A giant lava bubble is expanding at Kikai volcano, a supervolcano just 31 miles south of Japan’s main island of Kyushu.
More than 31 cubic kilometers (7.4 cubic miles) of lava have shoved the seabed up around 2,000 feet, creating a giant dome with a diameter of about six miles.
The area also contains active hydrothermal springs and dense streams of gas bubbling up from the sea bed.
“The most serious problem that we are worrying about is not an eruption of this lava dome, but the occurrence of the next supereruption,” said Yoshiyuki Tatsumi a volcanologist at Kobe University in Japan and lead author of the new study published in Nature Scientific Reports.
Dr. Tatsumi thinks the chances of a supereruption in the within the next 100 years are only about 1 percent. But when that eruption comes, it could eject nearly 10 cubic miles of magma (not ash, but magma!), enough to cover almost all of Japan in ash nearly eight inches thick, he found.
Researchers say such an eruption could kill some 100 million people who live within its fallout zone, which includes the cities of Nagasaki, Hiroshima and Osaka.
Such an eruption would also have a serious effect on global climate. Temperatures would plunge and crops would fail.
Kikai has exploded catastrophically before. Japanese volcanologists have found evidence of an eruption of 500 cubic kilometres (120 cubic miles!) of magma some 7,300 years ago (the Akahoya eruption), another about 95,000 years ago, and yet another about 140,000 years ago.
(Look at this graph on one of my previous posts: Temperatures plummeted about 7,300 years ago.)
Although you may not have heard of it before, Kikai is already considered an active volcano. Minor eruptions occur frequently on Mount Iō on the island of Iōjima, which lies on the caldera rim.
The most recent eruptions occurred in 2001, 1982, 1980, 1978, 1976, 1974?, 1969?, 1967, 1957 and 1943.
Kikai Caldera was the source of the Akahoya eruption, one of the largest eruptions during the last twelve thousand years.
Thanks to Laurel and several others for these links