,illustration3 ,eunice ,lake1 northwest of ,mount ,rainier4 ,the lake lies in a small bedrock basin that was scoured out by a glacier between about #ae1jjj and #bj1jjj years ago4 ,the rounded green slopes at the far edge of the lake are underlain by rock that has been smoothed and grooved by glacier ice4 ,this side of ,mount ,rainier rises to ,liberty ,cap1 which hides the true summit of the volcano4 ,the ,geologic ,story of ,mount ,rainier ,by ,dwight ,r4 ,crandell ,a look at the geologic past of one of ,america's most scenic volcanoes ,,geological ,,survey ,,bulletin #abib ,,united ,,states ,,department ,,of ,,the ,,interior ,,walter ,j4 ,,hickel1 ,secretary ,,geological ,,survey ,william ,t4 ,pecora1 ,director ,library of ,congress ,catalog-,card ,no4 #gi-fjagjd ,u4,s4 ,,government ,,printing ,,office3 #aifi ,for sale by the ,superintendent of ,documents1 ,u4,s4 ,government ,printing ,office ,washington1 ,d4,c4 #bjdjb--,price #fe cents 7paper cover7 contents ,page ,the changing landscape of #ab-fj million years ago #c ,thumbnail biography of ,mount ,rainier #aa ,results of recent eruptions #ab ,why glaciers8 #bc ,work habits of glaciers #be ,yesterday's glaciers #bi ,landslides and mudflows--past1 present1 and future #ce ,the volcano's future8 #db ,further reading in geology #dc ,frontispiece4 ,eunice ,lake1 northwest of ,mount ,rainier4 ,figure ,page #a4 ,outcrop of sandstone and shale in the ,puget ,group #f #b4 ,outcrop of welded tuff in the ,stevens ,ridge ,formation #h #c4 ,granodiorite looks like granite #i #d4 ,geological cross section of ,mount ,rainier #aj #e4 ,an old lava flow which forms ,rampart ,ridge #ac #f4 ,columns of andesite at the end of an old lava flow #ac #g4 ,layers of pumice on the floor of a cirque #ad #h4 ,generalized distribution of some pumice layers #af #i4 ,breadcrust bomb enclosed in a mudflow deposit #ai #aj4 ,pumice layer ,c1 which consists of light-brown fragments #bj #aa4 ,the recent lava cone lies in a depression #ba #ab4 ,two ice streams meet to form ,cowlitz ,glacier #bc #ac4 ,glacier-smoothed and grooved rock #bf #ad4 ,a lake lies behind an end moraine of ,flett ,glacier #bg #ae4 ,recessional moraines on the valley floor of ,fryingpan ,creek #bh #af4 ,extent of glaciers between #ae1jjj and #be1jjj years ago #cj #ag4 ,lateral moraine at ,ricksecker ,point #ca #ah4 ,rock-glacier deposit at ,the ,palisades #cc #ai4 ,hummocky end moraine in front of ,emmons ,glacier #cd #bj4 ,avalanche deposits in the ,white ,river valley #cg #ba4 ,the northeast flank of ,mount ,rainier #ci ,table #a4 ,characteristics1 sources1 and ages of pumice layers1 ,mount ,rainier ,national ,park #ag #b4 ,summary of important geologic events in the history of ,mount ,rainier ,national ,park #da ,the ,geologic ,story of ,mount ,rainier ,by ,dwight ,r4 ,crandell ,illustration3 ,map of ,cascade ,range ,,washington ,seattle ,tacoma ,,cascade ,,range ,mount ,rainier ,mount ,adams ,mount ,st ,helens ,,oregon ,portland ,mount ,hood ,crater ,lake ,ice-clad ,mount ,rainier1 towering over the landscape of western ,washington1 ranks with ,fuji-yama in ,japan1 ,popocatepetl in ,mexico1 and ,vesuvius in ,italy among the great volcanoes of the world4 ,at ,mount ,rainier1 as at other inactive volcanoes1 the ever-present possibility of renewed eruptions gives viewers a sense of anticipation1 excitement1 and apprehension not equaled by most other mountains4 ,even so1 many of us cannot imagine the cataclysmic scale of the eruptions that were responsible for building the giant cone which now stands in silence4 ,we accept the volcano as if it had always been there1 and we appreciate only the beauty of its stark expanses of rock and ice1 its flower-strewn alpine meadows1 and its bordering evergreen forests4 ,mount ,rainier owes its scenic beauty to many features4 ,the broad cone spreads out on top of a major mountain range--the ,cascades4 ,the volcano rises about #g1jjj feet above its #g1jjj-;foot foundation1 and stands in solitary splendor--the highest peak in the entire ,cascade ,range4 ,its rocky ice-mantled slopes above timberline contrast with the dense green forests and give ,mount ,rainier the appearance of an arctic island in a temperate sea1 an island so large that you can see its full size and shape only from the air4 ,the mountain is highly photogenic because of the contrasts it offers among bare rock1 snowfields1 blue sky1 and the incomparable flower fields that color its lower slopes4 ,shadows cast by the multitude of cliffs1 ridges1 canyons1 and pinnacles change constantly from sunrise to sunset1 endlessly varying the texture and mood of the mountain4 ,the face of the mountain also varies from day to day as its broad snowfields melt during the summer4 ,the melting of these frozen reservoirs makes ,mount ,rainier a natural resource in a practical as well as in an esthetic sense1 for it ensures steady flows of water for hydroelectric power in the region1 regardless of season4 ,seen from the ,puget ,sound country to the west1 ,mount ,rainier has an unreal quality--its white summit1 nearly #c miles high1 seems to float among the clouds4 ,we share with the populace of the entire lowland a thrill as we watch skyward the evening's setting sun redden the volcano's western snowfields4 ,when you approach the mountain in its lovely setting1 you may find something that appeals especially to you--the scenery1 the wildlife1 the glaciers1 or the wildflowers4 ,or you may feel challenged to climb to the summit4 ,mount ,rainier and its neighboring mountains have a special allure for a geologist because he visualizes the events--some ordinary1 some truly spectacular--that made the present landscape4 ,such is the fascination of geology4 ,a geologist becomes trained to see 8in his mind's eye0 geologic events of thousands or even millions of years ago4 ,and1 most remarkable1 he can 8see0 these events by studying rocks in a cliff or roadcut1 or perhaps by examining earthy material that looks like common soil beneath pastureland many miles away from the volcano4 ,our key to understanding the geology of ,mount ,rainier is that each geologic event can be reconstructed--or imagined--from the rocks formed at the time of the event4 ,with this principle as our guide1 we will review the geologic ancestry of this majestic volcano and learn what is behind its scenery4 ,the ,changing ,landscape of #ab-fj ,million ,years ,ago ,the rocks of the ,cascade ,range provide a record of earth history that started nearly #fj million years ago4 ,even then1 as today1 waves pounded on beaches and rivers ran to the sea1 molding and distributing material that formed some of the rocks we now see in the park4 ,you may find it difficult to imagine the different landscape of that far distant time4 ,there was no ,mount ,rainier nor ,cascade mountain range4 ,in fact1 there was very little dry land in the area we call western ,washington4 ,instead1 this was a broad lowland of swamps1 deltas1 and inlets that bordered the ,pacific ,ocean4 ,rivers draining into this lowland from the east spread sand and clay on the lush swamp growth4 ,other plants grew on the deposits1 and they were covered1 in turn1 by more sand and clay4 ,in this way1 thousands of feet of sand and clay and peat accumulated and were compacted into sandstone1 shale1 and coal4 ,we can see some of the rocks formed at that time in cuts along the ,mowich ,lake ,road west of the park 7fig4 #a74 ,seams of coal were mined at ,carbonado and ,wilkeson1 #aj miles northwest of the park1 during the late #aith and the early #bjth centuries4 ,these beds of sandstone1 shale1 and coal make up a sequence of rocks called the ,puget ,group1 which is #aj1jjj feet thick4 ,wave-ripple marks and remains of plants show that the rocks were formed in shallow water fairly close to sea level4 ,how could the rocks have piled up to this great thickness8 ,the coastal plain and adjacent basin must have been slowly sinking1 and the influx of sand and clay must have just barely kept pace with the downward movements4 ,illustration3 ,mount ,rainier ,a little less than #dj million years ago1 the western ,washington landscape changed dramatically4 ,geologists ,r4 ,s4 ,fiske1 ,c4 ,a4 ,hopson1 and ,a4 ,c4 ,waters have discovered that volcanoes then rose on the former coastal plain at the site of ,mount ,rainier ,national ,park and became islands as the area sank beneath the sea4 ,when molten rock was erupted underwater from the submerged flanks of these volcanoes1 steam explosions shattered the lava into countless fragments4 ,the resulting debris1 mixed with water1 flowed as mud across great areas of the submerged basin floor4 ,illustration3 ,outcrop of gray to brown sandstone and dark-gray to black coaly shale in the ,puget ,group along the ,mowich ,lake ,road4 7,fig4 #a7 ,you can see rocks formed from these layers of volcanic mud and sand in cuts along the highway on the east side of ,backbone ,ridge and between ,cayuse ,pass and ,tipsoo ,lake4 ,look there for alternating beds of grayish-green sandstone and breccia1 a concretelike rock in which the pebbles have sharp corners4 ,these rocks are known as the ,ohanapecosh ,formation4 ,like the ,puget ,group1 the ,ohanapecosh ,formation is at least #aj1jjj feet thick4 ,yet1 nearly all of it accumulated in shallow water as western ,washington continued to sink slowly during the volcanic eruptions4 ,the long-continued sinking finally ended after the ,ohanapecosh volcanic activity ceased4 ,western ,washington was then lifted several thousand feet above sea level1 and the ,puget and ,ohanapecosh rocks were slowly compressed into a series of broad shallow folds4 ,before eruptions began again1 rivers cut valleys hundreds of feet deep1 and weathering of the rocks produced thick red clayey soils similar to those that are forming in some areas of high rainfall and high temperature today4 ,look for the red rocks formed from these old soils in roadcuts as you drive along the ,stevens ,canyon road about #b miles southeast of ,box ,canyon4 ,the next volcanic eruptions1 which may have begun between #be and #cj million years ago1 differed from those of ,ohanapecosh time4 ,these volcanoes1 somewhere beyond the boundaries of the park1 erupted great flows of hot pumice that1 being highly mobile1 rushed down the flanks of the volcanoes and spread over many square miles of the adjacent regions4 ,the pumice flows were 8lubricated0 by hot volcanic gas emitted from inside each pumice particle1 which buffered it from other particles4 ,some hot pumice flows were #cej feet deep4 ,the heat still remaining in the pumice after it stopped flowing partly melted the particles to form a hard rock known as welded tuff4 ,repeated pumice flows buried the hilly landscape and eventually formed a vast volcanic plain4 ,the rocks1 which are mostly welded tuffs1 are now the ,stevens ,ridge ,formation1 which you can see along the highway in ,stevens ,canyon #a-b miles west of ,box ,canyon4 ,you can recognize the welded tuff by its light-gray to white color and its many flattened and sharp-edged inclusions of darker gray pumice 7fig4 #b74 ,another period of volcanism followed1 of still a different kind1 when lava flowed outward from broad low volcanoes4 ,the flows were of two kinds3 basalt1 the kind now erupted by ,hawaiian volcanoes1 and andesite1 the type erupted by ,mount ,rainier4 ,individual flows #ej-ejj feet thick were stacked on top of one another to a total depth of fully #b1ejj feet4 ,we know these rocks as the ,fifes ,peak ,formation4 ,they form many of the cliffs and peaks in the northwestern part of the park4 ,you can examine them in cuts along the ,mowich ,lake ,road between ,mountain ,meadows and ,mowich ,lake4 ,the time of the eruption of the ,fifes ,peak lavas may have been between #bj and #cj million years ago4 ,when the ,fifes ,peak volcanoes finally became extinct1 this part of western ,washington changed again4 ,the rocks once more were uplifted and compressed into broad folds parallel to those formed at the end of ,ohanapecosh time4 ,the rocks buckled and1 in places1 broke and shifted thousands of feet along great fractures1 or faults4 ,illustration3 ,outcrop of light-gray welded tuff in the ,stevens ,ridge ,formation along the road in ,stevens ,canyon4 ,the angular dark-gray fragments in the welded tuff are chunks of pumice4 7,fig4 #b7 ,about #ab million years ago one or more masses of molten rock1 many miles across1 pushed upward through the ,puget ,group and younger rocks4 ,when this molten rock cooled and hardened1 it formed granodiorite1 a close relative of granite4 ,although most of the molten rock solidified underground1 some of it reached the land surface and formed volcanoes at a few places within the area of ,mount ,rainier ,national ,park4 ,illustration3 ,granodiorite looks like granite and has a light-gray speckled appearance4 ,the knife is about #c inches long4 7,fig4 #c7 ,granodiorite is probably the most attractive rock in the park4 ,it is mostly white1 but it contains large dark mineral grains that give it a 8salt-and-pepper0 appearance 7fig4 #c74 ,the large size of the grains is a result of the molten rock cooling slowly at a considerable depth below the land surface--the individual minerals had a long time to grow before the 8melt0 solidified into rock4 ,in contrast1 the rocks formed from lavas that flowed onto the ground surface are generally fine grained because the lavas cooled too quickly for the mineral grains to grow appreciably4 ,granodiorite underlies the ,white ,river valley1 the ,carbon ,river valley1 and parts of the upper ,nisqually ,river valley and the ,tatoosh ,range4 ,you can see it in roadcuts between ,longmire and ,christine ,falls and at several places along the road between ,white ,river ,ranger ,station and ,white ,river campground4 ,illustration3 ,geological cross section of ,mount ,rainier and its foundation rocks from ,mother ,mountain southward to ,tatoosh ,range4 ,true-scale cross section is nearly #ag miles long4 ,slightly modified from ,u4,s4 ,geological ,survey ,professional ,paper #ddd1 ,plate #a4 7,fig4 #d7 ,after the granodiorite solidified1 the foundation of ,mount ,rainier was complete except for one other landscape change that preceded the birth of the volcano4 ,not long after the granodiorite was formed1 the ,cascade mountain range began to rise--not rapidly1 but little by little over many thousands of years4 ,as the land rose1 rivers cut valleys into the growing mountains so that by the time the new volcano began to erupt1 the ,cascades had already been carved into a rugged range of high ridges and peaks separated by deep valleys4 ,deep erosion thus laid bare the rock layers in which we today read the geologic history of the park 7fig4 #d74 ,thumbnail ,biography of ,mount ,rainier ,the life span of a volcano can be compared to that of an individual--after his birth and a brief youth1 he matures and grows old4 ,the birth date of ,mount ,rainier is not known for sure1 but it must have been at least several hundred thousand years ago4 ,we cannot tell much about the volcano's complex youth because most of its earliest deposits are now buried under later ones4 ,at an early age1 well before the cone grew to its present size1 thick lava1 like hot tar1 flowed repeatedly #e-ae miles down the deep canyons of the surrounding mountains4 ,because these lava flows resisted later erosion by rivers and glaciers1 most of them now form ridgetops1 as at ,rampart ,ridge1 ,burroughs ,mountain1 ,grand ,park1 and ,klapatche ,ridge 7figs4 #e and #f74 ,violent explosions occasionally threw pumice onto the slopes of the growing volcano and the surrounding mountains4 ,as the volcano matured1 the long thick flows were succeeded by thinner and shorter ones which1 piled on top of one another1 built the giant cone that now dominates the region4 ,even though ,mount ,rainier has grown old now1 it has revived briefly at many times during the last #aj1jjj years or so and may erupt again in the future4 ,the events of the last #aj1jjj years1 because they are so recent1 in terms of geologic time1 are better known than those of any earlier time1 and we can examine this part of the volcano's history in some detail4 ,we will study three principal subjects3 eruptions--because they have had widespread effects2 glaciers--because they are such conspicuous features on the mountain2 and landslides--because they have drastically changed the volcano's shape4 ,results of ,recent ,eruptions ,while hiking1 you soon become aware that there is a large amount of pumice along the trails in ,mount ,rainier ,national ,park4 ,pumice is a