Aso, Kyushu, Japan

Space Shuttle Photo of Aso caldera.

Aso volcano has produced more explosive eruptions than any other volcano in the world.

Aso is a caldera about 12 miles (20 km) in diameter. Of the numerous stratovolcanoes and cinder cones inside the caldera only Naka-dake has been active in historic time. The first documented eruption in Japan was at Naka-dake in 553. Since then, Naka-dake (shown above) has erupted 167 times. The most recent eruption ended in 1993. Most eruptions of Naka-dake are small to moderate in size. Most are simple explosions that produce ash or blocks. Aso has not produced lava flows in historic time. Only 8 eruptions have caused fatalities. Most fatalities are tourists on the rim of the cone. Note people sledding and skiing in the foreground. Photograph courtesy of and copyrighted by Paul J. Buklarewicz.

The level of thermal activity rose during the last few months and a new "mud eruption" occurred from Crater 1 on 14 January at 1541. The eruption was accompanied by volcanic tremor and ash emissions that rose to low levels and fell in Takamori Town about 10 km ESE of the crater. The Alert Level was raised from 2 to 3, and entrance within 1 km of the crater was restricted.

Between July 12 and 14, seismic signals associated with five small phreatic eruptions were recorded and on the 27th, continuous volcanic tremor began. Such activity had not been recorded at Aso since November 1995. On the 28th the crater lake in Crater 1 was
gray, 76 °C, and bubbling in the center, and since, ~10 earthquakes occurred per day.

The color of the crater lake' surface changed from green to dark gray on 8 July. On the 10th, a tremor event with a moderate amplitude was recorded and following an inspection of the area around Nakadake crater, a small amount of tephra, newly produced by a phreatic eruption, was deposited about 6 km ENE of the crater was found. Mud emitted during the eruption reached as far as 10 km from the crater.

This information was summarized from the GVP/USGS Weekly Volcanic Activity Report

Looking across Aso caldera. One of the numerous cones inside the caldera is in the foreground. Photograph courtesy of and copyrighted by Paul J. Buklarewicz.

Aso viewed from the visitors center. Small plume above Aso during a period of mild Strombolian eruptions, December 30, 1991. Photograph by Mike Lyvers.

Aso Panorama Ground View

Additional Photos of Aso

Kuno, H., 1962, Part XI, Japan, Taiwan and Marianas: Catalogue of the active volcanoes of the world including solfatara fields, International Association of Volcanology, Rome, Italy, 332 p.

McClelland, L., Simkin, T., Summers, M., Nielsen, E., and Stein, T.C., 1989, Global Volcanism 1975-1985: Englewood Cliffs, New Jersey, Prentice Hall, 655 p.

Simkin, T., and Siebert, L., 1994, Volcanoes of the World: Geoscience Press, Tucson, Arizona, 349 p.

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