Alaska’s Sitkin Volcanoes


You might already have heard of one of the two Alaskan “Sitkin” volcanoes, since headline writers at a few news websites are giving Great Sitkin Volcano the “about-to-explode” treatment.

Indeed, the Alaska Volcano Observatory (AVO) recently raised the aviation code on Great Sitkin Volcano to Yellow, since it is having a period of elevated seismicity.

Again.

Great Sitkin has been having swarms of small earthquakes off and on since 2016. There also was a small ash emission in early June.

Magma probably has moved into the volcano. But there is no sure way to predict exactly what Great Sitkin Volcano will do in coming weeks and months, as volcanologists told local journalists late last year.

Instead of going by the doom-and-gloom headlines, let’s get to know these volcanoes a little better.

Great Sitkin

Great Sitkin is this bad boy, filmed from nearby Adak Island in 1995, while it was sleeping majestically, its summit 5709 feet (1740 meters) above the restless waves.



This volcano, which forms the northern part of Great Sitkin Island–part of the Andreanof island group–is far from major population centers. Anchorage is about 1200 miles (1900 km) to the east.

You need to keep that geographical factoid in mind or you’ll confuse Great Sitkin Volcano with Alaska’s other “Sitkin.”

Little Sitkin is some 200 miles (300 km) west of Great Sitkin and it belongs to the Rat island group. The only things these two volcanoes have in common is that they have formed in the Aleutian Trench subduction zone, each has had relatively recent eruptions (as well as long-ago caldera eruptions), and both sit under the heavily traveled North Pacific air routes.

Those last two facts mean that Great Sitkin and Little Sitkin must be monitored, if humanly possible.


Addendum: As of July 12, 2018, low-level unrest continues at Great Sitkin. Here is a photo of it on July 10th, steaming, by Andy Lewis via Alaska Volcano Observatory.


Little Sitkin

While Great Sitkin forms the northern part of its island, Little Sitkin is its own island–one that doesn’t look much like a volcano as you sail in towards its rocky beach with other geoscientists.




It’s relatively flat because this composite volcano formed in the midst of two calderas. If such features are too big to see, smaller ones show that Little Sitkin is not extinct:



Although it stirred a little bit in 2012, Little Sitkin now has an unassigned aviation code, while Great Sitkin is presently at Aviation Code Yellow.

Incredible as it may seem, given their remoteness, both of these two fire mountains are monitored.

Webicorder

AVO doesn’t have webcams for either of the two Sitkins (by the way, I don’t know of an explorer named “Sitkin” and suspect that the name comes from native languages).

However, in addition to satellite imagery and some infrasound equipment (at least for Great Sitkin), there are public webicorders (a seismographic image of data transmitted live to a web page) for both volcanoes.


Screenshot_2018-07-02-13-53-48

Given that the equipment is solar powered and way out in the wild, it is amazing, but both sets are transmitting right now, too!


Before you check these out, you might want to read AVO’s guide to what you are seeing, because these sensitive instruments pick up wave impacts and the wind, as well as passing wildlife, and even some barometric pressure changes in the atmosphere!

  • Great Sitkin: GSCK
  • Great Sitkin: GSTR
  • Little Sitkin (I can’t believe they’ve got an instrument this far out! Go! AVO!)

If you’re like me, you’ll get all excited when you see signals on a webicorder and then wonder why the volcano observatory is silent. Slowly you realize that volcanologists are completely in tune with their instrument’s reading and recognize what is important and what isn’t. Always go by the observatory’s official information releases, which you can sign up for by email: they’re free. AVO and USGS Volcanoes are also on Twitter.

Why go by the old doom-and-gloom headlines when you can up close (well, sort of) and (a little) personal with two fantastic Alaskan “Sitkin” volcanoes this summer!



Featured image: Greater Sitkin (in the distance), by Paxson Woelber via Wikimedia, CC BY-SA 4.0.


Other Sources:
Power, J. n. d. Alaska Volcanoes. US Geological Survey. https://woodshole.er.usgs.gov/operations/obs/rmobs_pub/html/alaska.html Last accessed July 2, 2018.


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