USGS Logo Geological Survey Professional Paper 160
Geologic History of the Yosemite Valley



The Yosemite (yo-sem-i'ity) Valley20 is situated about 150 miles due east of San Francisco, on the west flank of the Sierra Nevada, the great mountain range that extends lengthwise through eastern California. (See pl. 1.) It is the principal scenic feature of the Yosemite National Park, which embraces a tract 1,124 square miles in extent—almost as large as Rhode Island. (See pl. 2.) Compared with the entire park, however, the Yosemite Valley is small, measuring but 7 miles in length and 2 miles in breadth. It is, in fact, only a widened portion of the prevailingly narrow canyon of the Merced (mare-sed') River, which traverses the south half of the reservation from east to west. Nor is it the only chasm of note within the park. A dozen miles to the north, and parallel to it, is the Grand Canyon of the Tuolumne (tuol'um-ne) River, a prodigious gash which exceeds the Yosemite Valley in length and in depth, though scarcely in scenic grandeur, and which opens into the Hetch Hetchy Valley, a lesser yosemite that now holds an artificial lake, impounded by a dam at its lower end.

20Yosemite comes from "uzumati" or "uhumati," which in the language of the southern Miwoks meant "grizzly bear." It is said to have been originally the name of the tribe of Indians who inhabited the valley; or at least of that part of the tribe which dwelt on the north side of the river. The name was given to the valley, at the suggestion of Dr. Lafayette Houghton Bunnell, by the Mariposa Battalion, the first party of white men to enter the valley, in 1851.

PLATE 1.—RELIEF MAP OF CALIFORNIA. (click on image for an enlargement in a new window)

Broadly viewed, the canyons of the Tuolumne and Merced Rivers are two long furrows in the west flank of the Sierra Nevada—two of a great series of such furrows, all of notable depth and nearly all arranged roughly parallel to one another and at right angles to the crest line of the range. The Yosemite, therefore, is but one chasm in a land of many chasms. It is, however, by far the most strikingly modeled of all.

From most other parts of the Merced Canyon, and indeed from most other canyons in the Sierra Nevada, the Yosemite is distinguished by its great width relative to its depth, by its exceptionally sheer walls, and by its level, almost gradeless floor. As is manifest from the views on Plates 3 and 16, B, the Yosemite is broadly U-shaped in cross section. Even in the portal between El Capitan and the Cathedral Rocks, which is the narrowest part of the valley, the floor is many times broader than the channel of the river. By contrast the canyon immediately above and immediately below the valley is little more than a narrow, V-shaped gorge. In the valley, moreover, the river has so gentle a gradient that it meanders about in leisurely fashion, but in the gorges above and below it makes a direct, tumultuous descent. The absence of prominent spurs, finally, gives the valley an open, roomy aspect; it permits a vista to be had from one end almost through to the other, in spite of the fact that its course is sinuous. Muir aptly likened the Yosemite to "an immense hall or temple lighted from above."

In depth the valley does not greatly exceed the deepest of the other parts of the Merced Canyon; it measures between 3,000 and 4,000 feet. But in the valley the effect of depth is enhanced, in spite of the breadth of floor, by the exceeding boldness of the cliffs, by the continuity of the bordering plateaulike uplands, and by the seeming deliberacy with which the great waterfalls descend from the lofty rims.

Because of its walled-in character, its sequestered position more than halfway up the flank of the Sierra Nevada, and the ruggedness of the surrounding country, the Yosemite was originally very difficult of access. The Merced Canyon in its primeval wildness afforded no convenient avenue of approach. It had to be conquered by engineering skill and the use of dynamite. Before either railroad or highway had been constructed there was only a precarious trail for pack animals. All the earlier routes of travel to the Yosemite led over the mountainous uplands, so that one was obliged laboriously to ascend to altitudes of 5,000 and 6,000 feet and then to descend 1,000 to 2,000 feet to reach the floor of the valley.

