The massive plume from the Tonga eruption reached the third layer of Earth’s atmosphere

The massive plume from the Tonga eruption reached the third layer of Earth's atmosphere
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When the Hunga Tonga-Hunga Ha’apai volcano erupted underwater in January, it produced a plume of ash and water that ruptured the third layer of Earth’s atmosphere.

It was the highest volcanic plume on record, reaching the mesosphere where meteors and meteorites normally break up and burn up in our atmosphere.

The mesosphere, about 31 to 50 miles (50 to 80 kilometers) above the Earth’s surface, is above the troposphere and stratosphere and under two other layers. (The stratosphere and mesosphere are dry atmospheric layers.)

The volcanic plume reached a height of 57 kilometers at its highest point. It surpassed previous record holders such as the 1991 Mount Pinatubo eruption in the Philippines at 40 kilometers and the 1982 El Chichón eruption in Mexico at 31 kilometers.

The researchers used images taken by satellites flying over the eruption site to confirm the plume’s height. The eruption occurred on January 15 in the southern Pacific off the Tongan Archipelago, an area covered by three geostationary weather satellites.

A study detailing the results published Thursday in the journal Science.

The towering cloud was sent into the upper layers of the atmosphere contained enough water to fill 58,000 Olympic-size swimming poolsaccording to earlier discoveries by a NASA satellite.

Understanding the cloud’s height can help researchers study the impact the eruption could have on global climate.

Japan's Himawari-8 satellite captured this image about 50 minutes after the eruption.

Determining the height of the cloud presented the researchers with a challenge. Typically, scientists can measure a cloud’s height by examining its temperature — the colder a cloud, the higher it is, said lead study co-author Dr. Simon Proud of RAL Space and Research Associate at the National Center for Earth Observation and the University of Oxford.

However, this method could not be applied to the Tonga event due to the violent nature of its eruption.

“The eruption pushed the layer of atmosphere that we live in, the troposphere, into the upper layers, where the atmosphere warms up again as you get higher,” Proud said via email.

“We had to find a different approach, using the different views from weather satellites on opposite sides of the Pacific and some pattern matching techniques to determine the altitude. This has only become possible in the last few years because as recently as ten years ago in space we didn’t have the satellite technology to do this.”

This satellite image shows what the cloud looked like 100 minutes after the eruption began.

The research team relied on the ‘parallax effect’ to determine the cloud’s height and compared the difference in the cloud’s appearance from multiple angles as captured by the weather satellites. The satellites took pictures every 10 minutes, documenting the dramatic changes in the cloud as it rose from the ocean. The images reflected differences in the cloud’s position from different lines of sight.

The eruption “went out of nowhere into a 57-kilometer (35-mile) tower of ash and clouds in 30 minutes,” Proud said. Team members also noticed rapid changes at the top of the plume, which surprised them.

“After the initial large outburst at 57 kilometers, the cloud’s central dome collapsed inward before another cloud appeared shortly after,” Proud said. “I didn’t expect something like this to happen.”

The amount of water the volcano has released into the atmosphere is expected to temporarily warm the planet.

“This technique not only allows us to determine the maximum height of the cloud, but also the different levels in the atmosphere where volcanic material was released,” said study co-author Dr. Andrew Prata, a post-doctoral researcher in the Clarendon Laboratory’s Atmospheric, Oceanic and Planetary Physics sub-department at the University of Oxford, via email.

Knowing the composition and height of the cloud can shed light on how much ice was sent into the stratosphere and where ash particles were released.

Altitude is also critical to flight safety as volcanic ash can cause engine failures, so avoiding ash plumes is vital.

The plume’s height is another emerging detail of what has become known as one of the most powerful volcanic eruptions on record. When the underwater volcano erupted 40 miles (65 kilometers) north of Tonga’s capital, it triggered a tsunami and shock waves that traveled around the world.

Research is ongoing to find out why the eruption was so powerful, but it could be because it happened underwater.

The heat from the eruption evaporated the water and “created a steam explosion much more powerful than a volcanic eruption would normally be,” Proud said.

A full picture of Earth taken by Japan's Himawari-8 satellite shows the eruption on Earth's lower right.

“Examples such as the Hunga Tonga-Hunga Ha’apai eruption show that magma-seawater interactions play a significant role in generating highly explosive eruptions that can eject volcanic material to extreme heights,” Prata added.

Next, the researchers want to understand why the cloud was so high, its composition, and ongoing effects on global climate.

“When people think of volcanic plumes, they often think of volcanic ash,” Prata said. “However, preliminary work on this case shows that there was a significant amount of ice in the cloud. We also know that a fairly modest amount of sulfur dioxide and sulfate aerosols formed soon after the eruption.”

Proud plans to use the multi-satellite altitude technique in this study to create automatic alerts for severe storms and volcanic eruptions.

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