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New clues about the Hunga Tonga-Hunga Ha’apai eruption

On January 15, a volcano erupted and destroyed much of the island nation of Tonga. Immediately after the historic eruption, scientists began trying to analyze and reconstruct the events. An international team, including experts from UC Santa Barbara, has reported their findings in the journal Earthquake Research Advances

“This is definitely, without a doubt, the largest eruption since Mt. Pinatubo in 1991,” said study co-author Melissa Scruggs.

The research suggests that an early eruption the day before may have laid the foundation for the larger, more violent eruption by sinking the volcano’s main vent below the earth’s surface. Hunga Tonga-Hunga Ha’apai (HTHH) is a stratovolcano, a cone shaped volcano that can have periodically violent explosions but often has smaller ones. 

Part of the Tofua Volcanic Arc, HTHH is created by the Pacific Plate being pushed below the Indo-Australian Plate, causing heat and pressure and building a 100 kilometer volcano chain. The landscape is a dynamic one. In only 2015, two islands were joined by the volcano’s eruption and this second eruption destroyed that new island. 

When HTHH erupted, an ash plume shot 58 kilometers into the sky, “It went halfway to space,” Scruggs said. As the steam rose into the air, ice crystals formed and like a biblical pillar of smoke, lighting surrounded the ash cloud. In fact, the scientists estimate that as much as 80 percent of all the earth’s lightning at the time was around the eruption. 

Shockwaves traveled faster than predicted by models and caused tsunamis across the Pacific and farther afield. The shockwaves moved faster because the models are based on tsunamis caused by earthquakes, not volcanic eruptions. 

Atmospheric pressure waves seem to have caused a second meteo-tsunami in the Caribbean, which isn’t connected to the Pacific. This was something new for scientists, “Basically the whole ocean just kind of sloshed around for five days after the eruption,” Scruggs said. 

So much happened that was unprecedented to science, and the researchers emphasize there’s still much to learn. A better understanding of this eruption may ultimately help improve early warning methods in the future. 

Image Credit: Tonga Geological Services

By Zach Fitzner, Staff Writer

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