Blast from the past You can only imagine that what this climber saw at 8.32 a.m. on May 18th 1980 li

Blast from the past You can only imagine that what this climber saw at 8.32 a.m. on May 18th 1980 literally knocked her off her feet. The huge bulge that had been growing on the northern flank of Mount Saint Helens with approximately 2m a day collapsed into one of the biggest debris avalanches recorded in human history. John V. Christensen took this image of the lateral blast of the volcano from another volcano, Mount Adams, about 50km away. The bulge on the northflank of St Helens, at the time growing outwards 140m, actually had a cryptodome under it where magma had been accumulating for months. A 5.1. magnitude earthquake (which could have caused the climber to get knocked off her feet) occurred under the volcano and set loose the bulge, the cryptodome and hot water into one of the a debris avalanche accompanied by a lateral blast. This lateral blast moved at a speed of 480km/h. During this, the upper 400m of St Helens top was blasted off and the avalanche managed to reach at least 23km land inwards. Since Mount Adams was only 53km from Mt St Helens, the debris avalanche flow actually got pretty close to the climber on the picture and, as you might except, there is no way to outrun it. Finally, St Helens was rid of its bulge and able to release pressure by sending an eruption cloud more than 24km into the air. At noon, multiple pyroclastic flows had come down the new horseshoe shaped crater and the melting ice had caused lahars (surges of water mixed with debris) of which the largest managed to get 80km away from the volcano. Sadly, 57 people died during Mt St Helens 1980 eruption.-OW-Image: Jonathan F. Christensen (National Geographic). The eruption of Mt St Helens on May 18th as seen from Mount Adams. To check our our previous post on this please click here: http://on.fb.me/SAmR69. References:http://pubs.usgs.gov/gip/msh/http://volcanoes.usgs.gov/volcanoes/st_helens/ -- source link

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