LAUSR

The north slope of Mount St. Helens erupted catastrophi­ cally at 8:32 a.m. on 18 May 1980 in southern Washington state, about 50 miles northeast of Portland (Oregon, USA). This eruption was pre­ ceded by a magnitude 5.1 earthquake and a subsequent landslide that are thought to have triggered the main eruption. Although relatively “minor” compared to other US eruptions (e.g. Yellowstone Supervolcano in Wyoming, USA), Mount St. Helens was the deadliest and most eco­ nomically destructive eruption in United States’ history (Tilling et al. 1990): it killed 57 people, including U.S. Geological Survey (USGS) volca­ nologist Dr. David A. Johnston who was moni­ toring the volcano 6 miles north of Mount St. Helens. It’s somewhat ironic that Dave Johnston was killed “by an unusual eruptive event that was largely unanticipated, in magnitude or style, except perhaps by Dave himself” (Hildreth 1980).