ERDKUNDE BandXVIHeft2 FERD. DOMMLERS VER LAG/BONN Juli 1962

CASCADE ALP SLOPES AND GIPFELFLUREN AS CLIMA-GEOMORPHIC PHENOMENA Will F. Thompson

With 8 Figures and one Map.

des Kas Zusammenfassung: Alphange und Gipfelfluren Dawson did, in terms of a single level of ac kaden-Gebirges, USA, als klima-geomorphologische Pha cordance. that it extends far to the nomene. They reported south in that I. C. Bailey Willis, Die Erklarung der Obereinstimmung der Gipfelhohen range; Russell, im nordlichen Kaskaden-Gebirge, wie sie erstmals von G. O. Smith, and F. C. Calkins, all of the U. S. G. M. Dawson (1896) vorgeschlagen und durch Reginald Geological Survey, described it as a peneplain in Daly (1912) gestiitzt wurde, wird mit einer gewissen Mo studies between 1900 and 1906. difikation die Fastebenen in die published bestatigt; hypothetischen In 1912 Reginald Daly the sem Gebirge wurden jedoch als nicht bestehend gezeigt. challenged pene Abtragung durch Massenbewegung, die iiber der Baum plain explanation and supported Dawson's prior im grenze wesentlich kraftiger ist als darunter, hat ganzen theory, yet he may never have noticed Dawson's in von Alaska bis Kaskaden-Gebirge, den Kustenketten His work was done within the northern Kalifornien und im von Idaho gipfelflur. Felsengebirge ?Alphange" of the where a few (Daly's Ubereinstimmungsniveau) gebildet. Diese werden fringes high Cascades, only als Anzeichen eines maritimen klimatischen Einflusses in peaks approximating 2,500 meters can be seen at Hohen Die ihrer alpinen angesehen. Analyse Entwicklung once. Dawson's theory, as stated, drew his atten griindet sich auf die Beschreibung der alpinen Klima tion of the well defined accordance at timberline des Gebietes, die auch als Basis Geomorphologie geeignete in that area. He fiir klimatische und naturraumliche Vergleiche mit ande (about 1,800 meters) presumably ren Gebirgsregionen dienen kann. dismissed the 8,000 foot elevation given by der wahrend Inter Schwankungen Baumgrenze quartarer Dawson as an error. To explain the accordance glazialzeiten scheinen Alphangbildungen in verschiedenen he Dawson cited a difference in verursacht zu haben. Sie haben described, great grofieren Hohenlagen rates of and erosion above and below alpine Gipfel in diesen Hohenlagen gekopft und damit weathering zahlreiche Riicken mit bedeutender Erstreckung in der timberline, observable throughout the region. Es daB gleichen Hohenlage gebildet. wird angenommen, However, his description of the accordance he eine gut ausgepragte Gipfelflache (Dawson's Gipfelflur), saw in the Cascades from across the Fraser low die sich in 8000 FuB Hohe durch das nordliche ungefahr land makes it clear that the elevation was Kaskaden-Gebirge erstreckt, einer interglazialen Hohen given um un correct was lage der Baumgrenze entspricht, in der das Klima and that he looking at the high gip warmer war. gefahr 7? F als das gegenwartige Nur wenige felflur of that range, about 700 meters above tim Gipfel nicht vulkanischen Ursprungs erheben sich wesentlich berline. From that Daly's meter dariiber. Die bedeutenden im Kaskaden distance, 1,800 weniger Gipfel accordance was obscured haze. Gebirge von und Oregon, und in Idaho, wur probably by den einheitlich iiber weite Flachen an der Baumgrenze durch The true explanation of Dawson's gipfelflur die Alphange von Daly's Obereinstimmungsniveau ge seems to be a variant of his Keine der in niederen Hohen fairly simple original kopft. Lage Baumgrenze one but the issue has been confused for scheint genug angedauert zu haben, als dafi sie heute long lange reasons noch sichtbare morphologische Auswirkungen im Kaskaden various other discussed in this paper. Gebirge hinterlassen hatte. Neither alpine peneplains or Dawson and Daly's observations have ever been completely accepted Introduction as solutions of the problem of alpine accordances, either in this or in the In a report published in 1896, the pioneer Ca country Alps, though had advocates nadian geologist G. M. Dawson noted that a alpine peneplains long many among remarkable number of summits rise to altitudes geologists working in the Rockies. The problem has been discussed in recent de of about 8,000 feet (actually about 2,500 meters), only occasionally cades. It is revived here because of the usefulness both where he was working on the east flank of of such features in the southern British Columbia Coast Range and clima-geomorphic defining climatic inmountains. in the nearby northern Cascades (see location regions map). Nevertheless, very few non-volcanic peaks Our concern with alpine clima-geomorphology within the area of his observations rise much is even wider than that, however. Whether one's higher, and those only to about 2,800 meters. In interest in mountains is esthetic, scientific, eco the Alps such an accordance of alpine summits is nomic, conservational, or military, it iswell to un a called "peak plain" (gipfelflur). Later students derstand how their landscape is organized and the of the phenomenon in the Cascades thought, as significance of its elements. Various climate-re 82 Erdkunde Band XVI

