How did the Andes get so huge?

14 Apr. (EUROPE PRESS) –

Two abrupt changes that slowed down the dynamics of the South American tectonic plate in the last 15 million years could contribute to the unequaled widening of the Andes Mountains.

How did the Andes, the world’s longest mountain range, reach its enormous size? A new method developed by researchers at the University of Copenhagen allows estimating how the Earth’s tectonic plates have changed speed in the last million years.

Surprisingly, the two sudden slowdowns detected by these scientists occurred between periods when the Andes mountain range it was compressed and growing rapidly in height:

“In the periods leading up to the two slowdowns, the plate immediately to the west, the Nazca Plate, dipped into the mountains and compressed them, making them grow taller. This result could indicate that part of the pre-existing ridge acted as a brake on both both the Nazca plate and the South American plate. As the plates slowed down, the mountains widened,” he explains. it’s a statement first author and PhD student Valentina Espinoza from the Department of Geosciences and Natural Resources Management.

According to the new study, the south american plate slowed down 13% during a period that occurred 10-14 million years ago, and 20% during another period 5-9 million years ago. In geologic time, these are very rapid and abrupt changes. According to the researchers, there are mainly two possible reasons for the sudden slowdown in South America.

One could, as mentioned, be related to the spread of the Andes, where the pressure eased and the mountains widened. The researchers hypothesize that the interaction between the expansion of the mountains and the slower speed of the plate was due to a phenomenon called delamination. That is to say, a large amount of unstable material beneath the Andes broke off and sank into the mantle, causing important readjustments in the plate configuration.

This process caused the Andes to change shape and grow laterally. It was during these periods that the mountain range expanded into Chile to the west and Argentina to the east. As the plate accumulated more mountain material and became heavier, the movement of the plate slowed.

“If this explanation is correct, it tells us a lot about how this huge mountain range formed. But there’s still a lot we don’t know. Why did it get so big? How fast did it form? How is the chain holding up? mountainous, and will it eventually collapse, says Valentina Espinoza.

According to the researchers, who publish results in Earth and Planetary Science Letters, another possible explanation for why the plate slowed down is that there was a change in the pattern of heat flow from the Earth’s interior, known as convection, which moved into the viscous upper layer of the mantle on which the plates float. tectonics. above. That change manifested itself as a change in the motion of the plate.

Researchers now have the information and tools to start testing their hypotheses through modeling and experimentation.