Subsection M261Aj
Upper Scott Mountains

Lithology and Stratigraphy.  This subsection is dominated by ultramafic rocks of the Trinity terrane, which is a complex polygenetic assemblage of disrupted Cambrian, Ordivician, Silurian, and Devonian ocean crust that has been intruded by Mesozoic granitic rocks.  The terrane is represented by serpentinized peridotite, gabbro, diabase, and minor volcanic rock.  The granitic rocks are generally quartz diorite to slightly more silicic rocks.  Quaternary glacial till and outwash occur in many areas.

Geomorphology.  This is a subsection of mountains with rounded summits, steep sides, and narrow canyons.   Cirques and moraines are common in much of the subsection.  The elevation range is from about 4000 feet up to 9025 feet on Mount Eddy.  Mass wasting and fluvial erosion are the main geomorphic processes.  Glacial processes have been active extensively during the Pleistocene and locally during the Holocene.

Soils.  The soils are mostly Typic, Dystric, and Lithic Xerochrepts and Mollic and Ultic Haploxeralfs.  Some soils are in serpenitinitic families.  Soils on late Pleistocene moraines are mostly Typic Xerochrepts and those on Holocene moraines are mostly Xerorthents and Xerochrepts.  Soils on granitic rocks are mostly Entic, Typic and Lithic Xerumbrepts.  Typic, Lithic, and Pachic Argixerolls are common in drier areas at the northern end of the subsection.  Silica-cemented till is common in soils on moraines, and indurated till and alluvium are exposed in many stream beds.  Soils at the higher elevations are mostly rocky Lithic and Typic Cryorthents.  The soils are well drained, except in small glacial basins.  Soil temperature regimes are mostly frigid, with some cryic at higher elevations and mesic at the northern end of the subsection.  Soil moisture regimes are xeric.

Vegetation.   The predominant natural plant communities are Jeffrey pine series, Mixed conifer series, White fir series, and Montane meadow habitats.  Red fir series, Mixed subalpine forest series and Alpine habitats are predominant at higher elevations, and Foxtail pine series is common.  Port Orford-cedar series occurs in a few riparian areas.

Characteristic series by lifeform include:
Grasslands: Montane meadow habitat, Subalpine meadow habitat.
Seeps: Darlingtonia series.
Shrublands: Big sagebrush series, Greenleaf manzanita series, Holodiscus series, Huckleberry oak series, Low sagebrush series, Montane wetland shrub habitat, Mountain heather - bilberry series, Subalpine upland shrub habitat, Subalpine wetland shrub habitat, Tobacco brush series.
Forests and woodlands: Curlleaf mountain-mahogany series, Douglas-fir - ponderosa pine series,  Enriched stands in the Klamath Mountains, Foxtail pine series, Incense-cedar series, Jeffrey pine series, Lodgepole pine series, Mixed conifer series, Mixed subalpine forest series, Mountain alder series, Mountain hemlock series, Ponderosa pine series, Port Orford-cedar series, Red fir series, Sitka alder series, Western white pine series, White fir series, Whitebark pine series.

Surface Water.  Runoff is rapid.  It drains to the Trinity River on the west, the Sacramento and Shasta Rivers on the east, and the Scott River on the north.  Streams are mostly perennial.  There are many small lakes, or ponds, in cirque and paternoster basins.