LOCATION MAP: THE NORTHERN CASCADE MOUNTAINS

NUMBERS REFER TO PHOTOGRAPHS ACCOMPANYING THIS ARTICLE

lated landscape elements, such as the alp slopes rest of the northern Cascades. No significant and accordant summits discussed here, play con summit upland exists near or above the 2,500 sistent roles as summit follows summit and gorge meter level anywhere in the range. One gorge en follows gorge across a mountain region. Regional ters the quadrangle at an altitude of about 300 unity in climatically homogeneous mountains is meters only 4 kilometers from a 2,400 meter sum thus like that created by repetition of complex mit. Five other valleys enter below the 800 meter pattern-units in a very boldly-printed fabric. Be level. Most of the big valley-head cirques have cause regional climatic homogeneity can never be floors at about 1,000 meters, though the floor of complete, however, climate-induced consistency the McMillan Creek cirque, between the two of landscape elements is always imperfect and is serrate crests, is at about 850 meters. less in broad regions than in their sub-regions. Several large cirques near Mt. Redoubt have Nevertheless, it is very real and worthy of atten floors above 1,200 meters. tion. Within the small sector of the range covered by theMt. Challenger quadrangle, fourteen summits Dawson's Gipfelflur carry spot heights between 2,270 and 2,575 me One of the best places to see Dawson's gipfel ters; the map shows about fifty unsurveyed peaks flur is in and around the Picket Range (Figs 1 and minor pinnacles in that range of altitude also. a one and 4), part of the northern Cascades covered Only peak in the quadrangle rises higher, by the fifteenminute Mount Challenger quad to 2,730 meters. On it the map shows one minor are rangle (see location map). The Pickets pinnacle rising to about 2,680 meters. The gipfel most like of the high Cascades in having local flur thus forms a very distinct, though not abso more relief of than a kilometer and a half through lute, ceiling on summit heights in the Picket Range. out. Total relief in the quadrangle is about 2,400 The same is true of non-volcanic peaks throughout meters. The Pickets are deeply and completely the northern Cascades, very many of which ap are dissected by steep-walled glacial gorges, as the proximate 2,500 meters but only a thin scattering as Will F. Thompson: Cascade Alp slopes and gipfelfluren clima-geomorphic phenomena 83

on of which exceed 2,700 meters and those only by to different rates of weathering and erosion about a hundred meters at most. The Mount Terror timbered subalpine and open alpine slopes allows massif in the Picket Range is a 3 kilometer serrate us to assume development of his gipfelflur late in mass ridge, all summits of which are between 2,300 and the history of the range after the mountain 2,485 meters high. The 5 kilometer Challenger had become completely dissected. Long survival not Fury ridge is closely similar and has five surveyed of precariously sharp alpine ridges thus need peaks 2,450 to 2,530 meters high. The precarious be assumed. However, Dawson's 8,000 foot gip sharpness of those two serrate crests, and the felflur is 2,000 feet (actually about 100 meters) presence nearby of a number of accordant or above the present timberline and its once much moderately sub-accordant peaks now isolated more continuously accordant ridges are now being from them by convergence of erosion on flanking dismembered. Thus it seems a relic of times past valley walls, suggests strongly that they are rem and in that sense not related tomodern timberline. nants of much more extensive even-crested ridges The known variability of Pleistocene timberline to which have been dismembered by erosion to form levels has long been the leading objection the present topography. Dawson's explanation of alpine accordance. Study of the Cascades allow us to answer that ob In view of the considerable relief and complete may at the same time thatwe Dawson's dissection of the high Cascades, and the great jection explain number and sharpness of those of its peaks which gipfelflur. comprise Dawson's gipfelflur, that accordance Accordance can hardly be considered a peneplain or other Daly's ancient surface. On the crest of uplifted graded Brink has pointed out (1959) that the present the central Wind River Range inWyoming, which climatic timberline in the southern British Co because it stands on a has somewhat high plateau lumbia Coast Range lies somewhat above the less local relief than the there is a Cascades, lowerlying meadows of the accordance Daly felsenmeer-mantled sum strongly rolling graded studied and that it has recently been rising. The mit at meters upland roughly 3,700 which, though same is presumably true in the Cascades. Never not a is like one for peneplain, sufficiently pur theless, wherever it occurs along the northwest of poses discussion. Converging glacial cirques coast of , Daly's accordance cur have divided it into tablelands with precipitous rently remains the upper limit of dense, con walls. A considerable number of very sharp pin tinuous timber. It is not primarily an accordance often accordant with the are asso nacles, upland, of summits but rather one of moderated slopes, ciated with the tablelands but are not found re close to the present upper limit of tree growth, mote from them. such have been form Many spires which are kept more or less clear of timber by ed in the at the of the tablelands as past expense soil disturbance, avalanches, and in many places intersection in various cirques approached places, by persistence of heavy snowdrifts through much but have not retained either their they steepness of the growing season. The relatively moderate or their accordant status. None of those now in slopes of its timberline meadows are consistently existence will remain accordant with the' long in strong contrast with steep gorge walls, stabiliz since the flanks of the two classes big tablelands, ed by the root-mat of their heavy timber, in the of seem to be attacked about peaks equally vigor subalpine zone immediately below. Such timber ously and the pinnacles have relatively little linemeadows in the Cascades have not been inten substance to loose. sively grazed, nor have their clustered trees been As the num cut tablelands gradually dwindle, the much for fuel, but in other respects they are ber of new to accordant spires formed from them entirely equivalent typical alp slopes in Euro will none can dwindle, and long survive the last pean ranges, which are likewise closely and con remnant of the summit upland. The 3,700 meter sistently associated with the existing timberline accordance in theWind Rivers will then be gone. (Boesch, 1946). accordance due to a in the Cas Any peneplain Daly's accordance does include a great many cades must have had a similar the history, yet summits, and thus becomes a gipfelflur, on the peaks of Dawson's attacked on their flanks gipfelflur, of the northern Cascades (Fig. 2), throughout flanks at least as as are the Wind the central vigorously and southern Cascades including those River nevertheless in the accordance spires, persist ofOregon, and in theOlympic Mountains, wherev in numbers. of the er impressive Many peaks high peaks and ridges have commonly been truncated like those in the Picket even gipfelflur, Range, by headward expansion of its alp slopes. Cascade retain some ridge-continuity. trails often run for many miles along ridges thus Unlike the peneplain hypothesis, Dawson's truncated, climbing only to low summits and de of accordance in the Cascades as due explanation scending only into shallow cols. Daly pointed out 84 Erdkunde Band XVI

