Underwater volcano in Antarctica triggers 85,000 earthquakes

A long-dormant underwater volcano has woken up, causing a swarm of earthquakes.

The swarm, which began in August 2020 and ended in November 2020, was the strongest earthquake activity ever recorded in the region. New research shows that the earthquakes were caused by hot magma poking into the crust.

There have been similar intrusions in other places on Earth, but this is the first time we have observed it there, according to study co-author Simone Cesca.

The Orca Seamount is an inactive volcano that rises 2,950 feet (900 meters) from the seafloor in the Bransfield Strait, a narrow passage between the South Shetland Islands and the northwestern tip of Antarctica. According to a study in the journal Polar Science, the Phoenix tectonic plate is diving beneath the continentalAntarctic plate, creating a network of fault zones, stretching some portions of the crust and opening rifts in other places.

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Scientists at the research stations on King George Island were the first to feel small earthquakes. Word got back to Cesca and his colleagues around the world that they were collaborating on separate projects with the researchers on the island.

The team wanted to understand what was going on, but King George Island is remote, with just two seismic stations nearby. The data from the two ground stations for the global satellite navigation system were used by the researchers to measure ground displacement. The study authors reported in the journal Communications Earth and Environment that they looked at data from more far flung seismic stations and from satellites circling Earth that use radar to measure shifting at ground level.

The nearby stations were good for detecting small earthquakes. More distant stations use more sophisticated equipment that can give a more detailed picture of the larger earthquakes. Cesca said that the team was able to create a picture of the underlying geology that triggered the earthquake swarm.

In October 2020 there was a magnitude 5.9 earthquake and in November there was a magnitude 6.0 earthquake. Seismology waned after the November earthquake. The study found that the ground on King George Island moved by 4.3 inches. The scientists think the movement of magma into the crust is the cause of the dramatic shifting of the ground.

Cesca said that the magnitude 6 created some cracks and reduced the pressure of the magma dike.

If there was an underwater eruption at the seamount, it probably happened at that time. To confirm that the massive shield volcano blew its top, scientists would have to send a mission to the strait to measure the bathymetry, or seafloor depth, and compare it to historical maps.

It was originally published on Live Science.