<P> The Sierra Nevada lies in Central and Eastern California, with a very small but historically important spur extending into Nevada . 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 . The east slope forms the steep Sierra Escarpment . Unlike its surroundings, the range receives a substantial amount of snowfall and precipitation due to orographic lift . </P> <P> The Sierra Nevada's irregular northern boundary stretches from the Susan River and Fredonyer Pass to the North Fork Feather River . It represents where the granitic bedrock of the Sierra Nevada dives below the southern extent of Cenozoic igneous surface rock from the Cascade Range . It is bounded on the west by California's Central Valley and on the east by the Basin and Range Province . </P> <P> The geographical boundary between the Sierra and the Cascades is virtually indistinguishable, with the Fredonyer Pass designation being traditional . 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 . The California Geological Survey states that "the northern Sierra boundary is marked where bedrock disappears under the Cenozoic volcanic cover of the Cascade Range ." </P> <P> 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). The southern third of the range is drained by the Kings, Kaweah, Tule, and Kern rivers, which flow into the endorheic basin of Tulare Lake, which rarely overflows into the San Joaquin during wet years . </P>

Where do the sierras end and the cascades begin
find me the text answering this question