Fig- 1_

Fig. 2 Will F. Thompson: Cascade Alp slopes and gipfelfluren as clima-geomorphic phenomena 85

in 1912 that the same accordance is present as a Their subalpine slopes are often too gentle to belt of alp slopes on the faces of higher peaks contrast sharply with the alp slopes at their tim even in the more rugged parts of the northern berline, yet Daly's accordance seems quite dis Cascades, where it has been unable to truncate tinct, for example, at about 2,750 meters on sum enough crests to form a gipfelflur at timberline mits in the Carson Range east and northeast of (Figs. 5 and 6). He considered its role there in Lake Tahoe. compatible with interpretation of its gipfelflur Because, in a regional sense, timberline is very phase as a peneplain. Its alp slopes are closely closely controlled by climate, Daly's accordance overshadowed there by alpine crests much too is also, even though both are somewhat influenced spectacularly youthful in aspect to be considered by local structural geomorphic considerations. monadnocks. Also, alp slopes so located were sub Thus the accordance not only rises southward as ject to strong undercutting by Pleistocene valley temperature rises, but also rises from west to east glaciers and have maintained themselves only be across the northern Cascades as maritime influence cause processes similar to those now active on on their climate diminishes. Timberline and them have constantly renewed their surfaces and Daly's accordance are at about 1,500 meters on caused them to migrate headward at the expense the seaward flank of the range, at about 1,800 of the high ridges above. The alp slopes which have meters in its inner parts, and at about 2,100 me truncated and brought to accordance the lesser ters on its continental flank. The rise inland is summits which form the gipfelflur phase of due to warmer midsummer temperatures at any Daly's accordance support similarly vigorous given level away from the sea, and also to reduced processes. As forms thus in dynamic equilibrium snowfall permitting longer growing seasons. The with their environment, they, can hardly be con attitude of Dawson's gipfelflur is not as easy to sidered "fossil" features. determine away from the crest of the high Cas Geologic structure and history of past uplift cades as is that of Daly's accordance because of are no by means consistent in the various Pacific the scarcity of high peaks on the range flanks. Coast ranges in which Daly's accordance occurs, The two accordances seem closely parallel as far yet it rises gradually and regularly, as timberline as can be seen, however, the one being consistently rises, from Alaska to California. In Prince Wil about 700 meters higher than the other. liam Sound, Alaska, it is about 300 meters above the sea; in the Sierras both timberline and high Firn Glaciation of Alp Slopes; Richter's Hypo the alpine meadows reach 3,000 meters. The Sier thesis ras are much less dissected than the ranges in Another to the which Daly's accordance occurs further north. important objection peneplain hypothesis as an explanation of alpine accordance is the fact that processes dominant at alpine levels 1. Accordances in Fig. the Northern Cascades invoke not only great gravitational energy but Dawson's gipfelflur appears here at a height of about also great climatic energy because of their altitude meters on seen 2,500 the skyline of the Picket Range, to In the Cascades the northeast from over the lower The (Albrecht Penck, 1886/87). Skagit Valley. climatic is forested ridges in the foreground are part of Daly's tim alpine energy expressed geomorphically as berline accordance, here at about 1,500 meters. Alp slopes mostly frost riving, solifluction, avalanches, on the forested are to crests ridges confined their higher and glacial erosion. Because are and in this are out of on alpine gradients photograph sight their northern seldom low over considerable and above Considerable at any area, slopes (compare Fig. 2). ridge-continuity are levels intermediate between the two accordances is evident the alp slopes often extreme, wastes from on the peaks in the middle distance. alpine processes are for the most part carried rapidly away downslope instead of clogging their 2. Accordance on theWestern Flank Fig. Daly's action. Any really ancient surface at alpine levels of the Cascades must therefore have been destroyed ago In the zone on the western flank of the Cascades most long (Russell, 1933; Mackin, 1947). completely dominated by Daly's accordance, only the One of the most higher crests retain alp slopes, evident here as snowfields. distinctive features of the Peaks of Dawson's are an forming part gipfelflur roughly higher Cascades is abundance of hanging gla 700 meters than the timberline at higher accordance their ciers (firnfields), mostly lyingon thealp slopes. immediate bases, carry glaciers and broad snowfields, and are common It is in view of the only to the extreme left of the picture near especially noteworthy present crest of in the of the Cascades. Peaks of intermediate height are rarity valley glaciers the non-volcanic Cas common a in transition zone. All peaks which stand above cades, where such trunk glaciers have done great Daly's accordance The (timberline) carry alp slopes. Puget work in the past. Pleistocene of Sound lowland lies to the the last level firn-glaciation right beyond ridges Cascade seems to have been of the range. Mount Rainier is about 175 km. south; in that alp slopes universal, distance the general level of the western fringes of Daly's producing great numbers of moraines, roches accordance rises from about to meters. 1,500 nearly 1,800 moutonees, small cirques with floors at alp-slope 86 Erdkunde Band XVI

Fig. 3 Will F. Thompson: Cascade Alp slopes and gipfelfhiren as clima-geomorphic phenomena 87

