The massive January 2022 eruption of Hunga volcano in the Kingdom of Tonga took the world by surprise.
It blasted a plume more than 50 km into the atmosphere, sent pressure waves around the globe, and generated a series of tsunamis, devastating parts of Tonga and killing at least three people.
But one of the most important things we’ve learned since this historic event is that these tsunamis did not all stem from the same cause.
The first were generated by enormous explosions during the opening stages of the eruption. On nearby Tongatapu, waves with run-ups of one to four meters began arriving within minutes.
Then, more than an hour later, something much more destructive happened. A tsunami with run-ups reaching 18 to 40 meters struck islands within 100 km of Hunga, destroying resorts and villages across southern and central Tonga.
Our newly published research shows this largest tsunami was generated not by another explosion, but by the sudden collapse of the volcano’s caldera — and that the collapse produced an underwater sound detectable thousands of kilometers away.
That finding could point to a new way of warning communities about some of the most unpredictable types of tsunamis on Earth.
Listening to an underwater volcano
Monitoring submarine volcanoes is notoriously difficult. There are hundreds scattered around the Pacific “Ring of Fire,” yet we know relatively little about their state of activity – and even less about how to respond when they erupt.
Satellites can detect changes in heat and gas emissions, along with eruption plumes when clouds don’t obscure the view. These observations can provide timely warnings of eruptions and help protect aircraft.
But satellites cannot tell us whether a deadly tsunami is on its way. Nor are conventional seismometers necessarily much help.
The closest seismometer to Hunga during the 2022 eruption was in Fiji, about 750 km away. At that distance, many of the seismic signals produced by volcanic processes are poorly transmitted through the Earth.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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