Map showing geothermal resources of the Lake City-Surprise Valley Known Geothermal Resource Area, Modoc County, California

This report summarizes geothermal data from published and unpublished geophysical, geochemical, and geologic reports on Surprise Valley that have been prepared during the past 26 years.  Particular emphasis is placed on a comprehensive structural interpretation of the west half of the valley that is based on map compilation of concealed faults that have been inferred from geophysical methods and exposed faults that can be seen in the field and (or) on aerial photographs.  The faults apparently control the location of modern geothermal activity and are thus important to geothermal exploration.