levels, and ice-gouged alpine ponds. It would be perhaps partly because of criticism stirred up by easy to conclude from such evidence that glacia Richter's paper. Thus the way was cleared in tion had been the primary process forming the that respect for widespread acceptance, shortly alp slopes and that mass wasting (solifluction and after the turn of the century, of W. M. Davis5 related processes) had been secondary. Thus, simi very instructive system of geomorphology which lar evidence of glacial erosion on the alp slopes ignored altitudinal differentiation of processes. (fjelds) of Norway led the Austrian student, Davis did not deny or attempt to minimize such Eduard Richter, to describe them in 1896 as differentiation. He was presumably aware of the having been formed by the action of firn-glaciers problems involved in discussing it at that time such as commonly persist on them now. and simply avoided considering it for that reason. Guided by Penck's very reasonable hypothesis In alpine geomorphology, however, simplicity is (1886-87) that climate limits the height of moun not gained at that price. Furthermore, we know tains, Richter decided that firn-glaciers had more about climate-sensitive geomorphic processes truncated and reduced to accordance many sum such as solifluction than was known at the turn mits of Norwegian mountains. He would have of the century. reached the same conclusion in the since Cascades, The key to the geomorphology of the high Cas are limited existing firn-glaciers quite generally cades is the fact that their prevailing winds are to the zone in both and mass wast alpine regions onshore westerlies which greatly moderate their was little understood in his time. Richter's ing alpine frost climate by limiting the range of critics seem to have cited the of the variability thermal variation between day and night, and climatic controls of glaciation during the Pleisto between winter and summer. Seasonal freeze and cene and the altitudinal of the lower irregularity thaw are therefore relatively shallow even on limit of erosion in such as present glacial ranges high wind-swept ridges which have permafrost. the where are still Alps glaciers doing really Solifluction at timberline of soil which is protect work. Present in the significant alpine glaciers ed in winter by the heavy snowpack charac Cascades sometimes a deal carry downslope good teristic of the Cascades is plainly very effective, of debris riven from cliffs above other by frost; both because of the frequency with which freeze wise seem to be little. If they eroding very they and thaw alternate there in spring and early were big enough to do much work, they would summer, and because of the abundance of fines cease to be limited to the If mostly alp slopes. alp in such soils. (See Williams, 1949, on chemical had not been at accordant slopes initially present weathering, producing fine-textured soil, at alpine levels in the Cascades and no altitudinal Norway, levels on the Pacific Coast.) Nevertheless, such control is known which would induce to glaciers solifluction is so shallow as to be decisively form such an accordance of moderated slopes, checked by the roots of timber, as Dawson and much less produce the close correlation between Daly observed. Daly's accordance and timberline on the north Neither or any other west coast of North America which has been glaciation process likely to form is as sensitive to the described above. alp slopes presence of timber as solifluction is in such a climate. The clear-cut correlation which exists between Mass of alp Wasting Alp Slopes slopes and timberline on the northwest coast of Penck's of climatic limits on the concept height North America and in western Europe (Boesch, of mountains seems to have fallen from favor 1946) may therefore be considered evidence that some years before mass was much wasting studied, alp slopes have been developed there primarily by mass wasting (frost-caused solifluction and 3. associated Fig. Dawson's Gipfelflur around the Margins processes) and that the role of firn-gla the Suiattle of Watershed ciation has been secondary. However, we must Dawson's gipfelflur is especially well developed between still explain how the present situation can have the 48th and 49th parallels in the northern Cascades. Figs. 1, in the of a 5 were developed presence varying timberline. 4, and taken not far from the 49th parallel; Fig. 3 shows a region near the 48th parallel. A few non-volcanic The statement made above about the shallow Cascade peaks, including Mts. Bonanza and Dome on the ness on of freeze and thaw high, wind-swept skyline to the left, approximate 2,700 meters but none reach ridges in the Cascades is based on the modest size 2,800 meters. The gipfelflur as a whole is at about 2,500 meters. of boulders to form (View southwest over Mt. Buckindy.) upsorted felsenmeers in such sites. At high levels on Redface Mountain in the 4. Dawson's in the Picket Fig. Gipfelflur Range Picket and Ruth Mountain near Mt. Shuk This shows Range picture the characteristic form of its peaks. Their san are are there felsenmeers of stones four to summits nowhere of sufficient area to be interpreted as only a or inches across. The peneplain other ancient surface now uplifted. (The eight south ridge of Luna Peak "Terror Group" and Mts. Luna and Fury.) in the Pickets (2,525 meters) has the coarsest

en as Will F, Thompson: Cascade Alp slopes and gipfelflur clima-geomorphic phenomena 89

felsenmeer observed in the central northern Cas vection than is air in those crevices in winter cades; its stones are probably two to four feet while the rocks remain warmer than the outside across. Throughout the Cascades and Olympics air. alpine frost-sorting of stony soil, though often It is noteworthy, however, that the uncreviced active, is shallow except in sites (generally very surface of stony, silty alpine soil over which restricted) which are subject to non-climatic inten felsenmeers and rock glaciers are advancing down sification of soil frost. slope on Silver Star shows little evidence of What seemed to be an exception to that rule upsorting of its own stones by frost, even though was found on Silver Star Mountain (2,710 meters) it is continuously in the shadow of the mountain in theMethow drainage, in the part of the eastern for several months each winter. Formation of flank of the northern Cascades most protected felsenmeer on Silver Star is not due primarily to from marine influence. Coarse boulders on the frost heave but rather to sorting-out of coarse northern face of that peak are subject to mass boulders by free fall from the cliffs above. The wasting by felsenmeer creep (Thompson, 1960-61) larger boulders roll further than smaller rockfall and even by rock glacier flow (Wahrhaftig and debris and thus accumulate as open-jointed block Cox, 1959). The latter phenomenon implies the fields, subject to Balch ventilation. The mobility presence of permafrost in the silty, stony soil of such surfaces on Silver Star is thus due entirely which makes up the greater part of huge felsen to non-climatic intensification of soil frost, as in meer-mantled glacier-like masses of detritus. Such the rest of the Cascades, though because the Cas deep frost is due to refrigeration of the subsoil cades shelter the Methow region from the sea beneath the felsenmeer by Balch ventilation intensification occurs much more readily and on comparable to that which forms ice in caves a far larger scale there than elsewhere in the on (Balch, 1897, 1900). Air cooled by radiation range. adjacent surfaces seeps down into the crevices Troll (1943-44) showed that the horizontal among the boulders and chills them, and the soil dimensions of frost polygons, stripes, and other beneath, very deeply. The chill is retained in sum frost patterns in alpine and arctic soil vary with mer because cool air in the crevices is relatively the duration and intensity of freeze and thaw, heavy and thus stable, much less subject to con being very small in tropical mountains where the alternation typically occurs daily, and very large in the arctic where the alternation is annual. Be 5. Accordance at Levels within the Fig. Multiple High cause of its the cumulative effect of Cascades frequency, frost seems about as great in some of Troll's Dawson's gipfelflur (about 2,500 meters) is visible on and mountain as in arctic beyond the summits of the Picket Range (center). Some of tropical landscapes topo the peaks in Fig. 3 form part of the distant skyline at far graphy. (Dresch 1958 should be read from this More or less continuous at levels intermediate right. ridges point of view.) In the Cascades, the dimensions between 2,500 meters and timberline, such as Easy Ridge and character of frost patterns are very like those (center right), have been truncated during stands of Pleisto Troll describes for the ifwe make allow cene interglacial timberline intermediate in height between Alps, the present forest limit and the ancient interglacial timber ances for selection by Troll of interesting and line which determined the level of the high gipfelflur. well-defined 7 and Because the Picket summits are much too to especially examples (Figs. 8). Range bulky Solifluction terraces and various kinds of have yet been truncated at the present level of timberline, garland are common Daly's accordance is represented among them by an accor soils very in the Cascades. Polygons dance of moderated slopes (alp slopes) immediately above and stripes occur in favorable sites. Because slopes rather than an accordance of summits as in timberline, by on which such patterns form are often and 2. southeast over Brush Creek in the Picket irregular Fig. (View their soil thin and frost Range.) poorly sorted, patterns are much more often irregular and poorly defined Fig. 6. The Nooksack Cirque on Mt. Shuksan than not. The same is believed to be true on in the such Wisconsin and recent glaciation have been especially vig glaciated alp slopes Alps; patterns orous at the head of this representative cirque in the will be wellformed more often when mass wasting northern remain intact there at Cascades, yet alp slopes has had time to re-grade the alp slopes again more the same level as on the other walls of the valley. Present climate and timberline are believed to correspond to those completely. which have controlled alpine mass wasting, and thus the of a considerable of development alp slopes, during part Weathering and Erosion of Alpine Crests Pleistocene interglacial time; present conditions may prob on ably be considered as nearly normal for the Pleistocene as Relations between processes Cascade alp a any climate could be in such variable epoch. Persistence of slopes and those on and even sharpened alpine ridges present climate may permit timberline to regain towers above them are of considerable a continuity lost in this and similar localities be standing tually interest. On the are low cause of local glaciation extending below timberline during alp slopes gradients so the last few thousand years (the Little Ice Age of Matthes). enough that, though soils are very mobile, soil 90 Erdkunde Band XVI

