GLACIATION OF THE UPPER KERN BASIN: KERN GLACIER SYSTEM
As previously noted, the climax of glaciation in the Sierra Nevada occurred in the central part of the range. At the heads of the Merced and Tuolumne Basins, for instance, the cirques and their short outflow canyons were filled with Pleistocene ice nearly to their full depth; some were completely filled, and the ice overflowed the dividing ridges and spurs on a large scale. Still farther northwest, in the rugged northern part of Yosemite National Park and the adjoining headwater areas of the Stanislaus and Mokelumne Rivers, the ice, even during the relatively moderate Wisconsin Stage of glaciation, covered the mountains except for a few of the highest peaks. The ice formed a local, flatly domed cap whose gently curving surface did not reflect the character of the topography underneath. Only isolated nunataks stood out above the ice.
To any observer trained to read the signs of alpine glaciation, it cannot fail to be evident, as he travels southward from this area of maximum glaciation across the upper Merced, upper San Joaquin, and upper Kings River basins, that ice accumulation decreased by degrees, that the cirques and canyons were filled to progressively less depth, and that the intermediate peaks and crests stood above the ice with greater height and in more continuous chains. Nor did the ice in each of these basins possess a continuously domed surface; on the contrary, it had a broadly concave surface, each basin being an independent area of accumulation.
In the upper Kern Basin, it will be clear from the foregoing, the paucity of ice, as compared with that in the other major basins to the north, was greatest of all. In spite of the great altitude of the upper Kern Basinwhose floor ranges for the most part from 10,000 to 11,500 feetand in spite also of the great height of the surrounding peakswhich range from 12,000 to more than 13,000 feet on the Great Western Divide and the Kings-Kern Divide, and from 13,000 to well over 14,000 feet on the main crest of the Sierra Nevadathe upper Kern Basin at no time during the Pleistocene Epoch, not even during the earlier stages of glaciation, contained an extensive unbroken ice sheet such as filled the upper Tuolumne Basin above the Yosemite region (Matthes, 1930, p. 77 and map, pl. 39). The glaciers that issued from the cirques on the surrounding crests converged toward the central canyon as distinct ice streams separated from one another by mountain spurs or low divides. Coalescence of these glaciers across interspaces occurred only in the uppermost part of the basin, but even there several spurs remained emergent above the ice. Nor did the ice attain great thickness. It averaged little more than 1,000 feet in depth on the broad plateaulike benches and reached maximum depths of 2,000 to 3,000 feet only in the main canyons.
Systematic mapping of the individual branch glaciers showed that they filled the cirques to not more than two-thirds of their depth and filled the canyons leading out from the cirques to only about one-half of their depth. On the walls of those canyons, the upper limit of glaciation is in many places distinctly marked, owing to the fact that above that limit the walls are fluted directly downward by recurrent avalanche action, but below the limit they are smoothed by longitudinal glacial action.
The paucity of ice thus revealed at and near the centers of ice accumulation surrounding the upper Kern Basin contrasts strikingly with the abundance of ice in comparable places farther north in the High Sierra. The scarcity was due not only to the far southern latitude of the basin and to its southward exposure but also to the effect of the Great Western Divide, which exacted a toll of precipitation from the moisture-bearing westerly winds and thus reduced the amount of snow available for distribution over the upper Kern Basin. Nearness to the deserts east and southeast of the Sierra Nevada undoubtedly was also a determining factor, during Pleistocene time, as at present, the hot dry air from those areas causing much of the fallen snow to waste away by evaporation.
That the ice in the upper Kern Basin constituted a separate system, which was independent of ice accumulations in adjoining drainage basins and was of strictly local origin, may be attributed to the following circumstances: Only a few gaps in the encircling mountain crests were low enough to permit diversions of ice across them; furthermore, these few diversions were outgoing rather than incoming, owing to the great altitude of the upper Kern basin and the relatively deep dissection of the adjoining mountain areasthe Kaweah Basin on the west, the Kings Basin on the north, and the Sierra escarpment on the east.
The term "Kern glacier system" may appropriately be used to apply, broadly, to all the Pleistocene ice bodies, large and small, of the upper Kern Basin. The specific members of that system are: First and foremost, the great Kern glacier itselfthat is, the Kern trunk glacier and its many branches; the scattered little glaciers west of the canyon, at the sources of the Little Kern River and the Tule River; and, finally, those glaciers east of the Kern Canyon, also small, at the sources of Golden Trout Creek and the South Fork of the Kern River. In the following pages the various members of the Kern glacier system are discussed in the order in which they have just been named. By far the greater part of the system falls within Sequoia National Park but, in the interests of completeness, the parts of the system outside the park will also be considered briefly. Actually these outlying parts are, with but a few exceptions, only a short distance from the park boundaries.
The Kern glacier was a great, many-branched ice body fed from ranks of cirques along the high bordering ranges, the Great Western Divide (altitudes 10,000 to more than 12,500 ft), the Kings-Kern Divide (12,500 to more than 13,000 ft), and the main crest of the Sierra Nevada (13,000 to almost 14,500 ft), as well as on ridges subsidiary to these crests. Because the Kern Canyon extends in a nearly straight line through the middle of the upper Kern Basin and the tributary canyons branch from it like the ribs in an oak leaf from the main rib, the Kern glacier had much the same pattern. During the Wisconsin Stage, the tributary ice streams lay entirely confined in the side canyons, but during the El Portal Stage the ice spread locally across intervening divides and over the benchlands on either side of the main canyon.
It has long been assumed that the Kern glacier never extended beyond the terminal moraine that loops across the floor of the Kern Canyon a mile south of Golden Trout Creek. However, the present reconnaissance showed that this moraine marks only the limits which the glacier reached during the Wisconsin Stage and that during El Portal Stage the glacier extended about 7 miles farther down the canyon, to the vicinity of Hockett Peak. It appears, then, that during the Wisconsin Stage the Kern glacier attained a length of 25 miles, and during El Portal Stage a length of about 32 miles. In Glacier Point time, the glacier probably reached a length approximately equal to that reached during El Portal Stage.
