Geologic Background:
Kikai is a mostly submerged, 19-km-wide caldera
south of Kyushu that was the source of one of the world's
largest Holocene eruptions about 6,300 years ago.
Pyroclastic flows traveled across the sea for a total
distance of 100 km to southern Kyushu and ashfall reached
the northernmost Japanese island of Hokkaido. The
eruption devastated southern and central Kyushu, which
remained uninhabited for several centuries.
The small island of Satsuma-Iwo-jima (80 km S of
Kagoshima) forms part of the NW rim of the 19-km-wide
Kikai caldera. Thermal activity is concentrated on a
young rhyodacite dome (Iwo-dake), one of the island's two
post-caldera cones.
Historic Activity:
- A submarine eruption built temprary islands 2 km E of
Satsuma-Iwo-jima in late 1934 and early 1935.
Recent Activity:
- On January 18, 1988 gray ash plumes were ejected 400
to 500 meters above the summit crater. A new pit crater
(15 x 30 m) formed in June or July 1991 in the large
fumarole fields which exist within and around the 300 m
diameter summit crater.
- Ashfalls from July to September 1998
- Ashfall in early 1999
- Ashfall in mid July 2001
Data Sources:
- Smithsonian's SEAN Bulletin (V. 13, No. 1)
- Global Volcanism Network (V. 16, No. 10 and V. 26,
No. 7).
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