- I had the great privilege of
being able to join the crew of the Fukae Maru, a scientific research
ship from the Kobe Ocean-Bottom Exploration Center. The expedition
team studies the plate tectonics around Japan as well as the
Kikai Caldera underwater super-volcano. I boarded the ship with
an interpreter in Nagasaki, and we spent 5 days on board as they
used sonar and a magnetometer to map out parts of the sea floor.
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- Kikai Caldera is a
massive, mostly submerged caldera 19 kilometers (12 mi) in diameter
in the Osumi Islands of Kagoshima Prefecture, Japan.
- Kikai Caldera was the source
of the Akahoya eruption, one of the largest eruptions during
the Holocene (10,000 years ago to present). About 6,300 years
ago, pyroclastic flows from that eruption reached the coast of
southern Kyushu up to 100 km (62 mi) away, and ash fell as far
as Hokkaido. The eruption produced about 150 km³ of material,
giving it a Volcanic
Explosivity Index of 7 and making it
one of the most explosive in the last 10,000 years.
- Kikai is still an active volcano.
Minor eruptions occur frequently on Mount Io, one of the post-caldera
subaerial volcanic peaks on Iojima. Iojima is one of three volcanic
islands, two of which lie on the caldera rim. On June 4, 2013,
weak tremors were recorded. Shortly after, eruptions began and
continued off-and-on for several hours.
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