Origin of the Salton Volcanic Domes, Salton Sea, California

Abstract

The location of the Salton volcanic domes and the alinement of the associated mud volcanoes strongly suggests their affiliation with the buried extension of the San Andreas fault. Two surface trends are evident-the northeastward locus of the volcanoes, and the northwestward line of mud geysers. The latter coincides almost exactly with a southeastward extension of the San Andreas fault from 15 miles to the northwest. A detailed magnetic survey indicates that the subsurface material is not confined to the immediate vicinity of the domes. Steep magnetic gradients observed over the flats some distance from the line of volcanic hills are interpreted as the magnetic effect of the sloping surface of the underground igneous mass. In consequence of wind-directed wave attack during the presence of Lake Cahuilla and Salton Sea the lighter pumiceous materials have been concentrated to the lee of the hills in wave-built terraces or "tails," which at the southernmost volcano have accumulated in sufficient quantities to be of commercial importance. At this same volcano a peripheral distribution of obsidian with relation to pumice leads to a unique interpretation of its structure and origin. Fumarolic carbon dioxide gas trapped in the valley sediments to the northeast of the domes has been recently exploited for the manufacture of "dry ice."