lightweight volcanic rock so full of air spaces that it will float on water4 ,the air spaces1 or bubbles1 originated when fragments of gas-rich lava were explosively thrown into the air above the volcano1 and the molten rock hardened before the gas could escape4 ,if you examine pumice deposits in a trail cut1 in a streambank1 or in the roots of blown-over trees1 you may also note that there is more than one layer 7fig4 #g74 ,if you circle the volcano on the ,wonderland ,trail1 you may notice that the greatest number of pumice layers are on the east side of the park1 but the thickest single layer is on the west side4 ,the explanation lies partly in the source of the pumice deposits1 because some pumice was erupted not by ,mount ,rainier but by other volcanoes in the ,cascade ,range of ,washington and ,oregon and brought to the park by strong southerly or southwesterly winds4 ,the layers of pumice thrown out by ,mount ,rainier within the last #aj1jjj years lie mostly on the east side of the volcano4 ,strong winds evidently swept eruption clouds to the east during the outbursts and prevented the pumice from falling west of the volcano4 ,this pattern of distribution1 coupled with the coarsening and thickening of the pumice toward the volcano1 reveals that the layers were erupted by ,mount ,rainier4 ,illustration3 ,an old lava flow from ,mount ,rainier which forms ,rampart ,ridge west of the meadow at ,longmire4 ,the thick lava flowed down an old valley floor and cooled and solidified4 ,rivers then eroded new valleys along both sides of the flow4 ,these new valleys1 subsequently glaciated1 are today followed by the ,nisqually ,river and ,kautz ,creek4 ,thus1 the area of a former valley floor is now a ridge4 7,fig4 #e7 ,illustration3 ,columns of dark-gray andesite at the east end of an old lava flow from ,mount ,rainier4 ,this outcrop is near the point at which the highway to ,yakima ,park crosses ,yakima ,creek4 7,fig4 #f7 ,illustration3 ,layers of pumice on the floor of a cirque near ,paradise ,park4 ,the yellow bed at the bottom is layer ,o1 which was erupted by ,mount ,mazama volcano at the site of ,crater ,lake1 ,oregon1 about #f1fjj years ago4 ,the yellowish-brown layer a few inches above layer ,o is layer ,d1 a pumice that was erupted by ,mount ,rainier between #e1hjj and #f1fjj years ago4 ,the light-yellowish-brown pumice bed at the top of the outcrop is layer ,y1 which originated at ,mount ,st4 ,helens volcano between #c1bej and #d1jjj years ago4 ,photograph by ,d4 ,r4 ,mullineaux1 ,u4,s4 ,geological ,survey4 7,fig4 #g7 ,d4 ,r4 ,mullineaux of the ,u4,s4 ,geological ,survey has studied in detail the pumice deposits of ,mount ,rainier ,national ,park4 ,one of his first and most important discoveries was that even though some pumice layers are spread widely over the park1 they were erupted from other volcanoes4 ,strangely enough1 one layer is thicker and more widespread than any recent pumice erupted by ,mount ,rainier4 ,we can clearly see that these foreign pumice layers did not come from ,mount ,rainier1 for they thicken and coarsen southward1 away from the park4 ,the oldest was erupted by ,mount ,mazama volcano at the site of ,crater ,lake1 ,oregon1 about #f1fjj years ago2 this pumice forms a yellowish-orange layer about #b inches thick nearly everywhere in the park4 ,the pumice has a texture like that of sandy flour1 and it feels grainy when rubbed between the fingers4 ,it is so fine grained because of the great distance to its source1 #bej miles due south of ,mount ,rainier4 ,near ,crater ,lake this same pumice consists of large chunks and is many feet thick4 ,two other foreign pumice deposits in the park were erupted by ,mount ,st4 ,helens1 a symmetrical young volcanic cone about #ej miles southwest of ,mount ,rainier4 ,the older of the two is between #c1bej and #d1jjj years old2 it forms a blanket of yellow sand-sized pumice that is as much as #bj inches thick in the western part of the park4 ,the younger pumice layer is most conspicuous at the ground surface in the eastern part of the park1 where it is as much as #d inches thick and resembles a fine white sand4 ,it is about #dej years old4 ,illustration3 ,mount ,st4 ,helens as it appears from ,mount ,rainier4 ,an inconspicuous bed of pumice records the first eruption of ,mount ,rainier that occurred after ,ice ,age glaciers melted back to the slopes of the volcano4 ,it can be found on the east side of the mountain from ,grand ,park south to ,ohanapecosh campground 7fig4 #h74 ,in roadcuts near the east end of ,yakima ,park 7,sunrise7 the pumice forms a rusty-brown bed about #d inches thick which contains fragments as much as #b inches across4 ,wood from a thin layer of peat just above the pumice was dated by its content of radioactive carbon as about #h1gej years old2 thus1 the pumice is even older4 ,we call this pumice layer ,r for convenience2 other letter symbols have been assigned to the younger layers 7table #a74 ,illustration3 ,generalized distribution of some pumice layers within ,mount ,rainier ,national ,park4 ,the pumice of layers ,w and ,y was erupted by ,mount ,st4 ,helens2 all the other pumice originated at ,mount ,rainier4 ,letters represent the following localities3 ,c1 ,cougar ,rock campground2 ,i1 ,ipsut ,creek campground2 ,l1 ,longmire2 ,m1 ,mowich ,lake2 ,o1 ,ohanapecosh campground2 ,p1 ,paradise ,park2 ,s1 summit crater2 ,t1 ,tipsoo ,lake2 ,w1 ,white ,river campground2 and ,y1 ,yakima ,park4 ,based on studies by ,d4 ,r4 ,mullineaux4 7,fig4 #h7 ,illustration3 ,layer ,x 7,between #aaj and #aej years old7 ,illustration3 ,layer ,c 7,between #b1aej and #b1ejj years old7 ,illustration3 ,layer ,d 7,between #e1hjj and #f1fjj years old7 ,illustration3 ,layer ,l 7,between #e1hjj and #f1fjj years old7 ,illustration3 ,layer ,r 7,more than #h1gej years old7 ,illustration3 ,layer ,w 7line pattern71 and ,layer ,y 7stipple pattern7 7,about #dej years old and #c1bej to #d1jjj years old1 respectively7 ,,table #a4--;,characteristics1 sources1 and ages of pumice layers1 ,mount ,rainier ,national ,park ,based on studies by ,d4 ,r4 ,mullineaux ,common range of thickness in park ,pumice ,west ,east ,common ,color ,source ,approximate layer side side range in age in #aifh1 7inches7 7inches7 diameter or limiting of pumice dates 7years fragments ago7 7inches7 ,x ,absent #a -#b ,light olive ,mount #ajj-aej gray ,rainier4 ,w #j-a #a-c ,medium ,white ,mount ,st4 #bdej sand ,helens4 ,c ,absent #a-h -#h ,brown ,mount #b1aej-b1ejj ,rainier4 ,y #e-bj #a-e ,coarse ,yellow ,mount ,st4 #c1bej-d1jjj sand ,helens4 ,d ,absent #j-f -#f ,brown ,mount #e1hjj-f1fjj ,rainier4 ,l ,absent #j-h -#b ,brown ,mount #e1hjj-f1fjj ,rainier4 ,o #a-c #a-c ,flourlike ,yellowish ,mount ,about #f1fjj to fine orange ,mazama4 sand ,r ,absent #j-e -#a ,reddish ,mount #h1gej-aa1jjj8 brown ,rainier4 ,the next two eruptions of ,mount ,rainier occurred between #e1hjj and #f1fjj years ago4 ,again1 pumice spread over the area east of the volcano4 ,the older pumice1 which we call layer ,l1 covers a band only a few miles wide that extends to the southeast from the volcano 7fig4 #h74 ,the younger pumice1 layer ,d1 covers an area at least #aj miles wide directly east of the volcano4 ,the distribution of both deposits shows that there were strong directional winds during the eruptions4 ,the long1 narrow pattern of layer ,l probably was caused by strong northwesterly winds during a short-lived eruption4 ,the pattern of layer ,d was caused by winds from the west4 ,some time during these eruptions1 hot volcanic bombs and rock fragments were thrown out of ,mount ,rainier's crater and fell onto surrounding areas of snow and ice4 ,wholesale melting resulted1 and floods descended the east flank of the volcano carrying millions of tons of ash1 newly erupted rock debris1 and breadcrust bombs4 ,breadcrust bombs seem to be solid rock1 but if you would break one open1 you would find that the inside is hollow or is filled with a spongy mass of black glass4 ,their outer surfaces are cracked like the crust of a loaf of hard-crusted bread 7fig4 #i71 so we call them breadcrust bombs4 ,they originated as blobs of soft1 red-hot lava which were thrown out of the volcano's crater4 ,as the masses arched through the air1 they quickly chilled on the outside1 and a hardened skin formed