Volcanic mountains

Scientists use satellites to measure tallest volcanic plume on record

Volcanic eruptions can create serious impacts on human activity and weather behavior as ash, gases and water are thrown high into the sky. While most eruptions are relatively shallow in the atmosphere, the plume generated by the incredibly powerful eruption of January 2022 from Tonga’s Hunga Tonga-Hunga Ha’apai volcano has been crowned the tallest volcanic plume on record.

Researchers from Oxford University and Munich University of Applied Sciences used a new satellite method that relies on the parallax effect to determine the altitude of the January eruption. They found that the generated plume reached about 35 miles (57 kilometers) into the atmosphere, with some of the ash potentially reaching another half kilometer. The researchers also say the plume is the first to be seen entering Earth’s mesosphere, which begins about 50 kilometers above the planet’s surface. The team’s article was published in Science.

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Typically, the height of volcanic plumes is measured by measuring the temperature at the top of the cloud using infrared satellites. When the top of the cloud reaches the troposphere, where the temperature drops with altitude, the height of the cloud can be determined based on the temperature at the top as it cools. In the stratosphere, however, temperature increases with altitude, which means that the temperature of the already hot volcanic plume – and therefore its height – cannot be accurately estimated.

Since the team could not rely on temperature readings from a single satellite, they used a new method of observing the height of the plume based on data from multiple satellites. Observing a cloud at high altitude from a single satellite will distort the true height of the cloud and cause a false estimate. Instead, three geostationary satellites overlooking Tonga provided the data needed for the team’s calculations, with the help of the parallax effect: the phenomenon in which viewing an object from different viewpoints gives him the impression of changing position. You can experience this for yourself by holding your thumb in front of your face and looking at it one eye at a time; your thumb will appear to “jump” over the background.

“This is an extraordinary result, as we have never seen a cloud of such size before,” lead author Simon Proud said in A press release from Oxford University. “Also, the ability to estimate height like we did (using the parallax method) is only possible now that we have good satellite coverage. This wouldn’t have been possible a while ago. ten years. “

According to Proud and colleagues, the Hunga Tonga-Hunga Ha’apai plume reached an altitude of 15.5 miles (25 kilometers) 15 minutes after the eruption and 24.8 miles (40 kilometers) 10 minutes later. Thirty minutes after the eruption, the team observed an ash dome beginning 34 kilometers above the surface and reaching the plume’s record high, with an estimated diameter of 90 kilometers.

Researchers are eager to use this observation method to create an automated workflow for calculating volcanic plume heights with multiple satellites, which could create a detailed data set for use by volcanologists and scientists in the atmosphere. Even still, lingering questions about how the plume reached such a height and what effects it may have had on our climate remain unanswered.

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