of ,kansas2 the desolation of the ,badlands2 the beauty of the ,black ,hills4 ,before it was broken by the plow1 most of the ,great ,plains from the ,texas panhandle northward was treeless grassland4 ,trees grew only along the floodplains of streams and on the few mountain masses of the northern ,great ,plains4 ,these lush prairies once were the grazing ground for immense herds of bison1 and the land provided a bountiful life for those ,indians who followed the herds4 ,south of the grasslands1 in ,texas1 shrubs mixed with the grasses3 creosote bush along the valley of the ,pecos ,river2 mesquite1 oak1 and juniper to the east4 ,the general lack of trees suggests that this is a land of little moisture1 as indeed it is4 ,nearly all of the ,great ,plains receives less than #bd inches of rainfall a year1 and most of it receives less than #af inches4 ,this dryness and the strength of sunshine in this area1 which lies mostly between #b1jjj and #f1jjj feet above sea level1 create the semiarid environment that typifies the ,great ,plains4 ,but it was not always so4 ,when the last continental glacier stood near its maximum extent1 some #ab1jjj-ad1jjj years ago1 spruce forest reached southward as far as ,kansas1 and the ,great ,plains farther south was covered by deciduous forest4 ,the trees retreated northward as the ice front receded1 and the ,great ,plains has been a treeless grassland for the last #h1jjj-aj1jjj years4 ,for more than half a century after ,lewis and ,clark crossed the country in #ahje-f1 the ,great ,plains was the testing ground of frontier ,america--here ,america grew to maturity 7fig4 #a74 ,in #ahje-g1 explorer ,zebulon ,pike crossed the south-central ,great ,plains1 following the ,arkansas ,river from near ,great ,bend1 ,kans41 to the ,rocky ,mountains4 ,in later years1 ,santa ,fe traders1 lured by the wealth of ,new ,mexican trade1 followed ,pike's path as far as ,bents ,fort1 ,colo41 where they turned southwestward away from the river route4 ,those pioneers who later crossed the plains on the ,oregon ,trail reached the ,platte ,river near the place that would become ,kearney1 ,nebr41 by a nearly direct route from ,independence1 ,mo41 and followed the ,platte across the central part of the ,great ,plains4 ,although these routes may have seemed long and tedious to those dusty travelers1 they provided relatively easy access to the ,rocky ,mountains and had a continuous supply of fresh water1 an absolute necessity in these plains4 ,the minds of those frontiersmen surely were occupied with the dangers and demands of the moment--and with dreams--but the time afforded by the slow pace of travel also gave them ample opportunity for thought about the origins of their surroundings4 ,today's traveler1 who has less time for contemplation1 races past a changing kaleidoscope of landscape4 ,the increased awareness created by this rapidity of change perhaps is even more likely to stimulate questions about the origin of this landscape4 ,illustration3 ,figure #a4--;,index map of the ,great ,plains showing route of ,lewis and ,clark and the ,santa ,fe and ,oregon ,trails4 ,for instance1 the westbound traveler on ,interstate ,highway #gj traverses nearly a thousand miles of low1 rounded hills after leaving the ,appalachians2 the rolling landscape is broken only by a few flat areas where glacial ice or small lakes once stood4 ,suddenly1 near ,salina1 ,kans41 the observant traveler senses a difference in the landscape4 ,instead of rounded hills1 widely or closely spaced1 he sees on the skyline flat surfaces1 or remnants of flat surfaces4 ,as he climbs gently westward these broken horizontal lines stand etched against the sky4 ,about #ce miles west of ,salina he finds himself on a broad1 flat plateau1 where seemingly he can see forever4 ,true1 in places he descends into stream valleys1 but only briefly1 for he soon climbs back onto the flat surface4 ,this plateau surface continues for #cjj miles to the west--to within #ajj miles of the abrupt front of the ,rocky ,mountains4 ,east-flowing streams1 such as the ,smoky ,hill1 the ,saline1 the ,solomon1 and the ,republican ,rivers and their tributary branches1 have cut their valleys into this surface1 but these valleys become increasingly shallow and disappear entirely near the western rim of the plateau in eastern ,colorado4 ,the distant peaks of the ,rockies are seen for the first time as the traveler approaches the escarpment that forms the western edge of this great plateau4 ,after crossing the escarpment near ,limon1 ,colo41 he begins the long gentle descent to ,denver1 on the ,south ,platte ,river near the foot of the mountains that loom so awesomely ahead4 ,he has crossed the ,great ,plains4 ,the distances have been great1 but the contrasts have been marked4 ,had our traveler selected a different route1 either to the north or south1 he would have found even greater contrasts1 for the ,great ,plains has many parts1 each with its own distinctive aspect4 ,why should such diverse landscapes be considered parts of the ,great ,plains8 ,what are their unifying features8 ,and what created this landscape8 ,has it always been this way8 ,if not1 when was it formed8 ,how was it formed8 ,we will look here at some of the answers to those questions4 ,the history of events that produced the landscape of the ,great ,plains is interpreted both from the materials that compose the landforms and from the landforms themselves4 ,as we will see1 all landforms are the result of geologic processes in action4 ,these processes determine not only the size and shape of the landforms1 but also the materials of which they are made4 ,these geologic processes1 which form and shape our ,earth's surface1 are simply the inevitable actions of the restless interior of the ,earth and of the air1 water1 and carbon dioxide of the atmosphere1 aided by gravity and solar heating 7or lack of it74 ,they all have helped sculpture the fascinating diversity of the part of our land we call the ,great ,plains4 ,,what ,,is ,,the ,,great ,,plains8 ,the ,united ,states has been subdivided into physiographic regions that1 although they have great diversity within themselves1 are distinctly different from each other 7fig4 #b74 ,from the ,rocky ,mountains on the west to the ,appalachians on the east1 the interior of our country is a vast lowland 7see cover7 known as the ,interior ,plains4 ,these plains are bounded on the south by a region of ,interior ,highlands1 consisting of the ,ozark ,plateaus and the ,ouachita province1 and by the ,coastal ,plain4 ,in the ,great ,lakes region1 the ,interior ,plains laps onto the most ancient part of the continent1 the ,superior ,upland4 ,west of the ,great ,lakes it extends far to the north into ,canada4 ,certainly the ,rocky ,mountains are distinctly different from the region to the east1 which is the ,great ,plains4 ,the ,great ,plains1 then1 is the western part of the great ,interior ,plains4 ,the ,rocky ,mountains form its western margin4 ,but what determines its eastern margin8 ,during the ,pleistocene ,epoch or ,great ,ice ,age1 huge glaciers formed in ,canada and advanced southward into the great1 central1 low-lying ,interior ,plains of the ,united ,states4 7,see figure #b47 ,these glaciers and their deposits modified the surface of the land they covered1 mostly between the ,missouri and the ,ohio ,rivers2 they smoothed the contours and gave the land a more subdued aspect than it had before they came4 ,this glacially smoothed and modified land is called the ,central ,lowland4 ,although the ice sheets lapped onto the northern part1 the ,great ,plains is the largely unglaciated region that extends from the ,gulf ,coastal ,plain in ,texas northward into ,canada between the ,central ,lowland and the foot of the ,rocky ,mountains4 ,its eastern margin in ,texas and ,oklahoma is marked by a prominent escarpment1 the ,caprock escarpment4 ,its southern margin1 where it abuts the ,coastal ,plain in ,texas1 is at another abrupt rise or scarp along the ,balcones fault zone4 ,illustration3 ,figure #b4--,physical divisions of the ,united ,states and maximum extent of the continental ice sheets during the ,great ,ice ,age4 ,,the ,,great ,,plains--,,its ,,parts ,within the ,great ,plains are many large areas that differ greatly from adjoining areas 7fig4 #c74 ,the ,black ,hills stands out distinctively from the surrounding lower land1 and its dark1 forested prominence can be seen for scores of miles from any direction4 ,at the southern end of the ,great ,plains is another1 less imposing1 forested prominence--the ,central ,texas ,uplift4 ,most impressive1 perhaps1 is the huge1 nearly flat plateau known as the ,high ,plains1 which extends southward from the northern border of ,nebraska through the ,panhandle of ,texas1 and which forms the central part of the ,great ,plains4 ,the east and west rims of the southern ,high ,plains are at high1 cliffed1 erosional escarpments--the ,caprock escarpment on the east and the ,mescalero escarpment on the west4 ,the north edge of the ,high ,plains is defined by another escarpment1 the ,pine ,ridge escarpment1 which separates the ,high ,plains from a region that has been greatly dissected by the ,missouri ,river and its tributaries4 ,there1 several levels of rolling upland are surmounted by small mountainous masses and flat-topped buttes and are entrenched by streams4 ,this region is the ,missouri ,plateau4 ,the continental glacier lapped onto the northeastern part of the ,missouri ,plateau and altered its surface4 ,the ,south ,platte and ,arkansas ,rivers and their tributaries have similarly dissected an area along the mountain front that is called the ,colorado ,piedmont1 and the ,pecos ,river has excavated a broad valley trending southward from the ,sangre de ,cristo ,mountains in ,new ,mexico into ,texas4 ,the ,mescalero escarpment separates the ,pecos ,valley from the southern ,high ,plains 7fig4 #d74 ,south and east of the ,pecos ,valley1 extending to the ,rio ,grande and the ,coastal ,plain1 is a broad plateau of bare1 stripped1 flat-lying limestone layers bearing little but cactus that is called the ,edwards ,plateau4 ,green1 crop-filled valleys with gently sloping valley walls and rounded stream divides trend eastward from the ,high ,plains of western ,kansas and characterize a ,plains ,border section4 ,and finally1 between the ,colorado ,piedmont on the north and the ,pecos ,valley on the south1 volcanic vents1 cinder cones1 and lava fields form another distinctive terrain in the part of the ,great ,plains called the ,raton section4 ,illustration3 ,figure #c4--,the ,great ,plains province and its sections4 ,illustration3 ,figure #d4--,mescalero escarpment and the southern ,high ,plains 7,llano ,estacado7 south of ,tucumcari1 ,n4 ,mex41 ,photograph by ,c4 ,d4 ,miller1 ,u4 ,s4 ,geological ,survey4 ,can such diverse parts of our land have a sufficiently common origin to justify their being considered part of one unified whole--the ,great ,plains8 ,probably so1 but to understand why1 we must examine some of the earlier geologic history of the ,great ,plains as well as subsequent events revealed in the present landforms4 ,we will find that all parts of this region we call the ,great ,plains have a similar early history1 and that the differences we see are the results of local dominance of certain processes in the ultimate shaping of the landscape1 mostly during the last few million years4 ,the distinctive character of the landscape in each section is determined in part by both the early events and the later shaping processes4 ,,early ,,history ,the ,interior ,plains1 of which the ,great ,plains is the western1 mostly unglaciated part 7fig4 #b71 is the least complicated part of our continent geologically except for the ,coastal ,plain4 ,for most of the half billion years from #egj million 7fig4 #e7 until about #gj million years ago1 shallow seas lay across the interior of our continent 7fig4 #f 74 ,a thick sequence of layered sediments1 mostly between #e1jjj and #aj1jjj feet thick1 but more in places1 was deposited onto the subsiding floor of the interior ocean 7table #a74 ,these sediments1 now consolidated into rock1 rest on a floor of very old rocks that are much like the ancient rocks of the ,superior ,upland4 ,about #gj million years ago the seas were displaced from the continental interior by slow uplift of the continent1 and the landscape that appeared was simply the extensive1 nearly flat floor of the former sea4 ,,warping ,,and ,,stream ,,deposition ,most of these rocks of marine origin lie at considerable depth beneath the land surface1 concealed by an overlying thick1 layered sequence of rocks laid down by streams1 wind1 and glaciers4 ,nevertheless1 their geologic character1 position1 and form are exceptionally well known from information gained from thousands of wells that have been drilled for oil4 ,the initial1 nearly horizontal position of the layers of rock beneath the ,interior ,plains has been little disturbed except where mountains like the ,black ,hills were uplifted about #gj million years ago4 ,at those places1 which are all in the northern and southern parts of the ,great ,plains1 the sedimentary layers have been warped up and locally broken by the rise of hot molten rock from depth4 ,elsewhere in the ,interior ,plains1 however1 earth forces of about the same period caused only a reemphasis of gentle undulations in the ,earth's crust4 ,these undulations affected both the older basement rocks and the overlying sedimentary rocks1 and they take the form of gentle basins and arches that in some places span several ,states4 7,see sketch map1 figure #g47 ,a series of narrow basins lies along the mountain front on the west side of the ,great ,plains4 ,a broad1 discontinuous arch extends southwest from the ,superior ,upland to the ,rocky ,mountain front to form a buried divide that separates the large ,williston basin on the north from the ,anadarko basin to the south4 ,while the flat-lying layers of the ,interior ,plains were being only gently warped1 vastly different earth movements were taking place farther west1 in the area of the present ,rocky ,mountains4 ,along a relatively narrow north-trending belt1 extending from ,mexico to ,alaska1 the land was being uplifted at a great rate4 ,the layers of sedimentary rock deposited in the inland sea were stripped from the crest of the rising mountainous belt by erosion and transported to its flanks as the gravel1 sand1 and mud of streams and rivers4 ,this transported sediment was deposited on the plains to form the rocks of the ,cretaceous ,hell ,creek1 ,lance1 ,laramie1 ,vermejo1 and ,raton ,formations4 ,vegetation thrived on this alluvial plain1 and thick accumulations of woody debris were buried to ultimately become coal4 ,this lush vegetation provided ample food for the hordes of three-horned dinosaurs 7,triceratops7 that roamed these plains4 ,their fossilized remains are found from ,canada to ,new ,mexico4 ,illustration3 ,figure #e4--;,geologic time chart and the progression of life forms4 ,note ,cretaceous ,triceratops1 ,oligocene ,titanotheres1 and ,miocene ,moropus4 ,,geologic ,,time ,the ,age of the ,earth ,the ,earth is very old--#d4e billion years or more according to recent estimates4 ,most of the evidence for an ancient ,earth is contained in the rocks that form the ,earth's crust4 ,the rock layers themselves--like pages in a long and complicated history--record the surface-shaping events of the past1 and buried within them are traces of life--the plants and animals that evolved from organic structures that existed perhaps #c billion years ago4 ,also contained in rocks once molten are radioactive elements whose isotopes provide ,earth scientists with an atomic clock4 ,within these rocks1 8parent0 isotopes decay at a predictable rate to form 8daughter0 isotopes4 ,by determining the relative amounts of parent and daughter isotopes1 the age of these rocks can be calculated4 ,thus1 the results of studies of rock layers 7stratigraphy71 and of fossils 7paleontology71 coupled with the ages of certain rocks as measured by atomic clocks 7geochronology71 attest to a very old ,earth6 ,illustration3 ,figure #f4--;,generalized paleogeographic map of the ,united ,states in ,late ,cretaceous time 7#fe to #hj million years ago71 when most of the ,great ,plains was beneath the sea4 ,illustration3 ,figure #g4--,structural setting of the ,great ,plains4 ,williston basin and ,anadarko basin are separated by a midcontinental arch4 ,illustration3 ,table #a4--;,generalized chart of rocks of the ,great ,plains ,geologic age ,missouri ,high ,plains--,plains ,pecos ,millions of ,plateau--,black ,border--,colorado ,valley--,edwards years ago ,hills ,piedmont ,plateau--,central ,texas ,quaternary ,pleistocene ,glacial deposits1 ,alluvium1 sand ,piedmont1 terrace1 alluvium1 and dunes1 and loess and bolson terrace deposits deposits #b erosional surface ,tertiary ,pliocene ,,erosion #e ,flaxville ,gravel ,ogallala formation and ,ogallala ,formation ,miocene ,arikaree ,formation ,arikaree ,formation #bb-bd erosional surface ,oligocene ,white ,river ,group ,white ,river ,group ,mostly missing because of erosion or nondeposition #cg-ch erosional surface ,eocene ,wasatch and ,golden ,valley ,formations #ec-ed ,dawson ,arkose ,paleocene ,fort ,union ,denver1 ,poison ,formation ,canyon1 and ,raton ,formations #fe ,cretaceous ,hell ,creek and ,vermejo and ,laramie ,lance ,formations ,formations ,fox ,hills ,sandstone ,trinidad and ,fox ,hills ,sandstones ,shales1 sandstones1 and limestones deposited in ,late ,cretaceous sea ,dakota ,sandstone ,dakota ,sandstone and ,lakota ,formation ,glen ,rose and ,edwards ,limestones #acf ,jurassic ,sundance ,morrison ,formation ,jurassic rocks not ,formation1 ,ellis present ,group1 and ,unkpapa ,sandstone #aij-aie ,triassic ,dominantly red rocks #bbe ,,paleozoic ,paleozoic rocks1 undivided #egj ,,precambrian ,precambrian rocks1 undivided ,as the mountains continued to rise1 the eroding streams cut into the old core rocks of the mountains1 and that debris too was carried to the flanks and onto the adjoining plains4 ,the mountainous belt continued to rise intermittently1 and volcanoes began to appear about #ej million years ago4 ,together1 the mountains and volcanoes provided huge quantities of sediment1 which the streams transported to the plains and deposited4 ,the areas nearest the mountains were covered by sediments of ,late ,cretaceous and ,paleocene age 7table #a7--the ,poison ,canyon ,formation to the south1 the ,dawson and ,denver ,formations in the ,denver area1 and the ,fort ,union ,formation to the north 7fig4 #h74 ,vegetation continued to flourish1 especially in the northern part of the ,great ,plains1 and was buried to form the thick lignite and subbituminous coal beds of the ,fort ,union ,formation 7fig4 #i74 ,the earliest mammals1 most of whose remains come from the ,paleocene ,fort ,union ,formation1 have few modern survivors4 ,beginning about #de million years ago1 in ,eocene time1 there was a long period of stability lasting perhaps #aj million years1 when there was little uplift of the mountains and1 therefore1 little deposition on the plains4 ,a widespread and strongly developed soil formed over much of the ,great ,plains during this period of stability4 ,with renewed uplift and volcanism in the mountains at the end of this period1 great quantities of sediment again were carried to the plains by streams and spread over the northern ,great ,plains and southeastward to the arch or divide separating the ,williston and ,anadarko