How did the Andes, the longest mountain range in the world, reach its enormous size?

Two abrupt changes that slowed down the momentum South American tectonic plate over the past 15 million years, they may have contributed to the unprecedented expansion of the Andes.

A new method, developed by researchers at the University of Copenhagen, allows us to estimate how quickly the Earth’s tectonic plates have changed over the past few million years.

Surprisingly, the two sudden slowdowns these scientists discovered occurred between periods when Andes mountains it was compressed and grew rapidly in height.

“During the periods leading up to the two slowdowns, the plate immediately to the west, the Nazca plate, plunged into the mountains and compressed them, causing them to grow higher. This result may indicate that part of the pre-existing ridge acted as a brake. both on the Nazca plate and on the South American plate. As the plates slowed down, the mountains expanded,” explains first author and doctoral student Valentina Espinoza, from the Department of Geosciences and Natural Resources Management, in a statement.

According to a new study, the S American Plate slowed down by 13% during a period that occurred 10-14 million years ago, and by 20% during another period 5-9 million years ago. In geological time, these are very rapid and abrupt changes. According to the researchers, there are basically two possible reasons for the sudden slowdown in growth. South America.

Theories about it

As mentioned, this may be related to the extension Andeswhere the pressure eased and the mountains expanded. The researchers suggest that the interaction between the expansion of the mountains and the slower plate speed was due to a phenomenon called delamination. That is, a large amount of unstable material below Andes it broke off and plunged into the mantle, causing a major change in the configuration of the plates.

This process made Andes change shape and grow sideways. It was during these periods that the mountain range expanded into Chile in the west and Argentina in the east. As the slab accumulated more rock material and became heavier, the movement of the slab slowed down.

“If this explanation is correct, it tells us a lot about how this huge mountain range formed. But we still don’t know much. Why did he get so big? How quickly did it form? “mountainous and eventually it will collapse,” says Valentina Espinosa.

According to the researchers who published the results in Earth and planetary science letters, another possible explanation for why the plate has slowed down is that there has been a change in the heat flow pattern from the Earth’s interior, known as convection, that has moved into the viscous upper mantle on which the plates float. higher. This change manifested itself as a change in the movement of the cymbal.

Researchers now have the information and tools to start testing their hypotheses through simulations and experiments. (Europe Press)

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