The lower limits of the great Kern trunk glacier of Wisconsin time are clearly indicated by the remnants of moraines in the vicinity of the Kern Canyon Ranger Station (pl. 1). These moraines were first made known by Lawson (1904, p. 345-348). The author's reconnaissance provided opportunity for examination of the moraines described by Lawson and for noting several others belonging to the same series but not previously reported. The author's observations served to emphasize the close correspondence which exists between the Wisconsin moraines in Kern Canyon and the comparable series in the Yosemite Valley (Matthes, 1930, p. 56-58).
As was made clear by Lawson, the most southerly of the moraines is a V-shaped loop, whose apex is directed down the canyon, about three-quarters of a mile south-southwest of the Kern Canyon Ranger Station. The moraine is an inconspicuous one, being on the average only 25 feet high. Beginning at the west side of the canyon, this moraine runs out obliquely into a depression bounded, on the east, by a linear rock ridge rising from the central part of the Kern Canyon, adjacent to the Kern River. This rock ridge is in the category which Lawson designated as "kernbuts." After making a pointed loop in this depression, the moraine ascends to the top of the kernbut.
Immediately north of the end moraine, and very similar to it, are two recessional moraines, also reported by Lawson, the northerly one of which is double crested. In crossing from the west canyon wall to the kernbut, these moraines also form V-shaped loops.
As Lawson recognized, these moraines outline the positions of a small frontal lobe of the Kern trunk glacier which was thrust into the depression between the west canyon wall and the rock ridge. However, Lawson evidently did not observe that morainic material also lies on the steep east side of the rock ridge and that east of the Kern River there is at least one distinct moraine loop, standing 10 to 15 feet above an outwash terrace. This moraine must represent the eastern equivalent of one of the three loops west of the rock ridge, probably the southerly one. Thus the rock ridge appears to have divided the glacier, at its terminus, into two small lobes.
In this reconnaissance, several other indistinct moraines were noted a little farther upstream, in the area just south of Coyote Creek. Also, a prominent moraine was traced from the Kern Canyon Ranger Station west-northwest along the north side of Coyote Creek as far as the lower west slope of the canyon. Where Coyote Creek debouches on the canyon floor, it is difficult to distinguish the material of this moraine from that of the boulder levees along the stream. Still farther north, likewise on the west side of the Kern River (immediately north-northeast of Soda Spring), are two other fairly prominent Wisconsin moraines, each the remnant of a moraine loop.
Finally, outside the mouth of Golden Trout valley is the beautifully symmetrical moraine described by Lawson which is notable as the largest and most northerly member of the morainal series left by the Kern trunk glacier. This moraine also is V-shaped in ground plan and, having been breached at the apex by the Kern River, actually consists of two separate wings, one on either side of the river. These wings are even-crested massive ridges, each almost half a mile long and in places rising nearly 100 feet above the flat along the river. This moraine may correspond to the one in Yosemite Valley which formed the dam of Yosemite Lake (Matthes, 1930, p. 57).
Throughout the 1-1/2 mile section of the Kern Canyon occupied by these moraines a jumble of material, both morainal and outwash, mantles the rock floor to an appreciable depth. What this depth may be is suggested at a point a few hundred yards downstream from the ranger station where the river has cut through the mantle into the underlying granite (fig. 37). Here, on the east side of the river, the mantle does not appear to be over 30 feet deep, but up the valley, toward the upper moraine, the mantle may well gain in thickness.
Northeast of Volcano Falls, the old Conterno Trail connecting the floor of Kern Canyon with the valley of Golden Trout Creek climbs the left lateral moraine of the Kern trunk glacier, reaching the top at 7,000 feet. This fairly conspicuous moraine at one time evidently formed a barrier across the mouth of the small hanging valley north of the Conterno Trail, but the moraine is now crossed by a narrow gorge. The height of the moraine shows that the Wisconsin glacier at this point had a thickness of 600 feet plus the thickness of the glacial and alluvial material that now encumbers the valley floorprobably at least 50 feet. It follows that in a distance of nearly 2 miles the Kern trunk glacier tapered down from a thickness of about 650 feet to its terminus.
Farther up Kern Canyon, no moraines of the trunk glacier are found through a distance of more than 15 miles, but beyond that, in the head of the canyon, a fine series of lateral moraines is present (Lawson, 1904, p. 354, 358). (These moraines and others mentioned on following pages are not shown on pl. 1.) Those on the east side of the canyon are "several miles in length and rise to an altitude of probably 1,500 feet" above the bottom of the canyon (Lawson, 1904, p. 354); they extend from just beyond the mouth of Wallace Creek northward beyond the head of the Kern Canyon into the canyon of Tyndall Creek.
On the west side of the Kern Canyon, from Coyote Peaks to the Big Arroyo, the valleys tributary to the Kern are successively longer to the north, because the Great Western Divide, from which the tributary valleys descend, diverges northwestward away from the northward-trending Kern Canyon. Because of this situation and also because the Great Western Divide gains in altitude toward the northwest, the Wisconsin glaciers in these canyons were progressively larger to the north.
The valley of Coyote Creek and also two little valleys heading just south of the Coyote Peaks held glaciers which were the most southerly ice bodies generated along the Great Western Divide; in fact, they were among the most southerly in the Sierra Nevada. These glaciers were not long enough to fill the entire length of their canyons and reach the Kern Canyon. However, ice streams in two of the branches of Coyote Creek did unite to form a very short trunk glacier. The prominent right lateral moraine of the north branch of this glacier can be seen from the trail to Coyote Pass. Farther up toward the pass, the trail crosses the right lateral moraine of a small separate glacier which descended from the cirque north of Coyote Pass.
Considerably more impressive were the ice streams in the canyons of Laurel Creek and Rattlesnake Creek. These, like all the branch glaciers to the north of them, were tributaries of the Kern trunk glacier. They headed in compound cirques on the Great Western Divide, and at the mouths of their canyons, which were hanging, they cascaded down to the trunk glacier in the Kern Canyon. The Laurel Creek glacier was 6 miles long, the Rattlesnake Creek glacier 8 miles long.
