The tsunami triggered by the Hunga Tonga–Hunga Ha'apai eruption in early 2022 wreaked havoc over Oceania, Asia, North America, and South America, with waves reaching up to 15 meters (49 feet) in some places - the deadly result of a volcanic shockwave that set new records.
A new research has uncovered the mechanism that scientists believe caused the tsunami to travel such a long distance and with such energy — a phenomenon known as acoustic-gravity waves (AGWs), a lengthy form of sound wave that can move extraordinarily swiftly across the water or the air.
When the volcano explosion progressed, these AGWs seemed to move through the water, up into the sky, and then out over the waves, giving the resultant tsunami even more energy as several waves merged.
As a result, the tsunami was larger, lasted longer, and went further and faster than it would have otherwise.
"The idea that tsunamis could be generated by atmospheric waves triggered by volcanic eruptions is not new, but this event was the first recorded by modern, worldwide dense instrumentation, allowing us to finally unravel the exact mechanism behind these unusual phenomena," says geologist Ricardo Ramalho of Cardiff University in the United Kingdom.
The presence of these waves was determined using a mix of data from sea level, the atmosphere, and satellite measurements, and there was a "direct correlation" between the first signals of air disturbance caused by AGWs and the start of the tsunami in multiple sites.
The Hunga Tonga–Hunga Ha'apai volcanic eruption was massive, although tsunamis of this magnitude are unusual for underwater eruptions. The way AGWs excite the ocean-atmosphere interface, according to the scientists, was important in causing such dramatic and devastating outcomes.
AGWs may be caused by a variety of violent events, and they are impacted by gravity, as the name implies. A single one of these waves can be hundreds of kilometers or miles long, travel thousands of meters or feet beneath the sea's surface, and reach speeds near to the speed of sound in water.