Small undersea volcanoes may generate large tsunamis due to caldera collapse

Undersea Volcanoes and Tsunami Risk

Volcanic activity at sea can create hazards distinct from land-based eruptions. While deep ocean pressure can suppress explosive activity, shallower waters allow for violent explosions due to lower pressure and high temperatures. The specific conditions under which volcanic activity triggers tsunamis are not fully understood by scientists.

Hunga Eruption Study Reveals New Mechanism

An international research team investigated the 2022 Hunga eruption in Tonga to better understand these risks. Their focus was on the rapid caldera collapse, which they believe amplified the powerful tsunami. Calderas form when the ground above a magma reservoir collapses as magma drains away.

Caldera Collapse and Tsunami Amplification

Comparisons of seafloor topography before and after the Hunga eruption showed that a four-kilometer-wide caldera sank by approximately one kilometer. Researchers propose that this rapid collapse of the entire caldera enhanced the massive tsunami. This suggests that even relatively small calderas, depending on the speed and nature of their collapse, may generate dangerous tsunamis.

Implications for Future Risk Assessment

The findings imply that other underwater volcanoes could also produce dangerous tsunamis. However, the paper notes that the dynamics of submarine caldera-forming eruptions and their associated hazards are not well understood due to the inaccessibility of these calderas and their eruption products. The Hunga tsunami reached heights of 40 meters within 100 km, making it the highest recorded from an underwater volcanic eruption.