Ap ril 1977 GEOLOGY-Foundationof past; the key to Cal i f

GLACIERSOF MT. SHASTA

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Figure1. The CascadeRange. OF MT.SHASTA

By

MARY HILL.Geologist

U. S. GeologicalSurvey

Menlo Park.

This article was written while the author was a member of the CDMG stafL v

The CascadeRange is a string of vol- 1827 EXPLORATION canic peaks,all fairly young,geologically speaking.Only oneofthe volcaniccones- Americansin the easternUnited States LassenPeak-has erupted in this century. first knewof Mt. Shastafrom word spread by Peter SkeneOgden, fur trapper, who The southernmostpeak in the Cascade wrote "I have namedthe mountain Sas- chain-Mt. Shasta-dominatesthe land- tice" in his diary in February,1827. There scape of north central California. This is no record of a climb to the top until high (14,16l feet) mountainis about4O CaptainE. D. Pearceascended it in 1854. miles south of the Oregonborder and 80 It is a steepclimb (figure 3), but a popu- miles northwest of Lassen.All of the lar one; today there are ll recognized other main conesin the CascadeRange lie climbing routes,in addition to numerous north of Shastain Oregonand Washing- variations. ton (figure l). "Shasta,as a whole," wrote geologist In Pleistocenetime, Mt. Shastawas ClarenceKing, "is the singlecone of an coveredby glaciers;today, there are but 5. immense,extinct volcano.It occupiesal- In the interim, Shastahas beenactive as most preciselythe axial line of the Sierra a volcano.Its last activity may havebeen Nevada,but the range,instead of carrying as late as 1857.Certainly, many of the its great,wave-like ridge through this re- lavaflows of Mt. Shastaare no morethan gion,breaks down in the neighborhoodof 300to 500years old; the youngestportion Lassen's (Peak) and for eighty miles of the mountain is its crest. Sincethe 5 northward is only representedby low, glaciersprobably are not wastedremnants confusedmasses of mountaincut through of Pleistocenegiants, but like other gla- and through by the cafron of the ciers of California, date from the "Little McCloud, Pitt, and Sacramento." Ice Age" (the Matthesglaciation) of the last thousandyears, the mostrecent flows "A broad, volcanic plain, interrupted ofbasaltand daciteare not much younger here and there by inconsiderablechains, than the glaciers(hgure 2). occupies the country east of Scott's Mountains. From general this plain, shadow of the great peak. The volcanic white, its vast altitude, the pale-gray or whose altitude is from twenty-five hun- plain-land is partly overgrownby forest, rosy tints of its lavas,and the dark girdle dred to thirty-five hundred feet, rises and in part covers itself with fields of of forest which swells up over caflon- .About its basecluster hill- grassor sage.Riding overit in almostany carved foothills give it a grandeur ocks of a hundred little volcanoes,but part the one great point in the landscape equalledby hardly any American moun- \/, they are utterly inconspicuousunder the is the cone of Shasta;its crest of solid tain (King, 1923,p. 282-3)." --Y \-.r,*/ I"r.. \ l\"o \

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Figure 2. Mt' Shastaand the 5 glacierswhich occupy its higher slopes.From usGS Mt. Shastaquadrangte, lhminute series. Captain Pearce counted a "cluster of boiling hot sulphursprings, about a dozen in number,emitting any amountof steam, gas, - smoke, etc." Today,these springs are far lessactive; another group, called "Car- nealSprings" by B.A. Colonna,who spent 9 days on the summit of Mt. Shastaon behalf of the U.S. Coast and Geodetic Survey,are virtually extinct.

From'most vantagepoints, Shastais imposing.From the west,Shasta and its Figure 3. Mt. Shasta,southernmost peak in the CascadeRange, rises to an elevationof smallercone, Shastina (figure 4), form a 14.161feet and dominatesthe landscapeof northcentral California. In thisview from the east lookingover LittleGlass Mountain (lower from the top Mt. Hoffman,Mt. double mountain as they do from the c€nter) of Shasta is seen as a striking single cone. Photo by Mary Hill. northwest(front cover). From the east,

Figure4. Aerialviewof Shastina,covered by wintersnow.iThe small lava plug in itscrater forms a conspicuoushump. Photo by Ernest Carter.

