A major volcanic eruption shook Bedömningsö, Antarctica, 3,980 years ago, and not 8,300, as previously adopted, according to an international…
A major volcanic eruption shook Bedömningsö, Antarctica, 3,980 years ago, and not 8,300, as previously adopted, according to an international study published in Scientific Reports where scientists from the Institute of Earth Sciences Jaume Almera have attended. This event was the largest outbreak on the Australian continent during the Holocene (the last 11 700 years after the last Great Ice Age on Earth) and was comparable in the volume of rocked rock to the tomb of Tambora in 1815. The outbreak formed the caldera of the volcano, one of the most active in Antarctica, with more than 20 eruptions registered in the last 200 years.
In the study, whose first author was Dermot Antoniades, from the University of Laval, Canada has participated in researchers from the University of Barcelona (UB), Salamanca (USAL) and Cambridge and Leicester (UK), CREAF, Research and Monitoring and Evaluation Center of the Sierra de Guadarrama National Park and the Center for Hydrographic Studies (CEDEX).
According to the age published in this new study, a volcanic eruption scale collapsed 3980 years ago. The emptying of the magmatic chamber, the magma accumulation zone that caused the outbreak during this violent outbreak caused a sudden pressure drop, which in turn caused the collapse of the upper part of the volcano. As a result, a depression between 8 and 1
0 kilometers in diameter was formed, which today gives Deception Island its special horse shoe. The cold collapse would have caused a large-scale seismic event whose traces were recorded in the sediments accumulated in the lakes of Livingstone Island.
Lacustric sediment cores were recovered during the Antarctic campaigns from the HOLOANTAR project between 2012 and 2014. This field work was led and coordinated by Marc Oliva, since researcher at the Instituto de Geografia e Ordenamento at the University of Lisbon and now Ramon y Cajal researcher at the University of Barcelona (UB). Oliva is co-author of this study.
“The original purpose of the study was purely climatic because we wanted to reconstruct climate fluctuations in this region for the last 11,700 years using different proxies found in the settlements at the city center, about 40 kilometers north of Deception Island, but the presence of another sediment layers in all lakes and the same age after a thick tephralag has surprised us, “says Sergi Pla, scientist at CREAF, and co-author of the study.  “Later geochemical and biological analyzes indicated that these sediments had soil and deposited abruptly in the lake. These results suggested the existence of a major earthquake that affected all this area, setting us on the path that we may not face a normal earthquake , but that generated by the collapse of the volcano Deception Island volcano. From here we pulled the thread, explained Santiago Giralt, researcher at ICTJA-CSIC and co-author of the study.
The exact date of the eruption was achieved using different geochemical, petrological and paleolimnological techniques used on the sediment cores from 4 lakes in the city center of Livingston Island.
These sedimentary records contained several direct and indirect evidence of the volcanic event that occurred in Deception Island. “The restored sediment posts showed a common pattern: first volcanic ash from Deception Island eruption, island deposited by a sediment layer almost one meter thick composed of material dragged from the lakes’ beaches to the bottom due to the great earthquake and, finally, plain sea sediment, characterized by a change of clays and mosses, explained Santiago Giralt.
One of the challenges facing this study was to characterize the origin of ashes produced during the volcanic eruption. For this, the pressure and temperature ratios of the stomachs derived from this eruption were calculated using the ash contained in the sediment cores. “Using this method, we were able to estimate the depth of all the samples examined and to determine if they were in the same magma and eruption episode,” said Antonio Álvarez Valero, researcher at Salamanca University (USAL) and co-authors of this study.
The study also estimates that the eruption had a volcanic explosive index (VEI) about 6 which possibly makes it the largest known Holocene eruptive episode on the Antarctic continent.
“This colossal episode of eruptive caldera collapse emitted between 30 and 60 cubic meters of ash, comparable in volume to the outburst of the Tambora volcano 1815, an event related to a global temperature cooling that resulted in a series of bad crops in Europe, in so-called “year without summer,” explains Adelina Geyer, ICTJA-CSIC researcher and co-author of the study.
“It is very important to be able to judge this kind of outbreak that allows us to understand climate change caused by volcanic eruptions, in This particular case at high Australian latitudes, “adds Geyer.
As suggested by this study, this outbreak could have had significant climate and ecological effects in a large area in the southern region, although more studies and new tasks are needed to accurately characterize what the real impact on the climate for this major outbreak event.