The eruption of a volcano in Tonga in January 2022 has been confirmed as the largest explosion ever recorded in the atmosphere by modern equipment.
It was far larger than any 20thcentury volcanic event, or even any atomic bomb test conducted after World War II.
The assessment was presented in two scientific articles published in the journal Science, which reviewed all the data.
In recent history, it is likely that only the eruption of the Krakatoa volcano in 1883 can match the atmospheric disturbance it caused. This catastrophic event is believed to have killed more than 30,000 people in Indonesia.
Fortunately, the eruption of the Hunga TongaHunga Ha’apai (HTHH) underwater volcano in the South Pacific on January 15 this year resulted in very few fatalities, although it also produced large tsunamis.
“Tonga was a really global event, just like Krakatoa, but now we’ve got all these geophysical observing systems, and they’ve recorded something really unprecedented in modern data.”, in the US, who is the lead author of one of the articles.
Scientists now have access to an extraordinary array of ground and space instruments, including atmospheric pressure sensors, seismographs, hydrophones, and a fleet of satellites monitoring the Earth across the light spectrum.
The colossal blast in Tonga, which took place after several weeks of seamount activity, created various types of atmospheric pressure waves that traveled long distances.
In the audible frequency range, people 10,000 km away in Alaska have reported hearing repeated pops.
The global network of detectors created to monitor compliance with the Comprehensive NuclearTestBan Treaty picked up the infrasound signal.
Infrasound has frequencies just below what humans can hear.
The network data showed that the Tonga volcano’s explosion produced an atmospheric pressure wave comparable to the largest nuclear explosion on record ? the tsar bomb detonated by the Soviets in 1961? but lasted four times as long.
The articles discuss in detail the disturbances caused by socalled Lamb waves, named after the early 20thcentury mathematician Horace Lamb.
They are energetic waves in the air, propagating at the speed of sound along a guided path across the planet’s surface. In addition, they are nonscattering, that is, they keep their shape during movement and are therefore visible for a long time.
Lamb wave pulses produced by the Tonga eruption have been seen orbiting the earth at least four times.
In Britain, some 10,000 miles from Tonga, these pulses arrived on the night of the 15th, about 14 hours after they erupted on the other side of the planet.
They lifted the clouds over Britain.
“Back then we had a laser ceilometer (a device to determine cloud height) looking at the base of the cloud and as the wave went through the cloud it was perturbed,” recalls Giles Harrison, an atmospheric physicist at the University of Reading , in the UK, and coauthored one of the articles.
“If you’ve ever wanted proof that the atmosphere is remarkably connected, you’ll find it here. And what happens on one side of the planet can propagate to the other side at the speed of sound.”
Where lamb waves combined with ocean waves, could they create tsunamis? not only in the Pacific Ocean, but also in the Atlantic and Mediterranean.
Scientists are still investigating the generation of nearby tsunamis that hit the coasts of the Tonga archipelago.
Some were no doubt created by volcanic pressure waves pressing on the water’s surface, but investigations are ongoing to determine if the collapse of part of the volcano was also a significant contributor.
This will be evident in the seabed mapping projects, the results of which are expected in the coming weeks.