We have already almost forgotten it and yet, on January 15, 2022, one of the most powerful eruptions ever recorded took place: that of the underwater volcano Hunga Tonga-Hunga Ha'apai, located off the coast of the Tonga archipelago. . Scientists remember it well, and for good reason: the eruption was particularly well monitored, from start to finish, and the enormous amount of data acquired in just a few hours continues to be processed. current time.
A faint seismic signal recorded 750 km a quarter of an hour before the eruption
These data, of extremely diverse origin, allow us to better understand the mechanics eruptiveeruptive volcanoes and the consequences of powerful eruptions like this, whether they concern the atmosphere or the marine environment. However, many points still remain mysterious, particularly regarding the origin of this volcanic event.
However, a seismic signal recorded just minutes before the volcano's explosion could help to better understand what happened at this crucial moment.
Researchers have in fact identified the discreet arrival of seismic waves on the recordings of two seismological stations located on the islands of Fiji and Futuna, located 750 kilometers from the underwater volcano. These are Rayleigh waves, a type of seismic wave that travels across the Earth's surface. However, they were recorded at 3:45 a.m. UTC (coordinated universal timecoordinated universal time), while the eruption began about a quarter of an hour later, around 4:00 UTC. For researchers, who present the results of their analyzes in the journal Geophysical Research Lettersthis discrete seismic signal is directly associated with the eruption and indicates that an event occurred very shortly before its triggering. And if it was precisely the element which caused the explosion of the boilerboiler ?
The opening of a breach in the oceanic crust
For researchers, it is totally possible. This precursor signal could have been produced by the opening of a fracture in the oceanic crustoceanic crust under the caldera of the already active volcano, around 3:45 a.m. While the magmamagma rises in the crack, sea water infiltrates there. However, the encounter between cold water and magma is particularly explosive! It is this meeting which could therefore have triggered the violent eruption of Hunga Tonga, at 4:00 a.m.
Results which help to understand the stages of this eruption, but which could also have implications in the early detection of underwater eruptions.
