Tuesday 23 October 2012

Volcanic activity on Mount Alaid.

Alaid is the northernmost volcano of the Kurile Islands, a volcanic archipelago that stretches from the northeastern tip of Hokkaido in Japan to the tip of the Kamchatka Peninsula. It is a stratovolcano (cone shaped volcano made up of layers of ash and lava, the kind of volcano most often seen in films) with a breached crater open to the south. It rises 2339 m above sea level, making it the highest volcano in the Kuriles.

(Top) Mount Alaid photographed from sea level. Travel Doyenne. (Bottom) Mount Alaid photographed from the International Space Station. NASA/Earth Observatory.

On 5 October 2012 residents of Paramushir Island, roughly 20 km to the southeast, reported seeing a plume of gas and steam rising 200 m above the summit of Mount Alaid, and on 6 October satellites reported a thermal anomaly (hotspot) on the volcano that persisted at least 7.5 hours, causing the Kamchatkan Volcanic Eruption Response Team to raise the aviation alert level near Alaid. Such thermal anomalies, when detected by satellites using infra-red imaging, may represent heat from within a volcano or hot lava on the surface. The thermal anomaly was observed again on 15 October.

Despite occasional steam plumes and bouts of seismic activity, Alaid has not erupted in ernest since 1981, when an explosive eruption threw ash 15 km into the air, and covered an estimated 150 000 km³ (much of it at sea) in ash up to 30 cm thick, causing severe disruption to the town of Severokurilsk on Paramushir Island.

Map showing the relationship between Mount Alaid (top left) and Paramushir Island (centre). Google Maps.

The Kurile Archipelago is a volcanic island arc on the boundary of the Okhotsk and Pacific Plates. The Pacific Plate is being subducted beneath the Okhotsk Plate. As the Pacific Plate sinks into the Earth it is partially melted by the friction and the heat of the Earth's interior. Some of the melted material then rises through the overlying Okhotsk Plate, fueling the volcanoes of the Kurile Archipelago, Hokkaido and south Kamchatka.

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