The Big Arroyo glacier, almost 14 miles long, was the largest and most complex of the tributary ice streams in the entire Kern Basin; in fact, it constituted a major glacier system in itself. Most of the sources of this glacier lay along the Great Western Divide, in a 15-mile rank of capacious cirques, but some lay to the northeast, in cirques of the Kaweah Peaks Ridge.
As a result of severe glacial erosion, Big Arroyo Canyon, like Lyell Canyon in Yosemite National Park, has a smoothly U-shaped cross section, and the canyon shoulders are rounded from overriding by the main glacier (figs. 38, 39). Upper reaches of the canyon, which are mostly devoid of timber as a result of snowslides, are broadly open. Many of the cirques along the Great Western Divide are remarkably smooth-floored and clear of debris; the little debris that is present is usually concentrated in a few narrow belts. In these cirques lie numerous scattered lakes and chains of lakes.
These erosional features are strikingly visible from the High Sierra Trail, which crosses Kaweah Gap and descends along the left side of the Big Arroyo to Kern Canyon. So also are some of the Wisconsin lateral moraines of the main glacier and its tributaries. The sloping platforms at the base of the Black and Red Kaweah Peaks, for example, are littered with moraines and erratics, mostly above timberline.
The most interesting display of moraines is to be found on the southwestern part of the Chagoopa Plateau, which is also traversed by the High Sierra Trail. Moraine Lake, in this area, is one of the few wholly moraine-impounded lakes in the Kern Basin (figs. 40, 41). The little valley which the lake occupies was invaded by a side lobe of the Big Arroyo glacier. This lobe left a series of concentric moraine loops, the last-formed and smallest loop being one at the lower end of Moraine Lake (the impounded water seeps out from the lake through this embankment). West of Sky Parlor Meadow the concentric moraines are separated by strips of meadow formed where sand has been washed down from the flanking moraines. The outermost moraine forms the west boundary of Sky Parlor Meadow. This moraine, when followed to the southeast, reaches the crest of a ridge and here makes an abrupt turn toward the southeast; it then continues parallel to the general course of the Big Arroyo glacier. The moraine, when followed north along the edge of Sky Parlor Meadows, describes a big arc. In this section it has several subsidiary crests, and its steep front increases in height to 100 feet or more. Sky Parlor Meadow follows around the arc of the Wisconsin moraine and gradually narrows into a point. Beyond it lie the smooth older moraines.
The westerly tributary glaciers which remain to be considered ranged from 3 to 8 miles in length and there fore were small as compared with the Big Arroyo glacier. These ice streams headed along the Kaweah Peaks Ridge or its subsidiary spurs, with the exception of the Kern-Kaweah glacier, which originated along three different crests: the Kaweah Peaks Ridge, the Great Western Divide, and the Kern Ridge.
The several small glaciers on the southerly slopes of Mount Kaweah and the Red Spur descended onto the northern part of the Chagoopa Plateau; here they coalesced to form a small compound ice sheet which discharged southeastward into Kern Canyon through the hanging valleys of Red Spur Creek and the next stream to the south.
The Kern-Kaweah glacier had broad, capacious collecting basins which were among the largest of the entire Kern glacier system, and it was therefore a major affluent of the Kern trunk glacier. It will be recalled that the Kern-Kaweah glacier was one of the three ice streams whose union formed the head of the Kern trunk glacier.
The glacier formed the apex of the Kern Canyon glacier system, in that it lay in line with the trunk glacier at the very head of the main canyon; it was a complex ice body about 8 miles long and almost as broad. This glacier was the central member of the three whose union gave origin to the Kern trunk glacier. The many cirques of this central glacier lay on the four crests, Kern Ridge, the Great Western Divide, the Kings-Kern Divide, and the main Sierra crest, which formed a lofty rim encircling the Kern glacier on all sides except the southwest.
Where the canyon "steps up" from main Kern Canyon just above the junction of the Kern-Kaweah River, a moraine loop of this glacier is crossed by the trail. The river has cut through the moraine and into the underlying bedrock; it thus gives rise to a series of falls. More conspicuous evidence of the Wisconsin glaciation occurs at higher altitudes, where there are 60-odd lakes along the upper stream courses and within the cirques of this basin as well as a multitude of smoothly rounded ledges among which the trail precariously makes its way up to the sources of the Kern River. Many of the knolls and ridges, curiously, reverse the relationship typical of ordinary roches moutonnées in that they are more abrupt on the upvalley side than on the opposite side. Their anomalous profiles reflect the control of two joint sets, one dipping rather steeply upvalley, the other dipping less steeply downvalley.
The Tyndall glacier deposited a series of bouldery left lateral moraines which the John Muir Trail crosses in its course south of Tyndall Creek. One of these moraines holds in the long, narrow lake west of the long spur extending southwest from Mount Tyndall. The moraines are not very prominent, except for the topmost one which is a barren, sharply defined ridge contrasting rather sharply with the smooth bare slopes of the Bighorn Plateau above it (fig. 42).
The three easterly tributaries of the Kern trunk glacierWallace glacier, Whitney glacier, and Rock glacierall came from the highest of the crests bordering the Kern basinthat is, from the main Sierra divide, which in this section bears several 14,000-foot peaks and many summits which are but little lower.
Wallace glacier, about 7 miles in length, was joined by a major branch from the northeast, the Wright glacier. The numerous moraines of this glacier system are bouldery and regular (fig. 43), and some are unusually prominent. The John Muir Trail traverses them in its course across the basin, above the junction of Wright and Wallace Creeks. There are at least four right laterals and two left laterals of the Wright glacier, and three left laterals and two right laterals of the upper Wallace glacier. A medial moraine given off from the end of the ridge between Wright and Whitney Creeks extends west-southwestward down the valley for about a mile, as far as Wright Creek.
