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François Matthes and the Marks of Time: Yosemite and the High Sierra by François E. Matthes (1962)


The Watchtower, Tokopah Valley. Sequoia National Park, California. Courtesy George Mauger, Sequoia and Kings Canyon National Parks Company
[click to enlarge]
The Watchtower, Tokopah Valley. Sequoia National Park, California.
Courtesy George Mauger, Sequoia and Kings Canyon National Parks Company

LODGEPOLE CAMP AND TOKOPAH VALLEY

Lodgepole Camp is situated at an elevation of more than 6700 feet in what is properly termed the middle course of the Marble Fork Canyon. Tokopah Valley, which lies immediately upstream from it, is really its continuation, still in a pristine state of lovely wildness. Tokopah differs from Lodgepole chiefly in that it is flanked by towering cliffs instead of forested slopes. Both have broad and in places nearly level floors and are particularly inviting by reason of their charming groves of pine and fir and the pleasing alternations of pools, cascades, and riffles in the stream.

Below, from the highway bridge down to the junction with the Middle Fork of the Kaweah, is the lower canyon, through which the Marble Fork makes a tumultuous descent, falling as much as 1000 feet in a single mile, and dropping a total of 4800 feet. It is an extremely rugged canyon that attains a maximum depth of 3000 feet, west of the Giant Forest, and in some stretches is utterly impassable, even to the boldest mountaineer. It is so notably at the Marble Falls, where the river is actively cutting its channel across great upstanding beds of white and bluish marble—whence the name Marble Fork.

Above Tokopah Valley—that is, above the 1300-foot cliffs over which the Tokopah Falls descend—is the upper canyon, which again differs wholly in character from the middle and lower canyons. It is a broadly open basin, flanked by mountains of great height—Mount Silliman (11,188) on the north, and Alta Peak (11,211) on the south, and enclosed at its head by a lofty plateau, known as the Tableland, 11,300 feet in altitude. Its most remarkable characteristic is its barrenness. It presents a vast expanse of smooth, bare granite, from which all soil and vegetation have been removed. There are, it is true, a few groves of lodgepole pine and fir in its lower portion, but these seem, in a comprehensive view such as may be obtained from the Watchtower, merely dark, wooded islands in a dazzling, billowy sea of granite. The river there has but a shallow channel and races, white with foam, over the smooth, but scaling rock.

Why, it may be asked, are the lower, middle and upper portions of the Marble Fork Canyon so entirely unlike in form and aspect, and how does it come that Lodgepole and Tokopah in the middle course are so lovely and attractive, from man’s point of view, whereas the lower and upper canyons, though scenically impressive and in some respects amazing, are rather lacking in attractive qualities?

First of all it should be explained that the steep lower canyon is a much younger, more recently carved feature of the landscape than the middle and upper canyons. It was cut by the river, and is still in process of being cut, in consequence of a great uplift that added several thousand feet to the height of the Sierra Nevada, and steepened the river’s course, thereby accelerating its flow and increasing its cutting or eroding power. The middle and upper canyons, on the other hand, are relatively ancient features dating back to the period that preceded the great uplift, when the Sierra still had only moderate height. Lodgepole and Tokopah have not yet been reached by the vigorous canyon cutting below, which is proceeding from the foothills upward.

The Giant Forest, it may be remarked incidentally, stands on a portion of the same ancient landscape to which Lodgepole and Tokopah belong. The lower Marble Canyon has been trenched deeply beneath its surface, and so has the great canyon of the Middle Fork, and as a result the Giant Forest now stands on an elevated plateau. From the southern edge of that plateau, which has an altitude of about 6500 feet, to the channel of the Middle Fork below there is a drop of fully 4000 feet.

The plateau on which the Giant Forest stands is, however, by no means the highest part of the region, for above it rises Alta Peak, 11,211 feet in height. That peak, moreover, is merely the culminating point of a ridge about 1 1/2 miles in length that connects at the northeast by a shallow saddle with the Tableland. And the Tableland itself is without doubt a large remnant of a landscape far more ancient still than that on which the Giant Forest stands, indeed many millions of years more ancient. It antedates an earlier uplift of the range as a result of which the Marble Fork cut its course down to the level of Lodgepole Valley and the Giant Forest plateau. Small remnants of that very ancient landscape, or erosion surface, as geologists would call it, exist

Tokopah Falls on the Marble Fork of the Kaweah River, Sequoia. Courtesy George Mauger, Sequoia and Kings Canyon National Parks Company
[click to enlarge]
Tokopah Falls on the Marble Fork of the Kaweah River, Sequoia.
Courtesy George Mauger, Sequoia and Kings Canyon National Parks Company

on a number of the higher peaks of the Sierra Nevada, notably on Mount Whitney, Mount Langley and Table Mountain on the Great Western Divide. There are thus indicated in the features of the range two distinct periods of uplift and consequent canyon cutting.

