The Geysers
Map SatelliteThough highly disturbed, this area still retains geological and botanical features of interest. Foremost are the fumaroles and hot springs, with temperatures ranging from 50°C to boiling. The subterranean heat source is probably residual volcanic heat from the same sources that gave rise to the Lake County volcanics to the north. A number of unusual sulfate minerals, produced by the emanations, are found in the area; they include alunite, alunogen, boussingaultite, epsomite, halotrichite, mascagnite, melanterite, tschermigite and voltaite.
There are several plant communities in the area: Douglas fir forest, yellow pine forest, chaparral, valley grassland, serpentine chaparral, northern oak woodland, mixed evergreen, and riparian. The rare grass Panicum acuminatum var. acuminatum, which occurs near hot springs, is found here. A number of unusual thermophilic bacteria, fungi and algae are present in the various creeks and streams in the area.
Animal life is typical of the interior North Coast Ranges.
The area occupies the northerly end of a graben lying within Franciscan rocks. Most of it is drained by Big Sulphur Creek.
Integrity: Harnessing of the steam vents for power began in 1921 but did not reach a substantial level of activity until the 1960's. The area is now the world's largest producer of geothermally generated electricity. This development has severely disturbed portions of the area, by both actual cuts and erosion which have impacted, to a greater or lesser degree, many of the creeks. In addition to the wells and generating facilities, there is an old resort hotel in the area, together with numerous access roads, etc.
Use: Private
December 1977
Inventory of California Natural Areas
Revision © 2009 Steven Louis Hartman