basins 7fig4 #h74 ,those sediments form the ,white ,river ,group1 in which the ,south ,dakota ,badlands are carved4 ,in addition to the ,titanotheres1 huge beasts with large1 long horns on their snouts who lived only during the ,oligocene 7#cg to #bb million years ago71 vast herds of camels1 rhinoceroses1 horses1 and tapirs--animals now found native only on other continents--grazed those ,oligocene semiarid grassland plains4 ,illustration3 ,figure #h4--,progressive southeastward expansion of areas covered by ,paleocene1 ,oligocene1 and ,miocene-,pliocene sedimentary deposits4 ,powder ,river basin ,denver basin ,raton basin ,,plains ,margin of ,oligocene deposition ,margin of ,miocene-,pliocene deposition ,illustration3 ,figure #i4--;,big ,horn coal strip mine in ,fort ,union ,formation at ,acme1 ,wyo4 ,photograph by ,f4 ,w4 ,osterwald1 ,u4,s4 ,geological ,survey4 ,sometime between #bj and #cj million years ago the streams began depositing sand and gravel beyond the divide1 and1 for another #aj million years or more1 stream sediments of the ,arikaree and ,ogallala ,formations spread over the entire ,great ,plains from ,canada to ,texas1 except where mountainous areas such as the ,black ,hills stood above the plains4 ,between #e and #aj million years ago1 then1 the entire ,great ,plains was an eastward-sloping depositional plain surmounted only by a few mountain masses4 ,horses1 camels1 rhinoceroses1 and a strange horselike creature with clawed feet 7called ,moropus7 lived on this plain4 ,,sculpturing ,,the ,,land ,sometime between #e and #aj million years ago1 however1 a great change took place1 apparently as a result of regional uplift of the entire western part of the continent4 ,while before1 the streams had been depositing sediment on the plains for more than #fj million years1 building up a huge thickness of sedimentary rock layers1 now the streams were forced to cut down into and excavate the sediments they had formerly deposited4 ,as uplift continued--and it may still be continuing--the streams cut deeper and deeper into the layered stack and developed tributary systems that excavated broad areas4 ,high divides were left between streams in some places1 and broad plateaus were formed and remain in other places4 ,the great central area was essentially untouched by erosion and remained standing above the dissected areas surrounding it as the escarpment-rimmed plateau that is the ,high ,plains4 ,this downcutting and excavation by streams1 then1 which began between #e and #aj million years ago1 roughed out the landscape of the ,great ,plains and created the sections we call the ,missouri ,plateau1 the ,colorado ,piedmont1 the ,pecos ,valley1 the ,edwards ,plateau1 and the ,plains ,border ,section4 ,nearly all the individual landforms that now attract the eye have been created by geologic processes during the last #b million years4 ,it truly is a young landscape4 ,,landforms ,,of ,,today--,the surface features of the ,great ,plains ,the mountainous sections of the ,great ,plains were formed long before the remaining areas were outlined by erosion4 ,uplift of the ,black ,hills and the ,central ,texas ,uplift began as the continental interior was raised and the last ,cretaceous sea was displaced1 #fe to #gj million years ago4 ,they stood well above the surrounding plains long before any sediments from the distant ,rocky ,mountains began to accumulate at their bases4 ,in southern ,colorado and northern ,new ,mexico1 molten rock invaded the sedimentary layers between #bb and #bf million years ago4 ,the ,spanish ,peaks were formed at this time from hot magma that domed up the surface layers but did not break through2 the magma has since cooled and solidified and has been exposed by erosion4 ,elsewhere the magma reached the surface1 forming volcanoes1 fissures1 and basalt flows4 ,a great thickness of basalt flows accumulated at ,raton ,mesa and ,mesa de ,maya between #h and #b million years ago4 ,volcanism has continued intermittently1 and the huge cinder cone of ,capulin ,mountain was created by explosive eruption only #aj1jjj to #d1jjj years ago4 ,most of these volcanic masses were formed before major downcutting by the streams began4 ,other igneous intrusions and volcanic areas in the northern ,great ,plains similarly were formed before the streams were incised4 ,to examine the origin of the present landscape and of the landforms typical of the various sections of the ,great ,plains1 it is convenient to begin with the ,black ,hills1 the ,central ,texas ,uplift1 and the ,raton section simply because they were formed first--they existed before the other sections were outlined4 ,,black ,,hills ,the ,black ,hills is a huge1 elliptically domed area in northwestern ,south ,dakota and northeastern ,wyoming1 about #abe miles long and #fe miles wide 7fig4 #aj74 ,rapid ,city1 ,s4 ,dak41 is on the ,missouri ,plateau at the east edge of the ,black ,hills4 ,uplift caused erosion to remove the overlying cover of marine sedimentary rocks and expose the granite and metamorphic rocks that form the core of the dome4 ,the peaks of the central part of the ,black ,hills presently are #c1jjj to #d1jjj feet above the surrounding plains4 ,harney ,peak1 with an altitude of #g1bdb feet1 is the highest point in ,south ,dakota4 ,these central spires and peaks all are carved from granite and other igneous and metamorphic rocks that form the core of the uplift4 ,the heads of four of our great ,presidents are sculpted from this granite at ,mount ,rushmore ,national ,memorial4 ,joints in the rocks have controlled weathering processes that influenced the final shaping of many of these landforms4 ,closely spaced joints have produced the spires of the ,needles area1 and widely spaced joints have produced the rounded forms of granite that are seen near ,sylvan ,lake 7fig4 #aa74 ,marine sedimentary rocks surrounding the old core rocks form well-defined belts4 ,lying against the old core rocks and completely surrounding them are ,paleozoic limestones that form the ,limestone ,plateau 7fig4 #aj74 ,these tilted layers have steep erosional scarps facing the central part of the ,black ,hills4 ,wind ,cave and ,jewel ,cave were produced by ground water dissolving these limestones along joints4 ,these caves are sufficiently impressive to be designated as a national park and a national monument1 respectively4 ,encircling the ,limestone ,plateau is a continuous valley cut in soft ,triassic shale4 ,this valley has been called 8the ,racetrack10 because of its continuity1 and the ,red ,valley1 because of its color4 ,surrounding the ,red ,valley is an outer hogback ridge formed by the tilted layers of the ,dakota ,sandstone1 which are quite hard and resistant to erosion4 ,streams that flow from the central part of the ,black ,hills pass through the ,dakota hogback in narrow gaps4 ,illustration3 ,figure #aj4--;,diagram of the ,black ,hills uplift by ,a4 ,n4 ,strahler 7,strahler and ,strahler1 #aigh74 ,used by permission4 ,dakota ,sandstone hogback ,limestone plateau ,belle ,fourche ,river ,spearfish ,bear ,butte ,sundance ,red ,valley ,rapid ,city ,red ,valley ,hot ,springs ,cheyenne ,river ,edgemont ,mt4 ,rushmore ,national ,monument ,jewel ,cave ,national ,monument ,wind ,cave ,national ,park ,illustration3 ,figure #aa4--;,jointed granite rounded by weathering at ,sylvan ,lake1 in the central part of the ,black ,hills1 ,s4 ,dak4 ,the ,black ,hills1 then1 is an uplifted area that has been carved deeply but differentially by streams to produce its major outlines4 ,those outlines have been modified mainly by weathering of the ancient core rocks and solution of the limestone of the ,limestone ,plateau4 ,,central ,,texas ,,uplift ,the domed rocks of the ,central ,texas ,uplift form a topography different from that of the ,black ,hills4 ,erosion of a broad1 uplifted dome here has exposed a core of old granites1 gneisses1 and schists1 as in the ,black ,hills1 but in the ,central ,texas ,uplift1 erosion has produced a topographic basin1 rather than high peaks and spires1 on the old rocks of the central area4 ,a low plateau surface dissected into rounded ridges and narrow valleys slopes gently eastward from the edge of the central area to an escarpment at the ,balcones fault zone1 which determines the eastern edge of the ,great ,plains here4 ,northwest of the central basin the ,colorado ,river flows in a broad lowland about #ajj miles long1 but the northern edge of the uplift1 forming a divide between the ,brazos and the ,colorado ,rivers1 is a series of mesas formed of more resistant sandstone and limestone4 ,the cutting action of streams1 modified or controlled in part by differences in hardness of the rock layers1 has been responsible for the landforms of the ,central ,texas ,uplift4 ,weathering of the old core rocks has softened them sufficiently to permit deeper erosion of the central area1 and solution of limestone by ground water has formed such features as ,longhorn ,caverns1 #aa miles southwest of ,burnet1 ,tex4 ,,raton ,,section ,volcanism characterizes the ,raton section4 ,the volcanic rocks1 which form peaks1 mesas1 and cones1 have armored the older sedimentary rocks and protected them from the erosion that has cut deeply into the adjoining ,colorado ,piedmont to the north and ,pecos ,valley to the south4 ,the south edge of the ,raton section is marked by a spectacular south-facing escarpment cut on the nearly flat-lying ,dakota ,sandstone4 ,this escarpment is the ,canadian escarpment1 north of the ,canadian ,river4 ,northward for about #ajj miles1 the landscape is that of a nearly flat plateau cut on ,cretaceous rock surmounted here and there by young volcanic vents1 cones1 and lava fields4 ,capulin ,mountain is a cinder cone only #aj1jjj to #d1jjj years old 7fig4 #ab74 ,near the ,new ,mexico-,colorado border1 huge piles of lava were erupted #h to #b million years ago onto an older1 higher surface on top of either the ,ogallala ,formation of ,miocene age or the ,poison ,canyon ,formation of ,paleocene age4 7,see table #a47 ,these lava flows formed a resistant cap1 which protected the underlying rock from erosion while all the surrounding rock washed away4 ,the result is the high1 flat-topped mesas1 such as ,raton ,mesa and ,mesa de ,maya 7fig4 #ac71 that now form the divide between the ,arkansas and ,canadian ,rivers4 ,at ,fishers ,peak1 on the west end of ,raton ,mesa1 about #hjj feet of basalt flows rest on the ,poison ,canyon ,formation at about #h1hjj feet in altitude4 ,farther east1 on ,mesa de ,maya1 about #djj feet of basalt flows overlie the ,ogallala ,formation at altitudes ranging from about #f1ejj feet at the west end to about #e1bjj feet at the east end1 some #ce miles to the east4 ,the ,ogallala here rests on ,cretaceous ,dakota ,sandstone and ,purgatoire ,formation1 for the ,poison ,canyon ,formation was removed by erosion along the crest of a local uplift before the ,ogallala was deposited4 ,illustration3 ,figure #ab4--;,capulin ,mountain ,national ,monument in northeastern ,new ,mexico4 ,this huge cinder cone1 which erupted between #d1jjj and #aj1jjj years ago1 rises more than #a1jjj feet above its base4 ,photograph by ,r4 ,d4 ,miller1 ,u4,s4 ,geological ,survey4 ,east of the belt of upturned sedimentary layers that form the hogback ridges at the front of the ,rocky ,mountains1 the layered rocks in the ,raton ,basin have been intruded in many places by igneous bodies1 the two largest of which form the ,spanish ,peaks 7fig4 #ad71 southwest of ,walsenburg1 ,colo4 ,these two peaks are formed by igneous bodies that were intruded #bf to #bb million years ago and have since been exposed by removal of the overlying sedimentary rock layers by erosion4 ,radiating from the ,spanish ,peaks are hundreds of dikes1 nearly vertical slabs of igneous rock that filled fractures radiating from the centers of intrusion4 ,erosion of the sedimentary layers has left many of these dikes as conspicuous vertical walls of igneous rock that project high above the surrounding land surface4 ,some of these dikes north of ,trinidad1 ,colo4 extend eastward for about #be miles1 almost to the ,purgatoire ,river4 ,illustration3 ,figure #ac4--,lava-capped ,mesa de ,maya1 east of ,trinidad1 ,colo4 ,spanish ,peaks in left distance4 ,mesa rises about #a1jjj feet above surrounding area4 ,photograph by ,r4 ,b4 ,taylor1 ,u4,s4 ,geological ,survey4 ,the northern boundary of the ,raton section is placed somewhat indefinitely at the northern limit of the area injected by igneous dikes4 ,the eastern boundary of the ,raton section is at the eastern margin of the lavas of ,mesa de ,maya and adjoining mesas1 where lava-capped outliers of ,ogallala ,formation are separated from the ,ogallala of the ,high ,plains only by the canyon of ,carrizo ,creek4 ,,high ,,plains ,at the end of ,ogallala deposition1 some #e million years ago1 the ,great ,plains1 with the exception of the uplifted and the volcanic areas1 was a vast1 gently sloping plain that extended from the mountain front eastward to beyond the present ,missouri ,river in some places4 ,regional uplift of the western part of the continent forced the streams to cut downward2 land near the mountains was stripped away by the ,missouri1 the ,platte1 the ,arkansas1 and the ,pecos ,rivers1 and the eastern border of the plains was gnawed away by lesser streams4 ,a large central area of the plain is preserved1 however1 essentially untouched and unaffected by the streams1 as a little-modified remnant of the depositional surface of #e million years ago4 ,this ,ogallala-capped preserved remnant of that upraised surface is the ,high ,plains4 ,in only one place does that old surface still extend to the mountains--at the so-called 8,gangplank0 west of ,cheyenne1 ,wyo4 7fig4 #ae74 ,in places1 as at ,scotts ,bluff ,national ,monument1 ,nebr4 7fig4 #af71 small fragments of this surface have been isolated from the ,high ,plains by erosion and now stand above the surrounding area as buttes4 ,illustration3 ,figure #ad4--,spanish ,peaks1 southwest of ,walsenburg1 ,colo4 ,igneous rocks and many radiating dikes exposed by erosion4 ,photograph by ,r4 ,b4 ,taylor1 ,u4,s4 ,geological ,survey4 ,illustration3 ,figure #ae4--,looking east toward ,cheyenne at 8the ,gangplank40 ,interstate ,highway #hj and the ,union ,pacific ,railroad follow the ,gangplank from the ,high ,plains in the distance onto the ,precambrian rocks 7older than #egj m4y47 of the ,laramie ,mountains in the foreground4 ,photograph by ,r4 ,d4 ,miller1 ,u4,s4 ,geological ,survey4 ,illustration3 ,figure #af4--;,aerial view of ,scotts ,bluff ,national ,monument1 ,nebr4 ,buttes on the south side of the valley of the ,north ,platte ,river isolated by erosion from ,high ,plains in the background4 ,highest butte stands about #hjj feet above valley floor4 ,the ,high ,plains extends southward from the ,pine ,ridge escarpment1 near the ,south ,dakota-,nebraska border 7fig4 #c71 to the ,edwards ,plateau in ,texas4 ,the ,platte1 the ,arkansas1 and the ,canadian ,rivers have cut through the ,high ,plains4 ,that part of the ,high ,plains south of the ,canadian ,river is called the ,southern ,high ,plains1 or the ,llano ,estacado 7staked plain74 ,the origin of this name is uncertain1 but it has been suggested that the term ,llano ,estacado was applied by early travelers because this part of the ,high ,plains is so nearly flat and devoid of landmarks that it was necessary for those pioneers to set lines of stakes to permit them to retrace their routes4 ,the ,llano ,estacado is bounded on the west by the ,mescalero escarpment 7fig4 #d7 and on the east by the ,caprock escarpment4 ,the southern margin with the ,edwards ,plateau is less well defined1 but ,king ,mountain1 north of ,mc,camey1 ,tex41 is a scarp-bounded southern promontory of the ,high ,plains4 ,the remarkably flat surface of the ,llano ,estacado is abundantly pitted by sinks and depressions in the surface of the ,ogallala ,formation2 these were formed by solution of the limestone by rainwater and blowing away or deflation by wind of the remaining insoluble particles4 ,many of these solution-deflation depressions are aligned like strings of beads1 suggesting that their location is controlled by some kind of underlying structure1 such as intersections of joints in the ,ogallala ,formation4 ,the solution-deflation depressions are less abundant north of the ,canadian ,river1 but occur on the ,high ,plains surface northward to the ,arkansas ,river and along the eastern part of the ,high ,plains north of the ,arkansas to the ,south ,fork of the ,republican ,river4 ,covering much of the northern ,high ,plains1 however1 are sand dunes and windblown silt deposits 7loess7 that mantle the ,ogallala ,formation and conceal any solution-deflation depressions that might have formed4 ,the ,nebraska ,sand ,hills 7fig4 #ag71 the largest area of sand dunes in the western hemisphere1 is a huge area of stabilized sand dunes that extends from the ,white ,river in ,south ,dakota southward beyond the ,platte ,river almost to the ,republican ,river in western ,nebraska but only to the ,loup ,river in the northeast part of the ,high ,plains 7fig4 #ah74 ,loess covers the western ,high ,plains southward from the sand dunes almost to the ,arkansas ,river1 and to the ,south ,fork of the ,republican in the eastern part4 ,this extensive cover of loess has created a fertile land that makes it an important part of ,america's wheatlands 7fig4 #ai74 ,illustration3 ,figure #ag4--;,aerial view1 looking northwest1 of the ,nebraska ,sand ,hills west of ,ashby1 ,nebr4 ,other1 smaller areas of sand dunes lie south of the ,arkansas ,river valley4 ,the only large areas of sand dunes on the ,llano ,estacado1 or ,southern ,high ,plains1 are along the southwestern margin near ,monahans1 southwest of ,odessa1 ,tex4 ,oil and gas are present in the ,paleozoic rocks that underlie the ,high ,plains at depth4 ,gas fields are ubiquitous in much of the eastern part of the ,high ,plains between the ,arkansas and ,canadian ,rivers4 ,just south of the ,canadian ,river1 at the northeast corner of the ,southern ,high ,plains1 a huge oil and gas field has been developed near ,pampa1 ,tex4 ,oil and gas fields also are abundant in the southwestern part of the ,southern ,high ,plains1 south of ,littlefield1 ,tex4 ,illustration3 ,figure #ah4--,the ,sand ,hills region of ,nebraska4 ,arrows show inferred direction of dune-forming winds4 ,map from ,wright 7#aigj71 used by permission4 ,,wyoming ,badlands ,national ,monument ,missouri ,river ,valley ,,james ,,river ,,lobe ,,minnesota ,,iowa ,,south ,,dakota ,,nebraska ,rosebud ,valentine ,,des ,,moines ,,lobe ,,nebraska ,ashby ,,sandhills ,platte ,river ,valley ,,iowa ,,missouri ,,nebraska ,,kansas ,,colorado ,muscotah ,,topeka ,,explanation ,transverse dunes ,longitudinal dunes ,wind-blown sand ,loess thickness 7in feet7 ,illustration3 ,figure #ai4--,little-modified loess plain in southeastern ,nebraska4 ,photograph by ,judy ,miller4 ,the surface of the ,high ,plains1 then1 has been little modified by streams since the end of ,ogallala deposition4 ,it has been raised by regional uplift and pitted by solution and deflation1 and large parts of it have been covered by wind-blown sand and silt4 ,it has been drilled for oil and gas and extensively farmed1 but it is still a geological rarity--a preserved land surface that is #e million years old4 ,,missouri ,,plateau ,beginning about #e million years ago1 regional uplift of the western part of the continent forced streams1 which for #cj million years had been depositing sediment