Tonga’s volcanic eruption in January produced the highest plume ever recorded, scientists have confirmed.
Hunga Tonga-Hunga Ha’apai, an underwater volcano in the South Pacific, spewed an ash plume that was 187,000 feet (57 km/35 mi) high.
Its colossal eruption on January 15 of this year is also the first recorded to have penetrated the third layer of the atmosphere – the mesosphere.
The mesosphere begins about 160,000 feet (48 km) above us and is where passing meteors begin to burn up and form shooting stars.
Researchers from the University of Oxford and RAL Space used three geostationary weather satellites to precisely measure the height of the massive plume.
The previous record holder, the 1991 eruption of Mount Pinatubo in the Philippines, produced a plume that was recorded as 131,000 feet (40 km/25 mi) high.
“This is an extraordinary result as we have never seen a cloud this high before,” said lead author Dr Simon Proud.
“Furthermore, the ability to estimate height the way we did using the parallax method is only possible now that we have good satellite coverage.”
“It wouldn’t have been possible about a decade ago.”
Parallax-based retrievals of plume height at 04:30 GMT on 15 January 2022 superimposed on Himawari-8 data for the same time frame
WHAT IS THE ‘PARALLAX EFFECT’?
The parallax effect is the difference in the apparent location of an object viewed along two different lines of sight.
You can see this effect by closing your right eye and holding out one hand with the thumb up.
If you then switch the eyes so that the left is closed and the right is open, your thumb will appear slightly offset against the background.
Astronomers use this effect to measure great distances, for example between the Earth and the stars.
The parallax effect
The Hunga Tonga-Hunga Ha’apai eruption occurred in the South Pacific Ocean, about 40 miles (65 km) from the main island of Tonga.
It triggered a 7.4-magnitude earthquake that sent tsunami waves crashing across the island and felt as far away as Russia, the United States and Chile.
The eruption released more energy than the Tsar Bomba – the most powerful nuclear bomb ever detonated – and blew 20,000 Olympic-size swimming pools of water into the stratosphere.
For the study, published today in Science, scientists wanted to measure exactly how far into the atmosphere the towering column of ash and water produced extends.
This is usually done by measuring the temperature at the top of the plume using infrared satellites and comparing it to standard temperatures at various known altitudes.
This can be done because previous jets only extended into the troposphere, the first layer of the atmosphere where temperature decreases with height.
However, the Hunga Tonga-Hunga Ha’apai cloud went into the third layer of the atmosphere, the mesosphere.
Because the ozone layer absorbs the sun’s ultraviolet radiation, temperatures in the stratosphere and mesosphere actually increase with height.
So, to measure the jet, Dr. Proud’s team developed a different technique that exploits the “parallax effect” – the difference in the apparent location of an object viewed along two different lines of sight.
This technique allows researchers to calculate the distance between the object and the two viewers.
The location of the Tonga volcano is covered by three weather satellites, all 22,000 miles (36,000 km) up in space – GOES-17 from the US, Himawari-8 from Japan and GeoKompSat-2A from South Korea.
Aerial photographs taken by these satellites of known location were used to measure the height of the plume.
They also record images every ten minutes, meaning researchers can document rapid changes in the cloud’s trajectory.
Dr Proud said: “Thirty years ago when Pinatubo erupted our satellites were nowhere near as good as they are now. They could only scan the ground every 30 minutes. Or maybe even every hour.
Elevation evolution of the volcanic plume over time. Infrared (IR) heights are derived from Himawari-8 satellite measurements and known temperature standards from the European Center for Medium-Range Weather Forecasts. The blue lines show heights estimated by the stereoscopic method throughout the plume, and the green markers are parallax heights obtained from manual analysis of data from the Himawari-8, GK-2A and GOES-17 satellites
Animation showing the height evolution of the Hunga Tonga-Hunga Ha’apai eruption plume measured using a stereoscopic method applied to images from three weather satellites.
Dr. Proud also speculated that the estimate of Mount Pinatubo’s eruption may have been incorrect as a result of the reduced satellite data available at the time.
He said: “We think that for Pinatubo we actually missed the peak of activity and the points where it peaked – it fell between two of the satellite images and we missed it.”
The researchers now intend to construct an automated system to calculate the heights of the volcanic pillars using the parallax method.
They hope that a dataset of plume heights will help other scientists model the dispersion of volcanic ash in the atmosphere.
The Hunga Tonga-Hunga Ha’apai eruption occurred in the South Pacific Ocean, about 40 miles (65 km) from the country’s main island
Its colossal eruption on January 15 this year is the first recorded to have breached the third layer of the atmosphere – the mesosphere. It also caused many effects, such as atmospheric waves, extreme winds and unusual electrical currents, which were felt around the world and in space.
The previous record holder, the 1991 eruption of Mount Pinatubo in the Philippines, produced a plume that was recorded as 131,000 feet (40 km/ 25 miles) high (pictured)
WHAT HAPPENED DURING THE JANUARY TONGA Eruption?
Hunga Tonga-Hunga Ha’apai, an underwater volcano in the South Pacific, spewed debris up to 25 miles into the atmosphere when it erupted on January 15.
It triggered a 7.4-magnitude earthquake that sent tsunami waves crashing into the island, leaving it covered in ash and cut off from outside aid.
It also released somewhere between 5 to 30 megatons (5 million to 30 million tons) of TNT equivalent, according to NASA’s Earth Observatory.
Digital elevation maps from NASA’s Earth Observatory also show the dramatic changes at Hunga Tonga-Hunga Ha’apai, the top of a large underwater volcano.
Before the explosion earlier this month, the twin uninhabited islands of Hunga Tonga and Hunga Haapai were merged by a volcanic cone to form a single landmass.
Hunga Tonga and Hunga Ha’apai are themselves remnants of the northern and western rims of the volcano’s caldera, the depression that formed shortly after the magma chamber emptied.
NASA said the eruption “obliterated” the volcanic island about 41 miles (65 km) north of Tonga’s capital Nuku’alofa, on the island of Tongatapu (Tonga’s main island).
It covered the island kingdom of about 100,000 in a layer of toxic ash, poisoning drinking water, destroying crops and completely destroying at least two villages.
It also claimed at least three lives in Tonga and led to the drowning deaths of two beachgoers in Peru after freak waves hit the South American country.
Peruvian authorities have declared an environmental disaster after waves hit an oil tanker offloading near Lima, creating a huge blob on the coast.
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