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A dormant volcano opened its eyes and generated a swarm of earthquakes in Antarctica

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A long-dormant underwater volcano near Antarctica woke up in 2020, triggering a swarm of 85,000 earthquakes from then until today. This is the strongest seismic activity ever recorded in the region: the earthquakes were probably caused by a “finger” of hot magma penetrating the Earth’s crust, according to a new study.

Researchers from different parts of the world, led by the scientist Simone Cesca, from the German Research Center for Geosciences (GFZ) in Potsdam, describe in an investigation recently published in the journal Communications Earth & Environment how a volcano submarine that was reactivated in 2020 caused the greatest seismic activity recorded so far in Antarctica: 85,000 earthquakes have been verified to date.

something never seen

The earthquake swarm it began in August 2020 and began to decline in November of that year: in that short period, two earthquakes of greater intensity stood out among the large number of seismic episodes. As the researchers explain in an article published in Science Alert, although similar series have been recorded in other parts of the planet, it is the first time that something like this has been documented in Antarctica.

One of the two strongest earthquakes reached a magnitude of 5.9 on the Richter scale and developed in October 2020. Meanwhile, a magnitude 6.0 earthquake it took place in November of the same year, just before the violent series of seismic movements began to decay. According to records, the earthquakes managed to move the ground on King George Island about 11 centimeters.

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As the scientists detailed in the study, only 4 percent of that displacement could be explained directly by the earthquake: on the contrary, it is suspected that the movement of magma towards the crust explains more accurately the dramatic change in the ground. The researchers believe that the magnitude 6 earthquake created some fractures and reduced the pressure of the magma dam. Even at that time there could have been a underwater eruption in the volcano, a fact that has not yet been confirmed.

Something intense is happening under Antarctica

The series of earthquakes took place in the vicinity of the orca seamount, a dormant volcano that rises 900 meters from the seafloor in the Bransfield Strait. It is a narrow passage between the South Shetland Islands and the northwestern tip of Antarctica. According to a previous study published in 2018, in that area the Phoenix tectonic plate submerges below the continental Antarctic plate: this creates a network of fault zones, stretching some portions of the crust and opening cracks in other places.

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Although these geological features raised the possibility of seismic events at any time, scientists did not expect them to develop with such intensity. In addition, the experts highlighted that these processes usually occur in geological time scales and not in the course of a human life: much less in a period of less than two years.

Perhaps the most alarming thing about the new study is that the scientists found episodic magmatic intrusions in the Bransfield Strait: this provides unique information about the active continental breakup in that part of the planet. In other words, they will have to continue investigating to see if the seismic swarm, a name that indicates a set of earthquakes in the same area and in a short period of time, is related to still unknown and more intense geological processes.

Reference

Massive earthquake swarm driven by magmatic intrusion at the Bransfield Strait, Antarctica. Cesca, S., Sugan, M., Rudzinski, Ł. et al. Communications Earth & Environment (2022). DOI:https://doi.org/10.1038/s43247-022-00418-5

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