By Stephen Beech via SWNS
The Tongan volcano eruption was triggered by an explosion as big as five underground nuclear bombs, reveals new research.
The cataclysmic Hunga Tonga blast in January 2022 was the largest volcanic eruption since Krakatoa in 1883.
It triggered devastating tsunamis, leaving thousands of people homeless, while sound waves carried 6,200 miles to Alaska.
Previous research has shown that the eruption created the highest-ever recorded plume, reaching more than 35 miles into the atmosphere.
It also produced the most intense burst of lightning ever recorded with 2,615 flashes a minute at its height.
Now new research, published in the journal Geophysical Research Letters, has revealed its main trigger.
Until now, the cause of the massive blast had remained largely a mystery to scientists.
But a student-led team of Australian National University (ANU) seismologists has been able to shed new light on the natural explosion that initiated the event.
The team analyzed the climactic event’s noisy but valuable seismic records to decipher its mysterious physical mechanism.
Study co-author Jinyin Hu, an ANU PhD student, said: “Our findings confirm there was an explosion, possibly due to a gas-compressed rock, which released energy that equated to five of the largest underground nuclear explosions conducted by North Korea in 2017.
“Our model suggests the event resulted from the gas-compressed rock being trapped underneath a shallow sea, like an overcooked pressure cooker.
“This would be surprising to many because it had been commonly thought that the interaction of hot magma with cold seawater caused such massive underwater volcanic eruptions.
“We used a technique previously developed to study underground explosions for this natural explosion.”
Study co-author Dr. Thanh-Son Pham said the explosion caused a massive vertical push of water upwards into the atmosphere, causing tsunamis that reached as high as 45 meters (147.6 ft) at nearby islands.
Dr. Phạm said: “The water volume that was uplifted during the event was huge.
“Based on our estimates, there was enough water to fill about one million standard Olympic-sized swimming pools,”
Study co-author Professor Hrvoje TkalÄiÄ, also of ANU, said: “Using seismic waveform modeling, we observed a significant vertical force pointing upward during the event.
“At first, we were confused by it. But then we realized that the solid earth rebounded upwards after the water column got uplifted.”
He added: “A couple of weeks ago, we saw how seismology was used to explain an extraordinary sequence of events in Greenland that included a landslide due to glacial melting, a tsunami, and a seiche lasting for nine days observed globally.
“With Hunga Tonga, we have a relatively short-duration explosive event observed globally and, again, academically driven curiosity and forensic seismology at its best.”
The ANU team says the Tonga eruption is the best instrumentally recorded seismic event of its size.
Hu said: “This is one of the largest events in our lifetime.
“Luckily, we had multiple ways to record the event, from data from satellite images to seismic sensors that record the sound waves and structure.”
He added: “There was another event that happened in 1991 that was a similar size in Pinatubo in the Philippines, but back then, monitoring systems weren’t as sophisticated as they are now.”
The ANU team believe that monitoring the release of gases and micro-seismicity from volcanic sites can help better prepare for future eruptions.
