A giant volcano in Yellowstone National Park was created far from fault lines and other geological "hotspots" due to the sinking of a destroyed continental plate under the western part of the future United States, according to an article published in the journal Nature Geoscience.
“The heat needed to trigger volcanic processes is usually found in those points on the Earth where tectonic plates collide, and one of them goes into the bowels of the planet. Yellowstone and other volcanoes in the western United States are located far from the coast where the plate boundary passes. Our colleagues believed that the "engine" of their eruptions were the so-called plumes - hot currents of magma rising from the mantle to the planet's crust,”says Lijun Liu of California State University in San Diego (USA).
Yellowstone supervolcano today is a giant funnel 72 kilometers long and 55 kilometers wide, which is located in the national park of the same name in Wyoming. In the middle of the last century, scientists found out that this depression is the mouth of an ancient volcano, with a giant magma chamber located at a depth of about 8 kilometers.
Further observations of Yellowstone showed that it has erupted several times over the last million years, and that these eruptions were catastrophic in nature, capable of changing the planet's climate. On the other hand, scientists have not been able to find an obvious source of its lava and magma, which makes geologists today fiercely debate the possible reason for the appearance of a giant volcano in this part of the United States.
Liu and his colleagues tested all these theories by studying the structure of the interior of Yellowstone and its surroundings using the so-called "seismic tomograph" - a special device capable of revealing the structure and composition of deep layers of rocks by how seismic vibrations of different types pass through them.
These data alone cannot give an accurate picture of how the Earth's interior is arranged at one point or another - as a rule, scientists compare them with computer models of the crust and mantle and how vibrations generated by earthquakes and explosions would pass through them.
Guided by this idea, Liu's team compiled several dozen computer models based on the hypotheses of other geologists about the origin of Yellowstone, and rewound time 20 million years ago, when the progenitor of this volcano supposedly arose. Comparing the results of these calculations and real seismic data, scientists tried to understand which idea is closer to the truth.
As it turned out, the generally accepted theory of the "plume" origin of the main American supervolcano did not correspond to reality - the heat fluxes that appeared in most similar models of Yellowstone did not flow up, but down, towards the interior of the planet, or came to the surface in the wrong place.
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The real source of heat needed to "launch" Yellowstone, according to Liu and his colleagues, is in the near-surface layers of the mantle in the northeastern United States, and is one of the fragments of the so-called Farallon tectonic plate. In the distant past, it covered part of the Pacific Ocean floor and fell apart even in the days of the dinosaurs.
Its fragments continue to sink deep into the interior of the Earth today, and some of them, as scientists show, could have generated a supervolcano in Wyoming and other foci of volcanism that arose in the western United States in the last 20 million years. This same idea, Liu notes, fits well with the Farallon Plate-related "lava flood" trails in the western United States that his team discovered two years ago.
To test this idea, Liu and his colleagues believe, is quite simple - for this it is enough to analyze the chemical composition of the rocks from Yellowstone and compare them with typical plume emissions. American geologists are planning to do this in the near future.