One Year Later, a Tongan Eruption Is Still Reverberating

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Last year, Larry Paxton saw something he shouldn’t have seen while looking out into the universe. Paxton, a physicist at Johns Hopkins University in Maryland, uses a satellite-based instrument that overlooks the region of space just above the atmosphere. They see spectrums of light that we cannot see, such as far-ultraviolet, and monitor unusual space weather and more. But in late January, his team discovered something unusual in the scans. Part of the map was dark. Far-UV rays were absorbed by some molecule, creating a vague speck the size of Montana.

Its source was soon revealed: the Hunga Tonga–Hunga Ha’apai volcano. just erupted in the South Pacific. These molecules, as Paxton’s team later determined, were enough water to fill 100 Olympic pools, and, unlike anything previously recorded on Earth, would have been emptied faster than the speed of sound by the explosion, unlike anything previously recorded on Earth. was dumped on “It’s a huge amount of water to inject that high,” said Paxton, who presented his work at the American Geophysical Union a few weeks ago. “That’s unusual.”

A year later, scientists studying nearly every facet of the Earth, from the mantle to the oceans to the ionosphere, had a moment similar to Paxton’s, and were able to pin down some of the superlative discoveries made by the Hunga eruption. Amazing. In recent months, scientists have observed new wave It bounces around the world, causes tsunamis in distant oceans, Lightning recorded so farA new cosmic water molecule represented the top of a giant plume filled the upper atmosphere There’s enough water underneath to trap heat, which could warm the planet slightly over the next few years, according to Holger Fommel, a scientist at the National Center for Atmospheric Research.

January 15, 2022 the explosion was obviously strangeBut now researchers are asking: The answer affects the hundreds of submarine volcanoes that dot Earth’s oceans. “The Hanga eruption highlights a new type of volcano and a new type of underwater threat,” said Shane Cronin, a volcanologist at the University of Auckland in New Zealand. These include Axial Seamount, hundreds of kilometers off the Oregon coast, which has been studied since the 1970s, and Kick’, which has long been active near the Caribbean nation of Grenada. Includes em Jenny, both of whom are regularly visited by research cruises and are covered in sensors that monitor Rumble.

But there are many more in the remote Pacific Ocean, far from the big cities and ports where research ships dock. Its closest neighbors are small island nations like Tonga that lack the capacity to set up dedicated volcano monitoring programs and seismic monitors. Part of the reason is geography. For example, Tonga is a chain of islands that is not suitable for triangulating the source of seismic waves. A country with a population similar to that of a large U.S. city can be understaffed and underfunded. While there are international options for global coverage of extreme geological activity, such as the United States Geological Survey’s (USGS) seismic monitoring network, observatories are generally too few in number to predict future submarine eruptions. Jake says it can’t pick up a softer sound than it predicts. His Lowenstern, director of the USGS Volcano Disaster Assistance Program, said:

Few of these eruptions are likely to match the explosiveness of Hunga Tonga. But Sharon Walker, an oceanographer at the Pacific Ocean Environment Laboratory, said the event woke the world to the potential for activity in these volcanoes. “Things like this happen very rarely, but I don’t want them to happen under our scrutiny,” she says.

It’s clear that Hunga contains some very explosive recipes that may not be easily reproducible. For about a month, the eruption proceeded as expected. It was moderately violent, producing gas and ash, but manageable. Then everything went sideways. That’s the result of at least two factors, he says, Cronin. One was the mixing of sources of magma with slightly different chemical compositions underground. Under tremendous pressure, the rocks above began to crack and seep cold seawater. Massive explosions occurred, two of which were actually his, blasting trillions of tons of material straight out of the top of the caldera, some of it apparently all the way into space.

Both of these explosions caused large tsunamis. But the biggest wave came later. Cronin thinks it could have been caused by flooding a hole several kilometers deep that was suddenly dug from the ocean floor. “This is very new to us,” he says. This is a new type of threat that should be considered elsewhere. Until now, scientists thought that volcanoes of this type would only generate large tsunamis if the caldera flank collapsed. The bottom line is that submarine volcanoes are more diverse than anyone thought, and in some cases can take extreme actions.

But the process of stitching together the eruptions has also highlighted the challenges of studying submarine volcanoes. A typical mapping expedition includes a large, fully manned research vessel equipped with multi-beam sonar to map seafloor changes and an array of water-sampling instruments to look for chemical signatures of ongoing activity. included. But boating over a potentially active caldera is dangerous, not because the volcano could erupt, but because gas bubbles could form and sink the ship. . In Tonga, researchers have solved this problem with small and autonomous vessels.

Even Tonga, which has been visited four times in the past year, is unlikely to acquire another large manned mission in the next few years, Cronin says, due to the influx of research funding into groups studying the eruption. The cost is very high. It could take decades to study all the volcanoes in the Tonga Arc alone in detail. It’s a shame, says Walker. Because this kind of expedition is one of the few ways scientists can get close enough to actually see how volcanoes work. The ideal scenario would be to provide more funding for these missions and to invest in improving new technologies such as autonomous ships that are difficult to operate in dangerous open seas.

Without them, scientists would be watching from afar. This is difficult, but not impossible, to do if you are trying to observe an underwater event. Satellite technology can spot objects known as pumice rafts (sheets of buoyant volcanic rock that rise to the surface of the water) fed by minerals ejected from volcanoes, as well as flowers of algae. The USGS and its Australian counterparts are also in the process of installing a network of sensors around Tonga that can more accurately detect volcanic activity, combining seismic stations with acoustic sensors and web cameras to monitor active explosions. . Lowenstern said the challenge is to keep the system connected to data and power so that Tonga can staff the facility. He adds that Tonga is just one of many Pacific nations that can take advantage of this assistance. But it’s just the beginning.

One of the benefits of studying Hunga Volcano in detail is that it has identified new volcanic features that researchers should be aware of. Cronin foresees the process of identifying which volcanoes need more attention over the next few years. On his final Hunga voyage in 2022, Cronin’s team visited two of his other submarine volcanoes in the region on board. One of them, he, is about 160 kilometers north and has a mesa-like terrain similar to Hunga before the eruption. The maps will serve as a baseline for future surveys that can go above water as a way for researchers to get an idea of ​​how much activity is occurring under the sea and rocks. Cronin reports that the sea has been calm so far.