Dating topography of the sierra nevada
The Sierra Nevada is part of the American Cordillera, a chain of mountain ranges (cordillera) that consists of an almost continuous sequence of mountain ranges that form the western "backbone" of North America, Central America, South America and Antarctica.The Sierra runs 400 miles (640 km) north-to-south, and is approximately 70 miles (110 km) across east-to-west.Times of glacial advance in the Sierra Nevada may be connected to the melting history of the ice sheets, and to Heinrich events, by expansion and contraction of sea ice in the southern North Atlantic. Geological Society of America Bulletin 110, 1318-1332. These trends reflect increasing chemical and geomorphic maturity of the magmatic arc (Ingersoll, 1979, 1983).Paleocurrents are dominantly west-directed, indicating that the source was the southern Sierra Nevada (Ingersoll, 1979).The topography and geology of central California are dominated by petrotectonic elements of the Mesozoic convergent margin: the Sierra Nevada magmatic arc, the Great Valley forearc basin, and the Franciscan accretionary prism.These three domains are genetically linked, inasmuch as they were jointly formed by Pacific plate subduction beginning in the Late Jurassic (Dickinson , 1964) filled the forearc basin, and comprise one of the thickest sequences of Cretaceous sediments known (Ingersoll, 1982).
Conventional petrographic studies of Great Valley Group rocks indicate that, with time, the lithic fraction of the sediments decreased, the percentage of total feldspar increased and the composition of the feldspars became more potassic.
Variations in topography through time have profound implications for processes as obvious as erosion and sedimentation and as diverse as global climate and the formation of mineral deposits.
The interplay between topography and tectonics is exemplified by the evolution of topography of the Sierra Nevada and Great Basin (United States), and by geologists' interpretation of that evolution.
Notable Sierra features include Lake Tahoe, the largest alpine lake in North America; Mount Whitney at 14,505 ft (4,421 m), the highest point in the contiguous United States; and Yosemite Valley, sculpted by glaciers out of one-hundred-million-year-old granite.
The Sierra is home to three national parks, twenty wilderness areas, and two national monuments.