In this connection it may be explained that the Sierra Nevada, taken as a whole, is essentially one huge block of the crust of the earth, 430 miles long, that lies in a tilted position with its eastern edge upraised so as to form the crest line. Measured from the crest line to the western foothills the block is 40 to 80 miles broad, but as its surface dips under the silts that fill the Great Valley of California and probably continues beneath them for many miles more, the total breadth of the Sierra block may be considerably over 100 miles. That the Sierra Nevada is actually a tilted crust block, as here described, had long been recognized by geologists, but the history of the successive uplifts by which it has gained its great altitude was not known until the geologic history of the Yosemite Valley was worked out, in 1913 and 1914.

To return to Lodgepole and Tokopah, these portions of the middle course of the Marble Fork Canyon, though undoubtedly forming part of the ancient landscape on which the Giant Forest stands, nevertheless now present a very different appearance from that which was given them by the river. For during the Ice Age, which followed upon the last great uplift, they became the pathway of a glacier and for many thousand years were subjected to its excavating and remodeling action. That glacier originated on the Tableland, which was completely covered by ice, as is still clearly shown by the glacier polish and scratches on its surface; and it was reinforced by a number of short tributary glaciers that issued from deep semi-circular pockets, or “glacial cirques,” in the north flank of Alta Peak—the cirques in which lie Heather Lake, Emerald Lake, and Pear Lake. Other small branch glaciers came down the flanks of Mount Silliman, on the north side, and all united to form one mighty trunk glacier which plunged into Tokopah Valley, doubtless forming magnificent ice cascades. It moved probably at a rate of only a foot or two per day, but its motion was rapid enough to cause the relatively brittle ice in the upper layers to break and become rent by innumerable intersecting fissures or “crevasses.”

As the snow continued to accumulate, owing to the severity of the climate, the Tokopah Glacier, as it may be called, grew thicker and longer, until at last it reached a point in the canyon about three miles below the site of the present highway bridge. Its total length, measured from the top of the Tableland to its terminus was therefore about nine miles. It was one of the smaller glaciers of the Sierra Nevada, but nonetheless an extremely interesting one.

How can the former extent of such a glacier be determined, it may be asked? The glacier polish and scratches might suggest themselves as good evidence, but unfortunately they are not permanent enough, for the rock scales off as it weathers. A more reliable method is by tracing the boulder ridges that accumulated along the margins of the glacier and at its front. The blocks and slabs which the glacier plucked and quarried out in its upper course were deposited as it melted in its lower course, and so it built up marginal ridges or “moraines,” as they are termed by geologists, following the Swiss usage. These boulder ridges are enduring features and remain in existence for thousands of years after the glacier has vanished, outlining faithfully its precise shape and extent. Well preserved, continuous moraines are to be seen on both sides of the valley in which Lodgepole Camp is situated. Particularly prominent are those on the south side.

Alta Peak, Mount Silliman, Pear Lake and the Tableland. Courtesy George Mauger, Sequoia and Kings Canyon National Parks Company
[click to enlarge]
Alta Peak, Mount Silliman, Pear Lake and the Tableland.
Courtesy George Mauger, Sequoia and Kings Canyon National Parks Company

The trail to Heather Lake, which starts at the upper Wolverton Creek bridge, follows the crest of the highest moraine for part of the way, and where the crest is too bouldery, follows the outer or south slope of the moraine. In some places it follows the trough between two parallel moraines. Anyone who walks along this trail observantly will readily see that the glacier built two and in places three parallel moraines. They record periods of maximum ice volume each of which doubtless lasted a century or more and was separated from the preceding by an interval when the glacier, because of a short period of milder climate, had melted down somewhat.

From the crest of the highest moraine one looks down more than 100 feet upon Wolverton Creek, which for a distance of nearly two miles runs along the base of the embankment. Wolverton Creek, which heads in Panther Gap, runs northwestward throughout its upper course (which has remained unglaciated)— that is, it runs directly toward Lodgepole. Doubtless it continued northwestward all the way before the glacier came, but when the latter built its massive morainal embankments, the stream was deflected and forced to run southwestward for two miles. Then it found a weak place in the moraine and broke through.