Wallace, Tulainyo, and Wales Lakes, in upper Wallace Creek basin, are glacial lakes of exceptionally large size, each being more than half a mile long. Wallace Lake, which is probably at least 100 feet deep, lies in a great compound cirque; it marks the confluence of two ice streams, one from a cirque on Mount Barnard, the other from a larger, higher cirque under the summit of Mount Russell. Tulainyo Lake (fig. 44) lies in the latter cirque. The environment of both lakes, being above timberline, has a grim, barren aspect. Tulainyo Lake (altitude 12,856 ft), said to be the highest body of water in North America, occupies a cirque that doubtless held a small glacier until very recently. The lake is enclosed by a massive moraine through which the water seeps out. Wales Lake lies in a short tributary canyon which, from the evidence of glacial sculpturing on its walls, held an ice tongue about 1,000 feet deep.
On the granite around Wallace Lake, surprisingly little glacial polish remains, and in some places weather pits have been formed in the surfaces of horizontal platforms. This condition implies very rapid postglacial disintegration as compared with that observed in the Yosemite region.
Half a mile below Wallace Lake is a striking exhibit of glacially quarried rock; several sheer rock faces are determined by vertical master joints. The cliff be low Wales Lake also exhibits glacial plucking and abrasion guided by joints.
Where the John Muir Trail crosses Wallace Creek, the stream through a stretch of 400 feet has trenched the bedrock to a depth of 25 to 50 feet (fig. 45). The gorge has vertical walls along which stand tottering joint slabs. The stream cutting here, which must be wholly postglacial, contrasts vividly with the slight erosion effected by the Merced River above Vernal and Nevada Falls (Matthes, 1930, p. 69). The difference may be attributed to the fact that, at the gorge, Wallace Creek is cutting into granite having numerous intersecting joints which divide the rock into blocks and slabs of moderate size, whereas above Vernal and Nevada Falls the Merced is flowing over massive granite. Wherever the granite is sparsely jointed or wholly undivided over considerable distancesand there are many such places in the High Sierrapostglacial stream erosion can be measured in inches rather than feet. Along Wallace Creek, less than 300 yards to the north of the gorge the same granite, where sparsely crossed by joints (10-20 in. apart), forms a smooth, untrenched valley floor.
The Whitney glacier was a forked ice body, its south branch, the Crabtree glacier, being almost as long as the upper part of Whitney glacier itself. Thus this glacier system somewhat resembled the Wallace system but was smaller and only 6 miles long. It is noteworthy that the sources of this glacier were on that lofty section of the Sierra crest that includes Mount Whitney (14,495 ft), the highest peak in the continental United States outside of Alaska (figs. 10, 46). From the glacial sculpturing and avalanche fluting on its valley walls, described below, the Whitney glacier seems to have been about 1,200 feet thick in its upper reaches and 900 to 500 feet thick in its lower valley.
On both sides of the valley, below the fork, the trail from Sandy Meadow to Guyot Flat crosses several lateral moraines of the Whitney glacier. The left laterals, composed in large part of big angular boulders, are exceedingly rough. In places the trail follows sandy strips between the moraines.
Upper Whitney Creek, like upper Wallace Creek, has entrenched itself in the canyon floor to depths of about 20 feet in those places where stream erosion has been facilitated and directed by vertical master joints.
In Upper Whitney and Crabtree Canyons, the floors and sides are irregular as a result of selective glacial quarrying (figs. 47, 48); the sheer headwalls strikingly exhibit avalanche sculpture (Matthes, 1938, 1950a). The north wall of Mount Hitchcock, for example, is deeply cleft by numerous sharply incised recesses, a special form of avalanche chutes cut across a system of well-formed vertical joints (fig. 49). Debris cones, which were still covered with snow when observed, give evidence of continued avalanche action. The east face of Mount Hitchcock, on the other hand, has deeply cut avalanche chutes that have been controlled by vertically sheeted structure in the rock (fig. 50). The southwest flank of Mount Young is rather intricately sculptured by avalanches, and, between the chutes, the ribs stand out as sharp pinnacles. Parts of the west side of Mount Muir and the crest extending south from this peak have been subjected to avalanche erosion; that part of the ridge to the west of Whitney Pass has sharp ribs between chutes. The trail laid across these features is in a precarious position and is inevitably subject to being swept away periodically by avalanches. Some of the ribs are particularly frail and picturesque. The long spur south of Crabtree Creek is also avalanche scarred on the north side.
A small independent glacier that descended the north slope of Mount Guyot left records which attest to its great eroding power. The cirque of this glacier is shallow but unmistakable, and a bouldery outer moraine indicates that this little glacier turned west and, at an altitude of 10,000 feet, a mile below its source, ended in a narrow tongue.
The Rock glacier was the most southerly and the longest (11 miles) of the tributaries which joined the Kern trunk glacier from the east. The moraines of the Rock glacier cloak both slopes of the lower valley, and several small moraines forming partial loops occur on the bottom of the canyon. Intermediate spaces consist, for the most part, of wet, boggy meadow. In the lower valley of Guyot Creek, moraines outline a small Wisconsin glacier which fell short of joining the Rock glacier, and at the heads of two tributaries of the South Fork Rock Creek, southwest of Siberian Outpost, there are records of two other, even smaller, Wisconsin glaciers.
EL PORTAL STAGE
On the basis of the characteristics of the glacial deposits of El Portal age as set forth on previous pages, the deposits of this early stage in the Kern Canyon and in its branches may now be described.
To the author it was soon apparent that El Portal moraines in the Kern Canyon at the junction of Coyote Creek are situated with respect to the Wisconsin moraines precisely as are El Portal moraines in the Yosemite Valley. In that valley the author discovered, in 1913, that at a point 1 mile below the terminal moraine of the Wisconsin Stage the highest left lateral of El Portal Stage lay 2,200 to 2,300 feet above the valley floor (Matthes, 1930, p. 66-68). A few miles farther down the valley, the right lateral was at a corresponding height. Once identified, both laterals were readily traced down the Merced Canyon to the vicinity of El Portal. In the Kern Canyon, similarly, the lateral moraines of El Portal Stage lie at heights ranging from 1,600 to 2,000 feet above the terminal moraine of the Wisconsin Stage.
