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CVO Website - May 18, 1980 Eruption of Mount St. Helens |
 | | At 0832 on May 18, a complex earthquake (M=5.1) shook the volcano, probably causing (but possibly caused by) a huge, 2.7-cubic-kilometer-landslide that in three different blocks successively removed the bulge and upper 400 meters of the volcano (Voight, et.al., 1981, 1983), leaving a 600-meter-deep crater 2 kilometers wide rim-to-rim. |
 | | P.D.T. May 18 was apparently triggered by a magnitude 5.1 earthquake that caused the unstable north flank to fail as three great retrogressive landslide blocks. |
 | | Mount St. Helens, Washington: The catastrophic eruption on May 18, 1980, was preceded by 2 months of intense activity that included more than 10,000 earthquakes, hundreds of small phreatic (steam-blast) explosions, and the outward growth of the volcano's entire north flank by more than 80 meters. |
| vulcan.wr.usgs.gov /Volcanoes/MSH/May18/description_may18_1980.html (1590 words) |
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