Saturday, April 13, 2013

Augustine volcano

The almost perfect symmetrical Augustine volcano in Alaska is part of the Aleutian Island Arc. It is one of the most active volcanic belts in the world with approximately 130 volcanoes, of which 90 have been active for the last 10,000 years. Between 1957 and 1965 three earthquakes of around 9.0 on the Richter scale (9.2 in 1964, 9.1 in 1957 and 8.7 in 1965) have occurred in the Aleutian Arc, indicating that the area is very active.

Discovered in 1778 by Captain James Cook, Augustine had 10 major historic eruptions. Now 1260 m high, the height of its summit has changed frequently in the past due to dome collapse. Actually, almost every eruption Augustine’s dome collapses and subsequently a new dome is created. In 1883 a VEI 4 eruption (Volcanic Explosivity Index: triggered a landslide that generated a tsunami of a possible 19m high.

Due to location of the volcano near a subduction zone, Augustine’s magma is mostly andesitic and rhyolithic in nature although during the 2006 eruption basaltic magma was also produced. Eruptions at Augustine usually start with an explosive phase that lasts for days or weeks and is followed by an effusive (characterized by effusion of lava) phase which could go on for months.

The last major eruption occurred in 2006 and was very well monitored, which could help volcanologists in their future research. Aside from minor earthquake swarms in 2007 and slight degassing from 2008-2010 the volcano has been quit. Nonetheless, it was selected as Alaska’s potentially most hazardous volcano by the USGS.

Photo: Cyrus Read, Alaska Volcano Observatory. Augustine volcano during the 2006 eruption as viewed from the ship M/V Maritime Maid.

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