The massive eruption of the Hunga Tonga underwater volcano in 2022 was one of the largest volcanic events in history.
Now, two years later, researchers from The Australian National University (ANU) have uncovered the cause of this cataclysmic event.
Their findings, published in Geophysical Research Letters, reveal that the eruption was triggered by a powerful explosion equivalent to the force of five underground nuclear bombs.
A student-led team of ANU seismologists studied seismic data from the eruption to figure out what caused the explosion.
According to the researchers, the blast was likely caused by a gas-compressed rock trapped under the shallow sea, similar to how pressure builds in an overcooked pressure cooker.
“For a long time, it was believed that the eruption was caused by hot magma interacting with cold seawater,” explained Ph.D. student and study co-author Jinyin Hu.
“But our model suggests that the explosion came from gas-compressed rock, releasing a massive amount of energy.”
This natural explosion was so powerful that it caused a huge vertical push of water, triggering tsunamis as high as 45 meters (about 148 feet) on nearby islands.
According to Dr. Thanh-Son Pham, a co-author of the study, the amount of water displaced was staggering—enough to fill about one million Olympic-sized swimming pools.
Using seismic waveform modeling, the researchers also observed a strong upward force from the Earth’s surface during the event.
“At first, we were confused by this,” said Professor Hrvoje Tkalčić, another co-author. “But we realized that the solid Earth rebounded upwards after the massive water column was uplifted.”
This event is one of the largest of its kind in recent history and, thanks to modern technology, it was recorded with great accuracy.
“We had a lot of data from satellites and seismic sensors that allowed us to study this event in detail,” said Hu. “The last time we had an eruption of a similar size was in 1991 at Mount Pinatubo in the Philippines, but the monitoring systems back then were not as advanced.”
The researchers believe that closely monitoring gas emissions and small seismic activity from volcanoes could help predict future eruptions and better prepare for such large-scale natural disasters.
