Tonga volcanic eruption the most powerful in more than a century

Scientists began to piece together what happened during the eruption of January 15 of the underwater volcano Hunga Tonga-Hunga Ha’apai about 65 kilometers (40 miles) north of the capital of Tonga which killed at least three people. The eruption defined an easy explanation and upset scientists’ understanding of this type of volcano.
The volcanic eruption sent pressure waves rarely seen around the world for six days and triggered an unexpected type of tsunami wave, according to two new studies published Thursday in the journal Science. The huge plume of gas, water vapor and dust has also created hurricane winds in space, NASA said this in a separate published study this week.

Early data in the aftermath of the explosion suggested it was the largest since the 1991 eruption of Mount Pinatubo in the Philippines, but scientific studies, involving 76 scientists in 17 countries, have suggested that the pressure waves it unleashed were similar to those generated by the cataclysm 1883 Krakatoa eruption and 10 times bigger than 1980 eruption Mount St. Helens erupting in Skamania County, Washington.

The Tonga eruption was “unusually forceful,” the Science study researchers wrote. Low-frequency atmospheric pressure waves, called Lamb waves, detected after the eruption circled the planet four times in one direction and three times in the opposite direction, they revealed.

A relatively rare phenomenon, these waves travel at the speed of sound. They are not detectable by humans e are slower than shock waves, as they have sometimes been misrepresented, said study author Quentin Brissaud, a geophysicist at the Norwegian Seismic Array in Oslo. Lamb waves were also observed during the Cold War after atmospheric nuclear tests.

“It’s pretty rare. So Lamb waves are really related to large shifts in the volume of air. And they mainly propagate along the earth’s surface,” said co-author Jelle Assink, senior geophysicist in the Royal’s Department of Seismology and Acoustics. Netherlands Meteorological Institute.

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Moving across the surface of multiple oceans and seas, Lamb pressure waves from the explosion created a rapid wave of scattered tsunamis.

Traditional tsunamis are usually linked to sudden changes in the ocean floor such as during an earthquake. Basically, these so-called meteotsunami travel much faster than traditional tsunamis, arriving two hours earlier than expected and lasting longer, which could have implications for early warning systems.

And because an atmospheric pressure wave generated them, the tidal waves seemed to “blow over continents,” with tsunamis recorded from the Pacific to the Atlantic, said co-author Silvio De Angelis, professor of Volcano Geophysics at the Department of Earth, Ocean and Ecology Sciences at the University of Liverpool in the United Kingdom.

The research also revealed that the audible sound of the eruption was detected more than 10,000 kilometers (6,000 miles) from the source in Alaska. – where it was heard as a boom series. The Krakatoa eruption of 1883 was heard 4,800 kilometers (2,980 miles) away, according to the study, although it was less commonly reported than that of Tonga.

A lithograph illustrates the clouds pouring from Krakatoa volcano during the catastrophic 1883 eruption in southwestern Indonesia.

The researchers said more data was needed to understand the mechanism of the eruption.

It is thought that one of the reasons for such a vigorous explosion – the creation of an umbrella cloud 30 kilometers (about 19 miles) high and a plume about 58 kilometers (36 miles) – was because “the hot, gas-laden magma he came into contact with (the seawater) very quickly, “De Angelis said via email. “The rapid transfer of intense heat between hot magma and cold water it causes violent explosions capable of tearing apart the magma “.

Space disturbance

Another study, published Tuesday in Geophysical Research Lettersfound that the Tonga volcano also created chaos in space by spurring hurricane winds, based on data from NASA’s Ionospheric Connection Explorer, or ICON, mission and the European Space Agency’s Swarm satellites.
Giant plume of gas, water vapor and dust pushed into the sky by the eruption created large pressure disturbances in the atmosphere, leading to strong winds, NASA said in a statement. As these winds expanded upward into thinner layers of the atmosphere, they began to move faster.

“Once it reached the ionosphere and the edge of space, ICON recorded wind speeds of up to 450 mph, making them the strongest winds below the mission’s 120-mile altitude since its launch,” NASA said.

(From left) Satellite images of January 6 and January 18 show the impact of the volcanic eruption near Tonga.

In the ionosphere, where Earth’s atmosphere meets space, extreme winds have also slammed electric currents, pushing particles from their usual eastward-flowing electric current – called the equatorial electrojet – westward for a short time, and the electric jet rose to five times its normal peak power.

“It is very surprising to see the electro-project being significantly reversed by something that happened on the Earth’s surface,” said Joanne Wu, a physicist at the University of California, Berkeley, and co-author of the new Geophysical Research Letters study.

“This is something we’ve only seen previously with severe geomagnetic storms, which are a form of time in space caused by particles and radiation from the sun.”

Brian Harding, a UC Berkeley physicist and lead author, said the eruption of Tonga was “allowing us to test the poorly understood connection between the lower atmosphere and space.”

He added: “The volcano created one of the largest perturbations in space that we have seen in the modern era.”