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When the Hunga Tonga-Hunga Ha’apai volcano erupted underwater in January, it created a plume of ash and water that broke through the third layer of Earth’s atmosphere.
It was the tallest volcanic plume on record and reached the mesosphere, where meteors and meteorites typically break up and burn up in our atmosphere.
The mesosphere, approximately 50 to 80 kilometers (31 to 50 miles) above Earth’s surface, is above the troposphere and stratosphere and under another two layers. (The stratosphere and mesosphere are dry atmospheric layers.)
The volcanic column reached an altitude of 35.4 miles (57 kilometers) at its highest point. It surpassed previous record holders such as the 1991 Mount Pinatubo eruption in the Philippines at 40 kilometers (24.8 mi) and the 1982 El Chichón eruption in Mexico, which reached 31 kilometers (19.2 mi).
The researchers used images captured by satellites passing over the eruption site to confirm the height of the plume. The eruption occurred on January 15 in the southern Pacific Ocean off the Tonga archipelago, an area covered by three geostationary weather satellites.
A study detailing the findings published Thursday in the journal Sciences.
The imposing plume sent to the upper layers of the atmosphere. contained enough water to fill 58,000 Olympic swimming poolsbased on previous detections by a NASA satellite.
Understanding the height of the plume can help researchers study the impact the eruption might have on global climate.
Determining the height of the plume posed a challenge for the researchers. Scientists can usually measure the altitude of a plume by studying its temperature: the colder a plume, the higher it is, said study co-lead author Dr. Simon Proud of RAL Space and a researcher at the National Center for Earth Observation and the University of Oxford.
But this method could not be applied to the Tonga event due to the violent nature of its eruption.
“The eruption pushed through the layer of the atmosphere that we live in, the troposphere, into the upper layers where the atmosphere reheats as you go higher,” Proud said by email.
“We had to come up with another approach, using the different views provided by weather satellites located on opposite sides of the Pacific and some pattern matching techniques to calculate altitude. This has only been possible in the last few years, as even ten years ago we didn’t have the satellite technology in space to do this.”
The research team relied on “the parallax effect” to determine the plume’s height, comparing the difference in the plume’s appearance from multiple angles as captured by weather satellites. Satellites took images every 10 minutes, documenting the dramatic changes in the plume as it rose out of the ocean. The images reflected differences in the position of the plume from different lines of sight.
The eruption “went from nowhere to a 35-mile-high tower of ash and cloud in 30 minutes,” Proud said. Team members also noticed rapid changes at the top of the eruptive column that surprised them.
“After the initial big bang at 57 kilometers, the central dome of the column collapsed inwards, before another column appeared shortly after,” Proud said. “I didn’t expect something like this to happen.”
The amount of water the volcano released into the atmosphere is expected to warm the planet temporarily.
“This technique not only allows us to determine the maximum height of the plume, but also the various levels in the atmosphere where volcanic material was released,” said study co-author Dr. Andrew Prata, a postdoctoral research assistant in the subdepartment of atmospheric, oceanic and planetary physics at Oxford University’s Clarendon Laboratory, by email.
Knowing the composition and height of the plume can reveal how much ice was sent up into the stratosphere and where the ash particles were released.
Height is also critical to aviation safety because volcanic ash can cause jet engine failure, so avoiding ash plumes is key.
The height of the plume is another emerging detail from what is known as one of the most powerful volcanic eruptions on record. When the undersea volcano erupted 40 miles (65 kilometers) north of Tonga’s capital, it triggered a tsunami and shock waves that spread across the globe.
Research is underway to find out why the eruption was so powerful, but it could be because it happened underwater.
The heat from the eruption vaporized the water and “created a steam explosion much more powerful than a volcanic eruption would normally be,” Proud said.
“Examples such as the Hunga Tonga-Hunga Ha’apai eruption demonstrate that interactions between magma and seawater play an important role in producing highly explosive eruptions that can inject volcanic material at extreme altitudes,” Prata added.
Next, the researchers want to understand why the plume was so tall, as well as its composition and its ongoing impact on global climate.
“Often when people think of volcanic plumes, they think of volcanic ash,” Prata said. “However, preliminary work in this case reveals that there was a significant proportion of ice in the column. We also know that a fairly modest amount of sulfur dioxide and sulfate aerosols formed rapidly after the eruption took place.”
Proud wants to use the multisatellite altitude technique in this study to create automatic alerts for severe storms and volcanic eruptions.
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