Eruption at Suwanosejima, Volcanic Alert Level raised to 3, Japan

suwanosejima-eruption-volcanic-alert-level-raised-to-3-japan-september-2021

The Japan Meteorological Agency (JMA) has raised the Volcanic Alert Level for Suwanosejima volcano from 2 to 3 at 17:30 UTC on September 16, 2021.

Authorities are urging residents of Toshima Village, Kagoshima Prefecture to refrain from entering the danger zone.

The decision to change the Alert Level was made after an eruption at Mt. Otake crater at around 17:00 UTC. The eruption ejected large rocks hundreds of meters away from the volcano.

Multiple initial eruptions were registered at the crater, JMA said, and warned residents large rocks could affect an area within 2 km (1.2 miles) away from the crater.

Image credit: JMA

Image credit: Copernicus EU/Sentinel-2, TW. Acquired on May 31, 2021

Image credit: Copernicus EU/Sentinel-2, TW. Acquired on April 26, 2021

Geological summary

The 8 km (5 miles) long, spindle-shaped island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse.

Suwanosejima, one of Japan's most frequently active volcanoes, was in a state of intermittent strombolian activity from Otake, the NE summit crater, that began in 1949 and lasted until 1996, after which periods of inactivity lengthened.

The largest historical eruption took place in 1813 – 14 when thick scoria deposits blanketed residential areas, and the SW crater produced two lava flows that reached the western coast.

At the end of the eruption, the summit of Otake collapsed forming a large debris avalanche and creating the horseshoe-shaped Sakuchi caldera, which extends to the eastern coast.

The island remained uninhabited for about 70 years after the 1813 – 14 eruption.

Lava flows reached the eastern coast of the island in 1884.

Only about 50 people live on the island.

Featured image credit: JMA

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