Tonga’s volcanic eruption has unleashed the tallest plume on record
By Will Dunham
WASHINGTON (Reuters) – A powerful underwater eruption of Tonga’s Hunga Tonga-Hunga Haapai volcano in the South Pacific on Jan. 15 sent a plume that rose higher into the Earth’s atmosphere than any other eruption on record, about 35 miles (57 km). It has spread more than halfway into space, researchers said Thursday.
A white-gray plume from an eruption in a Polynesian archipelago has become the first documented to have penetrated the cold layer of the atmosphere called the mesosphere, according to scientists who used a new technique using multiple satellite images to measure its height.
The plume was composed mostly of water mixed with some ash and sulfur dioxide, said atmospheric scientist Simon Prude, lead author of the study published in the journal Science. Eruptions of terrestrial volcanoes usually have more ash and sulfur dioxide and less water.
The deafening eruption sent tsunami waves across the Pacific Ocean and generated an atmospheric wave that circled the globe several times. (See accompanying graph)
“What’s impressive to me is how fast the eruption is. It went from nothing to a cloud 57 kilometers high in just 30 minutes. I can’t imagine what it must have been like to see from the ground,” he said. Proud staff member of the UK’s National Earth Observation Center based at the University of Oxford and STFC RAL Space.
“Something that fascinated me was the dome-like structure in the center of the canopy plume. I’ve never seen anything like this before,” added Oxford atmospheric scientist and study co-author Andrew Prata.
Damage and loss of life—six deaths—were relatively few due to the eruption’s remote location, although it destroyed a small and uninhabited island. Tonga is an archipelago of 176 islands with a population of just over 100,000, 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 4 miles (7 km) into the mesosphere. The top of the mesosphere is the coldest part of the atmosphere.
“The mesosphere is one of the upper layers of our atmosphere and is generally quite calm; there is no familiar weather there and the air is very dry and very thin,” Proud says. “It’s one of the least understood parts of the atmosphere because it’s so difficult to get to. Below, we can use planes. Higher up, we have spaceships. Many meteorites burn up in the mesosphere, and it is also home to nocturnal light. -shining) clouds that are sometimes seen in the summer sky towards 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. The Kármán line, called the Kármán line, about 62 miles (100 km) above the Earth’s surface is generally considered the limit of space.
The tallest volcanic plumes ever recorded were from the 1991 eruption of Mount Pinatubo in the Philippines at 25 miles (40 km) and the 1982 eruption of El Chichon in Mexico at 19 miles (31 km). Volcanic eruptions in the past likely produced higher plumes, but occurred before scientists could make such measurements. Pride said the 1883 eruption of Krakatau in Indonesia probably also reached the mesosphere.
Scientists were unable to use their standard temperature-based technique to measure the volcanic plume because the January eruption passed the maximum height for which this method could be used. Instead, they turned to three geostationary weather satellites that received images every 10 minutes and relied on something called the parallax effect to determine the position of something by viewing it across multiple lines of sight.
“For the parallax approach we’re using to work, you need multiple satellites in different locations, and it’s only been in the last decade that this has become possible on a global scale,” Prade said.
(Reporting by Will Dunham Editing by Rosalba O’Brien)
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