^BB^^^^^^^^^B^^B^^B^HBWBBBPBBBBBfc 7 -Patterned Ground in thePicket Range Such in theCascades are believed to have dimen ^^^HB^^^^^^ patterns |^^HBHHH^^^^^^J|^^^^^^HHSH^9^^9H sionscontrolled by thermaland frostregimes. Analogy of formand dimension with patterns someparts, at least, H||^^^^|^^^^H^^^^^^^^^HHB9H|^B^RH an ^^^^^^^^^^^^^^^^^^^^^^^^^HBH^SmEj of theAlps is considered indicationof similarregional

8. ^B|H|||^^||^^^^^^^^^^^^H||HHHfHB9Qfl Fig. Nivationin thePicket Range Diurnalfreeze and thawover many years in moist ground ^^^^||^^^^^^^^^^^^^^^^^^^|HHHH?Hg2 mass ^^^^^^^^^^^^^^^^^^^^^^^^|^H||HRmM8B beneaththis snowfield has causedweathering and wasting,resulting in theadvance of a tongueof debris ^KB^^^^^^^^^^^^^B^^^^^^^^^^BKKtjf^^^ over HHH^^^^^^^^^HH^^^^^^H|^^M^B9MH heathersod downslope. Note similarcreeping debris WtB/BKmmKKBKtKKKbelow the snowfield in the background. Fig. 7

Fig. 8 Will F. Thompson: Cascade Alp slopes and gipfelfluren as clima-geomorphic phenomena 91

does re form and vegetation grows. However, riving of themoist cliff-base. A sharp knick-point a moval of soil by solifluction keeps great deal is therefore normal between the upper margin of of bedrock within reach of weathering at all a graded alp slope and the cliff above it; itmay times. The mobile soil of the alp slopes, which is even develop into a recess like the ones often on generally quite thin where it lies directly bed carved in the bases of sea-cliffs by waves. seems to accelerate in rock, actually weathering Even in the absence of firn-glaciation, which such in contact with places, partly by retaining generally acts powerfully to the same end, there the substratum moisture essential to active chemi a is thus strong tendency for alp slope processes cal and physical weathering, and partly because to undercut and steepen the cliffs above them, solifluction is able to coarse pick up moderately consequently sharpening and eventually truncat blocks and them mixed with finer carry away ing the high alpine summits. Generally speaking, materials instead of them to un to leaving protect firn-glaciation tends simplify the boundary weathered materials beneath. between alp slopes and cliffs. Other alp slope tend to Since the alp slopes of the Cascades seem to processes render it intricate, so that it runs into have been formed primarily by mass wasting, upslope avalanche gullies (couloirs) and around they must once have been quite well-graded. Lo downslope ridges. The high ridges are truncated cally they are stillwell-graded, in spite of having eventually in any case, however. (Com Spreitzer been glaciated, and are again completely domi pare 1960). nated mass one on by wasting. A graded slope is Destruction of the high alpine ridges does not which there is an equilibrium between detritus take place from the top down, however. The at available any given point and the capacity of higher ridge-crests and summits seem too dry, in active to move A to processes there the detritus. effect, support frost riving and weathering to on continuing deficiency of detritus exposes bedrock comparable that their flanks, though their to at an excess are more severe rapid weathering the surface; temperatures than those on alp the aggrades slope. Heavily glaciated alp slopes slopes and they probably get as much precipita are thus ordinarily a mosaic of bare bedrock tion. Snow blows off them or falls away as ava knolls and of or lanches. Rain pockets aggrading soil talus, with and meltwater seep promptly into gradiation beginning at the margins of the out bottomless joint systems which lead the moisture down to crops. Complete gradation removes such irregu cliff-faces and alp slopes below. The larities. A graded slope under fairly uniform escaping water often carries with it any soil thick soil is often eroded at formed on only slowly any the summits, leaving nothing but a given point because almost all of the detritus heavy cover of lichens on the rocks. Soil and even which can be at coarse handled by processes that point fairly rock fragments may also be picked is from and supplied upslope. Where the soil is thin up carried away by wind. Many high alpine but on crests are a nevertheless continuous, the other hand, thus mass of coarse blocks approxi much of the detritus load of in active processes may mately place, though generally dramatically be derived from local bedrock, which is conse riven. The slowness of the riving, because of lack wasted of quently down evenly but relatively moisture, is expressed by the completeness and rapidly. maturity of their lichen cover. Clean surfaces become common at cliff from which Where graded alp slopes head under cliffs, the only margins, stones fall Slow and erosion latter condition is usual on their upper parts, away freely. riving of summits are also the though the mantle covering the graded surface alpine expressed by long of the of the in of bedrock may be mostly rockfall debris rather persistence high peaks range a Daly's accordance in of the and than well-developed soil. Under such circum spite steepness of their stances, any soil, coarse or fine, tends to creep rapid wasting rockfall-swept faces. away from the base of the cliff and leave bedrock at as thinly covered that point. Because snow gener Accordances Records of Varying Timberline ally accumulates and lies late at the cliff base, Levels meltwater is abundant there in and to spring early Opposition Dawson's concept of the origin summer. At that a time, furthermore, gap several of alpine accordances at timberline has been based feetwide between a develops the cliff and the snow, to large extent on the argument that since tim conditions inwhich are similar to those in a berg berline is climate-controlled and must vary in schrund or a felsenmeer crevice. That the altitude as is, gap climate varies, its geomorphic effect the coldest traps lowest, layers of the downslope during the Pleistocene must have been diffused flow of air chilled by night radiation on surfaces over so wide a zone of mountainsides as to have On calm in upslope. clear, nights particular, the had no significant effect at any one level. To cold air freezes the rock and causes severe trapped point in rebuttal to the regularity and consistent 92 Erdkunde Band XVI

