Another eruption at Asosan volcano, Japan

Another eruption at Asosan volcano, Japan

Another minor eruption took place at Japanese Asosan volcano (Mount Aso) in Kumamoto Prefecture late Thursday, April 18, 2019.

The eruption started at 23:24 UTC on April 18 (08:24 JST, April 19) at the No. 1 Nakadake crater, spewing ash up to 400 m (1 312 feet) above the crater, the Japan Meteorological Agency said. This is the same source as the previous eruption on Tuesday, April 16.

JMA maintains the volcanic alert level at 2 of 5, restricting entry to areas 1 km (0.62 miles) around the crater.

Even a small eruption can be dangerous as pyroclastic flows could be produced and large flying rocks could be ejected far away from the crater, JMA said.

Tuesday's eruption was Asosan's first since October 2016 when the volcano produced a column of ash up to 11 km (36 000 feet) above sea level and sent large boulders down the slopes of the volcano.

Ash rained down on cars, houses and roads in the city Aso and was reported as far as 320 km (200 miles) from the crater. It was the first explosive eruption at the volcano since 1989. It came 6 months after a series of earthquakes shook Kumamoto Prefecture.

Geological summary

The 24-km-wide Asosan caldera was formed during four major explosive eruptions from 300 000 to 90 000 years ago. These produced voluminous pyroclastic flows that covered much of Kyushu. The last of these, the Aso-4 eruption, produced more than 600 km3 of airfall tephra and pyroclastic-flow deposits. A group of 17 central cones was constructed in the middle of the caldera, one of which, Nakadake, is one of Japan's most active volcanoes. It was the location of Japan's first documented historical eruption in 553 AD.

The Nakadake complex has remained active throughout the Holocene. Several other cones have been active during the Holocene, including the Kometsuka scoria cone as recently as about 210 CE. Historical eruptions have largely consisted of basaltic to basaltic-andesite ash emission with periodic strombolian and phreatomagmatic activity. The summit crater of Nakadake is accessible by toll road and cable car, and is one of Kyushu's most popular tourist destinations. (GVP)

Featured image credit: Mount Aso erupting on April 16, 2019. Credit: YonhapnewsTV

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