Tag Archives: USGS

The Islands of the Four Mountains

Volcano Week:

An Aleutian Caldera?

There is a cluster of volcanic islands in the Aleutian Chain that scientists have recently been asking a rather provocative question: Could they all be a part of one giant super volcano, similar to the Yellowstone Caldera?

This tight grouping of islands is home to six stratovolcanoes: Carlisle, Cleveland, Herbert, Kagamil, Tana and Uliaga. Mount Cleveland has been one of the most active volcanoes in North America over the past 20 years.

Most stratovolcanoes tend to have modest sized reservoirs of magma. Although that doesn’t mean they can’t have explosive eruptions, but they are dwarfed by caldera forming eruptions. A caldera is formed by tapping a huge reservoir of magma in the earth’s crust. A caldera forming eruption releases a massive amount of lava and ash, and they are catastrophic, often causing world-wide effects.*

Field work continues, although there is nothing easy about doing research in the Aleutians.

Mount Cleveland

Photo and map credit: USGS, *University of Alaska – Fairbanks

Alaska Jökulhlaup

A large glacial dam gave way in Southeast Alaska this summer. Known by its Icelandic term: jökulhlaup, the power of this sudden release of pent up water can be incredibly destructive.

The terminus of Lituya Glacier; Photo credit: NPS/J. Capra

Desolation Lake, which sits above the Lituya Glacier in Desolation Valley, collects meltwater from both the Desolation and Fairweather Glaciers. That meltwater is normally blocked by the Lituya Glacier, forming the roughly four square mile lake.

The water level suddenly dropped 200 feet.

A commercial fisherman, Jim Moore, along with his two grandsons, tried to enter Lituya Bay to fish for Chinooks in August. They should have been riding the tide into the bay, but the unusually muddy water was moving outward, and it was filled with trees and other debris. The bay was also filled with small icebergs. Moore managed to bring some of the ancient ice onboard for his coolers, then left the bay, instead of fighting the dangerous current.

Lituya Glacier terminus and delta; Satellite image credit: USGS

It is one of the largest jökulhlaups known to have occurred in Alaska. The water found a path under the Lituya Glacier, causing a rush that would have rivaled the hourly discharge of the Amazon River. It would have lasted for several days.*

Lituya Bay has a history. In 1958, an earthquake triggered a landslide that started one of the largest known tsunamis at over 1700 feet.

*NPS Geologist, Michael Loso