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On May 18, 1980, at 8:32 a.m. Pacific
Daylight Time, a magnitude 5.1 earthquake shook
Mount St. Helens. The bulge and surrounding
area slid away in a gigantic rockslide and
debris avalanche, releasing pressure,
and triggering a major pumice and ash eruption of the
volcano. Thirteen-hundred feet (400
m) of the peak collapsed or blew outwards. As a
result, 24 square miles (62 square
Km) of valley was filled by a debris avalanche, 250
square miles (650 square km) of recreation,
timber, and private lands were damaged by a
lateral blast, and an estimated 200
million cubic yards (150 million cubic meters) of
material was deposited directly by
lahars (volcanic mudflows) into the river channels.
Fifty-seven people were killed or
are still missing.
Images and information courtesy of USGS/Cascades Volcano
Observatory and Nasa Gov |
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