This subsection encompasses volcanic peaks and craters on a volcanic plain northeast of the Sierra Nevada below Mammoth Pass, Little Antelope Valley, and a high ridge north of Long and Little Antelope Valleys.   It has a cold to very cold, semi-arid to subhumid climate.  MLRA 26f, and 22e.

Lithology and Stratigraphy.  The bedrock is mainly Quaternary rhyolite, including obsidian, and tephra.  Also, there is some Mesozoic volcanic rock and Pliocene basalt.

Geomorphology.   This subsection contains mostly moderately steep mountains, a steep scarp on the north side of Long Valley Caldera, and gently to moderately sloping volcanic plain. The Inyo Craters are a series of hills in the same north-south alignment as the Mono Craters in subsection 341Dh.  The highest land is on an east-west arc along the north edge of Long Valley Caldera.  This oval caldera is a slightly elongated, east-west, depression formed by collapse about 3/4 million years ago of the vent for Bishop tuff.  It is now occupied by the Little Antelope and Long Valleys and, in the center, a hill formed by volcanic activity following collapse of the vent.  The elevation range is from about 7000 feet up to 11,123  feet on Glass Mountain.   Volcanism, fluvial erosion and deposition, and freeze-thaw are the main geomorphic processes.

Soils.  The soils are mostly Lithic and Lithic Ultic Argixerolls, Ultic Haploxeralfs, Dystric Xeropsamments,  Andic Xerumbrepts, Dystric Xeropsamments, and shallow Typic Cryopsamments.  Also, there are shallow Typic Torripsamments, Lithic Xerollic Haplargids, and Typic Argixerolls on granitic rocks.  The soils are well drained.  Soil temperature regimes are mostly frigid, and some cryic at higher elevations.  Soil moisture regimes are mostly xeric, and some aridic.

Vegetation.   The predominant natural plant community is Jeffrey pine series.  White fir series is common at higher elevations, Lodgepole pine series occurs in cold-air drainage-ways, and Singleleaf pinyon series is common in dry areas.  Other series in this subsection are Aspen in areas where snow accumulates, Bitterbrush, Big Sagebrush, and Curlleaf mountain mahogany.  Willow thicket alliances occur in wet areas, and there are Subalpine meadow habitats. Pumice forb habitats are present, but lack a description.

Characteristic series by lifeform include:

Grasslands: Alpine habitat, Ashy ryegrass series, Indian ricegrass series, Beaked sedge series, Creeping ryegrass series, Indian ricegrass series, Nebraska sedge series, Needle-and-thread series.

Shrublands: Big sagebrush series, Bitterbush series, Low sagebrush series, Parry rabbitbrush series, Rubber rabbitbrush series, Tobacco brush series.

Forests and woodlands: Jeffrey pine series, Limber pine series, Lodgepole pine series, Red fir series, Singleleaf pinyon series, White fir series.

Surface Water.  Runoff is rapid; most of the soils have high infiltration rates.   Most of the runoff is to the Owens River, but some is to Mono Lake.  Much of the area lacks integrated drainage systems, because of recent flows and tephra deposits.  The Owens River and streams from the Sierra Nevada run water through the summer.