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Panoramic view of the island from the disappointment. Credit: Antonio Álvarez Valero
A major volcanic eruption 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 scientists from the Institute of Earth Sciences Jaume Almera (ICTJA-CSIC). 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.
According to the new study, a volcanic caldera collapsed 3980 years ago. The emptying of the magma chamber, the area of accumulation of magma that fueled the eruption, during this violent eruptive event caused a sudden drop in pressure, triggering the collapse of the upper part of the volcano. As a result, a depression of eight to ten kilometers in diameter is formed, which now gives the Island of Deception its peculiar horseshoe shape. The collapse of the caldera was said to have caused a massive earthquake, the traces of which were recorded in the sediment accumulated in 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 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 the climatic fluctuations of this region over the last 11,700 years using various indirect indicators found in lake sediments. of the Byers Peninsula, about 40 km north of Deception Island, the presence of a different sediment layer in all lakes of 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 the whole area. and put us on the path that, perhaps, was not facing a common earthquake but generated by the collapse of the caldera of the Deception Island volcano.From 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 geochemical, petrological and paleolimnological techniques applied to sediment cores from four lakes on the Byers Peninsula, located on Livingston Island.
Panoramic view of Byers Peninsula, Livingstone Island. Credit: Santiago Giralt
These sedimentary records contained several direct and indirect evidence of the volcanic event on Deception Island. "The sedimentary records found showed a common pattern: first, the volcanic ash of the Deception Island eruption covered with a sediment layer of nearly a meter of ## 147 ## 39; thickness composed of materials dragged from the shores of lakes to their bottom because of the great earthquake, and finally, the lake's common sediments, which are characterized by alternating clays and mosses, "said Santiago Giralt.
One of the challenges 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 magmatic and eruptive episode," said Antonio Álvarez Valero, a researcher at the University of Salamanca ( USAL) and co-author of this document. study.
The study also estimates that the eruption had a volcanic explosion index (VEI) around six, making it probably the largest known Holocene eruptive episode on the Antarctic continent.
"This colossal episode of collapse of the eruptive caldera ejected between 30 and 60 cubic kilometers of ash, whose volume was comparable to that of the Tambora volcano of 1815, which is attributed to a cooling of the global temperature which resulted in a a series of poor harvests Europe, known as the "summer-less year," 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 eruption to understand the climatic changes caused by volcanic eruptions – in this particular case, at high latitudes Austral," adds the Geyer.
As suggested by the study, this eruption could have had significant climatic and ecological impacts over much of the southern region, although further studies and data are needed to accurately characterize the actual effects on the climate of this great eruptive event.
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More information:
Antoniades, D., Giralt, S., Geyer, A., Alvarez-Valero, AM, S. Pla-Rabes, I., Granados, I., Liu, EJ, M., Toro, M., Smellie, JL and Oliva, M. (2018). The moment and the generalized effects of the largest Holocene volcanic eruption in Antarctica. Scientific reports. (8) 1. DOI: 10.1038 / s41598-018-35460-x
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