Kuju volcano, Japan

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Kuju volcano, Japan

The 1995-1996 eruptions

volcano number: 1802-12= (according to Volcanoes of the World, 1994 edition)

summit elevation: 1788 m

location: 33.08°N, 131.25°E

Last modified on 6 April 1996. Thanks to Tatsuro Chiba who made the photos available.

Kuju is a volcano in the northern part of the Japanese island of Kyushu. Different from its frequently or recently and destructively active neighbors such as Unzen, Aso, Sakura-jima or Kirishima, Kuju has not been much known until October 1995. On the 11th of that month, Kuju became alive again after at least 267 years of inactivity, staging a minor phreatic eruption from numerous vents on its Hosho dome.

Eruption of Kuju, seen from the air on 13 October 1995. This and all other photos by Asia Air Survey, from the WWW site of Tatsuro Chiba.

The initial eruption produced mainly steam with minor amounts of lithic ash. A total volume of 22,000 cubic meters of ash was produced during this eruptive episode that continued at declining rate through late October.

Closer view of the steaming vents on Hosho dome on 13 October 1995.

Detailed view of fissure vents on Hosho dome, 18 October 1995. Vigorous steam emission is continuing. Vicinity of vents is covered with light gray lithic ash, appearing humid near the largest vent. What is probably some minor lahars is visible near that vent.

On the early morning of 18 December 1995, another eruptive episode occurred at Kuju. From the images below it seems to be of a very similar character to that of October. This phreatic activity might lead, like recent eruptions at Unzen (Japan) and Montserrat (Montserrat, Caribbean), to a dome-building magmatic eruption. Time will tell...

As of 31 December 1995, the eruption seems to be continuing. The latest news is that a small amount (about 1%) of juvenile material has been found in the ejected ash after 20 December.

On 21-22 December, volcanic tremor preceded an eruptive episode that caused slight ashfalls up to 15 km away. The 1995 eruption of Kuju until then had been aseismic. (Info from the Volcano division of the Japan Meteorological Agency. This site seems to have been removed or closed, as of 16 January 1996.)

This is apparently a stereo view of the reactivated fissure vent, with a superimposed close-up of the largest vent on the right. Thumbnail shows only part of the stereo image. Photos are from NHK News, Japan (from Tatsuro Chiba's WWW site).

On 13 January 1996, Kuju started another eruptive episode, accompanied by intense seismic activity. The eruption is still of a very small scale, but the ejected tephra contains minor amounts of juvenile glass.

More info about Kuju is available at the follwing sites:

The Current Eruptions page of Volcano Research Center, Japan;
The Kuju page of the Geological Survey of Japan;
CNN report about Kuju's re-awakening
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