around the still hot and plastic core4 ,as their outsides cooled1 gas pressure in their hot interiors caused the bombs to expand slightly and their solidified outer skin to crack4 ,when they struck the ground1 many of the bombs became flattened on one side1 but they were still plastic and sticky enough to remain whole4 ,bombs can be found in two deposits that form the south bank of the ,white ,river about half a mile downstream from the ,white ,river campground4 ,the deposits are mudflows caused by the mixing of hot rock debris with the water from melted snow and ice4 ,as the mudflows moved down the valley floor they must have resembled flowing masses of wet concrete4 ,mount ,rainier erupted several times between about #b1ejj and #b1jjj years ago4 ,during one of the first eruptions1 a mass of hot ash1 rock fragments1 and breadcrust bombs avalanched down the side of the volcano and buried the floor of the ,south ,puyallup ,river valley4 ,although this hot mass flowed like a wet mudflow1 the temperature of the rock debris was above #fjj;,f4 ,thus1 if any water had been present1 it would have been in the form of steam4 ,you can see the resulting deposit in cuts along the ,west ,side ,road on both sides of the bridge across the ,south ,puyallup ,river4 ,innumerable bombs have rolled from the cuts into the ditches beside the road4 ,a charcoal log found in the deposit had a radiocarbon age of about #b1ejj years4 ,illustration3 ,a large breadcrust bomb enclosed in a mudflow deposit that consists of a mixture of volcanic ash and rock fragments4 ,the outcrop is on the south bank of the ,white ,river about half a mile downstream from the ,white ,river campground4 7,fig4 #i7 ,large amounts of pumice were thrown out of the volcano at the same time as the bombs or soon after4 ,the pumice covers most of the eastern half of the park1 and fragments are scattered as far southwest as ,pyramid ,peak and as far northwest as ,spray ,park4 ,this pumice1 called layer ,c1 is especially thick and coarse at ,yakima ,park and ,burroughs ,mountain1 where it lies at the ground surface 7fig4 #aj74 ,here the light-brown layer is #e-f inches thick and consists of irregularly shaped pumice fragments as much as several inches across4 ,mingled with the pumice fragments are fist-sized chunks of light-gray rock that probably were simultaneously thrown out of the volcano by violent explosions4 ,some of these angular rocks were hurled as far as ,shriner ,peak1 #aa miles east of ,mount ,rainier's summit4 ,illustration3 ,pumice layer ,c1 which consists of light-brown fragments1 lies at the ground surface over much of the eastern part of the park4 7,fig4 #aj7 ,the eruptive period was climaxed by the building of the volcano's present summit cone1 which is at least #a1jjj feet high and #a mile across at its base4 ,although dwarfed by the tremendous bulk of ,mount ,rainier1 it is a little larger than the cone of the well-known ,mexican volcano ,parcutin that appeared in #aidc and erupted until #aieb4 ,mount ,rainier's present summit cone was built within a broad depression at the top of the main volcano that had been formed nearly #d1jjj years earlier 7fig4 #aa2 see p4 #dj74 ,the cone consists of a series of thin black lava flows1 and its top is indented by two overlapping craters4 ,rocks around the craters are still warm in places1 and steam vents melt caves in the summit icecap4 ,the first climbers who reached the top of the mountain1 in #ahgj1 spent the night in one of these caves1 as have many benighted climbers since4 ,illustration3 ,the snow-covered lava cone lies in a depression #a miles wide at the summit of the volcano4 ,the cone was probably built about #b1jjj years ago4 ,liberty ,cap is to the left and ,point ,success is to the right4 ,the cliffs below and to the right of ,liberty ,cap enclose ,sunset ,amphitheater4 7,fig4 #aa7 ,even though the lava flows that formed the summit cone were relatively short1 their eruption greatly affected some valleys at the base of the volcano4 ,the hot lava melted snow and ice at the volcano's summit1 causing floods that rushed down the east and south sides4 ,when the floods reached the valley floors1 they picked up great quantities of loose rock debris and carried it downstream1 sometimes forming mudflows4 ,the resulting flood and mudflow deposits raised the floors of the ,white and ,nisqually ,river valleys as much as #hj feet higher than they are today4 ,these valley floors1 as well as several others1 then became broad wastes of bare sand and gravel that extended beyond the park boundaries4 ,later1 the rivers cut down to their present levels1 but they left remnants of the flood and mudflow deposits as terraces or benches along the sides of the valleys4 ,you can camp on such a terrace in the ,nisqually ,river valley at the ,cougar ,rock campground4 ,the ,white ,river campground occupies a similar terrace in the ,white ,river valley4 ,when did ,mount ,rainier erupt last8 ,the most recent pumice eruption was just a little over a century ago4 ,however1 between #ahbj and #ahid1 observers reported at least #ad eruptions4 ,some of these may have been just large dust clouds1 caused by rockfalls1 that were mistaken for clouds of newly erupted ash4 ,other clouds may have been from genuine eruptions that left no recognizable deposits4 ,d4 ,r4 ,mullineaux has found that at least one eruption of that era did spread pumice over an area east of the volcano between ,burroughs ,mountain and ,indian ,bar to a distance of at least #f miles from the crater4 ,pieces of the pumice1 layer ,x1 are light brownish gray and as large as #b inches across4 ,we find only scattered fragments of the pumice1 and nowhere are they in a continuous layer4 ,where the ,x pumice is directly on top of layer ,c1 we cannot tell them apart4 ,the best areas for us to study the younger pumice1 therefore1 are glacial moraines formed within the last #aej years1 because no pumice other than layer ,x is present on the moraines4 ,fortunately1 ,r4 ,s4 ,sigafoos and ,e4 ,l4 ,hendricks of the ,u4,s4 ,geological ,survey have determined the ages of the moraines by counting the growth rings of trees on them4 ,their studies show that the pumice was erupted between about #ahbj and #ahed4 ,captain ,john ,frmont1 an early explorer of the ,oregon ,territory1 recorded that ,mount ,rainier was erupting in ,november #ahdc1 but his journals give no details4 ,others have reported eruptions in #ahbj1 #ahdf1 #ahed1 and #aheh4 ,pumice layer ,x probably was erupted during one or more of these times1 but we do not know exactly when4 ,and will ,mount ,rainier erupt again8 ,we think that it will1 but we now have no sure way of predicting the time1 the kind1 or the scale of future eruptions4 ,why ,glaciers8 ,we frequently hear the question3 8,why are there glaciers on ,mount ,rainier80 ,a glacier forms wherever snowfall repeatedly exceeds melting over a period of years4 ,above #f1ejj-g1jjj feet on ,mount ,rainier1 more than #ej feet of snow falls each winter1 and not all of it melts before the next winter4 ,the survival of this snow from one year to the next depends partly on the cooler temperatures at the higher altitudes1 and perhaps also on the somewhat deeper snowfalls there4 ,illustration3 ,two ice streams meet to form the half-mile-wide ,cowlitz ,glacier4 ,one heads on the flank of the volcano and the other 7,ingraham ,glacier7 at the summit4 ,the firnline is a short distance above the junction of the glaciers4 ,the high bare embankment at the extreme right is a lateral moraine that was formed about #ajj years ago when the glacier was thicker and about #a miles longer4 7,fig4 #ab7 ,,little ,,tahoma ,,peak ,,mount ,,rainier ,,ingraham ,,glacier ,,cowlitz ,,glacier ,a line that marks the limit on a mountain above which snow persists from one winter to the next is called the annual snowline1 and this line on a glacier is called the firnline 7fig4 #ab74 ,above the firnline1 snow that falls each year packs down and changes into glacier ice as air is slowly forced out of it4 ,this part of the glacier is its accumulation area1 where more snow falls each year than is lost by melting4 ,below the firnline is the ablation area1 where melting predominates4 ,the firnline on ,mount ,rainier's glaciers has been well above #f1ejj feet in recent years4 ,but some glaciers extend to altitudes below #e1jjj feet--that is1 far down into the ablation area4 ,they do this by slowly flowing downhill4 ,solid ice flows by sliding on the hard bedrock under the glacier and by slipping along the innumerable surfaces within the ice crystals that make up the glacier4 ,the rate of flow and the rate of ablation govern the distance a glacier extends down into the ablation zone4 ,if these rates remain fairly constant1 the glacier will be in balance and its size will be about the same from year to year4 ,but if changing weather patterns affect the rates of ablation or accumulation1 or both1 the glacier will either become smaller or grow larger4 ,the change you are most likely to notice is in the position of the glacier's terminus1 which may either recede or advance1 but precise measurements of the upper reaches of a glacier also show volume changes there1 some of which may not affect the glacier's terminus for many years1 if ever4 ,crevasses are a glacier's most awesome features and are a constant hazard for climbers4 ,they form where adjacent parts of a glacier are moving at different speeds4 ,some of ,mount ,rainier's glaciers may be flowing at a speed of several thousand feet per year along their centers but at a much slower rate along their margins4 ,this unequal rate of flow produces stresses in the ice that cause it to break4 ,groups of crevasses often form where the glacier flows over a steep place in its bed4 ,the ice moves faster here1 and pulls apart1 and a crevasse is formed4 ,although a large crevasse may seem to be bottomless to the observer1 most crevasses are less than #ajj feet deep because ice pressure tends to close the open spaces in the ice below that depth4#c ,ice covers #cg square miles of the park today4 ,individual glaciers that make up this ice blanket are placed into three groups1 depending on their place of origin4 ,those of one group originate at the volcano's summit and flow far down the valleys that radiate from the cone4 ,most of the snow that nourishes these glaciers probably falls on them at altitudes well below the summit4 ,the largest examples of the group are the ,emmons1 ,nisqually1 and ,tahoma ,glaciers4 ,glaciers of the second group originate on the flanks of the volcano1 mostly at altitudes between #g1jjj and #aj1jjj feet4 ,this group is represented by the ,south ,tahoma1 ,carbon1 and ,inter ,glaciers4 ,glaciers of the third group are on north-facing slopes in the mountains around ,mount ,rainier4 ,they are mostly at altitudes of about #f1jjj feet1 and they owe their existence to locations well protected from solar heat4 ,glaciers representing this group are the ,unicorn and ,pinnacle ,glaciers in the ,tatoosh ,range1 a small unnamed glacier near the west end of ,burroughs ,mountain1 and the somewhat larger ,sarvent ,glaciers east of ,mount ,rainier4 ,work ,habits of ,glaciers ,glaciers are extremely capable workers4 ,their work includes erosion1 transportation1 and deposition4 ,the smoothed and grooved bedrock at ,box ,canyon and at many points along the trail to the ice caves near ,paradise ,park shows erosion of rock by glacier ice4 ,rock fragments carried by glaciers cut grooves in the hard bedrock and polish its surface 7fig4 #ac74 ,although any one rock fragment might scrape away only #a millimeter of rock along a single groove1 the total effect is great when multiplied by countless thousands of similar fragments rasping a bedrock surface for hundreds or thousands of years4 ,glacier ice may also break chunks of rock loose as it overrides them and may even plow up sections of softer rocks4 ,glaciers transport not only the rocks that they quarry and scrape from their beds but also1 more conspicuously1 those that fall onto their surfaces from nearby cliffs4 ,these falling rocks range in size from tiny particles to individual masses that weigh tens of thousands of tons1 like those that fell onto ,emmons ,glacier from ,little ,tahoma ,peak in #aifc4 7,see p4 #ce47 ,a glacier deposits most rock debris at its terminus4 ,the steep snout of any major glacier is a dangerous place to approach closely because rock debris almost constantly falls1 rolls1 and slides down the melting ice faces4 ,much of this debris collects at the ice margin1 and if the margin stays in one place long enough a ridge-shaped end moraine of rock debris forms along the ice front 7fig4 #ad74 ,if such a moraine forms across the front of a glacier at its farthest advance it is called a terminal moraine4 ,end moraines that form as the ice recedes are called recessional moraines 7fig4 #ae74 ,ridges of rock debris that form along the sides of a glacier are called lateral moraines 7fig4 #ab74 ,some recent moraines of modern glaciers are only a few feet away from the present ice margin2 others1 formed thousands of years ago during the most recent major glaciation1 are on ridgetops and valley sides or floors miles away from modern glaciers4 ,by examining the shape and location of these moraines1 we can reconstruct the size and character of past glaciers1 as we will see in the next section4 ,illustration3 ,glacier-smoothed and grooved rock along the ,wonderland ,trail between ,indian ,bar and ,panhandle ,gap4 7,fig4 #ac7 ,illustration3 ,a muddy grayish-blue lake several hundred feet long lies behind a small horseshoe-shaped end moraine of ,flett ,glacier1 on the northwest side of ,mount ,rainier4 ,the glacier is mostly out of view to the left4 7,fig4 #ad7 ,glaciers erode1 transport1 and deposit huge quantities of rock debris4 ,so do their coworkers1 the melt-water streams4 ,these turbulent streams flow from tunnels beneath every glacier1 and their degree of muddiness roughly shows how active the glacier is4 ,glaciers that move very slowly1 or that are stagnant1 produce relatively clear melt water because they are not actively eroding bedrock4 ,in contrast1 streams of muddy water that look like chocolate milk often come from very active or 8live0 glaciers4 ,these streams carry rock debris ranging from flour-size particles to large boulders4 ,you can sense the carrying power of this swiftly moving water on warm summer days1 when large cobbles and boulders are bumping along in a stream swollen by rapid glacier melting4 ,although you can rarely see these boulders1 you can hear their constant low thunder4 ,their repeated impacts on other boulders in the streambed will vibrate the nearby streambanks beneath your feet4 ,hikers often find that a melt-water stream safe to cross in the early morning of a warm summer day is an impassable torrent at the same spot by early afternoon4 ,illustration3 ,four curved recessional moraines are spread over a distance of #b1jjj feet on the valley floor of ,fryingpan ,creek4 ,they were formed within the last few hundred years as ,fryingpan ,glacier lost volume and shrank back toward its present position above a line of cliffs4 7,fig4 #ae7 ,a melt-water stream generally deposits coarse material wherever the slope of the valley floor decreases and the stream loses some of its velocity and carrying power4 ,only a flood may move the boulders farther downstream4 ,however1 the current carries fine material far downstream to deposit it in lakes1 in ,puget ,sound1 or in the ,pacific ,ocean4 ,the ,puyallup ,river1 for example1 is still very muddy where it enters ,puget ,sound at ,tacoma1 more than #dj miles from its source in the glaciers on ,mount ,rainier4 ,during the last glaciation1 when glaciers were much larger than they are now1 melt-water streams carrying great quantities of sand and gravel built valley floors up to levels tens of feet higher than they are today4 ,later1 as the glaciers grew smaller1 the rivers cut down into their valley floors and remnants of the sand and gravel deposits were left standing in benches or terraces along the sides of the valleys4 ,you can see a good example of such a terrace in the ,nisqually ,river valley beyond ,ashford1 which is #e miles west of the park4 ,you cross it on the highway that leads to the park4 ,cuts beneath the terrace reveal deposits of sand1 cobbles1 and boulders that look the same as those deposits being formed today by melt-water streams4 ,the terrace west of ,ashford was formed a little more than #ae1jjj years ago1 when a glacier extended down the ,nisqually ,river valley to the vicinity of ,ashford4 ,yesterday's ,glaciers ,mount ,rainier's great sprawling cone would seem incomplete without the glistening sheets of ice that descend its flanks4 ,we have reason to believe that the volcano has borne glaciers ever since its origin--sometimes smaller than now1 at other times vastly larger4 ,mount ,rainier probably started to grow during the middle part of the ,pleistocene ,epoch1 or ,ice ,age1 which began more than #a million years ago1 but glaciers had covered this part of the mountains even before the volcano appeared4 ,masses of rock debris formed by ancient glaciers occur beneath lava flows from ,mount ,rainier on the west side of ,mazama ,ridge just upslope from ,narada ,falls1 on the north side of ,glacier ,basin1 and at a few other places in the park4 ,mount ,rainier may have reached its present size by about #ge1jjj years ago4 ,since that time great icefields and glaciers have formed at least three times on the slopes of the volcano and in the nearby mountains4 ,during the first two glaciations1 ice completely buried the flanks of the volcano and the surrounding mountains1 except for the very highest ridges and peaks4 ,these great ice masses slowly flowed down all the valleys that head at ,mount ,rainier4 ,the glacier in the ,cowlitz ,river valley1 for example1 extended #fe miles from the volcano and reached a point about #cc miles west of the community of ,randle4 ,deposits of the younger of these two glacial episodes can be seen in cuts along the ,mowich ,lake ,road for a distance of about #a miles inside the park boundary4 ,the glacial deposits were originally more widespread1 but in most of the park they have been removed by erosion or covered by the deposits of yet younger glaciers4 ,illustration3 ,extent of glaciers in the ,cascade ,range near ,mount ,rainier between about #ae1jjj and #be1jjj years ago4 ,arrows show the direction of ice movement2 solid black represents modern glaciers on ,mount ,rainier4 7,fig4 #af7 ,during the most recent major glaciation of the park1 which lasted from roughly #be1jjj to #aj1jjj years ago1 ice again sheathed the slopes of the volcano1 but glaciers in the nearby mountains were smaller than before4 ,most of the glaciers originated at the valley heads1 where they gouged out countless bowl-shaped bedrock basins called cirques4 ,many of the basins held lakes after the glaciers disappeared4 7,see frontispiece47 ,hikers on the trail to the ,paradise ice caves cross the floor of a typical cirque at the head of ,paradise ,valley4 ,from the ,sunrise ,visitor ,center at ,yakima ,park you can walk a short distance to a point along the crest of the ,sourdough ,mountains and stand at the rim of a deep north-facing cirque4 ,ice originating in this cirque and in the cirques adjacent to it moved northward down the valley of ,huckleberry ,creek at least as far as the park's north boundary 7fig4 #af74 ,these glaciers left most valley walls in the park covered with rock debris4 ,lateral moraines can be seen along the highway at and just east of ,ricksecker ,point 7fig4 #ag74 ,other glacial deposits are especially well displayed in roadcuts along the north wall of the ,white ,river valley4 ,illustration3 ,lateral moraine of rock debris at ,ricksecker ,point4 ,it was formed by ,nisqually ,glacier when the glacier was at least #a1jjj feet thick and about #ae miles longer than it is today4 7,fig4 #ag7 ,a little more than #ae1jjj years ago the long glaciers began to shrink and recede4 ,by #aa1jjj years ago there was only about as much ice on ,mount ,rainier as there has been within the last century4 ,then1 during a short period of renewed glacier growth1 most glaciers expanded short distances and new ones appeared in cirques from which ice had disappeared only a short time before4 ,in some of these cirques so much rock debris was being dislodged from surrounding cliffs by repeated freeze and thaw that a rock glacier1 consisting mostly of rock fragments bound together by ice1 was formed4 ,a trail to the ,huckleberry ,creek valley crosses hummocky rock debris left by such a rock glacier in a cirque on the southeast side of ,mount ,fremont4 ,a larger rock-glacier deposit lies about #b miles north of ,sunrise ,point in an east-facing cirque between ,the ,palisades and ,hidden ,lake 7fig4 #ah74 ,in other cirques1 where the proportion of ice to rock debris was greater1 the glacier transported the debris a short distance forward and built a terminal moraine4 ,you can see particularly good examples of moraines formed about #aa1jjj years ago near ,tipsoo ,lake1 where the pond southeast of the lake is dammed by a moraine1 and at ,mystic ,lake4 ,the ice that formed the terminal moraine at ,mystic ,lake was a tongue of ,carbon ,glacier4 ,in some places the orientation or altitude of the cirque did not permit enough snow to accumulate to form a glacier but just enough to create a permanent snowbank4 ,rock debris that fell from the surrounding cliffs rolled down these snowbanks and formed low ridges at their toes4 ,such a ridge is called a protalus rampart because it is found just in front of the apron of rock fragments1 called talus1 that lies beneath cliffs4 ,a trail at ,sunrise ,point leads to protalus ramparts along the north side of ,sunrise ,ridge4 ,during the last #aj1jjj years1 glaciers have been very small by comparison with the great ice mantles that overwhelmed the park earlier4 ,however1 glaciers have grown larger at least twice just within the last #c1jjj years4 ,during both of these periods most glaciers were slightly larger than they are today1 and ice occupied most cirques at altitudes above #f1ejj feet--even some that are now free of ice4 ,the most recent time of extensive glacier growth began at least #hjj years ago1 and various glaciers in the park reached their maximum size between the mid-#adth century and the mid-#aith century4 ,oddly enough1 even though all the glaciers headed on ,mount ,rainier1 they did not all attain their maximum size simultaneously4 ,the largest terminal moraine of this most recent glacial period was built by ,emmons ,glacier in the ,white ,river valley 7fig4 #ai74 ,it is now largely forested1 and cores taken from the trees with a special boring tool that does not harm the tree show ages indicating that the moraine was stable enough to permit seedlings to survive on it by the mid-#agth century4 ,a similar but smaller terminal moraine built by ,cowlitz ,glacier has trees on it that started to grow in the mid-#adth century4 ,illustration3 ,rock-glacier deposit 7light-gray rubble beyond the brown slopes in the foreground7 at ,the ,palisades1 which was formed about #aa1jjj years ago when the climate was colder than it is today4 ,rocks fell from the cliffs in such great quantity that a small glacier in front of the cliffs consisted of more rock debris than ice4 ,the melting of the ice left a mass of broken rock several hundred feet thick which covers about #hj acres4 7,fig4 #ah7 ,illustration3 ,the hummocky end moraine at the left still had blocks of ice buried in it when this picture was taken in #aied4 ,the front of ,emmons ,glacier was near the left edge of the bare moraine in about #aijj4 ,now the glacier ends #a mile farther upvalley at the upper right4 ,the valley floor and moraine were buried by an avalanche of rock debris from ,little ,tahoma ,peak in #aifc4 7,fig4 #ai7 ,nearly all the glaciers gradually decreased in size after the mid-#ahth century4 ,although the shrinkage was sometimes interrupted by short periods of renewed glacier growth1 by #aiej the glaciers at ,mount ,rainier covered only about two-thirds of the area that had been buried by ice only a century before4 ,the overall loss of volume by ,rainier's glaciers1 as well as those elsewhere in the ,pacific ,northwest1 was slowed or halted by slightly cooler temperatures and higher precipitation starting in the mid-#aidj's4 ,volume increases in their upper reaches caused the larger glaciers to grow from year to year1 and since the early #aiej's the terminuses of many glaciers have been advancing4 ,this renewed growth of glaciers is not unique at ,mount ,rainier--similar changes have been observed at other glaciers in the ,cascade ,range and elsewhere4 ,landslides and ,mudflows--,past1 ,present1 and ,future ,some