Y Figure5. Thisview entitled"Shastl Butte" was drawn by a lithographerduring Cap. tain J.C.Fremont'sexpedition in the mid- 1800s. looking over Little GlassMountain from the top of Mt. Hoffman,Shasta is a strik- ing single cone (figure 3). Captain J. C. Fremont's mid-l9th century vantage point .:',.:;,.'li::ii:iri :ril must have beenan unusualone to :l:il,;iiirr ;i',r.; give iitil ;i;;.:t;; his lithographerthe exaggeratedex- ..,: pressionof "Shastl Butte" (figure 5), as iffi# .- the drawing is labeled.

FIRST SCIENTIFIC STUDY

The first scientific party to ascend to the top of the mountainwas that led by J. D. Whitney, State Geologist,in the au- tumn of 1862,although botanist John Jef- frey had climbed to timberline in 1852. Whitney's party did not seeany of the glaciers-noteven the "Whitney " named in his honor by Clarence King 8 years later. King's description in l87l was the first of any glacier in the Pacific slope south of to be pub- lished in the scientificpress. Later, J. S. Diller studiedthe glacierson Mt. Shasta in more detail. His description of the 5 v glacierswas written in 1895. Figure6. (a) Headof Whitneyglacier, Mt Shasta;(b) Foot of Whitney glacier.Figures 6_tOfrom Bussetl. 1//J5.

MT. SHASTAGLACIERS great fields-many who saw a glacier for (asdescribed by J. S. DILLER, In comparing the morainat material 189S) the first time in their lives. In-the upper about Mount Shastawith that of the Al- portion of its coursepassing o"., pro.i- The glaciersof Mt. Shasta pine glaciers,a featurethat is particularly are five in nent irregularitiesin its bed,the Whitney number, and all are found side noticeableis the smallnessof the bowl- by side, Glacier becomesdeeply fractured, pro'- an almost continuous ders. On Alpine glaciers bowlders,fre- F-ing ouctng the extremelyjagged surface cor_ for that portion of the mountain"o"".ini quently have a diametergreater than l0 at ai responding to ice falls of the altitudeofabout 10,000feet Alpine feet,but aboutthe Whitneyand other gla- [figure 2]. glaciers.Lower down the crevasses'de_ On the northwesternslope of it Loun- ciers of Mount Shastathey are rarelf so velop; and these,with the great fissure tain is WhitneyGlacier, with its promi- much as 3 feetin diameter.This is readilv which separatesthe glacierfr6m the steeo nent terminalmoraine; to the eaitward explainedby the fact that the glacien of slopesof Shastina,attest the motion of thl Gtacier,with a largepile Mount Shastado not move in deepval_ Trla:n .LBolaml icy mass. They frequently open and of debrisat its lower end; next leys,bounded by long, steepslopes, with ih" yawning chasms,reaching 100 broad Hotlum Gl4cier,and then"ork :*o.." many high cliffs,affording an opportunity the Win- feet into the cleargreen ice beneath.-Near tun. McCloud for the formation of large bowiaers.ni- [Konwakitonl Ghcier. its middle, on the easternmargin, Whit_ whrchis the smallestof thegr6up, lies thoughWhitney Glacier has its bounda_ on ney Glacier receives contributions of the southeasternside of thJmountain. ries more clearly definedthan any of the sand,gravel, and bowldersfrom the verti_ other glaciersabout Mount Shasti by the cal cliffs aroundwhich it turns to movein depressionin which it moves,the valiev Whitney Glacier. a more northerly direction. is In this wav a very shallow,and onelooks in vain Whitney Glacier is more like those of prominent lateral along moraine is developed. its slopefor traces polished the Alps.thanany otherone of the group From of rocks fikI the very steepslopes ofshastina, on those so magnificently 6]. Its snowfield lies displayedin the [figure on the riorth'_ the westernside, the glacierreceives addi_ Alpine western slope of the valleys. Whitney Glacier looks mountain, from tionsin the form ofavalanches.Here the whencethe young: it has hardly made a beginning icy mass,with well_defined snow clings to the rocky bed limits, until the toward carving out a valley for itielf. movesdown a shallowdepression strain resulting from its accumulation between is Shastaand Shastina.Iti width great enoughto break it from varies its moor- Below the terminal morainethe milkv from l,O0Oto 2,000 feet, with a ings,and it rushesdown ,l upon the glacier water of Whitney Creek wends length of about 2 miles,reaching from below.The most its wav striking featureof-Wnit_ down the northern slope,plunges the summitof the mountaindown-to an ney Glacier, and over a that which is of the fall hundredsof feethigh into altitude of 9,500feet about the sea.It is greatestinterest a=deepcan_ from a geologicpoint of yon, and near the base but little morethan a decadesince the first of the mouniainis view, is the debris it brings consumedby glaciers were discovered within fmoraine] the thirsty air and earth. the down the mountainand pilesup, making United States;and the largest of them, a largeaccumulation The presenceofmarginal crevasses, about the culminatingpoini of the Cas_ [terminal-morainef lat_ at its lower end. This irorarne appearsto eral and terminal moraines, cade.Range, would perhapsappear Lil_ and the char_ be fully a mile in length,measured down acteristicmilky trputran besidethe great glacier of the streamwhich issuesfrom the slopeof the mountain.Its apparent the lower tsarneseOberland; and yet they are as end, are proofs that Whitnev length is much greater than the real, Glacier truly glaciers.Diller wrote thisln 1895. moves,but the rate of motion hai however,from the fact that the glacierici not been The world did not becomefully awareof definitely measured.The stakes extendsfar beneaththe coveringofdetri_ planted the magnitudeof Alaskan ghtiers until in July, 1884, were covered t":. so huge a pile of light_+olored with snow the gold rush of 1898to the Ktondike and It Ir beforethe party could reach oebns,Just about the timber line, that it is them in Yukon brought many argonautspast the October, and they have.since plainly visiblefrom afar. disappeared. v, e

