Huge Earthquake Swarm Detected in Antarctica as Inactive Volcano Awakens

A huge earthquake swarm was detected in Antarctica, which researchers say was likely the result of a long-dormant volcano awakening.

An earthquake swarm refers to incidents in which many seismic events occur in the same small area over a relatively short period of time without an accompanying main shock.

According to a study published in the Nature journal Communications Earth & Environment, the swarm affected the Bransfield Strait—a body of water around 60 miles wide that is located between the northwestern tip of the Antarctic Peninsula and the South Shetland Islands.

An iceberg in the Bransfield Strait, Antarctica
Stock image showing an iceberg floating in the Bransfield Strait, a body of water located off the northwestern tip of the Antarctic Peninsula. iStock

The swarm began in August 2020, with 128 quakes exceeding 4.0 on the moment magnitude (Mw) scale—a way to measure the power of earthquakes. Readings are generally similar to those of the Richter scale.

During the early phase of the swarm, 3,186 quakes were recorded—and it peaked with two large events on October 2 and November 6 that measured Mw 5.9 and 6.0 respectively.

After these events, the swarm tapered off and by February 2021, seismic activity in the area was substantially reduced, the authors of the study said.

In total, around 85,000 earthquakes were recorded over the course of the swarm, occurring close to the Orca underwater volcano, which scientists had previously considered to be inactive.

The underwater volcano (or seamount) consists of a nearly circular cone measuring nearly 7 miles across at the base and a crater measuring around 2 miles wide, according to the study. It has a height of around 2,950 feet.

The international team of researchers said the swarm was the most intense earthquake activity ever recorded in the region.

"There have been similar intrusions in other places on Earth, but this is the first time we have observed it there," study co-author Simone Cesca, a seismologist at the GFZ German Research Centre for Geosciences, told Live Science.

"Normally, these processes occur over geologic time scales," as opposed to over the course of a few months, Cesca said. "So in a way, we are lucky to see this."

The scientists used a variety of methods to track the swarm and its geophysical effects, including analyzing data from seismic stations in the region and satellites orbiting the Earth.

This data shed light on the potential causes of the huge swarm. According to the researchers, the movement of magma into the crust could explain the seismic activity.

The researchers said an eruption of the seafloor volcano was "likely" around the time of the magnitude 6.0 earthquake. But there is currently no direct evidence that this occurred and further research would be needed to confirm this.

While it may seem like Antarctica is totally devoid of volcanic activity, there is substantial evidence of volcanoes below the Antarctic Ice Sheet, according to NASA's Climate Change and Global Warming website. Some of these are currently active or have been in the recent geologic past.

The exact number of volcanoes in Antarctica remains a mystery but one recent study identified 138 of them in West Antarctica alone. Despite this, it appears from the available evidence that there have been no dramatic volcanic eruptions in the region in the recent geologic past.

It is important to note, however, there is a lack of data regarding volcanism in many parts of Antarctica because the continent is covered in ice and the remoteness of many of the volcanoes makes studying them a challenge.

The international team of researchers taking part in the study come from the GFZ German Research Centre for Geosciences Potsdam in Germany, the Italian National Institute of Oceanography and Applied Geophysics, the Polish Academy of Sciences' Institute of Geophysics, the Missouri University of Science and Technology, and the German Aerospace Center.