Search for these older glacial deposits was begun on the west side of the Kern Canyon. The upper zigzags of the trail that leads to the hanging valley of Coyote Creek were cut into a large body of El Portal mineral; they thus afford abundant exposures of the limonite-coated boulders in the material. The mass reaches all the way up to the mouth of the hanging valley, but inasmuch as this mass connects there with old deposits of the tributary Coyote glacier, it was deemed advisable to extend the search northward along the shoulder of the canyon. There, patches of the mass were found on a part of the upland where none could have been contributed by either the ancient Coyote glacier or the ancient Laurel glacier, the next tributary ice stream to the north. This old glacial material is for the most part hidden from view by a mantle of forest soil and granite sand, but cobbles of characteristic El Portal aspect occur in the holes left by uprooted trees. The upper margin of the deposit is ill defined but seems to range from 8,000 to 8,100 feet in altitude. It therefore lies 1,600 to 1,700 feet above the canyon floor; and, because the canyon floor is covered with late-glacial and alluvial deposits to a depth of probably 100 feet, the total thickness of the ancient Kern glacier indicated is about 1,700 to 1,800 feet.
The search on the east side of the canyon gave even better results. The old Conterno Trail to the upland valley of Golden Trout Creek first ascends the left lateral moraine of the Wisconsin Stage. The trail surmounts the sharp bouldery crest at an altitude of about 6,900 feet and then winds up the gully between the crest and the mountainside as far as the mouth of a small hanging valley at an altitude of 7,000 feet. The lateral moraine at one time doubtless formed a barrier across this hanging valley, but it has since been notched by the streamlet. In the hanging valley itself, which is little more than a recess in the canyon wall, the topographic forms are not in the least suggestive of glacial action. They consist of alternating spurs and ravines converging toward the central drainage line; yet these features, clearly because of normal subaerial weathering and stream erosion, are carved largely from glacial deposits of El Portal age. The entire recess is lined with such material, and because there is no evidence of this recess having contained a small tributary glacier, the deposits in question can be attributed only to the Kern glacier itself. In fact, several obscure lateral moraines of that glacier, arranged in tiers one above another, like terraces, are discernable. The highest, which lies at an altitude of about 8,500 feet, shows that the Kern glacier of the El Portal Stage here filled the main canyon to a depth of fully 2,000 feet above the present floor; and, inasmuch as this floor is underlain by an estimated 100 feet or more of late-glacial and alluvial deposits, the total depth of ice may have amounted to 2,100 feet.
The Conterno Trail, after making several zigzags, turns southward toward the valley of Golden Trout Creek. Along this stretch of the trail only occasional cobbles of El Portal age are found, the canyon sides being too steep to retain much loose material. But in the saddle behind the projecting crag marked 8,119 feet on the topographic map, a small body of El Portal material remains preserved (fig. 51). This body lies fully 500 feet above the adjacent part of the valley of Golden Trout Creek, and, inasmuch as the ancient Kern glacier doubtless rose at least 200 to 300 feet higher, there seemed good reason to believe that a side lobe of that glacier had pushed up into the valley. A rapid examination of the valley, indeed, showed that such had happened. Although the farthest limits reached by the lobe are not marked by a distinct moraine, granitic boulders left by the ice lie scattered on the surface of the basalt flow that fills the bottom of the valley. Along the southern edge of the basalt flow, at an altitude of about 8,100 feet, there is also a continuous moraine composed of a mixture of basaltic and granitic boulders. That moraine extends about 1 mile up the valley and indicates the approximate length of the ice lobe. At the mouth of the valley the moraine is indistinct, but it can be traced to an altitude of nearly 8,300 feet. Here, then, the ancient Kern glacier attained a thickness of about 1,900 feet in the main canyon. This measurement accords well with that obtained in the recess to the north of Golden Trout Creek, for the ancient glacier must have decreased in thickness downvalley in this part of its course.
Thus the great depth of ice in the Kern Canyon that is consistently indicated at three different points implies, of course, that the glacier of El Portal Stage extended several miles beyond the terminal moraine which Lawson believed marked the southernmost limit of glaciation. A methodical search for remnants of lateral moraine of El Portal age in recesses in the canyon walls was clearly called for, but because the time available did not permit such a search, it was deemed best to examine the area about the southern end of Grasshopper Meadow, where the canyon contracts from its broad U-shape to a narrow V-shape and where, presumably, glacial erosion had been largely supplanted by deposition under the thinning sluggish terminal part of the glacier. There, indeed, a considerable body of El Portal moraine was discovered to the east of the trail, in the reentrant through which the trail ascends to the col at the head of the defile called Trout Meadows. The deposit is partly covered by soil and forest litter, but the cobbles in it are plainly visible on the slope to the east of a sharp-cut gully. The upper limit was determined, by aneroid, at an altitude of about 6,600 feetthat is, at a height of 900 feet above the bed of the Kern River, according to the contour lines on the topographic map. If it be assumed that the river has deepened its bed 200 feet since El Portal timeobservations made in other canyons farther north in the Sierra Nevada indicate that a greater amount is not probablethe ancient Kern glacier at this lower point still was about 700 feet thick. The glacier may be reasonably supposed, therefore, to have penetrated at least 2 miles farther down the canyon, and the ice front, accordingly, must have lain at an altitude of approximately 5,700 feet about 7 miles south of the terminal moraine of the Wisconsin Stagethat is, at a place locally called "Hole-in-the-ground" (name not indicated on topographic map), which is within the bend of the canyon north of Hockett Peak.
Inasmuch as the morainal deposit has been traced to a point only 50 feet below the col at the head of the Trout Meadows defile and may not truly indicate the highest level attained by the ice, it seemed possible that for a brief period the ice had risen high enough to spill through the col. Search for morainal material was therefore made in the upper part of Trout Meadows, but none was found. It was concluded, therefore, that the Kern glacier of El Portal Stage had remained confined to the canyon.