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Figure7. Bolamglacier. Figure8. Hotlumglacier

Bulamfaotam] Glacier sionally to the depth of 100 feet. The McCloudfKonwakiton-l Glacier On the northwesternslope of the moun- thicknessof this glacierhas becn overesti- On the southeasternslope of Mount tain, to the left of Whitney Glacier,is the mated.In reality,instead of being 1,800to Shasta,at the headof a large canyon,is Buhm fBohm, figure7], differingchiefly 2,500feet thick, it doesnot appearwhere the McCloud [Konwakiton] Glacier ffig- in thatlt is containedin a broader,less greatest to be more than a few hundred ure l0l . It adjoinsthe Wintun, and is the definitevalley, and forming an intermedi- feet,for at a numberof placesit is so thin smallest glacier in the group. Notwith- ate steptoward ,which is that its bed is exposed.Its terminal mo- standingits diminutive size,its crevasses one of the most important and remarkable raine is a huge pile nearly half a mile in and the muddy streamit initiatesindicate of the group. width measuredin the directionof glacial clearly that the ice mass continues to motion, and twiceas long measuredalong move. The amount of morainal material the end of the glacier. upon its bordersis small, and yet, of all the glaciersabout Mount Shasta,it is the HotlumGlacier only one which has left a prominent Unlike the ordinary glaciers,Hotlum recordofimportant changes.The country [figure 8-l has no valley in which it is Wintun Glacier adjacentto the southwesternside of Mud confined, but lies on the convexsurface of Next south of Hotlum Glacier is Win- CreekCanyon has been distinctly glaciat- the mountain.Its uppersurface is convex tun [figirre 9] which attains a length of ed, so as to leaveno doubt that McCloud with an abrupt throughout from side to side, and its over two miles,and ends [Konwakiton] Glacier was once very width (1.23miles) is almostas great as its front ofice in a canyon.In this respectit much largerthan it is at the presenttime. lenglh (1.62miles). At severalplaces the is strongly contrastedwith the other gla- The rocksover which it movedwere deep- surface of the glacier is made very rough ciers of Mount Shasta.There is no well- ly striated,and so abradedas to produce by the inequalitiesof its bed.This is espe- markedterminal moraine,dthough there the smooth,rounded surface so common cially true of the southernportion, where are accumulationsof debrison the north- in glaciatedregions. At the time of its prominent cliffs furnish material for the ern side near the end.The detritus is ap- greatestextension the glacierwas over 5 only medial moraine discovered on parently sweptout ofthe canyonby Ash milesin length,and occupied an areaof at Mount Shasta.Throughout the greater Creek as fast as it is brought there by the least7 squaremiles, being twenty times its portion ofits expansethe glacieris deeply glacier, and thus the accumulationof a presentsize. Its limit is outlinedat several crevasscd,exposing the green ice occa- terminal moraineis prevented. placesby prominent terminal moraines, .=--, .:- l;tr'...=', i:: :x: -l

l;:.':':.

