Recording historic eruptions and modern volcano-monitoring in themselves are insufficient to fully determine the characteristic behavior of a volcano, because a time record of such information, though perhaps long in human terms, is much too short in geologic terms to permit reliable predictions of possible future behavior. A comprehensive investigation of any volcano must also include the careful, systematic mapping of the nature, volume, and distribution of the products of prehistoric eruptions, as well as the determination of their ages by modern isotopic and other dating methods. Research on the volcano’s geologic past extends the data base for refined estimates of the recurrence intervals of active versus dormant periods in the history of the volcano. With such information in hand, scientists can construct so-called “volcanic hazards” maps that delineate the zones of greatest risk around the volcano and that designate which zones are particularly susceptible to certain types of volcanic hazards (lava flows, ash fall, toxic gases, mudflows and associated flooding, etc.). A strikingly successful example of volcano research and volcanic-hazard assessment was the 1978 publication (Bulletin 1383-C) by two Geological Survey scientists, Dwight Crandell and Donal Mullineaux, who concluded that Mount St. Helens was the Cascade volcano most frequently active in the past 4,500 years and the one most likely to reawaken to erupt, “... perhaps before the end of this century.” Their prediction came true when Mount St. Helens rumbled back to life in March of 1980. Intermittent explosions of ash and steam and periodic formation of short-lived lava domes continued throughout the decade. Analysis of the volcano’s past behavior indicates that this kind of eruptive activity may continue for years or decades, but another catastrophic eruption like that of May 18, 1980, is unlikely to occur soon. On 18 May 1982, the U.S. Geological Survey (USGS) formally dedicated the David A. Johnston Cascades Volcano Observatory (CVO) in Vancouver, Washington, in memory of the Survey volcanologist killed two years earlier. This facility—a sister observatory to the Hawaiian Volcano Observatory—facilitates the increased monitoring and research on not only Mount St. Helens but also the other volcanoes of the Cascade Range of the Pacific Northwest. More recently, in cooperation with the State of Alaska, the USGS established the Alaska Volcano Observatory in March 1988. The work being done at these volcano observatories provides important comparisons and contrasts between the behavior of the generally non-explosive Hawaiian shield volcanoes and that of the generally explosive composite volcanoes of the Cascade and Alaskan Peninsula-Aleutian chains. Volcanoes and People