On January 15, 2022, the Hunga Tonga-Hunga Ha'apai eruption rocked the Pacific, generating a powerful and deadly tsunami and launching a plume of material beyond the stratosphere. Early estimates suggest that this was the biggest volcanic eruption of the 21st century so far – and now a new paper confirms it.

The work, published in the Geophysical Research Journal, estimated with a new method that the eruption reached a Volcanic Explosivity Index (VEI) of 6. That makes it the strongest volcanic eruption since Mount Pinatubo in the Philippines in June 1991, which also had a VEI of 6. 

The Hunga Tonga-Hunga Ha'apai eruption released over 500 times the energy of the atomic bomb the US dropped on Hiroshima in 1945. it was also 9,000 times more energetic than the explosion that took place in the harbor of Beirut in 2020. It caused a tsunami with waves as high as 15 meters (49 feet), which killed at least 6 people with several unfortunately still missing.  

The difficulty in estimating the size of the eruption stems mostly from the lack of close monitoring stations on the volcano, which was just about above the ocean water when it erupted. However, the size was so incredible that it was felt across the world – and from that data, researchers were able to make this estimate. 

“We show how the data recorded by seismographic stations operating all around the World, which are available in real time, can be analyzed to determine main eruption parameters including its location and size within less than 2 hr after its occurrence,” the team wrote in the paper.  

Many volcanos are in hard-to-reach areas, so this approach could be a very useful tool in volcanology. Thanks to future eruptions, better models, and tweaks to this method, the VEI could be estimated more accurately and even faster in the future.