One of the most devastating volcanoes erupted 7,300 years ago — and scientists say it’s filling with magma again

This situation is heating up.

One of the world’s most volatile volcanoes is silently refilling with molten rock, sparking fears that this caldera could be getting ready to unleash a torrent of lava, per a bombshell report in the journal Communications Earth & Environment.

“The magma that is now present in the magma reservoir under the lava dome is likely newly injected magma,” said co-author Seama Nobukazu, a geophysicist at Kobe University in Japan, in a recent statement.

Dubbed the Kikai caldera, this mostly-underwater caldera located south of Japan’s Ryuku Islands last erupted 7,300 years ago, marking the largest volcanic eruption in the current geological epoch, the Holocene.

The Kikai Caldera is located in the Ōsumi Islands in the Kagoshima Prefecture, Japan. AP

The blast, named the Akahoya eruption, reportedly expelled about 38 cubic miles of dense rock into the air —  approximately 11 times the volume ejected by Alaska’s Novarupta in 1912, which was the most powerful of the 20th century, Science Alert reported.

The violent blast spewed material across over 1,700 square miles, an area nearly three times the size of New York City, and sent pyroclastic flows fanning out 93 miles from the epicenter.

The eruption reportedly wiped out the Jōmon people, who populated ancient Japan between about 14,000 BC and 300 BC.

A map of the Osumi Islands, where the Kikai caldera is located. Peter Hermes Furian – stock.adobe.com

Over the last 3,900 years, a new lava dome has been forming beneath the 12-mile-wide caldera, sparking fears of a sequel. And while the caldera hasn’t done anything as bombastic since, there has been scattered volcanic activity with researchers noting that even a modest eruption could prove devastating.

To get to the bottom of the combustive phenomenon, the researchers dispatched research boats to scan the area with air-guns and seismometers that were planted on the sea floor.

Using these tools, they were able to measure how the pulses traveled through the Earth’s crust, discovering a large lava reservoir that seemingly supplied Akahoya.

Unlike with the last blast, however, this lava was all new material.

Chemical analyses revealed that the material and other recent activity was comprised of different magma than what was expelled during the last eruption, meaning that the reservoir has been infused with newly-injected molten rock.

In fact, Nobukazu found that this “magma re-injection model” mirrored other “large shallow magma reservoirs” such as the one beneath Yellowstone. Scientists have long feared that this caldera could potentially lead to human extinction, although studies have suggested that this concern is grossly overblown.

Nonetheless, the findings could help inform future models of how magma reservoirs under caldera volcanoes refill following major eruptions.

This would, in turn, help volcanologists better predict if and when a volcano’s going to blow its stack.

“We want to refine the methods that have proved to be so useful in this study to more deeply understand the re-injection processes,” said Nobukazu. “Our ultimate goal is to become better able to monitor the crucial indicators of future giant eruptions.”