A huge volcanic outburst near Tonga earlier this year was the biggest ever recorded using modern equipment, researchers have revealed.
On 15 January, Hunga Tonga–Hunga Ha'apai, a submarine volcano in the Tongan archipelago in the southern Pacific Ocean, violently erupted.
The explosion was the most powerful ever officially recorded, sending shockwaves around the world and triggering devastating tsunamis that left thousands homeless.
Hundreds of times more powerful than the Hiroshima atomic bomb, it released 2.3 cubic miles of material and debris shot 25 miles into the air.
It unleashed a tsunami that travelled across oceans at more than 600mph and has been described as the biggest explosion ever recorded in the atmosphere.
Now, researchers have said it was the largest volcanic eruption of the 21st century and one of the largest since Krakatoa in 1883.
Marine geologist Kevin Mackay, based at the National Institute of Water and Atmospheric Research (NIWA) in New Zealand, told AFP: "The eruption reached record heights, being the first we've ever seen to break through into the mesosphere."
The mesosphere is the layer above the stratosphere.
"It was like a shotgun blast directly into the sky," Mackay added.
He said: "While this eruption was large – one of the biggest since Krakatoa – the difference here is that it's an underwater volcano and it's also part of the reason we got such big tsunami waves."
In earlier research, scientists used a novel method to measure the towering column of ash and water which was ejected into the atmosphere.
The location of the Tonga volcano is covered by three geostationary weather satellites, so the researchers were able to analyse the images that were captured.
Crucially, during the eruption itself, the satellites recorded images every 10 minutes, enabling the rapid changes in the plume's trajectory to be documented.
The results showed that the plume reached an altitude of 35 miles at its highest extent.
This is significantly higher than the previous record-holders – the 1991 eruption of Mount Pinatubo in the Philippines.
It also makes the plume the first observational evidence of a volcanic eruption injecting material through the stratosphere and directly into the mesosphere, which starts at about 32 miles above the Earth's surface.
Lead author Dr Simon Proud, from the University of Oxford and the National Centre for Earth Observation, said: "It's an extraordinary result as we have never seen a cloud of any type this tall before.
"Furthermore, the ability to estimate the height in the way we did (using the parallax method) is only possible now that we have good satellite coverage. It wouldn't have been possible a decade or so ago."
Watch: Underwater eruption creates 'highest-ever plume'