coincidence of Daly's accordance and timberline glacial periods, in arguing that the geomorphic on the northwest coast of North America does effects of timberline must have been too greatly not in itself solve the problem. However, obser diffused to be obvious today. vations in the Cascades indicate that, rather than Old erosion surfaces below alp slope levels, being imperceptible, the geomorphic effect of seen this summer west of the Cascades, are too timberline is visible not only within the present broad to be due to ridge truncation at a lower timberline zone but at many higher levels. The timberline. They seem to be portions of old floors observations in question include extensive photo of the Puget Sound Basin. On the eastern flank graphic flights and several weeks of study on foot of the Cascades the crests of several ranges which in the northern Cascades and Olympics during the run from the high Cascades southeastward to the summer of 1961. About 350 aerial oblique photo Columbia between the mouths of theWenatchee graphs and a very large number of ground photo and Methow Rivers descend quite regularly in east graphs were taken on which to check the field that direction to form an accordance sloping observations. ward. It cannot be related to timberline, since timberline rises in that direction as far as If Daly's accordance were the only level at slowly are crests to reach it. The ac which the Cascade timberline had ever controlled there high enough cordance was described by Willis as the "Entiat the truncation of higher alpine crests, summits the eastern of his Cascade pene above that level should tend to be sharp (Matter Surface", margin Aerial of the River horn-type peaks) instead of being continuous ridg plain. photographs Twisp north of Lake show es. Only timberline, controlled by climate, can Valley, Chelan, similarly accordant northward toward have inhibited the differential erosion of alpine ridges descending that basin. Willis' can crests so sharply at certain levels as to produce hypothetical peneplain descend to the as those do, the even-crested which are very common hardly Twisp ridges ridges are as as crests on in the northern Cascades even above timberline. yet they just accordant the which he based his "Entiat Surface". Daly dis If we consider the region as a whole, the preva cussed various of such accordances lence of even-crested ridges seems to diminish up possible origins in 1905; his discussion of the effect of regular ward only gradually. Except locally, isolated stream and uniform slope development sharp peaks become the dominant summit form spacing may in this instance. only as we approach the level ofDawson's gipfel apply flur. There are many more or less continuous as serrate Cascade and as ridges even in the gipfelflur, such the Alp Slopes Gipfelfluren Regional Characteristics Related to Climate crests in the Picket Range (Figs. 1, 4 and 5). It may thus be said that the alpine geomorphology The forms and surface patterns of peaks in the and similar indicates of the Cascades ranges strong Cascades have great individuality. Such distinc of timberline levels variation during interglacial tions are particularly evident to people traveling recent was not so and time, though the fluctuation among them on foot because they have good views as to from itsmark rapid keep timberline leaving of only a few summits at a time. From the air, inmany places above the level of Daly's accord on the other hand, the more or less accidental ance. levels were due If the indicated timberline characteristics which make each peak distinctive simply to differences in temperature, they demons are subordinate to similarities among them which trate occurrence climate about the of interglacial create a strong sense of regional unity. The acci seven warmer than that of the degress present dental features are generally due to local geologic difference time, that being the temperature structure. The similarities are in large part respon to sustain timberline at the level of required ses to regional climate along the lines discussed Dawson's gipfelflur. in this study. Except as they are effected by local all the various features of Ridges and upland surfaces more or less accord geological situations, tim ant with one another exist on the fringes of the summits, cliffs, glaciers, cirques, alp slopes, northern Cascades below the level of Daly's ac berline, subalpine forests and slopes, and of the cordance but do not seem related to timberline. gorges between the peaks, thus conform to rules as we have been not The amount of valley glaciation in the range in such those discussing, only were as to altitude but also with to dicates that glacial climates severe there with respect respect and with ad as elsewhere, yet slopes within the range below exposure, grandient, relationship no features. the alp-slope accordance provide evidence of jacent are low stands of timberline. It therefore seems prob Regular as the circumstances in which such able that the critics of Dawson and Richter features occur and recur, however, there is a pro as were correct with respect to glacial periods during gressive change in the aspect of the Cascades one western to their eastern the Pleistocene, though not with respect to inter flies from their flank en as Will F. Thompson: Cascade Alp slopes and gipfelflur clima-geomorphic phenomena 93

