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slgwv

slgwv club

Posted: 13 Dec 2011

Taken: 01 Jun 1985

2 favorites     8 comments    316 visits

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state •
eruption •
aftermath •
USA •
Washington •
Mt. St. Helens •

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Driftwood in Spirit Lake

Driftwood in Spirit Lake
From the May 1980 eruption of Mt. St. Helens, Washington state, USA. Spirit Lake was enlarged due to damming by the mudflow when the north side of the mountain blew out. Still 5 years later much of the surface is covered with floating logs.

William Sutherland, have particularly liked this photo

8 comments - The latest ones
 slgwv
slgwv club
;)
11 years ago.
 William Sutherland
William Sutherland club
Magnificent capture!

Admired in:
www.ipernity.com/group/tolerance
10 years ago.
 Pam J
Pam J club
Savage Beauty.

Admired in ~ I ♥ Nature
10 years ago. Edited 10 years ago.
 Tractacus
Tractacus club
Can't help but compare this with photos of the Tunguska Event
10 years ago.
 slgwv
slgwv club
Thanks, everyone! The scale of the destruction is remarkable--and this was a _small_ eruption. As I used to tell classes, no geologist can say "mother" Earth with a straight face!
10 years ago.
 Tractacus
Tractacus club
Jeez! If that was a small eruption, I'd hate to think what you classify as a large one...
10 years ago.
slgwv club has replied to Tractacus club
The May, 1980 eruption of Mt. St. Helens ejected a bit more than 1 km^3 of tephra (ash), and that ash was nowhere near hot enough to weld when it settled out (see below). The eruption of Mt. Mazama about 6800 years ago, which formed the spectacular caldera now filled by Crater Lake, ejected about 160 km^3 of ash. Mt. Mazama ash forms a distinctive marker layer in young sedimentary units across much of western North America. Crater Lake is also in the Cascade Range, about 250 miles south in Oregon. The eruption of Tambora in Indonesia in 1815, the largest documented historical eruption, was comparable in size to Mt. Mazama. It caused the "year without a summer", due to aerosols high in the stratosphere.

Far larger eruptions have occurred in the geologic past. Huge "welded tuffs" (a.k.a. "ignimbrites") occur across much of the US west. These are ash-flow units in which the ash was still hot enough to weld together when it settled out--and some of these units extend for _miles_. Originally the ash must have extended much farther, but was not hot enough to weld. J. Hoover Mackin, who first studied these rocks in detail, said that "Tertiary eruptions of the Great Basin would compare with those of modern times as the explosion of a hydrogen bomb to the bursting of a firecracker." (American J. of Science, 1960). You usually can't get phrasing like that past the referees! The youngest such units are the Bishop Tuff in California, about 600K years old, and the Yellowstone Tuff. Such eruptions are the source of the concern about "supervolcanoes", which have recently gotten popular attention.
10 years ago. Edited 10 years ago.
Tractacus club has replied to slgwv club
Many thanks for the reply. Most interesting, and a little bit frightening... At least here in the UK we don't have to contend with volcanoes, though we're not immune to the after affects of an eruption, as witness the Icelandic eruption of a few years ago which brought air traffic to a halt over most of northern Europe.
10 years ago.

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