Considered the most violent of the 21st century, the recent eruption of an underwater volcano in Tonga has generated monstrous waves, having spread with unprecedented speed and distance. British researchers have recently established the mechanism behind it.
The key role of acoustic gravity waves
Devastating consequence of a record volcanic shock wave, the tsunami that followed the eruption monstrous of Hunga Tonga at the beginning of the year hit many countries ofOceaniaofAsia and D’Americawith waves up to 15 meters high.
Recently published in the journal Naturea new study reveals the mechanism that likely allowed the tsunami to move so far and with such force. This is a phenomenon known asacoustic gravity wavesparticularly long and able to move extremely quickly in the ocean or air.
These acoustic gravity waves apparently traveled through the water, rose through the atmosphere, before falling and propagating through the waves as the volcanic eruption developed. So the tsunami got bigger, lasted longer, and moved farther and faster than it otherwise would have.
” The idea that tsunamis can be generated by atmospheric waves triggered by volcanic eruptions is not new, but it is the first time that such an event has been recorded by modern instruments on a global scale, which allowed us to establish the exact mechanism behind these unusual phenomena », explains the geologist Ricardo Ramalholead author of the study.
Inevitable ocean-atmosphere interactions
To reach these conclusions, the researchers used a combination of data recorded at sea level, atmosphere and satellite readings, having revealed a “ direct correlation between the first signs of air disturbance caused by acoustic gravity waves and the beginnings of the tsunami.
Submarine eruptions generally do not produce tsunamis of the magnitude of those of the Tongathe study authors believe that the way these particular waves excite the interface between the ocean and the atmosphere has largely contributed to fueling it.
While different violent events can produce acoustic gravity waves, a single such wave type can extend for hundreds of kilometers, descend thousands of meters below the ocean surface, and there reach speeds close to that of sound.
” This eruption occurred in shallow water causing energy to be released into the atmosphere in the form of a mushroom of smoke and volcanic ash “, Explain Usama Kadri, co-author of the study. ” Thus, the interaction of these particularly energetic acoustic gravity waves with the surface of the water was inevitable.. »
A lightning tsunami
When acoustic gravity waves interact with the tsunamis they have already created, it is called nonlinear resonance, and the researchers say this phenomenon has been a major contributor to the transfer of energy in the ocean, having amplified the speed and the strength of the tsunami.
According to the team, the latter moved 1.5 to 2.5 times faster than a typical volcanic tsunamireaching speeds of around 1,000 km/h and crossing the oceans Peaceful, Atlantic and Indian in less than 20 hours. As it traveled partly through the atmosphere, the tsunami was able to reach the Caribbean and theAtlantic without first going through theSouth America.
” Such an extreme event will help us to develop more precise forecasting models and real-time warning systems, and also allows us to consider the development of devices exploiting this type of energy. », concludes Kadri.
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