On the way down the canyon, and on the way back, a lookout was kept for El Portal deposits. Only scattered boulders and occasional small patches of cobbles were observed on the canyon floor. The large kernbut to the south of Kern Lake was also examined for old glacial material because it was realized that if this kernbut, which stands only about 300 feet high, was in existence at the time of El Portal glaciation, it would have been overtopped by the ice. No glacial material was found on the main summit, which is directly east of the col that is traversed by the trail, but on the somewhat lower crest to the west of the trail there is a roundish boulder of granite nearly 3 feet in longest diameter. That boulder very probably is a glacial erratic; it owes its roundish shape not to glacial abrasion but to the spalling off of thin curving shells, some of which lie at its sides. A few feet away is a fragment derived from it that has an exposed part measuring 23 inches in length, 18 inches in breadth, and 9 inches in height. Boulders of pre-Wisconsin age in the Sierra Nevada commonly break up in this very manner. The boulder in question is composed of a fine-grained even-textured granite, as yet unstained by ferric oxides; however, the local rock, which crops out on the crest, only 10 feet away, consists of a coarse-grained and obscurely porphyritic granite stained a ruddy tint as the result of the oxidation of its ferromagnesian minerals. Nor was any fine-grained granite, such as that of this boulder, discovered elsewhere in the vicinity. That the boulder is foreign to the locality and was dropped on the crest by El Portal ice, therefore, seems a reasonable presumption.
To the south of this kernbut, the trail hugs the west side of the canyon (the location of the trail is not shown correctly on the topographic map), winding its way among the crags and blocks that have been brought down by rockslides. All this slide debris is angular and is gray in tone, but among the debris lie rounded rust-hued boulders and cobbles that are typical El Portal material. They must be derived from an old lateral moraine high up on the canyon side. Such boulders and cobbles are more abundant farther on, in the fan built by the streamlet that empties into Little Kern Lake. These doubtless have been washed down from the older moraines of the small hanging glacier that headed under the Coyote Peaks.
Particularly significant is the presence of El Portal material on the north slope of the next great kernbutthe one immediately south of Little Kern Lake. There is nothing to suggest that this material has been dislodged and redeposited; it appears to lie in the place where the Kern glacier left it.
A thorough search for morainal material on the top of the kernbut could not be made in the time that was available. None was found, but it is reasonably certain, nevertheless, that El Portal ice passed over the kernbut, because interpolation between the altitude, 8,300 feet, of the right lateral moraine south of Coyote Creek and its altitude, 6,600 feet, in the recess near the Trout Meadows col indicates that at the kernbut in question the surface of the ice lay at about 7,300 feet-that is, fully 300 feet higher than the top of the kernbut, which, according to the topographic map, has an altitude of 6,981 feet.
South of the kernbut, in the wide space of Grasshopper Meadow, the canyon floor is aggraded with large quantities of coarse angular rock debris derived from the toe of the great rockslide on the west side of the canyon. Some of this debris has recently been cut away by the river, and as a result there is now a flight of five clean-cut terraces about 50 feet in aggregate height; but the glaciated floor of the canyon and whatever morainal material may rest on it remain hidden from view.
No attempt was made to determine the farthest limits which El Portal ice might have reached in the Kern Canyon, previous search in other canyons on the west slope of the Sierra Nevada having demonstrated that as a general rule the trunk glaciers of El Portal Stage have left no recognizable terminal moraines and that, for this reason and because of the erosional changes that have taken place in the canyons, the farthest limits attained by those ancient glaciers are not definitely marked. Besides, it seemed probable that the aggraded conditions noted in Grasshopper Meadow would extend some distance farther down the canyon and that but little loose glacial debris would find lodgement on the steep canyon walls.
It remains to note the occurrences of El Portal moraine at scattered localities within some of the valleys tributary to the Kern Canyon and on the interfluves between these valleys. One of these deposits, at the mouth of the hanging valley of Coyote Creek, has already been mentioned. Farther north, the Chagoopa Plateau is littered with the relatively smooth moraines of this age, which extend across Sky Parlor Meadow and to the southeast of it.
Near the head of the Kern River basin, the smooth, bare slopes of the Bighorn Plateau, between Tyndall Creek and Wright Creek, though seemingly devoid of glacial features, are covered with formless older morainal material, the disintegration of which has produced the abundant sand on the plateau. In places the plateau bears scattered erratic boulders, many of which are in process of being broken up. One large erratic, south of the nameless pond in the middle of the plateau, measures 16 by 6 by 7 feet (fig. 26). It is composed of bluish granodiorite containing abundant biotite and hornblende crystals and is obscurely porphyritic. In these respects it contrasts with the local granite, which is conspicuously porphyritic, with phenocrysts or orthoclase 2 to 3 inches in length.
El Portal moraine also veneers several other wide tracts lying east of the Kern Canyon: the Sand Meadows region, between Wallace Creek and Whitney Creek, the broad upland south of the mouth of Whitney Canyon, and both sides of the lower valley of Guyot Creek. The deposits northwest of Guyot Creek are doubtless remnants of the right lateral moraine of the earlier Guyot glacier; those deposits southeast of the creek probably are composite, including both the left lateral of the Guyot glacier and the right lateral of the Rock glacier. The deposits are very sandy, except where the slope is sufficiently steep to permit rainwater to wash away the sand; there many boulders are exposed.
GLACIER POINT STAGE
In only three localities in the upper Kern Basin were any glacial deposits observed that might with some assurance be assigned to the Glacier Point Stage (see pl. 1). Two of these localities are on the Chagoopa Plateau and permit no safe inferences regarding the depth which the Glacier Point ice may have attained.4 The third locality is 2 miles north of Golden Trout Creek, and the deposit there, fortunately, is of such character and so situated that there can be little doubt that it belongs to the Glacier Point Stage and marks approximately the highest level attained by the ice of that stage.
The deposit last mentioned lies on the otherwise bare level summit platform of the rocky knob that stands north of the little hanging valley previously mentioned (page A46). The material is very scanty, consisting of some cobbles and pebbles of granitic rocks. These rocks, however, have, with one exception, subangular forms such as are produced characteristically by glacial action. The exception is a smoothly rounded elongate pebble that is unquestionably stream worn; but such pebbles are bound to occur here and there in glacial deposits. All the cobbles and pebbles are deeply stained by ferric oxides and break readily under the hammer. In general appearance these deposits do not differ from morainal material of El Portal age, but their position at an altitude of 9,000 feet, 500 feet above the highest El Portal moraines in the little hanging valley nearby, would seem to preclude the possibility of their belonging to that series of moraines. That these cobbles and pebbles do not look more deeply decayed than El Portal material is probably due to the fact that they lie on an almost clean platform that is well drained and thoroughly insolated, and where, consequently, the conditions are unfavorable for the action of chemical processes of rock decay.
