May 18, 1980. On that fateful day, Mount St. Helens Volcano in Washington exploded violently after 2 months of intense earthquake activity and intermittent, relatively weak eruptions, causing the worst volcanic disaster in the recorded history the United States.
The cataclysmic eruption and related events May 18 rank among the most significant geologic events in the United States during the 20th century. The processes, effects, and products of the chain of events were the most intensively studied and photographically documented of any explosive volcanic eruption in the world to date. The wealth of data on Mount St. Helens before, during, and after the May 18 eruption enabled geoscientists of the U.S. Geological Survey (USGS), the University of Washington, and other research institutions in the United States and abroad to put into perspective the devastating impact of suddenly unleashed volcanic energy.
In 1981 and 1982, the results of many of these studies were published by the USGS in two comprehensive volumes, Professional Papers 1249 and 1250, both dedicated to the memory of David A. Johnston, a USGS volcanologist killed while making scientific observations on May 18. Intermittently active through the 1980s, Mount St. Helens continues to receive intensive study. This booklet-updated and revised from the first edition (1984) on occasion of the 10th anniversary of the May 18, 1980, eruption-presents selected highlights of the volcano's eruptive history, reviews its activity in the past decade, and speculates about its possible future behavior. Materials cited in the Selected Readings provide more detailed information on topics that have been omitted or treated only briefly.