Slopes of Alta Peak. winter. By David Brower
[click to enlarge]
Slopes of Alta Peak. winter. By David Brower

On the north side of Lodgepole, Silliman Creek likewise breaks through the morainal embankment, but that stream is not deflected. The reason is, no doubt, that its upper valley formerly contained a glacier (which headed in two cirques on Mount Silliman), and when that glacier was actively melting, the stream had many times its present volume and correspondingly great eroding power. It is entirely probable that when the Tokopah Glacier finally subsided, Silliman Creek broke through the morainal embankment rather suddenly, for its trench is flanked on each side by a ridge of boulders, and such “boulder levees,” it is well known from observation on torrent channels, can be thrown up only by a tremendous rush of waters.

The top of the highest moraine on the south side of Lodgepole Valley indicates the highest level to which the ancient glacier’s surface rose. It is about 1300 feet above the floor of the valley at the lower end of Tokopah, and accordingly it is clear that the ice there actually had a depth or thickness of 1300 feet. Downvalleyward the depth of ice diminished by degrees until it was only about a hundred feet at the terminus. On both sides of the valley the moraines can readily be traced down to the highway, which cuts through them, revealing the boulders, cobbles, and sand of which they are made up. The best example is just below the Wolverton Creek bridge on the highway.

Below the highway the moraines are very fragmentary and finally are reduced to a few scattered boulders, the reason being that the rocky sides of the gorge are too steep to give lodgement to loose material. Most of the glacial boulders there have rolled down, and the sand has been washed away. As a consequence the precise spot at which the Tokopah Glacier ended can not be located definitely.

As the Ice Age drew to a close the glacier melted back toward its sources, but it made occasional feeble readvances as a result of climatic oscillations. Some of these readvances are attested by small moraines that extend from the sides of the valley partway across the floor. A particularly fine example of such a “recessional moraine” is to be seen a short distance above the campfire place. Another, somewhat less distinct recessional moraine is situated just above the highway bridge. Each of these moraines originally extended across the entire width of the valley in the form of a loop outlining the end of the glacier, but all of them have been cut through and in part demolished by the river.

During its further recession the Tokopah Glacier liberated enormous quantities of boulders, cobbles, and sand, and these were washed out from its front by the river and deposited in the deeper parts of the valley, and so it is that the latter is filled with “glacial outwash material” for considerable distances. Most of the campsites are on the fairly even, yet bouldery surface of this filling, which varies in thickness from a few feet to as much as 30 feet in some places. Since glacial times the river, being no longer overloaded, has trenched the filling, and it is at the present time still cutting the loose material away little by little.

The Ice Age, as a matter of fact, consisted not of a single longdrawn period of glacial conditions but of several distinct glacial epochs or “stages” that were separated from one another by lengthy “interglacial stages” when the climate was fully as warm as it is today and when the glaciers melted far back toward their sources or vanished entirely. The moraines just described are merely those of the last glacial stage, which ended 20,000 years ago. They are most readily recognized because freshest. But if one looks more closely one can also discern moraines of the next earlier stage. They are poorly preserved, have lost their sharp crests, and are now composed largely of badly weathered, partly decomposed boulders. Their age is probably at least 250,000 years. The best places to see these are in the road cuts along the highway. After one has passed Wolverton Creek (going towards Giant Forest) one can see yellowish boulders and cobbles embedded in granite sand for a distance of nearly half a mile. Similarly when driving toward the General Grant Grove, after one has passed the outermost moraine of the last glacial stage, half way between Silliman Creek and Clover Creek, one continues to see the yellowish, rotten boulders of the earlier glacial stage for another mile or more—far beyond Clover Creek bridge.

The Tokopah Glacier of the earlier ice stage reached much farther down the canyon of the Marble Fork than its successor of the last ice stage. The exact spot where it ended can not be determined for lack of morainal material on the steep sides of the canyon, but to judge from the positions of the older moraines as far as they can be traced, the glacier in all probability reached no farther than the mouth of Halstedt Creek. Since the glacier melted away, the canyon has been deepened considerably by the river, and so all traces of the earlier glaciation have been destroyed.

An essay written by Dr. Matthes, probably in the middle or late ’30’s, in connection with the interpretative program of Sequoia National Park. So far as known, it was not printed, but used only in typewritten form.


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