Largest volcanic eruption in a century sent atmospheric waves around the world, study finds

Scientists have found evidence that an underwater volcanic eruption in the South Pacific earlier this year, the biggest in decades, created pressure waves so strong they circled the planet multiple times and blasted through the Earth's atmosphere.

A team led by a researcher out of the University of California, Santa Barbara published a study this month in the journal Science that examined the atmospheric waves generated by the eruption of the Hunga volcano in mid-January 2022, which created a tsunami that devastated the island nation of Tonga.

The scientists say it had been nearly 140 years since an eruption of that scale shook the Earth, going back to the 1883 Krakatau eruption in Indonesia.

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The researchers say they were most interested in the behaviour of an atmospheric wave known as a Lamb wave, which was the dominant pressure wave produced by the Hunga eruption.

After the eruption, the researchers say the waves travelled along Earth's surface and circled the planet in one direction four times and in the opposite direction three times, similar to the Krakatau eruption.

The waves also reached the ionosphere, or where Earth's atmosphere meets space, rising more than 1,126 kilometres per hour to an altitude of approximately 450 kilometres.

The researchers say the Hunga volcanic eruption provided unprecedented insight into the behaviour of multiple atmospheric wave types.

"Lamb waves are rare. We have very few high-quality observations of them," study co-author David Fee from the University of Alaska Fairbanks Geophysical Institute said in a news release.

"By understanding the Lamb wave, we can better understand the source and eruption."

Low-frequency Lamb waves are associated with the world's largest atmospheric explosions such as large eruptions and nuclear detonations, the team says, and can last from minutes to several hours.

Due to the low frequency of Lamb waves, the effect of gravity also must be taken into account when determining their travel.

"This atmospheric waves event was unprecedented in the modern geophysical record," lead author Robin Matoza, an associate professor at UC Santa Barbara's department of Earth science, said.

Matoza led a team of 76 scientists from 17 countries to study the atmospheric waves.

"We have more than a century of advances in instrumentation technology and global sensor density," Matoza said. "So the 2022 Hunga event provided an unparalleled global dataset for an explosion event of this size."