As people in Tonga struggle to recover from a devastating volcanic explosion that smothered the Pacific island nation with ash and flooded it with water, scientists are trying to better understand the global effects of the eruption.
They already know the answer to a crucial question: Despite being the world’s largest eruption in three decades, Saturday’s explosion of the Hunga volcano most likely won’t have a temporary cooling effect on the climate. global, as some past huge eruptions have.
But following the event, there could be short-term effects on weather conditions in parts of the world and possibly minor disruptions to radio transmissions, including those used by global positioning systems.
The shock wave produced by the explosion, as well as the unusual nature of the tsunamis it generated, will keep scientists studying the event for years. Tsunamis have been detected not only in the Pacific, but also in the Atlantic, the Caribbean and the Mediterranean.
“It’s not that we were unaware of volcanic explosions and tsunamis,” said Lori Dengler, professor emeritus of geophysics at Humboldt State University in California. “But to witness it with the range of modern instruments we have is truly unprecedented.”
The explosion of the underwater volcano, officially known as Hunga Tonga-Hunga-Ha’apai, rained dangerous ash over the region, including Tonga’s capital, Nuku’alofa, about 40 miles north. South. The capital also experienced a four-foot tsunami and higher wave heights were reported elsewhere.
The government called the eruption an “unprecedented disaster”, although the extent of the damage was difficult to determine as the blast severed undersea telecommunications cables and the ash forced airports in Tonga to close .
Beyond Tonga, however, the enormity of the explosion was evident. Satellite photos showed a cloud of soil, rock, volcanic gas and water vapor hundreds of miles in diameter, and a narrower plume of gas and debris rose nearly 20 miles into the atmosphere.
Some volcanologists have drawn comparisons with the catastrophic explosion of Krakatau in Indonesia in 1883 and the most recent huge eruption, that of Mount Pinatubo in the Philippines in 1991.
Pinatubo erupted for several days, sending about 20 million tons of sulfur dioxide gas into the stratosphere or upper atmosphere. There, the gas combined with the water to create aerosol particles that reflected and scattered some of the sun’s rays, preventing them from reaching the surface.
This had the effect of cooling the atmosphere by about 1 degree Fahrenheit (about half a degree Celsius) for several years. (It’s also the mechanics of a controversial form of geoengineering: using airplanes or other means to continuously inject sulfur dioxide into the stratosphere to intentionally cool the planet.)
Hunga’s eruption “equaled the power of Pinatubo at its peak,” said Shane Cronin, a volcanologist at the University of Auckland in New Zealand who has studied the volcano’s past eruptions.
But Hunga’s eruption only lasted about 10 minutes, and satellite sensors in the days that followed measured about 400,000 tons of sulfur dioxide reaching the stratosphere. “The amount of SO2 released is much, much smaller than, say, Mount Pinatubo,” said Michael Manga, a professor of earth sciences at the University of California, Berkeley.
So unless Hunga’s eruption resumes and continues at such a strong level, which is considered unlikely, it will not have an overall cooling effect.
Dr Cronin said the power of the eruption was partly related to its location, around 500 feet underwater. When super hot molten rock, or magma, hit the seawater, the water instantly turned to steam, increasing the explosion multiple times. If it had been much deeper, the water pressure would have dampened the explosion.
The shallow depth created “almost Goldilocks” perfect conditions, he said, to supercharge the explosion.
The explosion produced a shock wave in the atmosphere that was one of the most extraordinary ever detected, said Corwin Wright, an atmospheric physicist at the University of Bath in England. Satellite readings showed the wave reaching well beyond the stratosphere, up to 60 miles high, and traveling around the world at more than 600 miles per hour.
“We’re seeing a very big wave, the biggest we’ve ever seen in the data we’ve been using for 20 years,” Dr Wright said. “We’ve never seen anything truly Earth-covering like this, and certainly not a volcano.”
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The surge occurred when the force of the explosion pushed huge amounts of air out and up, high into the atmosphere. But then gravity pulled him down. It then rose again and this up and down oscillation continued, creating an alternating high and low pressure wave that traveled outward from the source of the explosion.
Dr Wright said that although the surge occurred high in the atmosphere, it could potentially have a short-term effect on weather patterns closer to the surface, perhaps indirectly by affecting the jet stream.
“We don’t know very well,” he said. “We are waiting to see what happens over the next few days. It could just ripple and not interact.
Dr Wright said that because the wave was so high, it could also have a slight effect on radio transmissions and signals from Global Positioning Systems satellites.
The atmospheric pressure wave may also have played a role in the unusual tsunamis that occurred.
Tsunamis are generated by the rapid movement of water, usually by the movement of rock and soil. Large underwater faults can generate tsunamis as they move during an earthquake.
Volcanoes can also cause tsunamis. In this case, the underwater explosion and the collapse of the volcano’s crater may have caused the displacement. Or a flank of the volcano may have become unstable and collapsed, with the same result.
But that would only explain the local tsunami that flooded Tonga, scientists have said. Ordinarily, said Gerard Fryer, a researcher affiliated with the University of Hawaii at Manoa, who previously worked at the Pacific Tsunami Warning Center, “you would expect this energy to decay with distance.”
But this event generated tsunamis about the same size as the local one, and over several hours, in Japan, Chile and the west coast of the United States, and eventually generated small tsunamis in other basins. elsewhere in the world.
This is a sign that as it passed through the atmosphere, the pressure wave may have had an effect on the ocean, causing it to oscillate as well.
It will take weeks or months of data analysis to determine if this is what happened, but some researchers have said it is a likely explanation.
“We know that the atmosphere and the ocean are coupled,” Dr Dengler said. “And we see the tsunami in the Atlantic Ocean. He didn’t bypass the tip of South America to get there.
“The evidence is very clear that the pressure wave played a role. The question is what part.