Tonga volcanic eruption was triggered by explosion equivalent to ‘five underground nuclear bombs’, new research reveals

The Hunga Tonga underwater volcano was one of the largest volcanic eruptions in history and, two years later, new research from the Australian National University (ANU) has revealed its main trigger. The research is published in the journal Geophysical research letters.

Until now, the cause of the cataclysmic event has remained largely a mystery to the scientific community, but a student-led team of ANU seismologists has been able to shed new light on the natural explosion at the origin of the event.

Student researchers analyzed noisy but valuable seismic recordings of the climate event to decipher its mysterious physical mechanism.

“Our results confirm that there was an explosion, likely due to rock compressed by gas, that released energy equivalent to five of the largest underground nuclear explosions carried out by North Korea in 2017,” co-author of the study and doctor of the ANU. Student Jinyin Hu said.

“Our model suggests that the event resulted from the gas-compressed rock being trapped beneath a shallow sea, like an overcooked pressure cooker.

“This would surprise many because the interaction of hot magma with cold seawater was generally thought to cause 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 upward into the atmosphere, causing tsunamis that reached up to 45 meters height on neighboring islands.

“The volume of water lifted during the event was enormous. According to our estimates, there was enough water to fill about one million standard Olympic swimming pools,” said Dr Phạm.

Study co-author Professor Hrvoje Tkalčić, from ANU, added: “Using seismic waveform modeling, we observed a significant vertical force pointing upward during the event At first we were confused by this, but then we realized that the solid earth bounced upwards after the water column rose.

“A few weeks ago, we saw how seismology was used to explain an extraordinary sequence of events in Greenland, including a landslide caused by melting ice, a tsunami and a seiche that lasted nine days, observed on a global scale.

“With Hunga Tonga, we have a relatively short-lived, globally observed explosive event and, once again, academic curiosity and forensic seismology at its best.”

According to ANU seismologists, the Tonga eruption is the best instrumentally recorded event compared to events of similar size in the recent past.

“This is one of the most important events of our lifetime. Fortunately, we had several ways to record the event, from satellite image data to seismic sensors that record sound waves and structure.” , Mr. Hu said.

“In 1991, another event of a similar magnitude occurred in Pinatubo, Philippines, but at the time the monitoring systems were not as sophisticated as they are today.”

ANU seismologists believe that monitoring gas releases and microseismicity from volcanic sites can help better prepare for future events.