A thunderclap rocked the South Pacific region in January 2022 – the strongest recorded by modern instruments.
It happened as the undersea, Hunga Tonga-Hunga Ha’apai, located in the Tonga archipelago, erupted violently on January 15, 2022.
The blast was so powerful it was equivalent to hundreds of atomic bombs and set off the fastest-moving undercurrent on record. It was rated at least VEI-5 on the Volcanic Explosive Index (VEI), which puts it on par with the eruptions of Mount Vesuvius in AD 79. and Mount Agia Eleni in 1980.
However, two monitoring stations located far away recorded a seismic wave about 15 minutes earlier, a new study has revealed.
The wave was one “seismic precursor” for the explosion, the study’s authors say, Science Alert reported. Collapse in a weak section of oceanic crust beneath the volcano’s caldera wall was the trigger for both.
As a result of the collapse, seawater and lava flooded the area between the volcano’s underground magma chamber and the sea floor, triggering the eruption, according to the study authors.
The fault also triggered a type of seismic wave that travels along the surface of a solid, causing movement – known as a Rayleigh wave. This moved along the Earth’s surface and was detected 15 minutes before the main volcanic eruption, about 466 miles away.
Prior to the January 2022 eruption, moderate volcanic activity was recorded in December 2021 and earlier in January, as well as the day before the unprecedented eruption.
The eruption spewed 2.4 cubic miles of volcanic material and sent 146 million metric tons of water vapor into the air, an amount that would fill about 58,000 Olympic-sized swimming pools.
While in an isolated location, the explosion triggered a tsunami that killed at least four people in Tonga and two more 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, with only small sections remaining.