of the most effective means of erosion at ,mount ,rainier are landslides and mudflows4 ,erosion of this kind is sometimes spectacular4 ,within an interval of only minutes or a few hours huge masses of rock may fall1 slide1 or flow off the volcano and move far downvalley4 ,large landslides have occurred at many other places in the park--one in the area northeast of ,mount ,rainier is so conspicuous that its source has been named ,slide ,mountain4 ,the ragged scar left by another slide near ,grand ,park is aptly called ,scarface4 ,you cross a slide on the ,mather ,memorial ,parkway 7,u4,s4 ,highway #daj7 just north of ,cayuse ,pass4 ,broken and jumbled rock debris of many sizes borders both sides of the highway there4 ,this landslide broke loose in rocks of the ,ohanapecosh ,formation1 slid downslope to the bottom of the valley1 and dammed ,klickitat ,creek to form ,ghost ,lake4 ,rocks have also slid downslope on the west side of ,backbone ,ridge and on the east side of the ,ohanapecosh ,river valley a short distance north of ,ohanapecosh campground4 ,the slide on ,backbone ,ridge is still slowly moving today4 ,another slide moves a few inches each year on the west side of the ,nisqually ,river valley about #a mile northwest of the visitor center at ,paradise ,park4 ,you can recognize the slide by a jagged horizontal crack #a1jjj feet long at its top4 ,a far more spectacular variety of landslide occurs when a mass of rock drops from a cliff to form a rockfall4 ,the largest rockfalls on ,mount ,rainier in historic time occurred in ,december #aifc on the east flank4 ,masses of rock hundreds of feet across fell repeatedly from the steep north face of ,little ,tahoma ,peak onto ,emmons ,glacier4 ,the rock masses shattered into dust and countless fragments1 fanned out across the glacier1 then avalanched down the steep ice surface at tremendous speed4 ,when the avalanches reached the end of the glacier they shot out into space as sheets of rock debris4 ,as these hurtling sheets settled toward the valley floor1 a cushion of compressed air formed beneath them1 comparable to the air cushion that momentarily buoys up a sheet of plywood that is dropped onto a flat surface4 ,air that was trapped beneath these speeding avalanches reduced friction and permitted one of the avalanches to move almost #b miles beyond the end of the glacier4 ,this avalanche passed completely over a small wooden gage house about #e feet high on the valley floor without damaging it1 then ran headlong into the north base of ,goat ,island ,mountain where it scraped away trees and bushes4 ,a later avalanche stopped just short of the gage house1 and wind that was expelled from beneath the rock debris blasted the still-undamaged house several hundred feet forward4 ,it now rests in the scar left by the earlier avalanche on the side of ,goat ,island ,mountain4 ,at least seven rockfalls and avalanches descended from ,little ,tahoma ,peak1 separated perhaps by only minutes or hours4 ,the reddish-gray masses of broken and pulverized rock--some spread helter-skelter1 some piled in long sharp-crested ridges--now lie on the valley floor between the ,white ,river campground and ,emmons ,glacier 7fig4 #bj74 ,the rockfalls might have been caused by a steam explosion near the base of ,little ,tahoma ,peak4 ,steam jets and small explosions are not unusual phenomena at ,mount ,rainier1 although they never have had such dramatic effects in historic time4 ,incredibly larger avalanches of rock fell repeatedly from the sides of ,mount ,rainier during prehistoric time4 ,one such avalanche originated near the summit of the volcano and blanketed ,paradise ,park and ,paradise ,valley with a yellowish-orange mixture of clay and rocks sometime between #e1hjj and #f1fjj years ago4 ,you can see this avalanche deposit in shallow cuts along trails and roads in the ,paradise area4 ,huge blocks of rock that came down with the avalanche are scattered in the meadows of ,paradise ,park between the visitor center and ,panorama ,point4 ,although the deposit is now less than #ae feet thick in most places1 the mass that flowed down ,paradise ,valley must have been #fjj feet thick1 because we can find remnants of it on top of ,mazama ,ridge4 ,a tongue of the wet mass flowed through a low saddle near the south end of ,mazama ,ridge and extended into the basin now occupied by the ,reflection ,lakes4 ,you can see the yellowish-orange deposit in the first roadcut west of the lakes1 where it lies on top of gray glacial deposits4 ,illustration3 ,avalanche deposits in the ,white ,river valley4 ,the rockfalls and avalanches from ,little ,tahoma ,peak formed a mass of reddish-gray rock debris that contrasts with the darker gray glacial debris deposited by ,emmons ,glacier within the last century4 ,the avalanche deposits are about #a1ejj feet across at their widest point4 7,fig4 #bj7 ,the avalanche probably was wet when it crossed the ,paradise area1 and the moisture in it may have already been present in the rocks in which the avalanche originated4 ,the mass was fluid enough to move down the ,paradise and ,nisqually ,river valleys as a mudflow hundreds of feet thick1 and the resulting deposits extend at least #ah miles downstream from the volcano4 ,the volume of rock that slid off to produce the mudflow may have been as much as #ajj million cubic yards--or roughly enough to cover a #a-mile-square area to a depth of #ajj feet4 ,at about the same time as the ,paradise avalanche and mudflow occurred1 a tremendous rock mass also slid off the east side of the volcano in the area between ,steamboat ,prow and ,little ,tahoma ,peak4 ,this slide formed a mudflow on the floor of the ,white ,river valley that was several hundred feet deep at the north boundary of the park and that extended at least #cj miles beyond the base of the volcano4 ,the most remarkable feature of the deposit left by this mudflow is its surface1 which is dotted with scores of mounds #e-ce feet high and as much as several hundred feet in diameter4 ,these mounds have cores of huge rocks which are similar in size to those scattered on the surface of the avalanche deposits from ,little ,tahoma ,peak4 ,you can see the mounds best in an area which is a few miles north of the park boundary1 west of the ,white ,river1 and which can be reached by the ,huckleberry ,creek ,forest ,road4 ,the total volume of this mudflow deposit may be as much as one-fifth of a cubic mile4 ,these great landslides and mudflows were followed shortly by another whose size surpassed that of anything before or since4 ,this was the remarkable ,osceola ,mudflow1 which streamed down the valleys of the ,white ,river and ,west ,fork about #e1hjj years ago4 ,when these great rivers of mud joined in the ,white ,river valley1 they formed an even larger mudflow which swiftly flowed downvalley for a distance of #ae miles and then spread beyond the ,cascade mountain front into the ,puget ,sound lowland4 ,there the mudflow submerged a total area of more than #ajj square miles to depths as great as #gj feet and buried the sites of the present towns of ,enumclaw and ,buckley4 ,one tongue of it even flowed into an arm of ,puget ,sound1 south of ,seattle1 that has since been filled with river deposits to form the fertile valley occupied by the towns of ,kent1 ,auburn1 ,sumner1 and ,puyallup4 ,the ,osceola ,mudflow is remarkable in that it affected areas so far from its place of origin4 ,this long distance of travel was due to its great volume1 which we estimate to have been more than half a cubic mile1 and to the abundance of slippery clay in it4 ,the clay had been formed by the alteration of rocks in the volcano by hot gases and solutions over many centuries4 ,illustration3 ,the northeast flank of ,mount ,rainier4 ,a remnant of the ,osceola ,mudflow lies at the summit of ,steamboat ,prow in the center4 ,two and one-half miles to the left is ,little ,tahoma ,peak1 from whose steep north face at least seven large masses of rock fell in #aifc4 ,mount ,adams volcano can be seen at the left1 and ,mount ,hood1 ,oregon1 in the far distance4 7,fig4 #ba7 ,where did the ,osceola ,mudflow originate on the volcano8 ,this we must deduce from several lines of evidence4 ,the mudflow occurred so long ago that there is no historical record1 and volcanic events