Never seen this before- ashfall advisory

[Mark Sudduth]

http://forecast.weather.gov/wwamap/wwatxtget.php?cwa=usa&wwa=Ashfall%20Advisory

That is a new one for me. Makes sense but never seen it before.

[Billy Griffin]

Just got back from Dutch Harbor. The volcano is quite active at this point.

[Tim Vasquez]

Not only that but we appear to have a second volcano:


Mount Cleveland, a volcano in the Aleutian Islands about 90 miles west of still-simmering Okmok Caldera, erupted Monday, giving Alaska dueling volcanoes.
"Things are very hopping," research geophysicist Peter Cervelli of the Alaska Volcano Observatory said Monday afternoon. "We've been ramped up 24/7 for nine days because of Okmok, and to have Cleveland suddenly go off keeps us busy. I'm not sure I'd describe it as fun, but it's certainly exciting." -- source (http://www.kansascity.com/440/story/715072.html)I did look at the GOES imagery and it's barely showing anything if at all. The IR channel shows a little faint smudge of something today at Okmok starting on the 1930Z frame, but it's barely visible and I'm inclined to believe it might be a little puff of volcanic ash.

Tim

[Dennis Sherrod]

Here is one of the better sites for Alaska.

http://www.avo.alaska.edu/

[Angie Norris]

That is an incredible image of the caldera. I didn't realize that smaller volcanoes would be contained within the caldera.
I found this article earlier this afternoon
http://www.sciencedaily.com/releases/2008/07/080720093810.htm

[Tim Vasquez]

Just as an aside, this is the awesome Mt. Redoubt volcano explosion in 1990, on the northern fringes of the Aleutians (well, technically, just north of there):

http://upload.wikimedia.org/wikipedia/commons/thumb/1/17/MountRedoubtEruption.jpg/800px-MountRedoubtEruption.jpg

Mt. Redoubt is 10,100 ft high, so a crude calculation based on the geometry of the image and assuming 60 km distant on the shot, tan (arcsin(45400ft from extrapolation/196800ft) * 196800 ft), places the top of the ash cloud seen here at at least 47,000 ft. I didn't account for Earth curvature as that's getting out of my league with trig, so it may be higher.

Tim

[Bill Schintler]

Volcanic ash is a serious hazard for jet aircraft should one encounter it while in flight - bill

http://www.boeing.com/commercial/aeromagazine/aero_09/volcanic_story.html

[Angie Norris]

Volcanic ash is rather nasty stuff composed mostly of sulfur particles and very small (2mm or less diameter) shards of glass formed from the eruption.

The sulfur particles not only lead to acid rain but are part of the mechanism behind global cooling since the particles reflect sunlight back out to space.

The glass particles are incredibly abrasive and if inhaled can combine with the moisture present in the lungs to form a concrete like substance and cause suffocation. If I remember correctly from Dr. Weaver's lecture on volcanic hazards, the primary threat to aircraft occurs when the ash is ingested into the aircraft engine, melts back into glass from the heat of the engine and then resolidifies causing potentially catastrophic engine damage and failure.


But you have to admit, those pyroclastic clouds are quite awesome...from a VERY respectful distance.