Monday, May 18, 2009

29 years ago today...

It's hard to believe that it has been 29 years since the eruption of Mount St. Helens. Here are a few summaries of the 1980 eruption from Volcano World FAQ:

Time: The climatic eruption began at 08:32 PDT on May 18, 1980.

Deaths: 57 people were killed directly by the eruption. There was also a plane crash, a traffic accident, and shoveling ash which killed a total of 7 more.

Height of Mount St. Helens: The summit elevation was 9,760 feet (2,975 m) before the eruption. After the eruption the elevation of the new summit was about 8,525 feet (2,600 m).

Volume: About 0.25 cubic kilometers of new volcanic rock was erupted on May 18, 1980. This would make a cube about 600 meters (~2000 ft) on a side! But much more material was moved by the eruption: the entire northern side of the volcano collapsed and flowed down hill. The volume of this collapse was about 2.5 cubic kilometers - ten times bigger than the new lava.

Ash: The eruption began at 8:45 a.m. At noon, the ash plume (in the upper troposphere and lower stratosphere) had reached Moscow, Idaho. By about 3 p.m. it was near Missoula, Montana and starting to spread south. By 6 pm it was eas! of Pocatello, Idaho. At the end of the day, about 16 hours after the eruption started, the ash plume was near central Colorado.

A huge volume of ash was created by the various 1980 eruptions of Mount St. Helens. Every community affected had its own ways of dealing with the ash. Tons of ash was probably washed down storm drains and into sewer systems as people cleaned roofs and sidewalks. Local landfills received ash. Many tons of ash came down rivers and streams into the Columbia River. The river had to be dredged to allow shipping to pass, and the sand dredged from the bottom was deposited in large dikes along the Columbia. These dikes are now covered in grass and trees, but if a person was to dig down a few feet they would find the ash.

Here's how she looked this morning:

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