Tongan volcanic eruption causes highest plume ever
By Will Dunham
WASHINGTON (Reuters) – The powerful Jan. 15 underwater eruption of Tonga’s Hunga Tonga-Hunga Ha’apai volcano in the South Pacific produced a plume that rose higher in Earth’s atmosphere than any other on record — about 35 miles (57 km) — if it stretched more than halfway into space, researchers said Thursday.
The white-gray plume released by the eruption in the Polynesian archipelago became the first documented by invading an icy layer of the atmosphere called the mesosphere, according to scientists using a new technique using multiple satellite images. to measure the height.
The plume consisted mostly of water with some ash and sulfur dioxide mixed in, said atmospheric scientist Simon Proud, lead author of the study published in the journal Science. Volcanic eruptions on land usually contain more ash and sulfur dioxide and less water.
The deafening eruption sent tsunami waves across the Pacific Ocean, producing an atmospheric wave that traveled around the world several times. (See related image)
“What was impressive to me is how quickly the eruption happened. It went from nothing to a 35-mile cloud in just 30 minutes. I can’t imagine what that must have been like to see from the ground,” said Trots, a fellow at the UK’s National Center for Earth Observation, working at the University of Oxford and STFC RAL Space.
“Something that fascinated me was the dome-like structure in the center of the umbrella plume. I’ve never seen anything like it,” Oxford atmospheric scientist and study author Andrew Prata added.
Damage and loss of life – six dead – was relatively low due to the remote location of the eruption, though it obliterated a small and uninhabited island. Tonga is an archipelago of 176 islands with a population of just over 100,000 people, located southeast of Fiji and just west of the International Date Line.
“It could have been a lot worse,” Proud said.
The plume extended through the lower two layers of the atmosphere, the troposphere and stratosphere, and about 7 km into the mesosphere. The top of the mesosphere is the coldest place in the atmosphere.
“The mesosphere is one of the upper layers of our atmosphere and is generally quite calm — there is no known weather there and the air is very dry and extremely thin,” Proud said. “It’s one of the least understood parts of the atmosphere because it’s so hard to get to. Down below we can use airplanes. Higher up we have spacecraft. Lots of meteors burn up in the mesosphere, and it’s also home to night-luminous (night-glowing ) clouds, which are sometimes visible in the summer sky toward the poles.”
The plume was far from reaching the next atmospheric layer, the thermosphere, which begins about 53 miles (85 km) above Earth’s surface. A delineation called the Karman Line, about 100 km above the Earth’s surface, is generally considered to be the boundary of outer space.
So far, the highest recorded volcanic plumes have come from the 1991 eruption of Mount Pinatubo in the Philippines, 40 km away, and the 1982 eruption of El Chichón in Mexico, 31 km away. Past volcanic eruptions likely caused taller plumes, but occurred before scientists could make such measurements. Proud said that the 1883 Krakatoa eruption in Indonesia probably also reached the mesosphere.
Scientists were unable to use their standard temperature-based technique for measuring a volcanic plume because the January eruption exceeded the maximum height at which this method could be used. Instead, they turned to three geostationary weather satellites that collected images every 10 minutes and relied on what’s called the parallax effect — determining the position of something by viewing it along multiple lines of sight.
“The parallax approach we use to work requires multiple satellites in different locations — and it’s only in the last decade that this has become possible on a global scale,” Proud said.
(Reporting by Will Dunham, editing by Rosalba O’Brien)
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