It took place in northern Argentina and the ashes were scattered over an area as large as Spain.
The largest volcanic eruption in the last 5,000 years on Earth it took place in the Cerro Blanco volcanic complex in the central Andes, in Argentina. The analysis of the volcanic ash deposits present in an extensive region of the northwest of said country allowed the researchers to reconstruct the dynamics and scope of this great eruption.
The Cerro Blanco Volcanic Complex, located in the extreme south of the Andean highlands, erupted about 4,200 years ago. It was not just any eruptive episode. It was the largest eruption that occurred in the last 5,000 years in the Central Volcanic Zone of the Andes.
The volume of rock ejected also places it among one of the largest eruptions that occurred during the Holocene (the last 11,700 years). This was established by a study carried out in 2019 by a Spanish and Argentine research team. In the work, directed by José Luis Fernández Turiel, from the Jaume Almera Institute of Earth Sciences of the CSIC (ICTJA-CSIC), personnel from various universities and scientific institutions from both countries participated.
The Cerro Blanco Volcanic Complex, located in the Argentine province of Catamarca, was the source of extensive volcanic ash deposits, still recognizable in a wide area of the Andean highlands, of which until now its existence was known, but not its origin.
“It was possible to confirm that the eruption that occurred in Cerro Blanco was the one that generated these large Holocene ash deposits that cover a large area of the Puna and neighboring areas of northwestern Argentina,” explained José Luís Fernández Turiel.
Reconstruction with digital simulations
In addition, due to the plant remains present in the sediments adjacent to the ash layers studied, it was possible to determine by means of carbon 14 that the eruption took place 4,200 years ago.
Through digital simulations, the transport and fall of the ash was also reconstructed. The eruption of Cerro Blanco It was explosive in nature and its violence was such that the ashes were scattered over an area of about 500,000 km.2, an area equivalent to that of Spain. In fact, ashes from this eruption have been found 400 kilometers away from the volcano, near the town of Santiago del Estero.
Likewise, the pyroclastic flows that occurred filled the adjacent river valleys with thick deposits of ignimbrites, reaching a distance of about 35 kilometers from Cerro Blanco. The emptying of the magma chamber caused by this eruption caused the subsequent collapse of the volcanic edifice, forming a complex volcanic caldera.
“The geodynamic context of the area determines that they are very explosive eruptions. They are eruptions of rhyolitic magma, with a lot of silica and a very high gas content,” explains Francisco José Pérez Torrado, from the Institute of Environmental Studies and Natural Resources of the University of Las Palmas de Gran Canaria (IUNAT-GEOVOL). According to Pérez Torrado, “the eruption was not annular, following the edge of the caldera, but was concentrated at a point on this edge, it was explosive and created a very tall eruptive column, almost 32 kilometers high according to our simulations & rdquor ;.
The volume of ash deposited by this eruption was more than 170 km3which allows the authors of the study to estimate that the Cerro Blanco eruption had a Volcanic Explosivity Index (VEI) of 7. A VEI of these characteristics places the Cerro Blanco eruption among the largest volcanic events recorded in recent years. 10,000 years: it is similar to the one that occurred on the island of Santorini that marked the end of the Minoan civilization and with a volume of magma that doubles that of the eruption of the Tambora volcano in 1815, an event attributed to a cooling of global temperatures .
Differences in the behavior of northern and southern eruptions
Fernández-Turiel added that the discovery “changed the model of active volcanism in the Andean zone. Until now, it was thought that in the Central Volcanic Zone everything worked exactly the same as in the southern zone: many volcanoes with many eruptions over time. What we have seen here is that there are few eruptions, but with a large volume of magma and very high explosiveness.”.
This finding offers researchers an excellent temporal guideline for the study of many geological, archaeological, and paleoclimatic features, among others, that occurred around the mid-Holocene over a wide geographic area of South America.
According to Norma Ratto, an archaeologist at the Institute of Cultures of the University of Buenos Aires, “determining the scope and occurrence of this great eruption provides new information to interpret different aspects of the hunter-gatherer societies that inhabited the sector southwestern Argentina throughout the Holocene, such as the differential occupation of spaces, changes in the mobility of groups due to the modification and alteration of circulation routes that allowed the connection between different ecological levels, changes in ecosystems and the health of pre-Hispanic populations, among others& rdquor;.
Reference study: https://estudiosgeol.revistas.csic.es/index.php/estudiosgeol/article/view/982/1200%20
…….
Contact of the Environment section: [email protected]