Mount St Helens
Mount St. Helens, this 123 year dormant volcano, erupted on May 18, 1980 after being shaken by an earthquake measuring 5. ... Scientists have determined that the history of Mount St. Helens began about 40,000 years ago with dactic volcanism. ... This period marked a large change in eruptive behavior and the types of rocks erupted by Mount St. Helens. ... Pyroclastic flows of lithic dacite moved down the southwestern side of Mount St. Helens. ... Scientists soon began to study the deposits around Mount St. Helens in the 1950’s. They published a report in 1975 that predicted Mount St. Helens was the most likely volcano in the lower 48 states to erupt in the next century. ... The eruption of Mount St. Helens, one of worst in recorded history, caused cataclysmic destruction and distress.