Scientists Finally Have A Date For The Massive Volcano Eruption That Forged Antarctica's Deception Island

Alexandra Lozovschi (old)

Nestled within Antarctica's South Shetland archipelago, the remote Deception Island is considered to be the largest active volcano in the Antarctic Peninsula.

The entire island was forged during a massive volcanic eruption which gave it its trademark horseshoe shape — an explosive event so powerful that it caused the volcano to collapse onto itself and ended up carving a five-mile-wide depression in the center of the island.

Once the caldera filled with ocean water, Deception Island became the enigmatic landscape we know today — "a horseshoe-shaped ring of rock surrounding a flooded bowl," as Forbes describes it. While volcanologists have known for quite some time about the island's violent beginnings, the timeline of this cataclysmic eruption had largely remained a puzzle — that is, until now.

Previous estimations placed the volcanic eruption sometime around 10,000 years ago, as shown in this report by National Geographic. However, the estimated time window of this calamitous event ranged from the Late Pleistocene some 126,000 years ago until very recently in our planet's history — just a few thousand years before present times.

The mystery has finally been put to rest by a team of climatologists, reports In a study published last week in the journal Scientific Reports, the team argues that the massive volcano eruption which shaped Deception Island occurred 3,980 years ago — give or take a century.

The expedition, carried out between 2012 and 2014, led them to stumble upon an unexpected find — a thick layer of volcanic debris discovered in four lakebeds some 25 miles away from Deception Island. Made up of volcanic ash deposits, the debris was found under two distinct layers of younger sediment — mysteriously arranged after the same pattern in all the four instances.

As detailed by study co-author Santiago Giralt, the volcanic ash was dug up from under a 40-inch-thick layer of displaced material "dragged from the lakes' shores" and which fell to the bottom after a "large earthquake" — topped by a fresh layer of "common lake sediments" that typically accumulates in this type of ecosystem.

Subsequent geochemical and biological analyses revealed that the volcanic debris originated on land and formed abruptly during the same violent eruption. Moreover, the scientists were able to establish that the samples had a similar chemical makeup as other material largely believed to have formed during the violent outburst that put Deception Island on the map — literally.

"These results suggested the occurrence of a major earthquake that affected the entire area, and put us on the track that, perhaps, we were not facing a common earthquake — but one generated by the collapse of the caldera of the Deception Island volcano. From here on, we pulled the thread," said Giralt, who is a researcher at the Institute of Earth Sciences Jaume Almera (ICTJA-CSIC) in Barcelona, Spain.

"This colossal episode of eruptive caldera collapse ejected between 30 and 60 cubic kilometers of ash [roughly seven to 14 cubic miles], comparable in volume to the eruption of the Tambora volcano in 1815 — an event that is attributed to a global temperature cooling that resulted in a series of bad harvests in Europe, in what is known as the 'year without summer,'" explained study co-author Adelina Geyer, also from ICTJA-CSIC.

The recent findings place the event a lot closer to present day than we previously imagined. As Geyer pointed out, dating the eruption of Deception Island is vital to our understanding of how the region's climate changed throughout the ages — particularly since a volcanic eruption of that magnitude would have affected the climate of not just Antarctica, but other areas of the Southern Hemisphere as well.

"It is very important to be able to date this type of eruption to understand the climatic changes caused by volcanic eruptions — in this particular case, at high austral latitudes."