Subsection M261Be
Konocti Flows

Lithology and Stratigraphy.  This subsection is dominated by silicic Quaternary volcanic rocks.  The flows range from basalt or andesite to rhyolite, with the latter most prevalent, and there are interbedded pyroclastics.

Geomorphology.  There are a few steep composite volcanic cone-shaped mountains, such as Mt. Konocti and Mt. Hannan,  but most of the topography is gently sloping to moderately steep, somewhat chaotic terrain with a poorly integrated drainage system.  The elevation range is from about 1300 feet up to 4722 feet on Cobb Mountain.   Volcanic processes and fluvial erosion are the main geomorphic processes.

Soils.  The soils are mostly Ultic and Mollic Haploxeralfs and lesser amounts of Palexeralfs and Lithic Haploxerolls.  The soils are generally leached free of carbonates. Soil temperature regimes are mostly thermic, but are mesic on some north-facing slopes and at higher elevation.  Soil moisture regimes are xeric.

Vegetation.   The predominant natural plant communities are Chamise series on shallow soils; Mixed conifer series on moderately deep to deep soils with mesic soil moisture regimes; and Blue oak series, Mixed scrub oak series, and various other chaparral shrublands in other areas.

Characteristic series by lifeform include:
Grasslands: California annual grassland series.
Shrublands: Chamise series, Chamise - wedgeleaf ceanothus series, Scrub oak series.
Forests and woodlands: Blue oak series, Douglas-fir series, Foothill pine series, Interior live oak series, Knobcone pine series, McNab cypress series, Ponderosa pine series, Sargent cypress series.

Surface Water.  Runoff is rapid and the streams are dry through most of the summer.   There are many small areas with closed drainage basins, and some of them contain small lakes up to the size of Thurston Lake, which is the largest natural lake in the subsection.  There is some hydrothermal activity and accumulation of minerals from it.