nearly continuously on the ,great ,plains1 to change their behavior and begin to cut into the layers of sediment they so long had been depositing4 ,the predecessor of the ,missouri ,river ate headward into the northern ,great ,plains and developed a tributary system that excavated deeply into the accumulated deposits near the mountain front and carried away huge volumes of sediment from the ,great ,plains to ,hudson ,bay4 ,by #b million years ago1 the streams had cut downward to within a few hundred feet of their present level4 ,this region that has been so thoroughly dissected by the ,missouri ,river and its tributaries is called the ,missouri ,plateau4 ,about #b million years ago1 after much downcutting had already taken place and river channels had been firmly established1 great ice sheets advanced southward from ,canada into the ,united ,states4 7,see figure #b47 ,these continental glaciers formed1 advanced1 and retreated several times during the last #b million years4 ,at the north and east margins of the ,missouri ,plateau they lapped onto a high area1 leaving a mantle of glacial deposits covering the bedrock surface and forcing streams to adopt new courses along the margin of ice4 ,the part of the ,missouri ,plateau covered by the continental glaciers now is referred to as the ,glaciated ,missouri ,plateau4 ,south of the part once covered by ice is the ,unglaciated ,missouri ,plateau4 ,preglacial ,drainage ,before the initial advance of the continental ice sheets1 the ,missouri ,river flowed northeastward into ,canada and to ,hudson ,bay4 ,its major tributaries1 the ,yellowstone and the ,little ,missouri joined the ,missouri in northwestern ,north ,dakota4 ,the east-flowing ,knife1 ,heart1 and ,cannonball ,rivers in ,north ,dakota also joined a stream that flowed northward to ,hudson ,bay4 ,glaciated ,missouri ,plateau ,when the continental ice sheets spread southward into northern ,montana and the ,dakotas1 a few isolated areas in ,montana stood above the surrounding plain4 ,these are mostly areas that were uplifted by the intrusion of igneous bodies long before the streams began downcutting and carving the land4 ,the northernmost of these isolated mountains1 the ,sweetgrass ,hills1 were surrounded by ice and became nunataks1 or islands of land1 in the sea of advancing ice1 which pushed southward up against the ,highwood ,mountains1 near ,great ,falls1 the ,bearpaws south of ,havre1 and the ,little ,rockies to the east4 ,much of the northern part of ,montana is a plain of little relief that is the surface of a nearly continuous cover of glacial deposits1 generally less than #ej feet thick4 ,this plain has been incised by the east-flowing postglacial ,teton1 ,marias1 and ,milk ,rivers4 ,in ,north ,dakota1 a high area on the east side of the ,williston basin acted as a barrier to the advance of the ice1 most of which was diverted southeastward4 ,the margin of the ice sheet1 however1 lapped onto the bedrock high1 where it stagnated4 ,earlier advances moved farthest south2 the later advances stopped north of the present course of the ,missouri ,river--their maximum position marked by ridges of unsorted1 glacially transported rock debris 7till7 called terminal moraines4 ,north of the terminal moraines is a distinctive landscape characterized by a rolling1 hummocky1 or hilly surface with thousands of closed depressions between the hills and hummocks1 most of them occupied by lakes4 ,this is the deposit left by the stagnant or dead ice1 and it is called dead-ice moraine4 ,the rolling upland in ,north ,dakota that is covered by dead-ice moraine and ridges of terminal moraines from the last glacial advances is called the ,coteau du ,missouri 7fig4 #bj74 ,a gently sloping scarp1 several hundred feet high and mostly covered by glacial deposits 7referred to collectively as drift71 separates the ,coteau du ,missouri from the lower1 nearly flat1 drift-covered plains of the ,central ,lowland to the east4 ,this escarpment1 which is called the ,missouri escarpment1 is virtually continuous across the ,state of ,north ,dakota southward into ,south ,dakota4 ,the base of the ,missouri escarpment is the eastern boundary of the ,great ,plains in these northern states4 ,illustration3 ,figure #bj4--;,ground moraine on the ,coteau du ,missouri1 northwestern ,north ,dakota4 ,photograph by ,r4 ,m4 ,lindvall1 ,u4 ,s4 ,geological ,survey4 ,the advancing ice front blocked one after another of the northward-flowing streams of the region1 diverting them eastward along the ice front4 ,shonkin ,sag1 north of the ,highwood ,mountains near ,great ,falls1 ,mont41 is an abandoned diversion channel of the ,missouri ,river1 occupied when the ice front stood close to the north slopes of the ,highwoods4 ,much of the present course of the ,missouri ,river from ,great ,falls1 ,mont41 to ,kansas ,city1 ,mo41 was established as an ice-marginal channel1 and the east-flowing part of the ,little ,missouri ,river in ,north ,dakota was formed in the same way4 ,these valleys were cut during the last #b million years4 ,the north-flowing part of the ,little ,missouri ,river and the east-flowing courses of the ,knife1 ,heart1 and ,cannonball ,rivers in ,north ,dakota are for the most part older1 preglacial courses4 ,the ,little ,missouri was dammed by the ice1 and its waters impounded to form a huge lake during the maximum stand of the ice1 but the deposits of this glacial lake are few and make no imprint on the landscape4 ,the valley of the east-flowing1 glacially diverted part of the ,little ,missouri ,river1 however1 is markedly different from that of the north-flowing preglacial river4 ,it is much narrower and has steeper walls than the old valley4 ,because it is younger1 it is little modified1 except by huge landslides that have affected both walls of the valley4 ,tremendous rotated landslide blocks in the ,north ,unit of ,theodore ,roosevelt ,national ,memorial ,park are some of the best examples of the slump type of landslide to be seen anywhere 7fig4 #ba74 ,melting ice at the front of the glaciers provided large volumes of meltwater that flowed across the till-mantled surface in front of the glacier as it melted back toward ,canada4 ,this meltwater took many courses to join the glacially diverted ,missouri ,river1 and these sinuous meltwater channels wind across the dead-ice moraine and the older1 less hummocky ground moraine between the ,coteau du ,missouri and the ,missouri ,river4 ,locally the sediment carried by the meltwater streams was banked against a wall of ice to form a small hill of stratified drift that is called a kame4 ,streams flowing in tunnels beneath the ice formed sinuous1 ridgelike deposits called eskers1 and in places the meltwater deposits form broad flat areas called outwash plains4 ,illustration3 ,figure #ba4--,rotated slump blocks in huge landslide1 ,north ,unit of ,theodore ,roosevelt ,national ,memorial ,park1 ,n4 ,dak4 ,note that layering of ,fort ,union ,formation in cliffs on skyline1 where landslide originated1 is horizontal4 ,this rather limited variety of landforms1 then1 characterizes the landscape of the ,glaciated ,missouri ,plateau4 ,the landforms themselves are testimony to their glacial origin and to the great advances of the continental ice sheets4 ,this is a stream-carved terrain that has been modified by continental glaciers and almost completely covered by a thick blanket of glacially transported and deposited rock debris1 locally hundreds of feet thick4 ,subsequent stream action has not altered the landscape greatly4 ,unglaciated ,missouri ,plateau ,beyond the limits reached by the ice of the continental glaciers1 the ,unglaciated ,missouri ,plateau displays the greatest variety of landforms of any section of the ,great ,plains4 ,in western ,montana1 many small mountain masses rise above the general level of the plateau1 including the ,highwood1 ,bearpaw1 and ,little ,rocky ,mountains near the margin of the glaciated area1 and the ,judith1 ,big ,snowy1 ,big ,belt1 ,little ,belt1 ,castle1 and ,crazy ,mountains farther south 7fig4 #bb74 ,many of these1 such as the ,crazy1 ,castle1 ,judith1 and ,big ,snowy ,mountains1 are areas uplifted by large1 deeply rooted1 intrusive igneous bodies called stocks1 which have been exposed by subsequent erosion of the arched overlying sedimentary rock layers4 ,some1 such as the ,highwood and ,bearpaw ,mountains1 are predominantly piles of lava flows1 although in the ,bearpaws the related intrusive bodies of igneous rock form a part of the mountains4 ,the ,big and ,little ,belt ,mountains were formed by mushroom-shaped intrusive igneous bodies called laccoliths1 which have spread out and domed between layers of sedimentary rocks4 ,a number of igneous bodies also intrude the rocks of the ,missouri ,plateau around the periphery of the ,black ,hills4 ,devils ,tower1 the first feature to be designated a ,national ,monument1 is the best known of these igneous rock features 7fig4 #bc74 ,illustration3 ,figure #bb4--,the ,highwood ,mountains seen from the ,little ,belt ,mountains1 ,mont4 ,photograph by ,i4 ,j4 ,witkind1 ,u4 ,s4 ,geological ,survey4 ,the uplift and volcanism that formed these mountains took place before the streams began to cut downward and segment the ,great ,plains4 ,the mountains had been greatly dissected before the advent of the ,great ,ice ,age1 when alpine glaciers formed on the ,castle and the ,crazy ,mountains and flowed down some of the stream-cut valleys4 ,alpine glacial features such as cirques1 in the high parts of the mountains1 and glacially modified ,u-shaped valleys 7fig4 #bd7 are impressive evidence of this glaciation4 ,illustration3 ,figure #bc4--;,devils ,tower ,national ,monument1 ,wyo4 ,an igneous intrusive body exposed by erosion4 ,photograph by ,f4 ,w4 ,osterwald1 ,u4 ,s4 ,geological ,survey4 ,the ,missouri ,river and its tributaries--the ,sun1 ,smith1 ,judith1 ,musselshell1 and ,yellowstone ,rivers in ,montana and the ,little ,missouri ,river in ,north ,dakota--have cut down into the ,missouri ,plateau1 cut broad upland surfaces at many levels1 and established confined valleys with valley floors flanked by terrace remnants of older floodplains4 ,locally1 high buttes that are remnants of former interstream divides rise above the uplands4 ,large lakes also were formed in most of these tributary valleys because of damming by the continental ice sheets4 ,illustration3 ,figure #bd4--,u-shaped1 glaciated valley of ,big ,timber ,creek1 ,crazy ,mountains1 ,mont4 ,photograph by ,w4 ,c4 ,alden1 #aiba1 ,u4 ,s4 ,geological ,survey4 ,west of the ,black ,hills1 in ,wyoming1 the ,tongue ,river and the ,powder ,river have excavated the ,powder ,river ,basin and produced similar features 7fig4 #be74 ,the east-flowing tributaries of the ,missouri ,river--the ,knife1 ,heart1 and ,cannonball ,rivers in ,north ,dakota and the ,grand1 ,moreau1 ,belle ,fourche1 ,cheyenne1 ,bad1 and ,white ,rivers in ,south ,dakota--similarly have shaped the landscape4 ,most of these rivers flow in broad1 old valleys1 established more than #b million years ago1 before the first advance of the continental ice sheets4 ,some of these valleys have been widened by recession of the valley walls by badland development4 ,badlands are formed by the cutting action of rivulets and rills flowing down over a steeply sloping face of soft1 fine-grained material composed mainly of clay and silt4 ,the intricate carving by thousands of small streams of water produces the distinctive rounded and gullied terrain we call badlands4 ,badlands ,national ,monument in ,south ,dakota 7fig4 #bf7 has been established in the remarkable badlands terrain cut into the ,white ,river ,group along the north valley wall of the ,white ,river1 and the ,south ,unit of ,theodore ,roosevelt ,national ,memorial ,park is in the colorful badlands of the ,little ,missouri ,river1 formed on the ,fort ,union ,formation 7fig4 #bg74 ,the ,white ,river also has cut a steep scarp along its southern wall that is called the ,pine ,ridge escarpment4 ,this escarpment defines the boundary between the ,missouri ,plateau and the ,high ,plains here4 ,illustration3 ,figure #be4--,view northeast across the ,deckers coal mine and the ,tongue ,river in the ,powder ,river ,basin1 southeastern ,montana4 ,typical terrain of unglaciated ,missouri ,plateau4 ,small mesas with cliffed escarpments on capping layer of resistant sandstone1 such as those in the foreground1 are common4 ,coal mine is about #a mile across4 ,photograph by ,r4 ,b4 ,taylor1 ,u4 ,s4 ,geological ,survey4 ,the landscape of the ,unglaciated ,missouri ,plateau has been determined largely by the action of streams1 but in some areas igneous intrusions and volcanoes have produced small mountain masses that interrupt the plain1 and valley glaciers have modified the valleys in some of these mountains4 ,illustration3 ,figure #bf4--;,badlands in ,badlands ,national ,monument1 ,s4 ,dak4 ,photograph by ,w4 ,h4 ,raymond1 ,,iii1 ,u4 ,s4 ,geological ,survey4 ,illustration3 ,figure #bg4--;,badlands of the ,little ,missouri ,river in ,south ,unit of ,theodore ,roosevelt ,national ,memorial ,park1 ,n4 ,dak4 ,view looking northwest from ,painted ,canyon ,overlook along ,interstate ,highway #id1 west of ,belfield4 ,,the ,,colorado ,,piedmont ,the ,colorado ,piedmont lies at the eastern foot of the ,rockies1 7fig4 #a7 largely between the ,south ,platte ,river and the ,arkansas ,river4 ,the ,south ,platte on the north and the ,arkansas ,river on the south1 after leaving the mountains1 have excavated deeply into the ,tertiary 7#fe- to #b-million-year-old7 sedimentary rock layers of the ,great ,plains in ,colorado and removed great volumes of sediment4 ,at ,denver1 the ,south ,platte ,river has cut downward #a1ejj to #b1jjj feet to its present level4 ,three well-formed terrace levels flank the river's floodplain1 and remnants of a number of well-formed higher land surfaces are preserved between the river and the mountains4 ,along the western margin of the ,colorado ,piedmont1 the layers of older sedimentary rock have been sharply upturned by the rise of the mountains4 ,the eroded edges of these upturned layers have been eroded differentially1 so that the hard sandstone and limestone layers form conspicuous and continuous hogback ridges 7fig4 #bh74 ,north of the ,south ,platte ,river1 near the ,wyoming border1 a scarp that has been cut on the rocks of the ,high ,plains marks the northern boundary of the ,colorado ,piedmont4 ,pawnee ,buttes 7fig4 #bi7 are two of many butte outliers of the ,high ,plains rocks near that scarp1 separated from the ,high ,plains by erosion as is ,scotts ,bluff1 farther north in ,nebraska4 ,to the east1 about #aj miles northwest of ,limon1 ,colo41 ,cedar ,point forms a west-jutting prow of the ,high ,plains4 ,the ,arkansas ,river similarly has excavated much of the ,tertiary piedmont deposits and cut deeply into the older ,cretaceous marine rocks between ,canon ,city and the ,kansas border4 ,the upturned layers along the mountain front1 marked by hogback ridges and intervening valleys1 continue nearly uninterrupted around the south end of the ,front ,range into the embayment in the mountains at ,canon ,city4 ,skyline ,drive1 a scenic drive at ,canon ,city1 follows the crest of the ,dakota hogback for a short distance and provides a fine panorama of the ,canon ,city embayment4 ,illustration3 ,figure #bh4--;,hogback ridges along the ,front ,range west of ,denver1 ,colo4 ,south ,platte ,river emerges from the mountains and cuts through hogbacks in middle distance4 ,photograph courtesy of ,eugene ,shearer1 ,intrasearch1 ,inc4 ,extending eastward from the mountain front at ,palmer ,lake1 a high divide separates the drainage of the ,south ,platte ,river from that of the ,arkansas ,river4 ,the crest of the divide north of ,colorado ,springs is generally between #g1djj and #g1fjj feet in altitude1 but ,interstate ,highway #be crosses it at about #g1cej feet1 nearly #a1ejj feet higher than ,colorado ,springs and more than #b1jjj feet higher than ,denver4 ,from the crest of the divide to north of ,castle ,rock1 resistant ,oligocene ,castle ,rock ,conglomerate 7which is equivalent to part of the ,white ,river ,group of the ,high ,plains7 is preserved in many places and forms a protective caprock on mesas and buttes4 ,this picturesque part of the ,colorado ,piedmont looks quite different from the excavated valleys of the ,south ,platte and ,arkansas ,rivers4 ,much of the terrain in the two river valleys has been smoothed by a nearly continuous mantle of windblown sand and silt4 ,northwesterly winds1 which frequently blow with near-hurricane velocities1 have whipped fine material from the floodplains of the streams and spread it eastward and southeastward over much of the ,colorado ,piedmont4 ,well-formed dunes are not common1 but alined gentle ridges of sand and silt and abundant shallow blowout depressions inform us of the windblown origin of this cover4 ,illustration3 ,figure #bi4--,pawnee ,buttes in northeastern ,colorado4 ,buttes isolated by erosion from ,high ,plains in the background4 ,ogallala ,formation caps top of ,buttes4 ,white ,river ,group forms lower part4 ,the top of the highest butte is about #bdj feet above the saddle between the two buttes4 ,photograph by ,r4 ,d4 ,miller1 ,u4 ,s4 ,geological ,survey4 ,in the ,colorado ,piedmont1 then1 the erosional effects of streams are the most conspicuous features of the landscape1 but these are enhanced by the steep tilting of the layered rocks along the western margin as a result of earth movement and modified by the nearly ubiquitous products of wind action1 which have softened the landscape with a widespread cover of windblown sand and silt4 ,,pecos ,,valley ,south of the land of volcanic rocks that is the ,raton section1 the ,pecos ,river has cut a broad valley from the ,sangre de ,cristo ,mountains1 in ,new ,mexico1 southward to the ,rio ,grande1 and has removed the piedmont cover of ,ogallala ,formation and cut deeply into the underlying rocks4 ,the ,ogallala ,formation capping the ,high ,plains to the east forms a rimrock at the top of the sharp ,mescalero escarpment1 which is the eastern boundary of the ,pecos ,valley4 7,see figure #d47 ,the western boundary of the ,pecos ,valley is the eastern base of discontinuous mountain ranges4 ,the great thickness of ,tertiary deposits that formed on the northern ,great ,plains did not accumulate here1 and the ,pecos ,river has cut its valley into the older marine sedimentary rocks4 ,the rocks underlying the surface of much of the ,pecos ,valley are upper ,paleozoic limestones4 ,the soluble nature of limestone is responsible for some of the most spectacular features of the landscape in the ,pecos ,valley4 ,for about #aj miles north and #ej miles south of ,vaughn1 ,n4 ,mex41 collapsed solution caverns in upper ,paleozoic limestones have produced an unusual type of topography called karst4 ,karst topography is typified by numerous closely spaced sinks or closed depressions1 some of which are very deep holes1 caused by the collapse of the roof of a cave or solution cavity into the underground void1 leaving hills1 spines1 or hummocks at the top of the intervening walls or ribs separating the depressions4 ,although the karst in the vicinity of ,vaughn is perhaps the most conspicuous solution phenomenon1 sinks and caves are common throughout the ,pecos ,valley4 ,at ,bottomless ,lakes ,state ,park east of ,roswell1 ,n4 ,mex41 seven lakes occupy large sinkholes caused by the solution of salt and gypsum in underlying rocks4 ,the most spectacular example