Geologic map of the Mount Adams volcanic field, Cascade Range of southern Washington

One of the dominating peaks of the Pacific Northwest, Mount Adams, stands astride the Cascade crest, towering 3 km above the surrounding valleys. The icecapped 3742-m (12,276') stratovolcano has for centuries been called Pah-to by the region's indigenous people, who hold the mountain sacred as a symbol of continuity and a source of prosperity and inspiration. Comparable reverence helped secure inclusion of most of the great cone in the national wilderness system in 1964. Far less prominent than the central stratovolcano is an extensive field of subdued volcanic centers composing its heavily forested lowland periphery. Before the present investigation, little was known about the eruptive history, the distribution of eruptive vents, or the frequency, composition, and explosivity of past volcanic activity, for either the focal stratocone or the surrounding volcanic field. Our mapping began in 1981 as a Congressionally mandated assessment of the mineral- and geothermal-resource potential of the Mount Adams Wilderness (Hildreth and others, 1983). The project expanded to include assessment of the volcanic hazards and, as the long-lived eruptive complexity of the area became appreciated, it evolved into a fundamental investigation of how volcanoes work.