Scientists have discovered that one of the most powerful volcanoes in Earth’s recent history is slowly building up magma again—more than 7,000 years after its last massive eruption.
The finding offers important clues about how so-called “supervolcanoes” behave and may help scientists better predict future eruptions.
The volcano is the Kikai caldera, located mostly underwater south of Japan.
Around 7,300 years ago, it produced the largest volcanic eruption of the current geological period, known as the Holocene.
That eruption was so enormous that it emptied a huge underground magma chamber, leaving behind a wide, shallow crater called a caldera.
Other famous examples of these giant caldera volcanoes include the Yellowstone Caldera in the United States and the Lake Toba caldera in Indonesia. These volcanoes are capable of extremely large eruptions, but scientists still know very little about what happens inside them between eruptions.
To better understand this process, researchers from Kobe University worked with the Japan Agency for Marine-Earth Science and Technology.
Because the Kikai caldera lies underwater, scientists were able to carry out detailed surveys using special tools. They created artificial seismic waves using airgun arrays and recorded how these waves traveled through the Earth’s crust with instruments placed on the ocean floor.
By studying how the waves moved, the team could “see” what lies beneath the volcano. Their results, published in the journal Communications Earth & Environment, showed that a large magma reservoir is forming again under the caldera.
Importantly, this magma does not appear to be leftover from the ancient eruption. Over the past 3,900 years, a new lava dome has been slowly growing in the center of the caldera. Chemical tests show that this newer volcanic material is different from what was erupted 7,300 years ago. This suggests that fresh magma is being injected from deep within the Earth.
In simple terms, the volcano is “refilling” itself with new magma.
Based on these findings, the researchers proposed a model explaining how giant caldera volcanoes rebuild their magma chambers after a major eruption. This model may also apply to other supervolcanoes like Yellowstone and Toba.
Understanding this process is important because these volcanoes can have global impacts if they erupt again. While such eruptions are rare, they can release vast amounts of ash and gases, affecting climate and ecosystems worldwide.
The researchers hope that by improving their methods, they can better track the signs of magma buildup in these massive systems. In the future, this could help scientists identify early warning signals and improve our ability to predict when a giant eruption might occur.
For now, the Kikai caldera remains quiet—but deep below the ocean floor, it is slowly coming back to life.