of solution of limestone by ground water is ,carlsbad ,caverns1 ,n4 ,mex41 one of the most beautiful caves in the world4 ,this celebrated solution cavity is preserved in a national park4 ,the ,pecos ,river along much of its present course flows in a vertical-walled canyon with limestone rims4 ,the ,canadian ,river1 flowing eastward from the ,sangre de ,cristo ,mountains1 has cut a deep canyon along the northern part of the ,pecos ,valley section4 ,the sharp rims of the ,dakota ,sandstone at the ,canadian escarpment1 north of the ,canadian ,river1 form the northern boundary of the ,pecos ,valley section4 ,the sharp1 northeast-trending broken flexure called the ,border ,hills that is crossed by ,u4 ,s4 ,highway #gj-chj about #bj miles west of ,roswell is a unique landform of the ,pecos ,valley4 ,this markedly linear upfolded 7anticlinal7 structure forms a ridge more than #cj miles long and about #bjj feet high4 ,as in the ,colorado ,plateau1 windblown sand and silt mantle the landscape in many places1 but the greatest accumulations are along the base of the ,mescalero escarpment at the northeast and southeast corners of the ,pecos ,valley section4 ,east of the ,pecos ,river1 in the southeast part of the ,pecos ,valley1 the underlying rocks have yielded much oil and potash4 ,oil fields are common east of ,artesia and ,carlsbad1 and potash is mined east of ,carlsbad4 ,the ,pecos and ,canadian ,rivers and their tributaries have created the general outline of the landscape of the ,pecos ,valley1 but underground solution of limestone by ground water and the collapse of roofs of these cavities have contributed much detail to the surface that characterizes the ,pecos ,valley today4 ,,edwards ,,plateau ,south of the ,pecos ,valley section1 the ,pecos ,river continues its journey to the ,rio ,grande in a steep-walled canyon cut #djj to #ejj feet below the level of a plateau surface of ,cretaceous limestone from which little has been stripped except a thin ,tertiary cover of ,ogallala ,formation 7fig4 #cj74 ,to the east1 the plateau has been similarly incised by the ,devils ,river and the ,west ,nueces and ,nueces ,rivers4 ,east of the ,nueces to the escarpment formed by the ,balcones fault zone1 the southern part of the ,edwards ,plateau has been intricately dissected by the ,frio1 ,sabinal1 ,medina1 ,guadalupe1 and ,pedernales ,rivers and their tributary systems4 ,san ,antonio and ,austin1 ,tex41 are located on the ,coastal ,plain at the edge of the ,balcones fault zone4 ,illustration3 ,figure #cj4--,rio ,grande and the flat-lying limestone layers of the ,edwards ,plateau downstream from the mouth of the ,pecos ,river4 ,mexico on the left side of picture4 ,photograph by ,v4 ,l4 ,freeman1 ,u4 ,s4 ,geological ,survey4 ,the ,pecos ,river1 and to a lesser extent the ,devils and ,nueces ,rivers1 particularly in their lower courses1 have entrenched themselves deeply in the plateau in remarkable meandering courses of a type that is usually found only in broad1 low-lying floodplains4 ,these stream courses reflect the stream environment prior to regional uplift4 ,sinkholes pit the relatively undissected limestone plateau surface in the northeast part of the ,edwards ,plateau1 and some underground solution cavities in the limestone are well-known caves1 such as the ,caverns of ,sonora1 southwest of ,sonora1 ,tex4 ,oil and gas fields are widely developed in the northern part of the ,edwards ,plateau1 but only cattle ranches are found in the bare southern part4 ,ancient oceans deposited the limestones that now cap the ,edwards ,plateau2 streams planed off the surface of the flat-lying limestone layers and entrenched themselves in steep-walled valleys2 and ground water dissolved the limestone and created the solution cavities that are the caves and sinks of the ,edwards ,plateau4 ,water has created this landscape4 ,,plains ,,border ,,section ,the ,missouri ,plateau1 the ,colorado ,piedmont1 the ,pecos ,valley1 and the ,edwards ,plateau all were outlined by streams that flowed from the mountains4 ,on the eastern border of the ,great ,plains1 however1 headward cutting by streams that have their source areas in the ,high ,plains has dissected a large area1 mainly in ,kansas4 ,this ,plains ,border ,section comprises a number of east-trending river valleys--of the ,republican1 ,solomon1 ,saline1 ,smoky ,hill1 ,arkansas1 ,medicine ,lodge1 ,cimarron1 and ,north ,canadian ,rivers--and interstream divides1 most of which are intricately dissected4 ,north of the ,arkansas ,river1 the east-flowing ,republican1 ,solomon1 ,saline1 and ,smoky ,hill ,rivers have incised themselves a few hundred feet below the ,tertiary ,high ,plains surface and have developed systems of closely spaced tributary draws4 ,the interstream divides are narrow1 and the tributary heads nearly meet at the divides4 ,this intricately dissected part of the ,plains ,border section is called the ,smoky ,hills4 ,some isolated buttes of ,cretaceous rocks left in the upper valley of the ,smoky ,hill ,river are called the ,monument ,rocks4 ,a large area of rounded boulders exposed by erosion south of the ,solomon ,river1 southwest of ,minneapolis1 ,kans41 is called 8,rock ,city40 ,these boulders originated as resistant nodules 7concretions7 within the ,cretaceous rocks that contained them4 ,south of the ,arkansas ,river is a broad1 nearly flat upland sometimes referred to as the ,great ,bend ,plains4 ,the ,medicine ,lodge ,river has cut headward into the southeastern part of the ,great ,bend ,plains and created a thoroughly dissected topography in ,triassic red rocks that is locally called the ,red ,hills4 ,in a few places1 badlands have formed in the ,red ,hills4 ,some large sinks or collapse depressions have formed because of solution of salt and gypsum at depth by ground water4 ,big and ,little ,basins1 in ,clark ,county in south-central ,kansas1 were formed in this way4 ,sand dunes have accumulated in places1 especially near stream valleys4 ,dunes are common1 for example1 along the north side of the ,north ,canadian ,river4 ,oil and gas fields are widely developed in the southeast part of the ,plains ,border section--in the ,smoky ,hills1 the ,great ,bend ,plains1 and the ,red ,hills4 ,the ,plains ,border section1 like the ,missouri ,plateau1 the ,colorado ,piedmont1 and the ,pecos ,valley1 is primarily a product of stream dissection4 ,the differences in the outstanding landforms of the section are mainly the result of differences in the hardness of the eroded rocks4 ,,epilogue ,the ,great ,plains1 as we have seen1 is many things4 ,it contains thick layers of rock that formed in oceans1 and younger layers of rocks deposited by streams4 ,these rocks have been affected by earth movements and injected by hot molten rock1 some of which reached the surface as volcanic rock4 ,the rocks have been carved by streams1 dissolved by ground water1 partly covered by glaciers1 and blown by winds4 ,all of these agents have played important roles in determining the landscape and the landforms of the ,great ,plains4 ,but the streams were the master agent4 ,they formed the great depositional plain that was to become the ,great ,plains1 and then began to destroy it--leaving only the ,high ,plains to remind us of what it was4 ,those long miles we travel across the ,high ,plains are a journey through history--geologic history4 ,,acknowledgments ,this narrative history of geologic and biologic events in the ,great ,plains had its origin in a study intended to identify potential ,national ,natural ,landmarks in the ,great ,plains1 commissioned by the ,national ,park ,service4 ,william ,a4 ,cobban1 ,g4 ,edward ,lewis1 and ,reuben ,j4 ,ross of the ,u4 ,s4 ,geological ,survey were collaborators in that study1 and some of their contributions to the history of life on the ,great ,plains have been incorporated into this narrative1 which was undertaken at the urging of ,wallace ,r4 ,hansen4 ,the photographic illustrations1 other than those obtained from the film library of the ,u4 ,s4 ,geological ,survey1 were provided by the interest and effort of my friends and colleagues of the ,geological ,survey--including ,c4 ,r4 ,dunrud1 ,v4 ,l4 ,freeman1 ,c4 ,d4 ,miller1 ,r4 ,d4 ,miller1 ,f4 ,w4 ,osterwald1 ,r4 ,l4 ,parker1 ,w4 ,h4 ,raymond1 ,,iii1 ,kenneth ,shaver1 and ,r4 ,b4 ,taylor--and by ,eugene ,shearer1 ,intrasearch1 ,inc41 ,denver1 ,colo4 ,without their help this publication would not have been possible4 ,,some ,,source ,,references ,alden1 ,w4 ,c41 #aicb1 ,physiography and glacial geology of eastern ,montana and adjacent areas3 ,u4 ,s4 ,geological ,survey ,professional ,paper #agd1 #acc p4 ,bluemle1 ,j4 ,p41 #aigg1 ,the face of ,north ,dakota--the geologic story3 ,north ,dakota ,geological ,survey ,education ,series #aa1 #gc p4 ,colton1 ,r4 ,b41 ,lemke1 ,r4 ,w41 and ,lindvall1 ,r4 ,m41 #aifa1 ,glacial map of ,montana east of the ,rocky ,mountains3 ,u4 ,s4 ,geological ,survey ,miscellaneous ,geologic ,investigations ,map ,i-#cbg4 ,colton1 ,r4 ,b41 ,lemke1 ,r4 ,w41 and ,lindvall1 ,r4 ,m41 #aifc1 ,preliminary glacial map of ,north ,dakota3 ,u4 ,s4 ,geological ,survey ,miscellaneous ,geologic ,investigations ,map ,i-#cca4 ,curtis1 ,b4 ,f41 ed41 #aige1 ,cenozoic history of the southern ,rocky ,mountains--,papers deriving from a symposium presented at the ,rocky ,mountain ,section meeting of the ,geological ,society of ,america1 ,boulder1 ,colorado1 #aigc3 ,geological ,society of ,america ,memoir #add1 #bgi p4 ,darton1 ,n4 ,h41 #aije1 ,preliminary report on the geology and underground water resources of the central ,great ,plains3 ,u4 ,s4 ,geological ,survey ,professional ,paper #cb1 #dcc p4 ,flint1 ,r4 ,f41 #aiee1 ,pleistocene geology of eastern ,south ,dakota3 ,u4 ,s4 ,geological ,survey ,professional ,paper #bfb1 #agc p4 ,frye1 ,j4 ,c41 