The Sierra Nevada has its southern terminus at Tejon Pass, in southern California, and extending from there northward to Lassen Peak, in the northern part of the same State. With the exception of a small area to the east and north of Lake Tahoe, the entire range is included within the boundaries of California. This is geographically one of the best defined of the larger mountain ranges in the United States. Its eastern border especially is easy to trace, as for the most part it is determined by a great escarpment, corresponding to the fault scarp which borders one side of so many of the basin ranges. The Sierra Nevada, in fact, may be considered as one of the basin ranges of great size and forming the western wall of the region of interior drainage lying to the eastward. This abrupt eastward-facing mountain slope is in reality a great fault scarp, formed mainly by the upheaval of the west side of an intersecting system of fractures. It is not known, however, how much of the escarpment is due to the upheaval of the west side of the belt of fracture, or how much to the sinking of the eastern side. There have no doubt been many up and down movements along this belt, of which the present mountain wall is the algebraic sum. The escarpment rises in general from 5,000 to 6,000 feet above the desert valleys to the eastward, and reaches a maximum of about 14,000 feet in the vicinity of Death Valley. It is exceedingly precipitous and rises to an irregular serrate crest-line, from which the general slope westward to the Great Valley of California is gentle. The best idea of the generalized topographic form as well as of the origin of the Sierra Nevada, which the reader may be asked to hold in mind, is that the range consists of a block of the earth's crust about 500 miles long and from 70 to 100 miles broad, which has been upraised along its eastern edge so as to give its surface a westward inclination. From this vast monolith the profound canyons and multitude of sharp tapering spires which give to the range its magnificent scenery have been sculptured. Like most generalized pictures of great geographical features, however, this outline of the form and structure of the great mountain range of California has to be modified when studied in detail. From extensive and most painstaking studies by H. W. Turner, of the United States Geological Survey, the conclusion is reached that "the Sierra Nevada may be described as a monogenetic range, composed of highly compressed schists and slates with large areas of associated igneous rocks, chiefly granite and diabase, upon which lie uncomfortably a series of later Cretaceous and Tertiary sediments and volcanic rocks."