Giant Lava Dome Confirmed in Japan’s Kikai Caldera

This is a water column anomaly (the red plume in ‘a’) and gas released (b), observed at the lava dome by a remotely-operated vehicle. (Kobe University)

(CN) – One of the world’s largest lava domes has been discovered in the Kikai Caldera south of Japan’s main island.

The Kobe Ocean Bottom Exploration Center has confirmed that a giant lava dome was created after a super-eruption 7,300 years ago. The dome is among the world’s largest with a volume of 32 cubic kilometers, according to a study released Friday in the online version of Scientific Reports.

Roughly 7,300 years ago, the Kikai Caldera caused the most recent giant caldera-forming eruption in the Japanese archipelago, the study says, and there is a high possibility that a large buildup of magma may exist inside it.

Kikai Caldera, south of Kyushu Island in southwest Japan, collapsed during the latest super-eruption, resulting in the release of over 500 cubic kilometers of magma, according to the study.

“Super-eruptions leading to the huge caldera collapse are rare but extremely hazardous events, and also have severe global impacts such as ‘volcanic winter’,” the study says.

The Kobe Ocean Bottom Exploration Center, established in 2015, has made three survey voyages to the Kikai Caldera, a 17-kilometer wide by 20-kilometer long volcano in the East China Sea, using the training ship Fukae Maru from the Kobe University Graduate School of Maritime Sciences. In their three voyages to the Kikai Caldera, Kobe Ocean Bottom Exploration Center scientists carried out detailed underwater geological surveys, seismic reflection, observations by underwater robots and observations using underwater seismographs and electromagnetometers.

According to Friday’s report, there is roughly a 1 percent chance of a giant caldera-forming eruption occurring within the Japanese archipelago during the next 100 years. An eruption like this might have over 40 cubic kilometers of magma released in one burst, causing “enormous damage,” the report said.

Researchers are scheduled to return to the area in March to study the process of formation of the double caldera and to determine the existence of a giant magma buildup, according to the report released Thursday.

During the next expedition, researchers with the Japan Agency for Marine-Earth Science and Technology will carry out a large-scale underground survey and will attempt to capture high-resolution visualizations of the magma system within the Earth’s crust at a depth of 30 kilometers. The team also plans to evaluate undersea mineral resources, according to Thursday’s report.

Supervolcanoes – like the one that sits under Yellowstone National Park – store lithium, an important mineral in batteries, researchers from Stanford University reported last year.

Although volcanic activity is relatively quiet between super-eruptions, the post-caldera activity should provide a key to understanding the evolution of “magma-plumbing system” in the caldera cycle, researchers said in the report. “Dynamic activities … such as formation of resurgent domes, i.e., uplift of the caldera floor by extensive magmatic intrusions, and volcanic cones, may represent processes of not only calming down from the climactic eruption, but also preparation for the next super-eruption.”

The latest activity in this caldera volcano took place in 1934 and 1935, two kilometers east of Satsuma Iwo-jima in a 500-meter-deep seafloor.

Lava domes often emerge at the post at the post-caldera stage of large caldera volcanoes. The resurgent dome develops after the caldera collapse, by gradual upwarping of the caldera floor.

Up until this recent discovery, the largest lava dome activity reported is the formation of two domes Naka-jima and Usu-san – 8 cubic kilometers each – after the collapse of Toya caldera in Hokkaido.

“Formation of a 32-cubic-kilometer post-caldera giant lava dome in Kikai Caldera is therefore a noteworthy activity in the caldera cycle,” the report says.

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