Study finds delayed submarine caldera collapse triggered Tonga’s most destructive 2022 tsunami

The most destructive local tsunami from the January 2022 eruption of Hunga Tonga-Hunga Haʻapai was triggered by a delayed underwater collapse of the volcano’s caldera, not simply by the initial blast, according to a new study that also found the collapse sent detectable sound signals across much of the southwest Pacific.

The research, published online in September 2026 in Science Advances, ties the biggest near-field tsunami near Tonga to sudden submarine caldera subsidence — a collapse of the volcano’s summit structure beneath the sea. The finding matters beyond explaining a disaster that devastated Tonga: the same collapse produced hydroacoustic “T-wave” signals that were picked up as far as about 2,600 kilometers (1,615 miles) away, suggesting that distant sensors might someday help provide earlier warning for some volcano-generated tsunamis.

That possibility rests on speed. “Sound waves travel through the ocean at around 1.5 km per second — more than seven times faster than a tsunami,” researchers Shane J. Cronin of the University of Auckland and Jose C. Borrero wrote in an author summary published by The Conversation and republished by Phys.org. The study does not describe a ready-made warning system, but it suggests these signals could offer extra minutes in some future events.

Cronin and colleagues reconstructed the Jan. 15, 2022, disaster by combining hydroacoustic records, seismic data, eyewitness accounts, satellite and surface observations, and an unusual source of timing evidence: telecommunications-tower traffic data from Tonga. Their study, titled “Delayed submarine caldera subsidence creates extreme tsunami hazard,” concluded that the collapse began at about 6:28 p.m. local time. The destructive tsunami then reached parts of Tongatapu roughly 17 minutes later, consistent with wave travel over the roughly 60 kilometers (37 miles) from Hunga to western Tongatapu.

One key marker came when communications-tower traffic stopped at 6:45:24 p.m. local time, matching the expected arrival of the tsunami. Taken together, the authors said, the timing points to the caldera collapse as the dominant source of the largest destructive local wave.

The study also found that the hydroacoustic signals from the collapse were recorded at 14 seismic and hydroacoustic stations around the southwest Pacific, with detections extending to about 2,600 kilometers from the volcano. The collapse left or produced a caldera roughly 4 kilometers (2.5 miles) across and more than 850 meters (2,790 feet) deep.

The distinction is important because the Hunga eruption involved more than one tsunami-generating process. Earlier research had already shown that the 2022 event produced a global tsunami signal linked to atmospheric pressure waves, an unusual effect that helped make the eruption one of the most closely studied volcanic disasters in recent years. Volcanoes can also generate tsunamis through explosions, landslides, collapse and fast-moving flows entering the sea.

This new paper does not overturn that broader picture. Instead, it sharpens it by identifying which mechanism appears to have produced the biggest and most destructive local wave near Tonga.

The 2022 eruption and tsunami caused extensive damage in Tonga and killed three people. For hazard scientists, the study offers a clearer explanation of what happened in the crucial minutes after the eruption. For communities near submarine volcanoes, it points to a practical question: whether fast-moving underwater acoustic signals could eventually be folded into tsunami warning approaches.

That remains a research prospect, not an operational reality. But by showing that a catastrophic caldera collapse advertised itself through the ocean long before the tsunami finished crossing to shore, the study suggests a new way to think about warning from some underwater volcanoes.