One of the worst volcanoes in history, which erupted 7,300 years ago, is raising alarms again because its caldera is filling with magma once more in Japan.

Written by Romário Pereira de Carvalho

Published on 09/04/2026 at 14:47

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Research identifies new magma beneath Kikai caldera in Japan, where the largest eruption of the Holocene reignites alerts about future volcanic risk

The Kikai caldera, south of the Ryukyu Islands in Japan, is being replenished by newly injected magma, according to a study published in the journal Communications Earth & Environment, reigniting fears of a future eruption in one of the world’s most unstable volcanic systems.

Study identifies new magma beneath Kikai

Co-author Seama Nobukazu, a geophysicist at Kobe University, stated that the magma present in the magma reservoir beneath the lava dome is likely newly injected material.

The conclusion reinforces the assessment that the situation is worsening.

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The mark left by the eruption of Akahoya

Kikai last erupted 7,300 years ago. This event, known as the Akahoya eruption, was described as the largest volcanic eruption of the current geological era, the Holocene.

The explosion is believed to have released about 61 cubic kilometers of dense rock into the air. The volume is approximately 11 times the material ejected by the Novarupta eruption in Alaska in 1912.

The material was spread over more than 4,400 square kilometers, an area nearly three times larger than New York City.

The eruption also triggered pyroclastic flows that advanced 150 kilometers from the epicenter.

The episode is believed to have decimated the Jōmon people, who lived in ancient Japan from approximately 14,000 B.C. to 300 B.C. The magnitude of the eruption keeps Kikai among the most concerning volcanic systems.

New dome has been growing for 3,900 years

Over the past 3,900 years, a new lava dome has been forming beneath Kikai. Although there has not been another eruption as explosive since then, there has been sporadic volcanic activity.

Unlike the last explosion, however, this lava was composed entirely of new material. Chemical analyses showed that the recent material was different from that expelled in the previous eruption, indicating recharge of the reservoir with newly injected molten rock.

Nobukazu assessed that this magma reinjection model resembles that observed in other large shallow magma reservoirs, such as the one beneath Yellowstone.

How researchers investigated the reservoir

To investigate the phenomenon, researchers sent research boats to the area. They used air guns and seismographs installed on the seabed to examine the underground structure.

With these tools, it was possible to measure how the pulses propagated through the Earth’s crust. The data revealed a large lava reservoir that apparently supplied Akahoya.

What the discovery could change

Scientists observed that even an eruption of lesser magnitude could be devastating.

At the same time, the results may serve as a basis for future models on how magma reservoirs recharge after major eruptions.

This advancement could help volcanologists better predict if and when a volcano will erupt.

Nobukazu stated that the team wants to refine the methods used in the study to gain a deeper understanding of the reinjection processes and monitor future giant signals.

With information from New York Post.

One of the worst volcanoes in history, which erupted 7,300 years ago, is raising alarms again because its caldera is filling with magma once more in Japan.