The position of this ancient glacial material on the rocky knob implies that the ice of the Glacier Point Stage spread laterally over the upland to the east of the canyons. The ice may have invaded the upland for a distance of three-quarters of a mile, as far as the 9,000-foot contour line shown on the topographic map. There should consequently remain some patches of Glacier Point material here and there on the upland and, likewise, vestiges of a lateral moraine in the vicinity of the 9,000-foot contour line or even somewhat higher up. For such vestigial remnants, however, the author was unable to make a yard-by-yard search in the time that was available for the reconnaissance. It is hoped that others who may be interested in the problems of the Kern Canyon will someday make a thorough search on the upland surrounding the rocky knob and as far south as the valley of Golden Trout Creek.
Inasmuch as the rocky knob has an altitude of about 9,000 feet, the glacial deposit on it lies fully 2,500 feet above the present aggraded floor of the Kern Canyon and, therefore, probably as much as 2,600 feet above its glacially excavated rock floor. These relations, however, do not imply that the Kern glacier of the Glacier Point Stage here attained a maximum depth of 2,600 feet, for during that early stage the canyon had not yet been excavated to anywhere near its present depth (as measured to the rock floor)most likely 400 to 500 feet greater now at the locality under consideration than during the Glacier Point Stage. The glacier therefore was presumably only about 2,000 feet thick; but if so, it is noteworthy that this glacier was as thick as its successor of El Portal Stage. It does not follow, however, that the glacier was either as long or as powerful, for during Glacier Point time the canyon doubtless had not yet been much enlarged from its narrow stream-worn V-shape and therefore offered a much less perfect channel for the ice to flow through than later, when the canyon had acquired a capacious U-shape. Nor did the Kern glacier of the Glacier Point Stage possess as great kinetic energy as its successor of the El Portal Stage, for a larger proportion of its mass was diverted laterally over the uplands and therefore did not take part in the organized flow movement of the ice stream within the canyon. Yet, in spite of these adverse circumstances, the Kern glacier of the Glacier Point Stage probably extended down the canyon several miles beyond the terminal moraine of the Wisconsin Stage. The farthest point attained by this glacier remains, for the present, a matter of conjecture, but, to judge by the rates at which other trunk glaciers of comparable magnitude on the west slope of the Sierra Nevada appear to have decreased in thickness toward their termini, it seems not unlikely that the Kern glacier of the Glacier Point Stage reached at least as far as the upper end of Grasshopper Flat, perhaps even as far as the lower end.
The upper Kern Basin was occupied, in the Pleistocene Epoch, by the most southerly of the great glacier systems of the Sierra Nevada. Being less favorably situated, in certain respects, than its principal neighbors to the north, the Kern glacier was of smaller volume, but nevertheless it attained impressive size during each of the three recorded glaciations: the Glacier Point Stage, El Portal Stage, and the Wisconsin Stage.
Ranks of cirques on the Great Western Divide, the Kings-Kern Divide, and the main crest of the Sierra Nevada fed the many branch glaciers which, in imposing succession, joined the trunk glacier in the main canyon.
The maximum extent reached by the Kern glacier during the earliest, or Glacier Point Stage, cannot be determined with certainty; however, the fact that in the region above Golden Trout Creek the glacier attained about the same thickness as its successor of the second, or El Portal Stage, would seem to warrant the inference that it advanced approximately the same distancethat is, to a point in the Kern Canyon about 7 miles south of the park boundary.
The record of El Portal Stage, though incomplete and decipherable only with difficulty in many places where it is preserved, can be spelled out with much greater assurance. The distribution of El Portal glacial deposits in and about the Kern Canyon indicates that the ancient Kern glacier of this stage, though in most respects similar to its successor of the latest, or Wisconsin Stage, attained greater volume of ice and, accordingly, greater thickness and length. There being more ice than the canyons could hold, in some places, the ice locally spread across intervening divides and over the benchlands on either side of the main canyon to a total breadth of 4 to 6 miles; thus a central ice sheet of about 30 square miles was produceda remarkable fact considering that the entire expanse sloped southward and lay exposed to the rays of the midday sun. The trunk glacier extended fully 7 miles beyond the limit reached in the Wisconsin Stagethat is, it advanced 7 miles south of the boundary of Sequoia National Parkthe evidence indicating that the terminus of the glacier, when farthest down the canyon, lay at an altitude of 5,700 feet in the bend to the north of Hockett Peak, at lat 36°14' N. (This latitude may represent the most southerly point reached by glacial ice in the Sierra Nevada.) The overall length of the Kern glacier system was then 32 miles. The thickness of the trunk glacier is reliably indicated at several points where its gradually thinning lower portion once rested; this thickness ranged from about 2,100 feet at the mouth of the small hanging valley just north of Golden Trout Creek to 700 feet at the entrance to the Trout Meadows defile.
In the Wisconsin Stage the Kern glacier system remained a sprawling ice body whose trunk and branches lay confined within their respective canyons as distinct ice streams separated from one another by mountain spurs or low divides. The overall length of the system was 25 miles. Seven of its tributaries were 6 to 11 miles long, and the Big Arroyo tributary was 15 miles long. At the mouth of Wallace Creek canyon, the trunk glacier was fully 2,700 feet thick; and where joined by Whitney glacier, 2 miles farther downstream, its thickness was still almost undiminished, being between 2,600 and 2,700 feet. Thence, however, its thickness declined rapidly toward the terminus, being about 1,900 feet at the Big Arroyo glacier, 1,600 feet at the Rattlesnake glacier, 650 feet at the mouth of the hanging valley just north of Golden Trout Creek, and 200 feet opposite Tower Rock. The farthest point reached by the terminus of the trunk glacier coincides with the south boundary of Sequoia National Park, the boundary posts of the park standing, at an altitude of 6,350 feet, on the curving outer moraine marking the extreme limits of the Wisconsin glaciation.
