Just moments before the most powerful volcanic explosion ever recorded took place, a mysterious signal occurred, scientists have discovered.
A thunderous clap rocked the South Pacific region in January 2022 – the strongest explosion to be recorded with modern instruments.
It occurred as the underwater volcano, Hunga Tonga-Hunga Ha’apai, found in the Tongan archipelago, violently exploded on January 15, 2022.
The explosion was so powerful that it was equivalent to hundreds of atomic bombs and sparked the fastest moving underwater current on record. It rated at least VEI-5 on the Volcanic Explosively Index (VEI), which puts it on par with the explosions of Mount Vesuvius in 79CE and Mount St. Helens in 1980.
However, two monitoring stations located faraway recorded a seismic wave around 15 minutes earlier, a new study revealed.
The wave was a “seismic precursor” for the eruption, the study’s authors say, Science Alert reported. The collapse in a weak section of ocean crust below the volcano’s caldera wall was the trigger for both.
As a result of the collapse, seawater and lava flooded into the area between the volcano’s underground magma chamber and the sea floor, launching the eruption, the study’s authors said.
The fracture also triggered a type of seismic wave that moves along a solid’s surface, causing movement – known as a Rayleigh wave. This moved along Earth’s surface and was detected 15 minutes before the main volcanic eruption took place, around 466 miles away.
Mie Ichihara, volcanologist at the University of Tokyo and study co-author said: “Early warnings are very important for disaster mitigation.
“Island volcanoes can generate tsunamis, which are a significant hazard.”
Prior to the eruption in January 2022, modest volcanic grumblings were recorded in December 2021 and earlier in January as well as the day before the unrivalled explosion.
The explosion catapulted 2.4-cubic miles-worth of volcanic material and sent 146 million metric tonnes of water vapour into the air, a quanity that roughly fills about 58,000 Olympic swimming pools.
While in an isolated location, the blast launched out tsunamis that killed at least four people in Tonga, and a further two in Peru, thousands of miles away. Two fishermen were also injured in San Gregorio, California.
On January 15 a satellite radar survey showed that most of the island had been destroyed, and only small parts remained, including remnants of Hunga Tonga and Hunga Haʻapai.
