Is something up at Shishaldin?


Shishaldin volcano in Alaska.

Yesterday I mentioned in the SI/USGS Weekly Report update that things appear to be afoot at Shishaldin in the Aleutians. Well, I checked the Shishaldin webicorder today and indeed, [SPECULATION] something seems suspect. Now, the increasing signal might be wholly unrelated to any magmatic activity, but it is interesting to see an increase in the seismicity after the increase in the intensity of thermal anomaly at the summit crater.

AVO's latest statement (from yesterday) seems to think that nothing too much is up:

Cloudy conditions prevented views of Shishaldin today but it is likely that the thermal anomaly persists at the summit crater. Seismic, deformation, and gas emission data do not show anything abnormal at the volcano, and there is currently no indication that an eruption will occur. AVO will continue to carefully monitor activity at Shishaldin.

Shashaldin, located on Unimak Island, is possibly one of the most picturesque volcanoes on the planet. It is beautifully symmetrical and when covered with snow (as it is most of the time), it is a "textbook stratocone". The volcano tends to produce explosive (strombolian) basaltic eruptions with some lava flows. Shashaldin may have had a small eruption in 2008, but the last confirmed eruption was in 2004, when a VEI 2 eruption produced explosions and some ash fall. In 1999, the volcano had a VEI 3 eruption that also produced lahars. Shilshaldin has been very active since the mid-1800s, so a new eruption at the volcano would definitely not be surprising.

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How weird is that? This Shishaldin post was added after I'd started composing my response on the SI report, but before it was submitted! BTW surely Shishaldin is on Umnak Island?

Oops! It sure is on Unimak Island. I've been a little busy/distracted lately, but that is no excuse for misplacing a volcano.

The more I look at the current webicorder, the more I think it has to be a wind/weather signal rather than anything volcano. Any webicorder denizens want to chime in?

Spectrum analysis suggests that the increase in seismic activity as seen in webicorders may be due simply to bad weather. There's a lot of broadband signal tipically associated with strong winds and rains. This is a picture of a section from today, from 6:30 to 18:30 UTC:

http://i27.tinypic.com/2j1af05.jpg

By SHIRAKAWA Akira (not verified) on 16 Jul 2009 #permalink

Great pic BTW. The peak is so symmetrical it looks like an intro textbook drawing. What is its eruptive history?

Thanks Akira, I should've looked further in the AVO site. Its as I suspected based on the lack of any noticeable erosion.

Doug, a lot of the quakes on Mt. Baker have very shallow reported depths, they could be due to mass wasting events on the southern slope.

I found this weekend that when you play a Nickelback album backward you hear messages from Satan... but even worse: if you play it forward.. you hear Nickelback...

Great post. Thanks for sharing your thoughts. Iâll keep an eye out for more cool tips. - More than any other time in history, mankind faces a crossroads. One path leads to despair and utter hopelessness. The other, to total extinction. Let us pray we have the wisdom to choose correctly. Woody Allen Born 1935