Scientists say they have identified the mechanism responsible for the exceptional tsunami that spread quickly across the world after the massive eruption of the Tonga volcano earlier this year.
In a new study, a team including researchers from Cardiff University say the exceptional event was caused by acoustic-gravity waves (AGWs) triggered by the powerful volcanic blast, which traveled into the atmosphere and across the ocean as the volcano erupted.
As these waves converged with each other, energy was continuously pumped into the tsunami which caused it to grow bigger, travel further, quicker and for longer.
The eruption of the Hunga Tonga-Hunga Ha’apai on January 15th 2022 was the largest volcanic eruption of the 21st century and the largest eruption since Krakatoa in 1883.
It is described as the biggest explosion ever recorded in the atmosphere and was hundreds of times more powerful than the Hiroshima atomic bomb.
“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,” said co-author of the study Dr. Ricardo Ramalho.
AGWs are very long sound waves which travel under the effects of gravity. They can cut through deep ocean or the atmosphere at the speed of sound and are produced by volcanic eruptions or earthquakes, among other sources.
An AGW can stretch tens or hundreds of kilometers, and travel at depths of hundreds or thousands of meters below the ocean surface, transferring energy from the upper surface to the seafloor, and across the oceans.
https://phys.org/news/2022-06-scientists-explanation-exceptional-tonga-tsunami.html