Sierra Nevada, Merced River & Central Valley Connections
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Water, geology, climate & soils: Sierra Nevada, Merced River & Central Valley connections Roger Bales UC Merced Water, in all its forms, is indeed the crowning glory of the Sierra. Whether in motion or at rest, the waters of the Sierra are a constant joy to the beholder. Above all, they are the Sierra’s greatest contribution to human welfare. F. Farquhar, 1965. History of the Sierra Nevada Bierstadt, 1863-75 Contemplating the lace-like fabric of streams outspread over the mountains, we are reminded that everything is flowing somewhere, animals and so called lifeless rocks as well as water.. J. Muir, 1911, My First Summer in the Sierra Bierstadt, 1863-75 The Sierra Nevada & Central Valley Sacramento San Francisco Fresno N 050100 miles M. Hill, Geology of 4,500 million 570 million The longpastof theSierraNevada ancient seas the Sierra Nevada, 1975 225 million granite deposits forms gold 135 million erosive 65 million times & volcanoes days offire 38 million 3 million mountains tremble, lift&tilt days ofice 1 million Mammoth 400,000 Mountain erupts Melting of last ice age glacier 20,000 present Yosemite Valley & the days of ice before after M. Hill, Geology of the Sierra Nevada, 1975 Yosemite Valley today Douglas Alden UCSD-SIO 2005 “The Range of Light” & “Snowy Range” Obata, Yosemite Falls Audette, Half Dome above the Merced River Where has all of this rock gone? Douglas Alden UCSD-SIO 2005 Geology of the Sierra Nevada Diverse geological activities have produced a broad suite of rock formations in the Sierra Nevada, dominated by granite but including many types of igneous, sedimentary & metamorphic rocks. Geology of the Sierra Nevada Because the Sierra Nevada is underlain by mostly granitic rocks, soils are thin & rocky. Although the fertility of the soil in general over the Sierra Nevada is rather low, the range contains some of the most productive sites for conifers in the world. Many individual rivers drain the western slopes of the Sierra Nevada, flowing eventually into San Francisco Bay Topography of Upper Merced river basin Yosemite Valley Merced river headwaters are covered with snow in winter & spring Satellite snowcover Much of the precipitation falls as snow at high elevations % SCA 76-100 51-75 26-50 Tuolumne 1-25 Merced May 10, 2004 Streamflow peaks during spring snowmelt Peaks occur in late spring to early summer Headwaters receive little summer precipitation & are largely snow free by late summer Streams flow year round Merced river profile Triple Divide 10000 8000 6000 Yosemite Valley 4000 Elevation, ft Merced river canyon Snelling 2000 100 80 60 40 20 0 miles Streams enter the U-shaped Yosemite Valley from higher V-shaped canyons From Yosemite Valley the river drops to El Portal & the Merced River Canyon Merced river canyon near Briceburg .