since that time have covered up part of the scar it left on the volcano4 ,remnants of the ,osceola ,mudflow veneer the sides and ridges of ,glacier ,basin1 and a small amount of it is even preserved at the top of ,steamboat ,prow1 at an altitude of #i1gjj feet 7fig4 #ba74 ,this distribution tells us that the slides responsible for the mudflow originated somewhere on the volcano above ,steamboat ,prow4 ,but now there is no great chasm in the side of the volcano large enough to have provided a source of the mudflow2 so we must consider a former summit of the volcano itself as a possible source4 ,i4 ,c4 ,russell1 one of the first geologists to study ,mount ,rainier1 wrote in #ahif that the present summit of the volcano consists of a small lava cone4 ,enclosing this cone is a broad depression whose rim is partly preserved at ,gibraltar ,rock1 ,point ,success1 and ,liberty ,cap 7fig4 #aa74 ,high points on the rim indicate that the former summit of the volcano above an altitude of about #ad1jjj feet was removed in some way4 ,the destruction of the old summit1 which may have reached a height of #af1jjj feet1 left a broad east-facing depression in the top of the volcano between ,gibraltar ,rock and ,russell ,cliff4 ,the depression has since been mostly filled by the recent lava cone4 ,you can see these features best from high points east of the mountain4 ,our best explanation of how the former top of the volcano was removed also solves the problem of finding an adequate source of material for the ,osceola ,mudflow4 ,before #e1hjj years ago1 the topmost part of ,mount ,rainier probably consisted of rock that had been weakened by hot volcanic fumes and solutions and partly converted to clay4 ,then1 this mass of weak rock was jostled off or pushed off by a volcanic explosion and slid down the northeast side of the volcano4 ,one or more of these mighty avalanches of moist clay and rock resulted in the ,osceola ,mudflow4 ,large avalanches have also occurred many times during the last #c1jjj years on the west side of the volcano4 ,sunset ,amphitheater 7fig4 #aa7 is part of the large scar left by them4 ,about #b1hjj years ago one of these avalanches created a mudflow in the valleys of the ,south ,puyallup ,river and ,tahoma ,creek that was temporarily deep enough to submerge ,round ,pass 7on the ,west ,side ,road7 to a depth of nearly #djj feet4 ,this is especially remarkable when we see that ,round ,pass itself is #fjj-gjj feet above the nearby valley floors4 ,another deep mudflow1 started by an avalanche at ,sunset ,amphitheater1 moved down the ,puyallup ,river valley about #fjj years ago and buried the site of the present town of ,orting in the ,puget ,sound lowland under #ae feet of mud and rock4 ,table #b4--,summary of important geologic events in the history of ,mount ,rainier ,national ,park ,geologic ,years ago ,geologic events in the area of the park time scale 8,postglacial0 ,present summit cone of ,mount ,rainier probably was built about #b1jjj years ago4 ,the last known pumice eruption occurred between #ahbj and #ahed4 ,glaciers started to grow and advance about #c1jjj years ago4 ,maximum extents were reached about #ahej ,a4,d4 ,from then until about #aiee1 glaciers were receding2 now they are in balance or advancing4 ,huge masses of rock have slid from the volcano repeatedly during the last #aj1jjj years4 ,one of these destroyed the summit of ,mount ,rainier and formed the ,osceola ,mudflow about #e1hjj years ago4 #aj1jjj ,pleistocene ,last major glaciation4 7,ice ,age7 #be1jjj ,birth and growth of ,mount ,rainier volcano1 and repeated glaciation4 #b-c million ,pliocene ,uplift and erosion of the ,cascade ,range4 #ab million ,miocene ,intrusion of granodiorite4 ,folding of older rocks4 ,deposition of ,fifes ,peak and ,stevens ,ridge ,formations4 #bf million ,oligocene ,deposition of ,ohanapecosh ,formation4 #cg-ch million ,eocene ,deposition of ,puget ,group4 #ec-ed million ,avalanches and mudflows like those described are normal events at ,mount ,rainier and are expected to happen again in the future4 ,almost any cliff on the volcano can produce a large rockfall1 but which cliff will collapse next1 or when1 cannot be predicted4 ,should the volcano again become active1 earthquakes and volcanic explosions would trigger avalanches and mudflows that would rush down the mountain4 ,molten rock would melt snow and ice at the volcano's summit and send floods of water down the volcano's flanks4 ,these indirect effects of an eruption would be much more hazardous than lava flows and pumice1 if eruptions are on a scale similar to that of the past #aj1jjj years4 ,the ,volcano's ,future8 ,an active volcano changes continually4 ,repeated eruptions build the cone by piling one lava flow on top of others1 or on top of other volcanic formations4 ,simultaneously1 the combined processes of erosion wear the volcano down4 ,the relative importance of the two processes--one building1 the other destroying--is reflected in the volcano's shape4 ,the scarred and deeply gouged sides of ,rainier's cone show that erosion has been dominant here for a long time4 ,is ,mount ,rainier now doomed to continued piecemeal destruction until the lofty cone is reduced to a featureless mound8 ,will future eruptions of lava restore some of the volcano's bulk8 ,or will the volcano erupt violently some day1 and then collapse as did ,mount ,mazama to form the deep basin of ,crater ,lake8 ,the answers may not be known for centuries--or they may appear tomorrow4 ,further ,reading in ,geology ,crandell1 ,d4 ,r41 #aifi1 ,surficial geology of ,mount ,rainier ,national ,park1 ,washington3 ,u4,s4 ,geological ,survey ,bulletin #abhh4 ,a geologic map that shows where glacial deposits1 landslides1 and mudflows are located in the park is accompanied by an illustrated nontechnical description of these and other surficial deposits4 ,crandell1 ,d4 ,r41 and ,fahnestock1 ,r4 ,k41 #aife1 ,rockfalls and avalanches from ,little ,tahoma ,peak on ,mount ,rainier1 ,washington3 ,u4,s4 ,geological ,survey ,bulletin #abba-;,a1 #cj pages4 ,a description of the seven successive landslides of ,december #aifc that buried the upper ,white ,river valley under thick deposits of rock debris4 ,crandell1 ,d4 ,r41 and ,mullineaux1 ,d4 ,r41 #aifg1 ,volcanic hazards at ,mount ,rainier1 ,washington3 ,u4,s4 ,geological ,survey ,bulletin #abch1 #bf pages4 ,a discussion of ,mount ,rainier's eruptions during the last #aj1jjj years and the anticipated effects of similar future eruptions4 ,fiske1 ,r4 ,s41 ,hopson1 ,c4 ,a41 and ,waters1 ,a4 ,c41 #aifd1 ,geologic map and section of ,mount ,rainier ,national ,park1 ,washington3 ,u4,s4 ,geological ,survey ,miscellaneous ,geologic ,investigations ,map ,i-#dcb1 with text4 ,a geological map of the park's bedrock is accompanied by a brief nontechnical discussion of the geological evolution of the park as recorded by the rock formations4 ,sigafoos1 ,r4 ,s41 and ,hendricks1 ,e4 ,l41 #aifa1 ,botanical evidence of the modern history of ,nisqually ,glacier1 ,washington3 ,u4,s4 ,geological ,survey ,professional ,paper #chg-;,a1 #bj pages4 ,a description of the recent moraines of several glaciers and an explanation of how they are dated by counting the growth rings of trees growing on them4 ,u4,s4 ,,government ,,printing ,,office3 #aifh ,o--#cec-efj ,footnotes #a,the ,x pumice occurs as scattered fragments and does not form a continuous layer4 #b;,ages of more than #aej and less than #f1jjj years cited in this report are based on radiocarbon determinations which have been corrected by the use of a ,c half life of #e1gcj years and for variations in atmospheric ,c 7,h4 ,e4 ,suess1 written communication to ,meyer ,rubin1 #aifh74 #c;,for more information about glaciers read 8,glaciers0 by ,robert ,p4 ,sharp1 published in #aifj by the ,university of ,oregon at ,eugene4 ,illustration3 ,,department ,,of ,,the ,,interior ,,march #c1 #ahdi ,transcriber's ,notes --,copyright notice provided as in the original--this e-text is public domain in the country of publication4 --,silently corrected palpable typos1 leaving non-standard spellings and dialect unchanged4 --,only in the text versions1 delimited italicized text 7or non-italicized text within poetry7 in underscores 7the ,,html version reproduces the font form of the printed book47