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A major volcanic eruption has rocked Deception Island in Antarctica 3,980 years ago, and not 8,300, as previously thought, according to an international study published in Scientific reports, which was attended by researchers from the Institute of Earth Sciences Jaume Almera. This event was the largest eruption of the southern continent during the Holocene (the last 11,700 years after the last great glaciation on Earth) and was comparable in volume to the Tambora volcano eruption in 1815. The eruption has formed the caldera of the volcano, one of the most active of the Antarctic, with more than 20 eruptions recorded over the past 200 years.
In the study, whose first author was Dermot Antoniades, from Laval University, Canada, participated researchers from the Universities of Barcelona (UB), Salamanca (USAL) and Cambridge and Leicester (UK) , CREAF, the Center for Research and Monitoring and Evaluation of the Sierra de Guadarrama National Park and the Center for Hydrographic Studies (CEDEX).
According to the age published in this new study, a type of caldera volcanic eruption collapse occurred 3980 years ago. The emptying of the magma chamber, the area of accumulation of magma that fueled the eruption, caused during this violent eruptive event a sudden pressure drop which in turn caused the collapse of the upper part of the volcano. As a result, a depression of 8 to 10 kilometers in diameter was formed, which today gives the island of Deception its particular shape horseshoe. The collapse of the caldera would have caused a large-scale seismic event whose trace was recorded in the sediment accumulated at the bottom of the lakes of Livingstone Island.
The lake sediment cores were recovered during the HOLOANTAR project's Antarctic campaigns, between 2012 and 2014. This field work was led and coordinated by Marc Oliva, then a researcher at the Institute of Geography and Cultural Heritage. the University of Lisboa and now researcher Ramon y Cajal at University of Barcelona (UB). Oliva is co-author of this study.
"The initial objective of the study was purely climatic because we wanted to reconstruct the climatic fluctuations of this region over the last 11,700 years using various indirect indicators found in lake sediments. from the Byers Peninsula, about 40 km north of Deception Island .. the presence of a different sediment layer in all lakes and the same age after a thick layer of tephra surprised us Said Sergi Pla, researcher at CREAF and co-author of the study.
"Subsequent geochemical and biological analyzes indicated that these sediments had a terrestrial origin and were deposited abruptly in the bottom of the lake.These results suggest the presence of a major earthquake that affected this whole area; on the track that we may not be facing a common earthquake, but caused by the collapse of the caldera of Deception Island volcano .. From there we pulled the wire, "said Santiago Giralt, researcher at ICTJA-CSIC and co-author of the study.
The exact date of the eruption was obtained using various geochemical, petrological and paleolimnological techniques applied to sediment cores from 4 lakes in the Byers Peninsula, located on Livingston Island.
These sedimentary records contained several direct and indirect evidence of the volcanic event on Deception Island. "The sedimentary records found show a common pattern: firstly the volcanic ash from the Deception Island eruption, covered with a near sediment layer. a meter thick composed of materials dragged from the shores of lakes to their bottom due to the great earthquake and finally, common lacustrine sediments, characterized by an alternation of clays and mosses, "explained Santiago Giralt.
One of the challenges of this study was to characterize the origin of the ash produced during the volcanic eruption. For this, the conditions of pressure and temperature of the magmas at the origin of this eruption were calculated using the ashes present in the sediment cores. "Using this methodology, we were able to estimate the depth of all the samples studied and determine whether they were part of the same magma and the same eruptive episode," said Antonio Álvarez Valero, a researcher at the University of Salamanca (USAL) and co-author of this study.
The study also estimates that the eruption had a volcanic explosion index (VI) around 6, making it probably the largest known Holocene eruption episode on the Antarctic continent.
"This colossal episode of collapse of the eruptive caldera ejected between 30 and 60 cubic kilometers of ash, of a volume comparable to that of the Tambora volcano in 1815, which is attributed to a cooling of the global temperature which led to a series of poor harvests Europe, known as "year without summer" says Adelina Geyer, researcher at ICTJA-CSIC and co-author of the study.
"It is very important to be able to date this type of eruptions that allow us to understand the climatic changes caused by volcanic eruptions, in this particular case at the southern high latitudes," adds the Geyer.
As suggested by this study, this eruption could have had significant climatic and ecological impacts in much of the southern region, although more studies and new data are needed to accurately characterize the actual effects on the climate. of this great eruptive event.
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