A study finds that the volcanic eruption in Tonga was the biggest explosion ever recorded.
The eruption of a volcano in Tonga was the biggest explosion that modern sensors have ever seen.
It was so strong that it caused clouds to rise over the UK and small tsunamis in the Mediterranean Sea.
The journal Science published two research papers that looked at the data and found that the huge eruption of the underwater volcano at Hunga Tonga-Hunga Ha'apai in January was much bigger than any other volcanic event in the 20th century.
The papers also compared it to atomic bomb tests done after World War II and found that they were nothing compared to how big the explosion was.
Only the 1883 Krakatoa eruption, which is thought to have killed more than 30,000 people, caused as much chaos in the air.
"Tonga was a truly global event, just like Krakatoa was," Dr. Robin Matoza from the University of California, Santa Barbara, told BBC News. "But now we have all these geophysical observation systems, and they recorded something that had never been seen before in modern data."
Even though the explosion at Hunga Tonga-Hunga Ha'apai and the ash cloud and tsunamis that followed were not nearly as bad, their effects on people tens of thousands of kilometers away surprised scientists.
Lamb waves are a type of shock wave that are talked about in detail in the papers. They are named after the mathematician Horace Lamb, who lived in the early 20th century.
They are energetic waves in the air that move at the speed of sound and can keep their shape as they move along a path set by the planet's surface.
Scientists found that the Tonga eruption sent out Lamb wave pulses that went around the Earth at least four times.
About 14 hours after Hunga Tonga-Hunga Ha'apai erupted, the pulses started to reach Reading, England, which is more than 16,000 km from Tonga. As soon as they did, the clouds lifted.
Professor Giles Harrison, an atmospheric physicist at the University of Reading and co-author on one of the papers, told the BBC, "At the time, we had a laser cloud-base recorder looking at the cloud base. As the wave went through, the cloud was disturbed."
"If you ever needed proof that the atmosphere is a complex web of connections, this was it. At the speed of sound, what happens on one side of the planet can spread to the other side."
After the eruption, when the Lamb waves met ocean waves, they caused tsunamis, not just in Tonga, New Zealand, and other parts of the Pacific Ocean, but also in the Atlantic Ocean and the Mediterranean Sea.
People in Alaska, which is 10,000 km from Aotearoa, could also hear the shockwaves that were felt in Aotearoa.
The infrasound signal was picked up by a global network of detectors set up to check for compliance with the Comprehensive Nuclear-Test-Ban Treaty. This showed that the blast caused an atmospheric pressure wave that was similar to the biggest nuclear explosion ever, the Soviet Tsar bomb, which went off in 1961, but lasted four times longer.
There is still more research to be done to find out what caused the tsunamis that hit the Tongan islands right after. A look at the seafloor will tell how much, if anything, a part of the volcano falling down had to do with them.