Ancient 850-Foot Tsunami Could Happen Again

Could a sudden volcano collapse create a wave over 50 stories high? Scientists think so. Continue reading →

Imagine this premise for a Hollywood disaster movie: A giant volcano on an island collapses during an eruption, generating a massive landslide that in turn causes an absolute Godzilla of a tsunami, an 840-foot-tall wave that travels for 30 miles and engulfs anything in its path.

Sound far-fetched? Well, it's already happened at least once and some scientists say it could actually happen again.

Evidence that a 9,300-foot-tall volcano on the island of Fogo, one of the world's largest and most active volcanoes, collapsed during an eruption 73,000 years ago and generated a wave so big that it swept over nearby Santiago Island. The findings, recently published in the journal Science Advances, raise the possibility that Fogo or another volcano could cause a similarly scary event today.

"Our observations therefore further demonstrate that flank collapses may indeed catastrophically happen and are capable of triggering tsunamis of enormous height and energy, adding to their hazard potential," the scientists noted in the article.

The study's lead author, Ricardo Ramalho, is an adjunct scientist at Columbia University's Lamont-Doherty Earth Observatory. He said in a press release that while such massive volcano collapses don't happen very often, "we need to take this into account when we think about the hazard potential of these kinds of volcanic features."

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Ramalho and fellow researchers were working on the island of Santiago several years ago when they spotted a strange phenomenon at 650 feet above sea level - giant boulders, as big as delivery vans, that turned out to match the marine-type rocks that line the island's shoreline.

The only explanation that the scientists could find was that a giant wave must have picked up the 770-ton rocks and swept them uphill. They came up with the size of the wave by calculating the amount of energy it would have taken to move the massive rocks.

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When Ramalho and Lamont-Doherty geochemist Gisela Winckler measured isotopes of the element helium embedded near the boulders' surfaces, they found that the rocks had been lying in the open for about 73,000 years.

That conclusion is bound to provoke some scientific controversy, since not all scientists believe that volcanoes would collapse suddenly and generate huge tsunamis. But others have theorized about much larger prehistoric collapses and resulting megatsunamis - in the Hawaiian islands, at Italy's Mt. Etna, and the Indian Ocean's Reunion Island.

The latest study, however, seems to provide the best evidence that such an event already has occurred. The researchers note that other volcanic islands, including some in the northeastern Atlantic Ocean, are close to heavily-populated areas.

"It doesn't mean every collapse happens catastrophically," Ramalho said. "But it's maybe not as rare as we thought."

The volcanic island of Fogo had an ancient landslide that triggered a massive tsunami, according to a new study.

UPDATE: March 11, 2012

-- This collection of satellite images was originally produced on March 14, 2011, days after the 9.0-magnitude earthquake and resulting tsunami struck the northeast coast of Japan. The known death toll came to 15,848 with 3,305 missing. The tsunami also inundated the Fukushima Daiichi Nuclear Power Plant causing a series of failures that led to the world's largest nuclear disaster since Chernobyl. The above photos show Yuriage in Natori (top); and Yagawahama (bottom) -- both are in Miyagi prefecture.

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Fukushima I Nuclear Power Plant

Image taken in 2004.

Fukushima I Nuclear Power Plant

Image from March 12, 2011 (before outer shell collapse).

Industrial Site Just South of Fukushima I Power Plant

Image taken in 2004.

Industrial Site Just South of Fukushima I Power Plant

Image from March 12, 2011.

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Village Two Miles South of Fukushima I Power Plant

Image taken in 2004.

Village Two Miles South of Fukushima I Power Plant

Image from March 12, 2011.

Fukushima II Power Plant

Image taken in 2004. Fukushima II Power Plant is located about 7 miles south of the Fukushima I Power Plant.

Fukushima II Power Plant

Image from March 12, 2011.

Tomioka in Futaba District, Fukushima Prefecture

Image taken in 2004.

Tomioka in Futaba District, Fukushima Prefecture

Image from March 12, 2011.

Central Ishinomaki, Miyagi Prefecture

Image taken in 2003.

Central Ishinomaki, Miyagi Prefecture

Image from March 12, 2011.

Ishinomaki

Image taken in 2002.

Ishinomaki

Image from March 12, 2011.

Iwaki Onahama

Image taken in 2005.

Iwaki Onahama

Image from March 12, 2011.

Iwaki Ueda

Image taken in 2005.

Iwaki Ueda

Image from March 12, 2011.

Minamisoma Haranomachi

Image taken in 2003.

Minamisoma Haranomachi

Image from March 12, 2011.

Minamisoma Kashima

Image taken in 2006.

Minamisoma Kashima

Image from March 12, 2011.

Minamisoma Kashimaku

Image taken in 2003.

Minamisoma Kashimaku

Image from March 12, 2011.

Oshika Peninsula Iigohama

Image taken in 2007.

Oshika Peninsula Iigohama

Image from March 12, 2011.

Oshika Peninsula Yagawahama

Image taken in 2007.

Oshika Peninsula Yagawahama

Image from March 12, 2011.

Sendai Airport

Image taken in 2003.

Sendai Airport

Image from March 12, 2011.

Sendai Arahama

Image taken in 2008.

Sendai Arahama

Image from March 12, 2011.

Sendai Fujitsuka

Image taken in 2008.

Sendai Fujitsuka

Image from March 12, 2011.

Sendai Terashima

Image taken in 2003.

Sendai Terashima

Image from March 12, 2011.

Sendai Yamoto

Image taken in 2004.

Sendai Yamoto

Image from March 12, 2011.

Sendai Yuriage

Image taken in 2008.

Sendai Yuriage

Image from March 12, 2011.

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