and ,leonard1 ,a4 ,b41 #aife1 ,quaternary of the southern ,great ,plains1 in ,wright1 ,h4 ,e41 ,jr41 and ,frey1 ,d4 ,g41 eds41 ,the ,quaternary of the ,united ,states--,a review volume for the #gth ,congress of the ,international ,association for ,quaternary ,research3 ,princeton ,university ,press1 p4 #bjc-baf4 ,howard1 ,a4 ,d41 #aieh1 ,drainage evolution in northeastern ,montana and northwestern ,north ,dakota3 ,geological ,society of ,america ,bulletin1 v4 #fi1 no4 #e1 p4 #ege-ehh4 ,johnson1 ,r4 ,b41 #aifa1 ,patterns and origin of radial dike swarms associated with ,west ,spanish ,peak and ,dike ,mountain1 south-central ,colorado3 ,geological ,society of ,america ,bulletin1 v4 #gb1 no4 #d1 p4 #egi-eij4 ,judson1 ,s4 ,s41 ,jr41 #aiej1 ,depressions of the northern portion of the southern ,high ,plains of eastern ,new ,mexico3 ,geological ,society of ,america ,bulletin1 v4 #fa1 no4 #c1 p4 #bec-bgd4 ,keech1 ,c4 ,f41 and ,bentall1 ,ray1 #aiga1 ,dunes on the plains--,the ,sand ,hills region of ,nebraska3 ,nebraska ,university ,conservation and ,survey ,division ,resources ,report #d1 #ah p4 ,lemke1 ,r4 ,w41 ,laird1 ,w4 ,m41 ,tipton1 ,m4 ,j41 and ,lindvall1 ,r4 ,m41 #aife1 ,quaternary geology of northern ,great ,plains1 in ,wright1 ,h4 ,e41 ,jr41 and ,frey1 ,d4 ,g41 eds41 ,the ,quaternary of the ,united ,states--,a review volume for the #gth ,congress of the ,international ,association for ,quaternary ,research3 ,princeton ,university ,press1 p4 #ae-bg4 ,mansfield1 ,g4 ,r41 #aijg1 ,glaciation in the ,crazy ,mountains of ,montana3 ,geological ,society of ,america ,bulletin1 v4 #ai1 p4 #eeh-efg4 ,pettyjohn1 ,w4 ,a41 #aiff1 ,eocene paleosol in the northern ,great ,plains1 in ,geological ,survey research #aiff3 ,u4 ,s4 ,geological ,survey ,professional ,paper #eej-;,c1 p4 ,c#fa-;,c#fe4 ,robinson1 ,c4 ,s41 #aief1 ,geology of ,devils ,tower ,national ,monument1 ,wyoming3 ,u4 ,s4 ,geological ,survey ,bulletin #ajba-;,i1 p4 #bhi-cjb4 ,smith1 ,h4 ,t4 ,u41 #aife1 ,dune morphology and chronology in central and western ,nebraska3 ,journal of ,geology1 v4 #gc1 no4 #d1 p4 #eeg-egh4 ,stormer1 ,j4 ,c41 ,jr41 #aigb1 ,ages and nature of volcanic activity on the southern ,high ,plains1 ,new ,mexico and ,colorado3 ,geological ,society of ,america ,bulletin1 v4 #hc1 no4 #h1 p4 #bddc-bddh4 ,strahler1 ,a4 ,n41 and ,strahler1 ,a4 ,h41 #aigh1 ,modern physical geography3 ,new ,york1 ,john ,wiley ,sons1 #ejb p4 ,thornbury1 ,w4 ,d41 #aife1 ,regional geomorphology of the ,united ,states3 ,new ,york1 ,john ,wiley1 #fji p4 ,wright1 ,h4 ,e41 ,jr41 #aigj1 ,vegetational history of the ,central ,plains1 in ,pleistocene and recent environments of the central ,great ,plains3 ,kansas ,university ,department of ,geology ,special ,publication #c1 p4 #aeg-agb4 ,,index ,italic page numbers indicate major references ,a ,page ,acknowledgments #di ,agriculture #cj ,alaska #aa ,anadarko basin #aa1 #af ,arikaree ,formation #ah ,arkansas ,river #b1 #g1 #bc1 #be1 #bi1 #cj1 #db1 #dc1 #dd1 #dh ,artesia1 ,n4 ,mex4 #df ,austin1 ,tex4 #dg ,b ,bad ,river #ci ,badland development #ci ,badlands ,national ,monument #ci ,balcones fault zone #bc1 #df ,basalt flows #bj1 #bd ,bearpaw ,mountains #cc1 #cf ,belle ,fourche ,river #ci ,bents ,fort1 ,colo4 #b ,big ,basin1 ,kans4 #dh ,big ,belt ,mountains #cf ,big ,snowy ,mountains #cf ,bison #a ,black ,hills #g1 #aa1 #ah1 #ai1 #bj1 #cg ,border ,hills #df ,bottomless ,lakes1 ,n4 ,mex4 #de ,brazos ,river #bc ,burnet1 ,tex4 #bc ,c ,camels #af1 #ah ,canada #a1 #e1 #cc ,canadian escarpment #bc1 #df ,canadian ,river #bc1 #bi1 #cj1 #df ,cannonball ,river #cc1 #ce1 #ci ,canon ,city1 ,colo4 #dc ,caprock escarpment #g1 #bi ,capulin ,mountain #bj1 #bc ,carlsbad1 ,n4 ,mex4 #df ,carlsbad ,caverns1 ,n4 ,mex4 #de ,carrizo ,creek #be ,castle ,mountains #cg ,castle ,rock1 ,colo4 #dc ,castle ,rock ,conglomerate #dc ,caverns of ,sonora #dg ,cedar ,point #dc ,central ,lowland #e1 #cd ,central ,texas ,uplift #g1 #ai1 #bj1 #bb ,cheyenne1 ,wyo4 #bg ,cheyenne ,river #ci ,cimarron ,river #dh ,cirques #ch ,clark ,county1 ,kans4 #dh ,climate #b ,coal #af ,coastal ,plain #e1 #g1 #aj1 #dg ,colorado #ai ,colorado ,piedmont #g1 #aj1 #ai1 #bc1 #db1 #dh1 #di ,colorado ,plateau #df ,colorado ,river #bc ,colorado ,springs1 ,colo4 #dc ,coteau du ,missouri #cd1 #ce ,crazy ,mountains #cg ,creosote #a ,cretaceous ,period #aa1 #af1 #ai1 #bd1 #dc1 #df1 #dh ,d ,dakota hogback #dc ,dakota ,sandstone #bb1 #bc1 #bd1 #df ,dawson ,formation #af ,dead-ice moraines #cd ,definition #a ,deformation #aa ,denver1 ,colo4 #db ,denver ,formation #af ,deposition #aj1 #aa1 #cb1 #dd ,devils ,river #df ,devils ,tower1 ,wyo4 #cg ,differential erosion #bc1 #be1 #db ,dikes #be ,dinosaurs #af ,drift #cd ,e ,edwards ,plateau #aj1 #ai1 #bi1 #df1 #dh ,eocene ,epoch #af ,epilogue #di ,erosion #ah ,escarpments #d1 #g1 #bc1 #cd ,eskers #ce ,f ,farming #cj ,fishers ,peak #bc ,fissures #bj ,forests #a1 #b1 #g ,fort ,union ,formation #af1 #dj ,fossils #af ,frio ,river #df ,front ,range #dc ,g ,gangplank #bg ,gas #cj1 #dg1 #di ,glaciation #b1 #e1 #aa1 #cc ,grand ,river #ci ,great ,bend1 ,kans4 #b ,great ,bend ,plains #dh1 #di ,great ,falls1 ,mont4 #cc1 #ce ,great ,ice ,age #e ,great ,lakes #e ,guadalupe ,river #df ,gulf ,coastal ,plain #g ,h ,harney ,peak #bj ,havre1 ,mont4 #cc ,heart ,river #cc1 #ce1 #ci ,hell ,creek ,formation #aa ,high ,plains #g1 #aj1 #be1 #de1 #dh ,highwood ,mountains #cc1 #ce1 #cf ,horses #af1 #ah ,hudson ,bay #cb1 #cc ,i ,ice ,age #e ,independence1 ,mo4 #b ,interior ,highlands #e ,interior ,plains #e1 #aa ,interstate ,highway #be #dc ,interstate ,highway #gj #d ,introduction #a ,j ,jewel ,cave #ba ,joints #bj ,judith ,mountains #cf ,judith ,river #ch ,juniper #a ,k ,kames #ce ,kansas #aj1 #dh ,kansas ,city1 ,mo4 #ce ,karst topography #de ,kearney1 ,nebr4 #b ,king ,mountain #bi ,knife ,river #cc1 #ce1 #ci ,l ,laccoliths #cg ,lake development #cd1 #ci ,lance ,formation #aa ,laramie ,formation #af ,lava flows #cg ,lewis and ,clark expedition #b ,limestone ,plateau #ba1 #bb ,limon1 ,colo4 #d1 #dc ,little ,basin1 ,kans4 #dh ,little ,belt ,mountains #cf ,little ,missouri ,river #cc1 #ce1 #ch1 #dj ,little ,rocky ,mountains #cc1 #cf ,littlefield1 ,tex4 #cj ,llano ,estacado #bi1 #cj ,loess #bi ,longhorn ,caverns #bc ,m ,marias ,river #cc ,mc,camey1 ,tex4 #bi ,medicine ,lodge ,river #dh ,medina ,river #df ,mesa de ,maya #bj1 #bd1 #be ,mescalero escarpment #g1 #bi1 #de1 #df ,mesquite #a ,mexico #a1 #aa ,milk ,river #cc ,minneapolis1 ,kans4 #dh ,miocene ,epoch #bc ,missouri escarpment #cd ,missouri ,plateau #g1 #ai1 #bj1 #cb1 #dh1 #di ,missouri ,river #e1 #g1 #be1 #cb1 #cc1 #ce1 #ch ,montana #cc ,monument ,rocks #dh ,moraines #cd ,moreau ,river #ci ,moropus #ah ,mount ,rushmore #bj ,musselshell ,river #ch ,n ,nebraska #g1 #bi ,nebraska ,sand ,hills #bi ,needles area1 ,black ,hills #bj ,new ,mexico #g1 #ai1 #de ,north ,canadian ,river #dh1 #di ,north ,dakota #cc1 #cd1 #ce ,nueces ,river #df ,nunataks #cc ,o ,oak trees #a ,odessa1 ,tex4 #cj ,ogallala ,formation #ah1 #bc1 #bd1 #be1 #bg1 #bi1 #de1 #df ,ohio ,river #e ,oil #cj1 #df1 #dg1 #di ,oklahoma #g ,oligocene ,epoch #af1 #dc ,oregon ,trail #b ,ouachita province #e ,outwash plains #ce ,ozark ,plateaus #e ,p ,paleocene ,epoch #af1 #bc ,paleozoic ,era #ba1 #cj1 #de ,palmer ,lake #dc ,pampa1 ,tex4 #cj ,pawnee ,buttes #db ,pecos ,river #g1 #be1 #de1 #df ,pecos ,valley #g1 #aj1 #ai1 #bc1 #de1 #dh1 #di ,pedernales ,river #dg ,pike1 ,zebulon iii1 #b ,pine ,ridge escarpment #g1 #bi1 #dj ,pioneers #b ,plains ,border ,section #ai1 #dh ,platte ,river #b1 #be1 #bi ,pleistocene ,epoch #e ,poison ,canyon ,formation #af1 #bc1 #bd ,powder ,river #ci ,powder ,river ,basin #ci ,purgatoire ,formation #bd ,purgatoire ,river #be ,r ,racetrack1 ,the #bb ,rainfall #b ,rapid ,city1 ,s4 ,dak4 #bj ,raton ,basin #bd ,raton ,formation #af ,raton ,mesa #bj1 #bc ,raton section #aj1 #bj1 #bc1 #de ,red ,hills #dh1 #di ,red ,valley #bb ,republican ,river #d1 #bi1 #dh ,rhinoceroses #af1 #ah ,rio ,grande #g1 #de ,rocky ,mountains #e1 #ai ,roswell1 ,n4 ,mex4 #de ,s ,sabinal ,river #df ,salina1 ,kans4 #d ,saline ,river #d1 #dh ,san ,antonio1 ,tex4 #dg ,sand dunes #dd1 #di ,sand ,hills1 ,nebr4 #bi ,sangre de ,cristo ,mountains #g1 #de1 #df ,scotts ,bluff ,national ,monument #bg1 #db ,sedimentation #aj1 #aa1 #cb ,shonkin ,sag #ce ,sinkholes #dg1 #dh ,skyline ,drive1 ,canon ,city1 ,colo4 #dc ,smith ,river #ch ,smoky ,hill ,river #d1 #dh ,smoky ,hills #dh1 #di ,soil development #af ,solomon ,river #d1 #dh ,solution cavities #de1 #dg1 #dh ,sonora1 ,tex4 #dg ,south ,dakota #bj1 #bi1 #cc1 #cd ,south ,dakota ,badlands #af ,south ,platte ,river #d1 #g1 #db1 #dc1 #dd ,spanish ,peaks #ai1 #bd ,spruce trees #b ,stream deposition #aa1 #cb ,summary #di ,sun ,river #ch ,superior ,upland #e1 #aj ,sweetgrass ,hills #cc ,sylvan ,lake #bj ,t ,tapirs #af ,tertiary ,period #db1 #dc1 #de1 #df1 #dh ,teton ,river #cc ,texas #g ,theodore ,roosevelt ,national ,memorial ,park #ce1 #dj ,till #cd ,titanotheres #af ,tongue ,river #ci ,trails #b ,trees #a1 #b1 #g ,triassic ,period #ba ,triceratops #af ,trinidad1 ,colo4 #be ,u ,uplift #aa1 #af1 #ai1 #cb1 #cg ,v ,valley development #ci ,vaughn1 ,n4 ,mex4 #de ,vegetation #a1 #b1 #g1 #aj1 #af ,vermejo ,formation #af ,volcanoes #af1 #bj1 #dj ,w ,walsenburg1 ,colo4 #bd ,warping #aa ,well-drilling #aa ,west ,nueces ,river #df ,white ,river #bi1 #ci1 #dj ,white ,river ,group #af1 #dj1 #dd ,williston basin #aa1 #af1 #cc ,wind ,cave #ba ,wind deposition #dd ,wyoming #bj1 #ci ,y ,yellowstone ,river #cc1 #ch ,illustration3 ,u4 ,s4 ,,department ,,of ,,the ,,interior ,march #c1 #ahdi ,transcriber's ,notes --,retained publication information from the printed edition3 this e,book is public-domain in the country of publication4 --,in the text versions only1 text in italics is delimited by underscores4