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Many hundreds of smaller earthquakes accompanied these larger events, the largest of which were felt by people living close to the volcano. Helens during the week of seismic buildup revealed small earthquake-induced avalanches of snow and ice, but no sign of an eruption.
With a thunderous explosion, or possibly two nearly simultaneous ones, widely heard in the region at about p.m. Helens began to spew ash and steam, marking the first significant eruption in the conterminous United States since that of Lassen Peak, California, from 1914 to 1917.
The crown of the ash column rose to about 6,000 feet above the volcano.
The effect of the prevailing easterly wind was striking during the March-April eruptive activity, transforming the snow-covered Mount St. The ash blown out between March 27 and May 18 was derived entirely from the 350-year-old summit dome, shattered and pulverized by phreatic (steam-blast) processes driven by the explosively expanding, high-temperature steam and other gases.
No magma (molten rock and contained gases) was tapped during the initial eruptions.
The first crater was joined on the west by a second, slightly larger crater, and as the activity continued, both craters enlarged and ultimately merged.
Several avalanches of snow and ice, darkened by ash, formed prominent streaks down the mountain's slopes.
Helens, located in southwestern Washington about 50 miles northeast of Portland, Oregon, is one of several lofty volcanic peaks that dominate the Cascade Range of the Pacific Northwest; the range extends from Mount Garibaldi in British Columbia, Canada, to Lassen Peak in northern California. Helens a composite volcano (or stratovolcano), a term for steepsided, often symmetrical cones constructed of alternating layers of lava flows, ash, and other volcanic debris.
Composite volcanoes tend to erupt explosively and pose considerable danger to nearby life and property.Helens, other active Cascade volcanoes, and those of Alaska form the North American segment of the circum-Pacific "Ring of Fire," a notorious zone that produces frequent, often destructive, earthquake and volcanic activity.Some Indians of the Pacific Northwest variously called Mount St.Vancouver also named three other volcanoes in the Cascades--Mounts Baker, Hood, and Rainier--for British naval officers. According to one Indian legend, the mountain was once a beautiful maiden, "Loowit".Indians on the Cowlitz River watching an eruption of Mount St. Helens blew its top is was a beautifully symmetric rounded snow-capped mountain that stood between two powerfully jagged peaks Mt. When two sons of the Great Spirit "Sahale" fell in love with her, she could not choose between them. He smote the three lovers and erected a mighty mountain peak where each fell.Pacific Standard Time (PST), preceded by several much smaller earthquakes beginning as early as March 16, was the first substantial indication of Mount St. Earthquake activity increased during the following week, gradually at first and then rather dramatically at about noon on March 25.Tags: Adult Dating, affair dating, sex dating