Hydrothermal heat discharge in the Cascade Range includes the heat discharged by thermal springs, by “slightly thermal” springs that are only a few degrees warmer than ambient temperature, and by fumaroles. Thermal-spring heat discharge is calculated on the basis of chloride-flux measurements and geothermometer temperatures and totals ~ 240 MW in the U.S. part of the Cascade Range, excluding the transient post-1980 discharge at Mount St. Helens (~ 80 MW as of 2004–5). Heat discharge from “slightly thermal” springs is based on the degree of geothermal warming (after correction for gravitational potential energy effects) and totals ~ 660 MW. Fumarolic heat discharge is calculated by a variety of indirect and direct methods and totals [...]
