Saturday, 4 January 2020

Eruption on Mount Shishaldin, Alaska.

The Alaska Volcano Observatory has reported a large eruption on Mount Shishaldin, a 2870 m stratovolcano (cone-shaped volcano made up of layers of ash and lava), located on Unimak Island in the Aleutian Island Chain. The volcano began erupting some time before 9.50 am on Friday 3 January 2020 (when the eruption was first observed by a pilot), and produced an ash column that rose to about 8000 m above sealevel, and drifted to the south. The eruption is not thought to present any threat to Human life or habitation, due to the remote location of the volcano, but a warning has been issued to aviation. This is the latest in a series of eruptions on the mountain that began in October 2019.

An eruption on Mount Shishaldin on 26 December 2019. Aslaska Volcano Observatory.

Mount Shishaldin is the westernmost of three volcanoes located in an east-west line across Unimak Island. It is the largest volcano in the Aleutian Islands, and considered to be coincided to be the most symmetrical volcano on Earth, with contour lines forming near perfect circles, although the north and south slopes are steeper than the east and west slopes. The current cone structure of Mount Shishaldin is thought to be less than 10 000 years old, and is built on the remnants of an older cone, which is exposed to the west and northeast sides. To the northwest of the main volcano is an area of massive lava flows, with 24 smaller cones, thought to be parasitic on the main volcano.

The volcanoes of the Alaskan Peninsula and Aleutian Islands are fed by magma rising from the Pacific Plate, which is being subducted beneath the North American Plate to the south along the Aleutian Trench. As the subducting plate sinks into the Earth it is subjected to enormous heat and pressure, causing more volatile minerals to melt. These then rise through the overlying North American plate as magma, fuelling the Alaskan volcanoes.

 How the subduction of the Pacific Plate beneath the North American Plate fuels the volcanoes of Alaska. Alaska Volcano Observatory.

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