# Undersea Volcanoes Pose Disproportionate Tsunami Risks New research reveals how shallow volcanic eruptions can trigger catastrophic tsunamis. - **Source:** [Science - Ars Technica](https://arstechnica.com) - **Published:** 2026-09-23 - **Topic:** [Business](https://brifing.si/c/business) - **Original article:** - **On Brifing:** https://brifing.si/s/a8db38a4-3048-4c23-93fe-42bdee2e27ff ## Historical volcanic tsunamis The 1883 Krakatau eruption demonstrated how volcanic tsunamis can surpass eruption dangers, claiming over 30,000 lives. Unlike land volcanoes, undersea eruptions create unique hazards through seawater interaction. Deep ocean pressure typically suppresses explosive activity, but shallow eruptions near the surface allow violent steam explosions. This phenomenon remains poorly understood despite its catastrophic potential, driving current research into eruption-triggered wave mechanics. ## Depth determines destruction Water pressure plays a critical role in undersea volcanic behavior. Below 500 meters, the ocean's weight prevents explosive eruptions by containing magma-gas expansion. However, in shallower depths below 200 meters, reduced pressure enables rapid steam generation when 1200°C magma contacts seawater. This creates sudden volume expansion, potentially generating tsunamis through both explosive force and caldera collapse displacement. ## Hunga eruption case study The 2022 Hunga Tonga-Hunga Ha'apai eruption provided crucial data on tsunami generation mechanisms. Researchers analyzed pre- and post-eruption seafloor topography using sonar mapping. They discovered a 4km-wide caldera had collapsed approximately 1km downward during the event. This sudden subsidence displaced massive water volumes, amplifying the tsunami beyond what typical eruption explosions would produce. ## Caldera collapse mechanics Calderas form when magma chamber roofs collapse following subsurface magma drainage. The Hunga research revealed this process can occur rapidly during eruptions, creating piston-like downward movement. Unlike gradual subsidence, abrupt collapse generates more powerful tsunami waves. The study measured collapse speeds exceeding initial estimates, explaining the unexpectedly large waves observed across the Pacific. ## Risk assessment challenges Current tsunami warning systems primarily monitor seismic activity, often missing volcanic precursors. The Hunga event produced minimal earthquake signals before eruption. Researchers emphasize the need for real-time seafloor deformation monitoring near active submarine volcanoes. Existing detection gaps leave coastal communities vulnerable to these fast-developing threats. ## Comparative eruption impacts The study contrasts Hunga's tsunami with historical events like Krakatau. While both involved caldera collapse, Hunga's waves propagated further despite smaller eruption magnitude. This suggests collapse speed and geometry influence tsunami power more than total erupted volume. Such findings challenge conventional tsunami prediction models based solely on eruption size. ## Monitoring technology gaps Conventional ocean observation systems lack resolution for sudden volcanic deformation. The research team advocates for permanent seafloor geodesy networks near active volcanoes. These would measure millimeter-scale crustal movements using pressure sensors and acoustic positioning. Current satellite-based methods cannot capture rapid precursory changes preceding explosive eruptions. ## Policy implications Findings underscore the need for specialized volcanic tsunami warning protocols. Coastal regions near shallow submarine volcanoes require updated evacuation plans accounting for faster wave arrival times. The research supports developing dual seismic-volcanic monitoring systems, particularly in the Pacific Ring of Fire where 75% of active undersea volcanoes are concentrated. ## Sources covering this story - https://arstechnica.com/science/2026/09/small-undersea-volcanoes-may-unleash-outsized-tsunamis/ — --- _Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._