Komaga-take, Hokkaido, Japan
On the evening of March 5, 1996, Usu Volcano Observatory reported volcanic
tremor beneath Komaga-take volcano. Additional small volcanic earthquakes
were also recorded. More than 6 miles (10 km) from the summit ash was
observed falling on the southern flank of the volcano. Local residents
recognized an eruption plume rising from a fissure of the 1929 eruption.
On the morning of March 6, the Japan Meteorological Agency reported
a 500 foot (150 m) high white plume rising above the summit. No precursor
activity to the eruption was detected. Volcanic tremor ended on the
evening of March 5.
- Komaga-take, an andesite stratovolcano,
is located 18 miles(30 km) north of Hakodate City (population 320,000).
The summit is a horseshoe-shaped caldera about a 1.3 miles (2 km) wide.
The caldera formed about 30-40 thousand years ago when a large part
of the volcano collapsed. Komaga-take has produced several large-scale
pumice-flow eruptions from craters within the caldera, including three
historical major eruptions; 1640, 1856, and 1929. During the 1640 eruption,
an avalanche entered the sea, which generated a tsunami that killing
700 people. The 1929 eruption lasted only one-day. It produced ash falls
and pumice flows that killed 2 people. The most recent eruption, in
1942, was moderate in scale with an eruption column that reached 5 miles
(8 km) above the volcano. Major eruptions at Komaga-take are characterized
by very short activity duration (less than several days).