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12.4 miles high. 300 miles wide. Details of how the Tonga volcano eruption was felt around the world

USA TODAY
USA TODAY
 2022-01-22

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The Jan. 15 eruption at Hunga Tonga - Hunga Ha'apai sent shock waves around the world, literally.

Tsunami waves created by the eruption arrived first at the islands of Tonga. At least three people died and at least 50 homes were destroyed, while another 100 homes were severely damaged, public officials said Tuesday. Satellite images show ash blanketing everything.

From Tonga, tsunami waves traveled across the Pacific in all directions, from Australia to Japan and from Alaska to Chile. A maximum tsunami height of 5.7 feet was reported in Chanaral, Chile, more than 6,000 miles eastward, according to preliminary reports from the Pacific Tsunami Warning Center.

To the west, a tsunami height of 4.6 feet was reported on the island nation of Vanuatu, northwest of the volcano and about 1,400 miles east of Australia.

Along the U.S. coast, a maximum tsunami height of 4.3 feet was reported in Port San Luis, California , the warning center reported. Tsunami wave heights of up to a foot or more were detected in Alaska, Kauai, Hawaii; Peru and Japan, while heights between a few inches and a foot were reported elsewhere in Hawaii and in Australia, Costa Rica and Acapulco, Mexico. The Associated Press reported two people drowned in the waves off of Peru.

The birth and death of a new island

The underwater volcanic eruption, at 5 p.m. local time, was far from the first for this pair of islands, Hunga Ha'apai and Hunga Tonga. There has long been evidence of a large, submerged volcano with a summit caldera beneath the sea surface of the islands, said Marco Brenna, a senior lecturer in the geology department at the University of Otago in New Zealand. Calderas, or large craters, form when magma and gas are released and the empty system cannot support the weight above it.

An eruption in late 2014 and 2015 left a new cone of loose material above the caldera, Brenna said. As the material was eroded and moved around by the waves, it merged the islands. This NASA simulation shows how that happened:

Although NASA scientists expected the new island might last only a few months, it remained for roughly seven years.

The eruption at Hunga Tonga-Hunga Ha'apai

The volcano is one of a series of volcanoes along a trench known as the Tonga-Kermadec Arc. Brenna, the researcher in New Zealand, said some of the volcanoes are "traditional" cones, some of which formed calderas.

It seems a sequence of growth and destruction causes the conical edifices to collapse and form calderas in very large explosive eruptions, he said. "Someday in the future, the same will happen at those other volcanoes. It's just a matter of knowing when. Active monitoring for signs of unrest will be essential."

Other notable calderas are Mount Katmai in Alaska and Oregon's Crater Lake.

During an underwater eruption, magma that can reach temperatures of more than 2,000 degrees rushes into the colder seawater. Scientists speculate this interaction in a volcano so close to the surface of the sea created the massive pillar of steam and ash that exploded into the sky over Hunga Tonga-Hunga Ha'apai.

View of Tonga volcano from space

While scientists say the umbrella cloud reached the height of 12.4 miles, particles rose even higher reaching nearly 25 miles into the atmosphere.

Because much of this happened in daylight, at least three satellites caught the explosion in true color, yielding spectacular images shown below:

Overall eruption size is generally measured by the volume of erupted material, not the size and height of the cloud shooting into the sky, said Dave Schneider, a research geophysicist at the U.S. Geological Survey's Alaska Volcano Observatory. Researchers measure that material by calculating the amount of sulfur dioxide released.

The eruption created atmospheric pressure waves that circled the globe at least twice, researchers said. Low, rumbling booms were heard in Alaska and Australia, and the fluctuations in pressure were measured in those locations, as well as in the mainland U.S., Europe, Africa and Australia.

The waves were even captured visually in cloud camera videos at Maunakea, Hawaii, by the International Gemini Observatory, a program of the National Science Foundation’s NOIRLab , shown below .

Other types of volcanoes

The 1,350 potentially active volcanoes worldwide come in all shapes and sizes. About 500 of them have erupted in historical time, according to the Geological Survey. Monogenetic volcanoes erupt only once. The most common are polygenetic, which continue to erupt multiple times over thousands of years.

Many of the volcanic eruptions in history, including this one in Tonga, occurred in what's known as the "Ring of Fire" around the perimeter of the Pacific Ocean. It's the world's most active seismic and volcanic zone.

Sources: U.S. Geological Survey; South Carolina Department of Natural Resources; National Park Service; Oregon State University

This article originally appeared on USA TODAY: 12.4 miles high. 300 miles wide. Details of how the Tonga volcano eruption was felt around the world

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