2022 Hunga Tonga–Hunga Haʻapai eruption

Hunga Tonga–Hunga Haʻapai is a submarine volcano in the South Pacific, about 65 kilometres northwest of Tongatapu, Tonga's main island. The volcano had been active in the days before 15 January 2022. Its major eruption that day sent volcanic material and gases high into the atmosphere and generated pressure disturbances that were detected around the world. The U.S. National Centers for Environmental Information (NCEI) assigned the eruption a Volcanic Explosivity Index of 5, classified as very large.

The eruption triggered a destructive tsunami near Tonga, where waves inundated low-lying communities and damaged buildings and infrastructure. NOAA's NCEI reports four fatalities in Tonga and estimates that damage there totaled about US$118 million, most of it from tsunami impacts. Tsunami effects were also recorded in other Pacific countries and at distant coasts. Some of the far-reaching waves were associated with the eruption's atmospheric pressure wave, illustrating that volcanic tsunamis can be generated and propagated through interacting air and ocean processes rather than only through seafloor displacement from earthquakes.

The details of volcanic tsunami generation are complex, and research continues. A 2024 study in Communications Earth & Environment combined atmospheric and ocean observations with modelling to investigate the Tonga event. Its authors proposed that the eruption's pressure wave could help predict tsunami behavior and described a coupled mechanism involving eruption-driven air pressure changes and water movement around the crater. This is a research interpretation, not a universal model established for every volcanic tsunami.

Tsunami warning systems have historically focused largely on earthquakes, which account for most recorded tsunamis. The 2022 event prompted greater attention to volcanic sources and interim procedures for tsunami alerts linked to eruptions. It also demonstrated the value of combining tide gauges, atmospheric measurements, satellite observations and field surveys. Improving detection of volcanic tsunami sources is important because an eruption may produce hazardous waves rapidly and through mechanisms that conventional earthquake-centered alerts do not fully capture.