The trunk glacier, so much more powerful than its confluent tributaries, excavated its trough hundreds of feet below the level of their canyons, leaving them hanging. The many side valleys joining the Kern Canyon farther south have also been left hanging. Doubtless they became so in the first place in preglacial time as a result of the rapid trenching of the Kern River induced by the latest Sierra uplift (Matthes, 1950a, p. 9-13). Some of the smaller side valleys, like those in the interval between Rock Creek and Golden Trout Creek, remained unglaciated and had their hanging aspect greatly enhanced by the glacial deepening and widening of the main canyon. The larger side valleys contained glaciers of their own, and therefore were themselves deepened and widened into U-shaped troughs, but nevertheless they remained hanging because of the superior eroding power of the trunk glacier. (The small valleys on the Chagoopa Plateau were glaciated but on the whole probably underwent little changethat is, with reference to their gradients.) As a result of postglacial stream cutting, the lower reaches of the hanging valleys are now deeply trenched for some distance back from the Kern Canyon. The larger and more powerful streams, such as Wallace Creek, have made the most progress in cutting their hanging valleys down to the level of the master stream.
The pronounced U-shaped form of the Kern Canyon has been evolved by glacial erosion from a narrow V-shaped trench which the Kern River had cut as a result of the latest Sierra uplift. The canyon has been glaciated three times and is therefore a product of alternating stream and glacial erosion. Its present U-shaped form is not precisely the one which was cut by the glacier, for many changes have taken place in the canyon since glacial action ceased. The rock floor is buried under thick deposits of boulders, gravel, and sandin part morainal, in part stream borne. The low gradient of the canyon floor over a stretch of several miles suggests that the glaciated rock floor underneath was excavated into a chain of lake basins which are now filled and covered up. The walls, once smooth, are now furrowed by gullies; and talus slopes at the base of the walls form the curves of a new U-shaped form superimposed upon the glacially eroded one. Deposition in the canyon is at present proceeding faster than erosion by the river.
SOURCES OF THE LITTLE KERN RIVER
The extreme head of Shotgun Creek in Wisconsin time held a small glacier that excavated the cirque now occupied by Silver Lake. In the main valley of the Little Kern, above the junction with Shotgun Creek, Wisconsin moraines plaster the slopes on both sides of the stream. These moraines were noted by Lawson (1904, p. 355), who wrote, "* * * huge lateral moraines were deposited notably on the east side of the canyon above the mouth of Shotgun Creek. This moraine has a height of perhaps 500 feet above the Little Kern, and spilled over the crest of the spur which separates Shotgun Creek from the Little Kern into the basin of the former." There is here the record of a glacier of considerable volume that descended the valley from the vicinity of Vandever Mountain. Its length was about 6 miles, and it reached down to an altitude of 7,300 feet. This glacier was joined by another ice stream that cascaded down from the large cirque above Wet Meadows. The trail from lower Wet Meadows to Quinn Horse Camp crosses the lateral moraines of this system. Moraines of the older stage are probably present in Shotgun and Little Kern valleys, but opportunity to search for them was not provided.
Glaciers also formed in the two valleys of Soda Spring Creek, immediately south of Wet Meadows. In the more southerly of these branches, vigorous glacial erosion has attenuated the ridge at the valley head, and the floor of the cirque is roughened by many converging bouldery moraines of both stages. Quinn's Ranger Station is at the lower edge of a wet meadow held in by one of the many older moraines. The positions and outlines of the small glaciers that occupied the several headwaters of Soda Spring Creek in the Wisconsin Stage are clearly indicated by other moraines.
At the head of Pecks Canyon is another broad compound cirque, in which lie a number of scattered tarns. This cirquethe rim has an altitude of 9,800 feetwas produced by a shallow glacier that, at least in Wisconsin time, lay on the slopes southeast of the ridge bearing Sheep Mountain.
SOURCES OF THE TULE RIVER
On the northwest side of Sheep Mountain, at one of the headwaters of the Tule River basin, is another tarn, Summit Lake, in a little cirque that straddles the south boundary of Sequoia National Park. The lake is held in partly by ledges of metamorphic rock and partly by a small moraine. The moraine has been supplemented by an artificial dam, 4 to 5 feet high, that formerly had a gate with a handwheel and screw stem to raise it. These no longer function properly, and the water finds its way through the dam as best it can.
Northwest of Summit Lake, two other valley heads, also draining into tributaries of the Tule River, have been mildly glaciated, the westerly one apparently only in the earlier stage. Headwalls of the cirques here and at Summit Lake are only 9,000 to 9,500 feet in altitude.
SOURCES OF GOLDEN TROUT CREEK AND THE SOUTH FORK OF THE KERN RIVER
Southeast of Sequoia National Park, five glaciers formed on the southerly flanks of the ridge between Rock Creek and Golden Trout Creek basins. These glaciers originated in cirques whose headwalls are at altitudes of 11,000 to 12,000 feet, and they descended the tributary valleys of Golden Trout Creek distances of 1 to 3-1/2 miles in the Wisconsin Stage and somewhat greater distances in El Portal Stage. During the earlier glaciation, the three glaciers south of Siberian Pass united to form a common ice mass that spread widely over Whitney Meadows.
East of this rank of glaciers, a sixth and even smaller ice body formed on the west side of the main Sierra crest, about a mile southeast of Cirque Peak. A typical cirque, containing a lake, attests to the existence of this glacier. Thirteen miles farther southeast on the Sierra crest, at one of the headwaters of the South Fork of the Kern River, a small glacier formed on Olancha Peak. Situated at an altitude of about 10,000 feet at lat 36°15' N., this glacier (not shown on pl. 1) may have originated farther south than any other in the Sierra Nevada.
South of the Golden Trout Creek basin, the configuration of certain valley heads on the steep northerly slopes of the Toowa Range (highest summit, Kern Peak, 11,493 ft) indicate that the range bore several small glaciers, at least in the later glacial stage. The most easterly of these glaciers discharged into one of the sources of the South Fork of the Kern River.
Last Updated: 03-Aug-2009