Figureg. Wintunglacier. rrgure 10. Konwakitonglacier

which mark stagesin the recession of the Harrison, glacier. The thickness REFERENCES A. 8., 1960,Exploring glacien with of the glacier, camera: where greatest, ,..a SierraClub, SanFrancisco, 7l p. was probably noi more rrng, ctarence, than Av_ery, p., lg7l, Active glacierswithin 200 feet; for severalhills within the Benjamin 1874,Ascent of Mount the United Shasta: States:The Atlant-icf"fontf,lj, glaciatedarea were not covered,and the OverlandMonthly, lst series,v. 12, 21, p. 371-377. ". May, p. 466-416. striatedsurfaces and morainesdo not ex_ King, Clarence,1871, On the Blakely,Richard J., discoveryofactu_ tend up their slopesmore and Christiansen,R. L., al glacierson the p"cifrc than 200 feet. 19f6,The mountain. of tfr" The thickness magnetizarionof Mount Shasta: Slope: American of the glacieris completely EOS,v.57, no. Journal of ScienceanJ ^ 12,p.9O3 (abstract). Arts, third in harmonywith the limitedexteni of its ur-onaugh, series,v. l, no.3, March,p. 157_ Jerry E., 1915, Mount Shasta: t67. erosion.Although the rocksare Mazama, distinctlv v.4, no.4, p. 5-9. King, Clarence, planed off, so that the Chesterman, 1923,Mountaineering in the low knobs and CharlesW., 1971,Volcanism in SierraNevada: edgeshave regularly California: CharlesScribnert Son's,Ner" curvedoutlines, it is CaliforniaGeology, Z+,no. g, York, 4th_edition evident p. 137-147. ". (originally puUiislJ that a greatthickness has not been l87l), p. 275-324. removedby the Colonna,B.-A., 1953 Nine ice,and that the periodof [1880], dayson the MacNeil,F. H., 1915,Some facts about ice summit of Mt. Shasta:Journal Mount erosionhas beencomparativily brief. of the Coast Mazama,v. 4, no. 4, p. and GeodeticSurvey, . -Sfasla; 19_22. During the lapseof time, no. 5, June,p. 145_ Muir, John, 1961,The mountains howevei,there Reprinted of Califor- havebeen climatic !12. from The Caliiornian, nia: AmericanMuseum oscillations,embracing March, 1880. of Natural Hi*;, epochs DoubledayAnchor Book, of glacial advanceand recessionl Diller,J. S.,1896, GardenCity,Niw MountShasta, a typicalvol_ york, 300p. First pubtished cano. In The physiography in 1g94. of the United Muir, John,| 872,Living glaciers With the exceptionof McCloud States:National of California: f Kon- GeographicSociety, Mono- OverlandMonthly, wakiton] graphs,v. lst series,v. 9, Decem- Glacier, there are no ricords I, no. 8, p.237_269. ber, p. 547-549. uponthe slopesofshasta Diller,J. S., 1915,Mount Shasta_some that any ofthe of its Roper, Steve, 1968,Climber's guide existing glaciers gmlogic aspects:Mazama, v. 4, no. to Mt. were ever very much 4, p. 9_ Shasta:Ascent: Sierra Club larger 16. Mountaineering than at present. Journal,v. l, no.2,May, p. 3g_41. Freeman,F. C., 1882,An ascentof Mount _ Russell,Israel C., 1885,Existing glaciers ofthe Shasta:Overland Monthly, 2nd series,v. 10, p.205-210. United States:U. S. Geologiiil Survey5th Annual Report, Gilbert, GroveKarl, _ 1883-94,p. 303_355. 1904,Variations of Sierra Russell,Israel glaciers:Sierra C., 189g,The glaciersof North Club Bulletin,v. 5, no. I America:,Geographical (publicationno. p.2O_j2. Journal,v. 12,no. 6, 30), p. 553-564. Exceryts from HalL Ansel F., 1926, _ Diller, J. S., 1g96, Mount Shasta:Sierra Williams, Howel, Club Bulletin,v. 1932,Mount Shasta,a Cas- \founf Shasta, a typical volcano, in 12,no. 3 (publicationno cadevolcano: 6l), p. 250-267. JournalofGeology, v.40, no. the physiographyof the United States: 5, p. 417429. HlldT,I, w . p., l9 physical NationalGeographic Society t 5, geographyof Williams,Howel, Monographs, the Mo_untShasta 1934,Mount Shasta,Califor_ v. l, no. 8, p.237-268. region:Mazama, v.'4,io. nia: Zeitschrift 4, p. l7-i8. fiir Vulkanologie1934, Band 15, p. 225-253.X

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