Continuous explosive activity, strong sulfur dioxide emission over Suwanosejima volcano, Japan

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Continuous explosive activity was reported at Japan's Suwanosejima volcano over the past several days, with another eruption recorded on Thursday, August 6, 2020, in which the ash plume reached up to 2.3 km (7 000 feet) a.s.l. The Alert Level remains at 2 (on a 5-level scale) since December 1, 2007.

JMA is reporting continuous activity at Suwanosejima volcano over the past weeks, with several notable explosions and nighttime incandescence at Ontake Crater.

An explosion on July 27 generated a gray plume that rose as high as 2 km (6 550 feet) above the crater rim.

According to the Tokyo VAAC, ash plumes rose to 1.8 – 2.4 km (6 000 – 8 000 ft) a.s.l. from August 1 to 3 and drifted NW and W.

On August 4, a satellite image from Tropomi showed strong sulfur dioxide (SO2) emissions that extended to the south of the volcano across the Pacific Ocean.

According to Tokyo VAAC, the last eruption at the volcano took place at around 01:21 UTC (10:21 LT) on August 6, spewing ash up to 2.3 km (7 000 feet) a.s.l., extending NE.

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 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.

Featured image credit: DLR/BIRA/ESA

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