flank. The forest becomes more open and less tall. Bibliography on W. Bedrock crops out more generally alpine Atwood,W.W. and Atwood, W. Jr., 1838: A Working meadows and Hypothesis for the Physiographic History of the Rocky subalpine slopes. Southfacing slopes v. become more folded into and Mountain Region, Bull. Geol. Soc. Amer., 49, pp. sharply gullies ridg 957?980. es. are less continuous on the faces Alp slopes Balch, Edwin Swift, 1897: Ice Caves and the Causes of on v. of high peaks and may be entirely absent Subterranean Ice, Jour, of the Franklin Institute, 143, southern exposures, as on Silver Star Mountain. no. 3. or The of Daly's accordance is ?, 1900: Glaciers, Freezing Caverns, Philadelphia: gipfelflur phase Allen, Lane, and Scott. but the mountains which widely present compose Boesch, Hans H, 1946: Die Formen des Hochgebirges, Die are on v. it truncated by alp slopes developed north Alpen, 22, pp. 293?299. V. 1959: faces only; south faces are steep to their crests. Brink, C, A Directional Change in the Subalpine The same west of the Cascades but Forest-Heath Ecotone in Garibaldi Park, British Colum thing happens bia, v. 40, no. 1, pp. 10?15. not as The eastermost Cascades are Ecology, consistently. Daly, R. A., 1905: Summit Levels among Alpine Moun a within with thus distinct subregion the range tains, Jour, of Geol., v. 13, no. 2, p. 105. respect to alpine climate. The subregion is prob ?, 1912: The Geology of the North American Cordillera, best on the Methow watershed Canada, Dept. of Mines, Geol. Surv. Memoir No. 38. ably exemplified W. 1899: because that area is sheltered from ma Davis, M., The Peneplain (original version), especially Amer. Geol., v. 23, no. 4, pp. 207?239. rine influence. Dawson, G. M., 1896: Report on the Area of the Kam The more westerly parts of the Idaho Rockies, loops Map Sheet, British Columbia, Canadian Geol. New Series B for 1894. such as the Sawtooth may have an Survey, VII, Rpt Range, alpine 1958: Problemes climate and like that of the Drech, Jean, Morphologiques des Andes landscape quite Centrales. Ann. Geogr. v. 67, pp. 130?151. Methow further there is desirable. G. peaks; study Gilbert, K., 1904: Systematic Asymmetry of Crest In a to reconnaisance from the Lost River Range Lines in the High Sierras, Jour, of Geol., v. 12,, pp. the Sawtooths this summer itwas evident that the 579?588. much-discussed "Idaho is cor Mackin, J. Hoover, 1947: Altitude and Local Relief of Peneplain" closely the Area the Field related with timberline that Bighorn during Cenozoic, Guidebook, throughout region Conf. in the Bighorn Basin, Published by the Univ. of an and is thus eastward extension of Daly's ac Wyoming, the Wyoming Geol. Assn., and the Yellows cordance. Even on the face of the Lost River tone-Bighorn Rsch Assn. east of which is so that it has ?, 1948: Concept of the Graded River, Bull. Geol. Soc. Range Mackay, dry v. no. 463?511. a of well above the Amer., 59, 5, pp. only fringe pines valley floor, F. 1960: Matthes, E., Reconnaissance of the Geomorpho a series of from the mountain and spurs projecting logy Glacial Geology of the San Joaquin, Sierra crests at Calif, front have very regularly accordant Nevada, (edited by Fritiof Fryxel), U. S. Geol. timberline. How much further into the Rockies Survey Professional Paper 329. Misch, Peter, 1952: of the Northern Cascades the accordance might be followed is hard to say; Geology of The v. no. 4?22. as far as the winter westerlies a Washington, Mountaineer, 45, 13, pp. perhaps deposit Penck, Albrecht, 1886?87: Uber Denudation der Erd winter snow cover. oberflache. Wien: Schriften zur really heavy d. Vereins Verbreitung Contrasts between theCascade Naturwissenschaftlicher Kenntnisse. alpine landscape 1919: ?, Die Gipfelflur der Alpen. Sitzber. Preufi. Akad. and that of New England mountains (Thompson, Wiss. have been mentioned are 1896: 1960-61) earlier. They Richter, E., Geomorphologische Beobachtungen aus greater than would be guessed by a person com Norwegen. Sitzber. K. K. Akad. Wien, Math. Naturw. Classe CV, Abth. I. 147?189. paring the lowland climates of the two pp. regions. I. 1900: A who has much Russell, C, Preliminary Paper on the Geology Anyone spent time in both the Cas of the Cascade Mountains in Northern Washington, cades and the Presidentials can vouch for themuch U. S. Geol. Survey, 20th Annual Report, Part 2, greater violence of alpine winds in the latter. Dif pp. 193?204. R. 1933: ferences in frost regime are mostly due to the fact Russell, J., Alpine Land Forms of the Western United Bull. Geol. Soc. v. 927?950. that the alpine winds blow off the continent in States, Amer., 44, pp. George 1903: New are Smith, Otis, Geology and Physiography of England, but accentuated by the fact Central Washington, U. S. Geol. Surv. Prof. Paper 19, that westerly winds remove most of the snow pp. 3?40. from New G. O. and F. England alpine uplands. Regionally Smith, Calkins, C, 1904: Geological Re connaissance across the near speaking, western timberlines are control the 49th closely U. S. Geol. Surv. Bull. 235. led and but those Parallel, by temperature growing season, ?, 1906: U. S. Geol. Surv. Folio 139. are Snoqualamie Folio, of New very sensitive to wind. Ob 1960: England Spreitzer, Hans, Hangformung und Asymmetrie der servation of such climate-sensitive characteristics Bergrucken in den Alpen und im Taurus, Zeitschr. fiir Contributions a of the mountains of the world may eventually Geomorph., Internationales la Morpho a logie des Versants pp. 211?236. provide sound basis for study of the regional Thompson, Will F., 1954: Environmental Handbook for physical geography of mountains and will also Whittier, Alaska, Rpt No. 226, QM R. & E. contribute to related Command, substantially sciences. U. S. Army, Natick, Mass. 94 Erdkunde Band XVI

?, 1960?61: The Shape of New England Mountains, Army Engineers, Snow, Ice, and Permafrost Research Appalachia, v. 33, no. 2, pp. 145?159; v. 33, no. 3, Establishment, Wilmette, 111. pp. 316?335; v. 33, no. 4, pp. 458?478. Wahrhaftig, C. and Cox, A., 1959: Rock Glaciers in the Alaska Bull. Geol. Soc. v. 383?436. Troll, Carl, 1941: Studien zur Vergleichenden Geographie Range, Amer., 70, pp. at der Hochgebirge der Erde. Bonn: Bonner Universitat Williams, Joseph E., 1949: Chemical Weathering Low Buchdr., Gebr. Scheur. Temperatures, Geog. Rev., v. 39, no. 1. ?, 1943?44: Strukturboden, Solifluction und Frostkli Willis, Bailey, 1903: Physiography and Deformation of S. mate der Erde. Geologische Rundschau, Band 34, Heft 7 the Wenatchee-Chelan District, Cascade Range, U. und 8, pp. 545?694. Translated in 1958 for the U. S. Geol. Surv. Prof. Paper 19, pp. 41?101.

