Science

The eruptive history of Mount St. Helens began about 40,000 years ago with dacitic volcanism, which continued intermittently until about 2,500 years ago. This activity included numerous explosive eruptions over periods of hundreds to thousands of years, which were separated by apparent dormant intervals ranging in length from a few hundred to about 15,000 years. The range of rock types erupted by...

Some Native Americans of the Pacific Northwest variously called Mount St. Helens 'lawilátɬa ', or 'one from whom smoke comes'. The volcano lawilátɬa is listed (as Lawetlat’la) on the National Register of Historic Places and acknowledged as a Traditional Cultural Property of significance to the Cowlitz Indian Tribe and Confederated Tribes and Bands of the Yakama Nation. The modern name, Mount St...

The May 18, 1980 eruptive column at Mount St. Helens fluctuated in height through the day, but the eruption subsided by late afternoon. By early May 19, the eruption had stopped. By that time, the ash cloud had spread to the central United States. Two days later, even though the ash cloud had become more diffuse, fine ash was detected by systems used to monitor air pollution in several cities of...