Science
Underwater Volcanic Collapse Could Trigger Unexpectedly Severe Tsunamis
Analysis of the 2022 Hunga eruption reveals how rapid seafloor subsidence during submarine volcanic events may generate tsunami waves far more dangerous than scientists previously understood.
Ars Technica
When a volcano erupts beneath the ocean, the hazards it poses differ markedly from those of land-based volcanoes. Research into the catastrophic 2022 Hunga eruption in Tonga is revealing that even relatively modest undersea volcanic structures can trigger tsunami waves of alarming proportions—a finding that has prompted scientists to reassess tsunami risk globally.
The 1883 eruption of Krakatau in Indonesia illustrated this danger vividly: while the explosive event itself was devastating, the majority of the 30,000+ deaths resulted from the tsunami it spawned rather than from volcanic debris.
How Water Pressure Shapes Undersea Eruptions#
The behavior of underwater volcanoes depends heavily on their depth. In the deep ocean, crushing water pressure actually suppresses explosive activity, limiting destructiveness. By contrast, volcanoes closer to the surface face lower water pressure while contending with intense heat from erupting material—a combination that can trigger violent explosions as water and magma interact violently.
Despite decades of study, researchers have struggled to predict precisely when volcanic activity will generate a tsunami. The mechanisms remain incompletely understood, leaving a significant gap in hazard assessment.
The Hunga Case: Rapid Ground Collapse Amplified Tsunami Danger#
An international research team focused on the Hunga eruption of January 15, 2022, examining how the volcano's structure may have intensified its tsunami-generating potential. The key finding centers on what happened after the magma chamber emptied: the ground above it—a basin roughly four kilometers across—collapsed suddenly, sinking approximately one kilometer during the eruption.
Seafloor surveys conducted before and after the event provided direct evidence of this dramatic subsidence. Researchers propose that the speed and scale of this caldera collapse may have enhanced the tsunami substantially. The eruption itself proved extraordinarily powerful, with its column reaching altitudes exceeding 55 kilometers and pushing vaporized seawater into the stratosphere. The resulting pressure wave circled the globe.
The tsunami generated by this event reached estimated heights of 40 meters within 100 kilometers of the source—the tallest tsunami ever documented from an undersea volcanic eruption.
