GEOLOGIC FRAMEWORK FOR GEOTHERMAL ENERGY IN THE CASCADE RANGE.

Quaternary volcanoes of the Cascade Range form a 1200-km-long belt from northern California to southwest British Columbia and lie above the subduction zone formed as the Juan de Fuca plate is consumed beneath North America. Volcanoes throughout this belt may have been active during Quaternary time, and many have erupted within Holocene time. Thermal springs are few and inconspicuous. Surface expression of hydrothermal systems possibly is masked by infiltration of abundant rainwater and snowmelt. Several geologic and geophysical features suggest that the Oregon and California parts of the Cascades are characterized by moderate east-west crustal extension, tectonic regime conducive to relatively widespread volcanism and to the formation of normal fault zones of potentially high permeability. Refs.