Key facts
- The 2022 Hunga eruption in Tonga may have been amplified by a rapid caldera collapse.
- The Hunga caldera, about four kilometers wide, sank by nearly one kilometer.
- The collapse of the caldera floor alone accounts for about 6.85 cubic km of volume.
- The caldera floor dropped in a 'piston-style collapse,' maintaining its shape as it subsided.
- Even relatively small submarine calderas could generate dangerous tsunamis depending on collapse speed and nature.
Scientists are investigating how underwater volcanoes can generate powerful tsunamis, with a new study focusing on the 2022 Hunga eruption in Tonga. The research suggests that the rapid collapse of the volcano's caldera, even a relatively small one, may have amplified the resulting tsunami. Calderas form when the ground above a magma reservoir collapses as the magma drains away.
The Hunga volcano's eruption on January 15, 2022, was one of the most powerful volcanic events this century, with an eruption column reaching over 55 km and generating a tsunami estimated at 40 meters high. Despite its significant impact, the Hunga caldera is small, measuring about four kilometers in diameter. However, its depth relative to its size is notable.
Researchers compared pre-eruption seafloor maps with post-eruption surveys and found that the caldera sank by nearly one kilometer. They identified this as a 'piston-style collapse,' where the floor dropped as a whole unit. This rapid subsidence, potentially triggered by a thin and broad magma reservoir roof that could cave in with a modest loss of magma, likely displaced a large volume of water quickly, contributing to the massive tsunami.
The study did not directly prove the caldera collapse caused the tsunami but indicated it as a significant amplifying factor. This suggests that other underwater volcanoes with similar collapse dynamics could also pose substantial tsunami risks, though the dynamics of submarine caldera-forming eruptions remain poorly understood due to their inaccessibility.