The Little Volcano That Could

100 miles west/southwest of Anchorage lies Mt. Redoubt. It's part of the famed Pacific Rim "Ring of Fire" which is a continental subduction zone that surrounds the Pacific Ocean. One tectonic plate subducts (or is forced under) the various continental plates. This creates a geologic situation that gives birth to volcanos. Click on the image above that I grabbed from Google Earth to get an idea of the geographic relationship between Anchorage and Mt. Redoubt.

For a couple of weeks now Redoubt has been rumbling. Geologists thought they had this particular volcano pegged. An eruption in 1989 provided them with a template for predicting any future eruption. A certain level and pattern of seismic activity was noted in conjunction with that earlier eruption and they saw a very similar seismic signature recently prompting them to raise the alert level. Unfortunately, Mt. Redoubt isn't following the template.

As it stands, the volcano literally could erupt at just about any time. Recent flyovers show active fumeroles expelling typical pre-eruptive volcanic gases. The activity right now appears to be something the volcano-types call dome building. A large pocket of magma is moving up inside the mountain accounting for a myriad of what are called shallow earthquakes. At some point it is likely that increasing pressure inside this lava dome will reach a critical point and some sort of explosive eruption will follow.

Here's the important part: Nobody really has any clue what sort of explosive eruption will happen, when it might happen and frankly whether or not it will reach that point. If an eruption does occur, two things will be important for residents of Anchorage (and/or visitors): the scale of the eruption and the prevailing winds. If the eruption is large enough and the winds are in the right direction then Anchorage could see some ashfall.

In 1989 a KLM 747 unwittingly flew through a Mt. Redoubt ash-plume and suffered engine loss and a couple of minutes of horror for it's passengers before the crew restarted the engines and returned to the Anchorage International Airport. The KLM flight was outbound from Anchorage and using an atypical flight path. Typically, approaching airliners come into Anchorage from the east/southeast. With Mt. Redoubt 100 miles to the west/southwest there should be little concern for any inbound flights. The constant vigil by the Alaska Volcano Observatory in conjunction with airport operations in Anchorage means that any such future incident is all but eliminated.

With the St. Cloud Huskies travelling north this week for games in Anchorage there really shouldn't be too much to worry about. But then again ... who knows? This picture below was taken on January 31st and along with many others can be found at the Alaska Volcano Observatory website.

image credit: Christina Neal, Alaska Volcano Observatory/USGS