A PRELIMINARY REGIONAL DYNAMIC CLIMATOLOGY OF THE ANTARCTIC CONTINENT1) Michael E. Sabbagh

With 14 Figures, 5 Tables

ein Maximum erreichen. und ZHsammenfassung: Eine vorlaufige regionale dynamische sehen Elemente Temperatur- sind in Oberflachennahe als Klimatologie des antarktischen Kontinentes. Luftdruckablaufe sowohl auch in der durch grofie unperiodische Schwan Die vorliegende Arbeit versucht trotz der, infolge der Troposphare von charakterisiert, von denen die ausgepragtesten sich Kiirze der Beobachtungszeit und der geringen Zahl kungen iiber weiteste Gebiete erstrecken und durch machtige Luft Beobachtungsstationen bestehenden Beschrankungen, eine schichten der Atmosphare hindurch gleichzeitig vonstatten vorlaufige Basis fiir eine regionale dynamische Klimatologie Diese sind eine Art Singulari von Antarktika zu geben. Zunachst wird eine grundsatz gehen. Hauptschwankungen ost taten und konnen mit grofiraumigen Wetterlagen in Zu liche Differenzierung zwischen dem Klima des hohen werden. antarktischen Plateaus und dem der Kustengebiete ge sammenhang gebracht Wahrend des Teiles des Jahres ist das Innere troffen; das Klima des niedereren westantarktischen Pla grofiten des Kontinentes von einer Schicht kalter Luft iiberzogen. teaus gehort, obwohl es Ubergangscharakter zeigt, dennoch Diese ?Oberflachenhautw von Kaltluft, die ungefahr 200 in hoherem Grad dem Klima der Kustengebiete an. Ober bis 300 m und durch Inversionen und diese werden aus machtig ausgepragte grundsatzliche Zweiteilung hinaus, gut zu katabatische Luftstromungen charakterisiert ist, bildet gepragte Klimagebiete innerhalb des Gebietes mit Kiisten der eine Diskontinuitat. klima identifiziert. dariiberliegenden Atmosphare Storungen in bestimmten Wetterlagen und die Auswirkun Die ausgepragten regionalen Klimacharakteristika sind gen einer Wolkendecke auf die Strahlung zerstoren die In ein Ergebnis des Perturbationselementes. In hauptsachlich versionsschicht im entfernten Inneren nur aufierst selten, den mittleren Breiten entstehen zahlreiche Storungen, die an der Kiiste wesentlich haufiger. Das Bestehen einer in das Innere des Kontinentes vordringen. jedoch spiralenformig Diskontinuitat zwischen der Oberflachen-Inversionsschicht Sie werden, hauptsachlich durch antizyklonale Sperrung, und der Atmosphare dariiber und der Konflikt zwischen auf Gebiete hingesteuert, wobei sie sowohl bevorzugte auf hinzielende Kontrolle mit den Perturbations Strecken des Kiistensaumes als auch das niederere west Isolierung elementen sind die Determinanten des ant antarktische Plateau klimatisch stark beeinflussen, wahrend hauptsachlichen arktischen Wetters und Klimas. nur selten in das hohe innere vor sie ganz Ostplateau zur Die Aussichten fiir zukiinftige Forschungsarbeiten dringen. zu Klimatologie von Antarktika sind nun besser als je Wahrend der Jahreszeit niederen Sonnenstandes besteht vor. Mit der Weiterfiihrung des Programmes des I. G. J. eine von Storungen, und daraus ergibt groBere Haufigkeit und der dafi antarktische zu dieser die Variationen aller klimati Wahrscheinlichkeit, Beobachtungs sich, daB Jahreszeit von stationen vergleichbare Werte iiber eine Periode fiinf werden oder mehr Jahren zur Verfiigung stellen werden, This paper is a summary of a doctoral dissertation of *) zweifellos neue fiir klimatische Charakter the same title submitted to the of Erklarungen Department Geography, von wobei viele der which ziige Antarktika entwickelt werden, University ofWisconsin, inAugust 1961. The research, hier entwickelten Erklarungen entweder ihre Bestatigung included 6 months field work, was made possible by funds oder finden werden. Science Foundation the Widerlegung provided by the National through Antarctic Research Program. to to Pro are to The author would like express appreciation The specific objectives of this paper fessor Glenn Trewartha, who acted as dissertation ad describe and the and seasonal and explain regional visor, encouraged the writing of this paper, generously over a of the Ant and offer valuable variations of climate large part gave time to read the manuscript arctic continent. The is based almost suggestions. analysis term is in Inter The 'regional dynamic climatology' employed entirely on 1958 data collected during the areal differences in this paper to mean explanations of national Year at 7 United considered as Geophysical (IGY) climate. 'Dynamic climatology' is therefore some States Antarctic stations (fig. 1). Although climatology. The term has however simply explanatory international stations the been defined in a variety of ways, generally conflicting, twenty operated during F. K. 7 stations were by both geographers and meteorologists. (See Hare, IGY, data from only the U.S. "The dynamic aspects of climatology", Geografiska Annaler, available in a form useful for this study.Although XXXIX, 4 p. 90, and Glossary of Meteorology, ed., (1957), the few stations and their short period of record R. E. Huschle, American Meterological Society [Boston, a serious this is for 1959], p. 184). impose handicap, compensated