At first the journey to the Yosemite could be made only on horseback. It consumed several days and was so arduous that only those inured to this mode of travel might undertake the trip with any real enjoyment. A vivid portrayal of those old-time conditions was given by Prof. Joseph Le Conte21 in his delightful narrative of his first excursion to the High Sierra in 1870.

21Le Conte, Joseph, A journal of ramblings through the High Sierra of California by the University excursion party, San Francisco, 1875 (republished as Ramblings through the High Sierra: Sierra Club Bull., vol. 3, pp. 1-107, 1900).

PLATE 3.—YOSEMITE VALLEY FROM WAWONA ROAD. At the left is the great cliff of El Capitan, at the right the Cathedral Rocks and the Bridalveil Fall. Through the portal between the opposing rock masses is seen the upper or main chamber of the Yosemite Valley. In the foreground is the lower chamber, flanked at the left by the Rock Slides. The U shape of the valley is manifest throughout. Photograph by J. T. Boysen.

In the fifties and sixties of the last century wagon roads were extended up from the foothills to mining camps west and south of the Yosemite, but it was not until 1874 that roads were opened to the valley itself (the Coulterville and Big Oak Flat Roads). The picturesque 4-horse stage then made its appearance, and although the roads were steep, rough, and notoriously dusty, tourist travel increased rapidly. The completion of the Yosemite Valley Railroad in 1907 naturally afforded a much easier route of approach. The first motor stage entered the valley in 1913, and by 1916 travel by motor car was rendered possible also in an eastward direction by the improvement of the old wagon trail known as the Tioga Road, and thus a scenic route was opened to the crest of the Sierra and thence by another road to Mono Lake.

The construction of the State highway up the Merced Canyon, to connect with the Government road at El Portal, may be regarded as the crowning achievement in man's conquest of the mountain wilderness that guards the Yosemite. This highway affords the motorist a modern, well-graded route available in winter as well as in summer and is now the main artery of Yosemite-bound traffic.

The sequestered position of the valley accounts also for the lateness of its discovery by white men. To the Spanish settlers in California the chasm remained wholly unknown. The great mountain range which from afar they named Sierra Nevada22 was a forbidden land of mystery and lurking enemies. Even the early American miners who dug for gold in the foothills remained unaware of the existence of the Yosemite Valley for two years, although they were only 30 or 40 miles from it. It is probably true that the valley was first viewed from a distance in 1833 by Joseph Reddeford Walker, who in that year first crossed the Sierra Nevada by the Mono Pass and, guided by Indians, made his way westward over the upland north of the valley. But the effective discovery of the Yosemite, through which it became known to the world, was not made until March, 1851, when the Mariposa Battalion of volunteers under Maj. James D. Savage, in pursuit of Chief Ten-ei-ya (Tenaya) and his marauding band of Yosemite Indians, unexpectedly came upon the natural stronghold of the tribe23 after a hard march over the snow-covered mountains.

22The Spanish word "sierra" means literally "saw" and is by the Spaniards commonly applied to serrate mountain ranges; "sierra nevada" therefore means "snowy mountain range." The great California range now known as the Sierra Nevada was first sighted, described, and placed on a map by the Franciscan missionaries Francisco Garces and Pedro Font, who accompanied the Anza expedition that marched overland from Sonora, Mexico, in 1775-76, for the purpose of founding San Francisco. "Looking to the northeast [from a point just south of Suisun Bay]," wrote Font in his diary on April 2, 1776, we saw an immense treeless plain into which the water spreads widely, forming several low islets; at the opposite end of this extensive plain, about 40 leagues off, we saw a great snow-covered mountain range [una gran sierra nevada], which seemed to me to run from south-southeast to north-northwest." (The Anza expedition of 1775-76, Diary of Pedro Font, edited by Frederick J. Teggart: Acad. Pacific Coast History Pub., vol. 3, No. 1, pp. 84-85, 1913.)

23Bunnell, L. H., Discovery of the Yosemite, and the Indian War of 1851, 4th ed., Los Angeles, 1911.

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Last Updated: 28-Nov-2006