Photograph courtesy of and copyrighted by Paul J. Buklarewicz.

The 24-km-wide Aso caldera was formed during four major explosive eruptions from 300,000
to 80,000 years ago. These produced voluminous pyroclastic flows that covered much of Kyushu.
A group of 17 central cones was constructed in the middle of the caldera, one of which,
Naka-dake, is one of Japan's most active volcanoes. It was the location of Japan's first
documented historical eruption in 553 AD. The Naka-dake 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 AD.

Historical eruptions have largely consisted of basaltic to basaltic-andesite ash emission with
periodic strombolian and phreatomagmatic activity. The summit crater of Naka-dake is accessible
by toll road and cable car, and is one of Kyushu's most popular tourist destinations.

29.juli 2003
As of the 29th of July, the Global Volcanism Network (GVN) and the Japanese Meteorological
Agency (JMA) has reported that Aso Volcano on the afternoon of 28 July 2003 had a continuous
volcanic tremor event started around 2 p.m. 27 July. The same event had not been observed afte
r November 1995. Though the daily number of volcanic quakes ranges around 10, that of isolated
tremor around 100 since 23 July. This day, water of crater lake in the Crater 1 was gray in colour,
and the temperature was 76 C. Boiling was observed in the centre. JMA had observed seismic
signals implying small phreatic eruptions 5 times during 12-14 July.

Geologists surveyed the deposit of the 10 July eruption on the following day, and estimated
the total mass of eject as about 130 t. Ash was deposited as distant as 14 km EWE of the
crater. They confirmed small amount of fresh vesicular glass particles in the ejecta under the
microscope. They posed a possibility that the juvenile material may be related to the eruption.

 
Naka-dake crater. Believe the signs means something like 'STAY AWAY!'


View of the Aso-crater. One of the many cones may be seen in the foreground.
Photograph courtesy of and copyrighted by Paul J. Buklarewicz.

there is rich flourishing here....

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