Ralph Dawes compares his geologic map with what is found on the ground.
Dacite, from lava flow.
•Northwest Exposures -- a Geologic Story of the Northwest,
by David Alt and Donald Hyndman
•Roadside Geology of Washington,
also by David Alt and Donald Hyndman, Mountain Press Publishing (Missoula, Montana). ISBN number 078-0-87842-160-2
•Note: The Roadside Geology series of books also includes other states that may be of interest.