The largest volcanic eruption ever recorded on Earth

The eruption of a volcano in Tonga in January 2022 has been confirmed as the largest explosion ever recorded in the atmosphere by modern equipment.

It was far larger than any volcanic event of the 20th century, or even any atomic bomb test conducted after World War II.

The assessment was presented in two academic papers, published in the journal Science, which reviewed all the data.

In recent history, it is likely that only Eruption of the Krakatoa volcano, in 1883, can compete with the atmospheric disturbance produced. This catastrophic event in Indonesia is believed to have killed more than 30,000 people.

Fortunately, this year’s January 15 eruption of the Hunga Tonga-Hunga Ha’apai (HTHH) submarine volcano in the South Pacific caused very few fatalities, although it also produced large tsunamis. .

“Tonga was a truly global event, as was Krakatoa, but now we have all these geophysical observing systems, and they’ve recorded something truly unprecedented in modern data.” , in the United States, who is the main author of one of the articles .

Scientists now have access to an extraordinary array of ground and space-based instruments, including atmospheric pressure sensors, seismographs, hydrophones and a fleet of satellites that monitor Earth across the entire light spectrum.

The colossal Tonga explosion, which occurred after several weeks of underwater activity, produced various types of atmospheric pressure waves that traveled great distances.

In the audible frequency range, people 10,000 km away in Alaska reported hearing repeated bangs.

The global network of detectors created to monitor compliance with the Comprehensive Nuclear Test Ban Treaty picked up the infrasonic signal.

Infrasound has frequencies that are just below what humans are able to hear.

Network data indicated that the explosion of the Tonga volcano produced an atmospheric pressure wave comparable to the largest nuclear explosion of all time? the Tsar Bomba, detonated by the Soviets in 1961 ?, but lasted four times longer.

The articles deal in depth with the disturbances caused by so-called Lamb waves, named after the early 20th century mathematician Horace Lamb.

They are energetic waves in the air that propagate at the speed of sound, along a guided path through the surface of the planet. They are also non-dispersive, meaning they retain their shape as they move and are therefore visible for a long time.

Lamb wave pulses produced by the Tonga eruption have been seen circling the Earth at least four times.

In the UK, about 16,500 km from Tonga, these pulses started arriving on the night of the 15th, about 14 hours after the eruption on the other side of the planet.

They lifted the clouds over the UK.

“At the time, we had a laser ceilometer (a device used to determine the height of clouds) that looked at the base of the cloud, and when the wave passed through the cloud, it was disturbed,” recalls Giles Harrison, physicist from atmosphere at the University of Reading. , UK, and co-author of one of the articles.

“If you’ve ever wanted proof that the atmosphere is remarkably interconnected, it’s here. And what happens on one side of the planet can travel to the other side at the speed of sound.”

Where Lamb waves joined ocean waves, could they generate tsunamis? not only in the Pacific Ocean, but also in the Atlantic Ocean and the Mediterranean Sea.

Scientists are still studying the generation of nearby tsunamis that hit the shores of the Tonga archipelago.

Some were undoubtedly created by pressure waves from the volcano pushing the surface of the water, but investigations are ongoing to determine if the collapse of part of the volcano also contributed significantly.

This will be evident in seabed mapping projects, the results of which are expected to be released in the coming weeks.

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