Tongan volcanic eruption sent record-breaking ash cloud more than 35 miles into the sky, experts say

Tongan volcanic eruption sent record-breaking ash cloud more than 35 miles into the sky, experts say

The powerful underwater eruption of Tonga’s Hunga Tonga-Hunga Ha’apai volcano earlier this year produced a plume that experts say rose higher in Earth’s atmosphere than any other ever recorded.

Researchers say the plume reached about 35 miles into the sky and stretched more than halfway into space.

The white-gray plume unleashed by the eruption became the first documented to have penetrated an icy layer of the atmosphere called the mesosphere, according to scientists who used multiple satellite images to measure altitude.

The plume was mostly 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 on January 15 sent tsunami waves across the Pacific Ocean, producing an atmospheric wave that traveled around the world several times.

A large dust explosion over water
The January volcanic eruption triggered a tsunami warning for several island states in the South Pacific.(Reuters: NOAA/CIRA/Handout)

“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 Mr. Proud said.

“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.

The damage from the eruption destroyed a small and uninhabited nearby island and resulted in the deaths of six local residents.

Its plume extended through the lower two layers of the atmosphere, the troposphere and the stratosphere, and about 7 km into the mesosphere. The top of the mesosphere is the coldest place in the atmosphere.

The plume is far from reaching the next atmospheric layer, the thermosphere, which begins about 85 km above the 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.

Scientists used three geostationary weather satellites that acquired images every 10 minutes to measure the blast 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.

So far, the highest recorded volcanic plumes have come from the 1991 eruption of Mount Pinatubo 40 km away and the 1982 eruption of El Chichón in Mexico at 31 km.

Past volcanic eruptions likely caused taller plumes, but occurred before scientists could make such measurements.


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