ash cloud from the eruption of Pinatubo (Philippines) volcano in 1991, one of the most violent of the twentieth century. / Wikipedia
The current Iberian Peninsula suffered a gigantic volcanic eruption 477 million years ago, when it was located on the shore of a large continent called Gondwana and was near the south pole. The precise dating of a layer of volcanic ash preserved in the Cantabrian mountain range indicates that the rocks are coeval a vast area and, therefore, probably originated in the same eruption that by its large volume, must correspond to a supervolcano .
“We knew there was volcanic rocks in Asturias, Leon and Cantabria, but not considered a single layer. We have now shown that the same age and belonging to the same eruption, “said Gabriel Gutierrez Alonso, a researcher at the University of Salamanca and lead author of the study published in the journal Tectonophysics.
In their calculations conservative, scientists can ensure that the cover of ash covered at least 15,000 km2, equivalent to the province of Leon area. The eruption would have issued more than 80,000 million tons of rock into the atmosphere and the volume of ashes would have reached 60 km3, although later this pumice loses its original porosity and today is much more compact by the effect of weight rocks deposited above.
With these data, it would be a rash of “colossal” type, which in the Volcanic Explosivity Index (VEI, for its acronym in English) used by the experts reach a 6 on a scale of 1 to 8. In this classification, each value means that the eruption is 10 times more virulent than the lower value. For example, the Vesuvius that wiped out Pompeii has a VEI of 5 and expelled from 1-3 km3 of material into the atmosphere; and that of Mount Pinatubo (Philippines) in 1991 a VEI 6 more than 10 km3. In these cases, ash layers extend for hundreds or thousands of km2.
However, it is possible that the dimensions of supervolcano were much higher, since there is much more remote geographical areas with similar volcanic rocks that could also correspond to the same event. The scientists do not rule out an eruption of “mega-colossal” type, a VEI 7, with a volume of 600 km3 of ash and 900,000 million tons in current geographical terms, it would have reached across the north of the peninsula, from Galicia in the Iberian mountain range, in Aragon.
Even could have had a VEI 8 magnitude of “supervolcánicas-apocalyptic” characteristics, reaching Armorica (France) and Sardinia (Italy) project after 1000 km3 of ash the.
If air can not confirm the true size of the event is because there dating of volcanic rocks of the places where these have been studied are not as precise as those contained in this study, performed with samples taken from various parts of Asturias and Leon.
Indeed, the key to this research is the geochronological dating using radioactive isotopes in a mineral called zircon, which has determined that all samples have the same antiquity, that is 477 million years, with an uncertainty of a million years (an error of less than 0.25%).
This clarification has obtained the researcher Fernando Corfu in laboratories University of Oslo (Norway). In research also participated Juan Carlos Gutierrez Marco (IGEO-CSIC), Javier Fernández Suárez (Universidad Complutense de Madrid) and Enrique Bernardez (University of Atacama in Chile).
The layer of volcanic ash the Cantabrian mountain range can have a meter thick and is exploited to obtain a mineral called kaolin, used, among other things, to obtain high-quality ceramic products.
According to the researcher Gabriel Gutierrez Alonso, was just one of these farms, in Mina Conchita, where they were stolen the explosives used in the Madrid attacks of March 11 in 2004. This Asturian enclave also be one of the samples for this research.
“Yellowstone is the most famous and the one most likely to be the next to return to star in a supervolcánica eruption, although it can occur in the environment of the Pacific,” says geologist
Two others were also taken in Asturias, in an old farm in Peñaflor, near Grado, and Caravia (during tunneling “Ordovician” the Fabar); and in the swamp of Barrios de Luna, Leon.
Yellowstone can be as follows
The volcanic eruptions of “cataclysmic magnitude” occur relatively frequently, between 10,000 and 100,000 years and only last weeks or months. The last supervolcano known is the Toba, on the island of Sumatra (Indonesia), whose eruption 74,000 years ago had great climatic effects on the planet.
In the United States, the Yellowstone caldera has erupted three times in the last two million years. The last time was 640,000 years ago. “It is probably the most famous and the one most likely to be the next to return to star in a supervolcánica eruption, although it can occur in the environment of the Pacific,” says geologist at the University of Salamanca.
According to experts, a senior, there is less chance of distinguishing an event such as ash deposits of thick covering huge areas that are often erode and end up being very difficult to recognize. For example, in Europe the most similar to this supervolcano northern Spain would have to be found in Scandinavia only 14 million years later.
As for the implications for life on the planet, volcanic cataclysms more Recent assumed no major global extinction. In the case of the Iberian Peninsula, at that time there was not even life colonizing the surface of continents, oceans alone.
The layer of ash cover large areas of the shallower parts of an ocean that was being formed at that time, called Rheico, and probably destroyed life forms living on the seabed throughout the affected region. Although the ash would have remained in the atmosphere for years, altering its composition, the absence of life outside the waters would have minimized the impact of these changes.
In addition, scientists believe that there was a recovery immediate life after the deposit of ashes in the bottom of the sea. The proof is that in all the places where the ashes recognize a layer that you can see lots of cylindrical holes made by living organisms in sediments, vertical in origin, called Skolithos is.
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