The giant volcano in the Yellowstone National Park arose far from the fault lines and other geological “hot spots” due to the immersion of the dead continental plate under the western part of the future US.
“The heat needed to start volcanic processes is usually found at those points of the earth where tectonic plates collide, and one of them goes into the bowels of the planet.” Yellowstone and other volcanoes in the west of the USA are located far from the coast where the boundary between the plates passes. believed that the “engine” of their eruptions are the so-called plumes – the hot currents of magma rising from the mantle to the crust of the planet, “says Lijun Liu of the University of California in San Diego, USA.
Yellowstone super-volcano today is a giant funnel 72 kilometers long and 55 kilometers wide, which is located on the territory of the homonymous national park in the state of Wyoming. In the middle of the last century, scientists found 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 have shown that it has erupted repeatedly over the last million years, and that these eruptions were catastrophic, capable of changing the planet’s climate. On the other hand, scientists could not find the obvious source of his lavas and magma, which makes geologists today fiercely argue about the possible reason for the appearance of a giant volcano in this part of the United States.
Liu and his colleagues checked all these theories by studying the structure of the bowels of Yellowstone and its environs with the help of the so-called “seismic tomograph” – a special device capable of revealing the structure and composition of deep layers of rock by how seismic vibrations of different types pass through them.
These data alone can not provide an accurate picture of how the Earth’s interior is located at one or another point – 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 made dozens of computer models based on the hypotheses of other geologists about the origins of Yellowstone, and “rewound” the time 20 million years ago, when the progenitor of this volcano supposedly originated. 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 conventional theory about the “plume” origin of the main American super volcano was not true – the heat flows that appeared in most similar models of Yellowstone flowed not upwards, but downwards, toward the bowels of the planet, or came to the surface not where needed.
The real source of heat necessary for the “launch” of 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. It covered in the distant past part of the bottom of the Pacific Ocean and disintegrated during the time of the dinosaurs.
Its fragments continue to plunge deep into Earth’s interior and today, and some of them, according to scientists’ calculations, could produce a super volcano in the state of Wyoming and other volcanic foci that arose in the western United States in the last 20 million years. The same idea, as Liu notes, is in good agreement with those traces of the “lava floods” in the west of the United States associated with the Faralon plate, which his team discovered two years ago.
To check this idea, as Liu and his colleagues believe, it is quite simple – for this it is enough to analyze the chemical composition of the rocks from Yellowstone and compare them with the typical emissions of plumes. American geologists plan to do it in the near future.