Dating topography of the sierra nevada
Starting in 1981, hikers were unable to enter the Area from May 15 through December 15, in order to protect the sheep.
Physiographically, the Sierra is a section of the Cascade-Sierra Mountains province, which in turn is part of the larger Pacific Mountain System physiographic division.
Due to inaccessibility, the range was not fully explored until 1912.
The Sierra Nevada lies in Central and Eastern California, with a very small but historically important spur extending into Nevada.
The California Geological Survey states that "the northern Sierra boundary is marked where bedrock disappears under the Cenozoic volcanic cover of the Cascade Range." The range is drained on its western slope by the Central Valley watershed, which discharges into the Pacific Ocean at San Francisco.
The northern third of the western Sierra is part of the Sacramento River watershed (including the Feather, Yuba, and American River tributaries), and the middle third is drained by the San Joaquin River (including the Mokelumne, Stanislaus, Tuolumne, and Merced River tributaries).
West-to-east, the Sierra Nevada's elevation increases gradually from 1,000 feet (300 m) in the Central Valley to an average height of about 10,500 feet (3,200 m) at its crest only 50–75 miles (80–121 km) to the east. Unlike its surroundings, the range receives a substantial amount of snowfall and precipitation due to orographic lift.