Subsection M261El
Tahoe Valley

Lithology and Stratigraphy.   Quaternary glacial till, outwash, lacustrine deposits, and alluvium dominate this subsection.  A small hill of Mesozoic granitic and Jurassic marine sedimentary rocks sticks up through the Quaternary deposits.

Geomorphology.   The main landforms are gently sloping to moderately steep glacial moraines and nearly level to very gently sloping outwash plain, lake plain, floodplain, and alluvial fans.  The elevation ranges from 6230 feet along the shore of Lake Tahoe up to about 7500 feet.  Fluvial and lacustrine erosion and deposition are the main geomorphic processes.

Soils.  The soils are mostly Entic and Pachic Xerumbrepts on till and Alfic Xeropsamments, Entic Xerumbrepts, and Aquic Cryumbrepts on alluvial deposits.  The soils are mostly well to somewhat poorly drained with some poorly drained soils.  Soil temperature regimes are mostly frigid,  but cryic in somewhat poorly drained soils.  Soil moisture regimes are mostly xeric, with some aquic.

Vegetation.   The predominant natural plant communities on well drained soils are Jeffrey pine series and White fir series, with the latter increasing in dominance toward the west.  Sedge meadow communities and Willow thickets predominate in wet areas, with Lodgepole pine series around the margins of wet areas.  Aspen series occurs in moist habitats.

Characteristic series by lifeform include:
Grasslands: Ashy ryegrass series, Breaked sedge series, Idaho fescue series, Montane meadow habitat, Needle-and-thread series, Rocky Mountain sedge series.
Shrublands: Big sagebrush series, Bitterbrush series, Low sagebrush series, Rubber rabbitbrush series.
Forests and woodlands: Aspen series, Jeffrey pine series, Lodgepole pine series, White fir series.

Surface Water.  Runoff is slow from most of the area.  The runoff flows to Lake Tahoe, which is drained by the Truckee River.