Science & Environment

Scientists May Have Solved The Mystery of How The Andes Got So Big : ScienceAlert

By any measure, the Andes mountains are very, very huge. Running for some 8,900 kilometers (5,530 miles) by means of South America, they attain as much as 7 kilometers (4.3 miles) in height and stretch as much as 700 kilometers (435 miles) in width.

But how did the vary develop to this gigantic scale? Plate tectonics – the motion of nice slabs of Earth’s crust throughout the planet – can create mountain ridges as slower sections are compelled up by quicker transferring areas.

Though the idea is easy in principle, monitoring the pace of tectonic actions throughout timescales shorter than 10 to 15 million years in period is difficult for geologists.

Researchers from the University of Copenhagen used a recently developed method to get a extra detailed have a look at the motion of the South American plate that shaped the Andes. They recognized a 13 p.c slowdown in elements of the plate round 10 to 14 million years in the past, and a 20 p.c slowdown 5 to 9 million years in the past – sufficient to clarify some of the options we see in the present day.

Tectonic plates map. (Ttsz/iStock/Getty Images Plus)

“In the periods up until the two slowdowns, the plate immediately to the west, the Nazca Plate, plowed into the mountains and compressed them, causing them to grow taller,” says geologist Valentina Espinoza from the University of Copenhagen in Denmark.

“This result could indicate that part of the preexistent range acted as a brake on both the Nazca and the South American plate. As the plates slowed down their speed, the mountains instead grew wider.”

The approach used within the examine begins with absolute plate motion (APM), the motion of plates in phrases of mounted factors on Earth. APM is usually decided by means of the examine of volcanic exercise within the crust, the place trails of magma inform geologists how the plates have shifted.

Then there’s relative plate motion (RPM), the motion of plates in relation to one another. This is calculated utilizing a broader vary of clues, together with magnetization information embedded within the ocean flooring signifying rock motion, and affords greater decision (smaller timescale) information than APM.

To decide the speed of motion within the South American plate, the geologists used the high-resolution RPM information to estimate APM through some detailed math. By validating predicted information with geological information that we’re positive of, the strategy permits consultants to know rather more concerning the interactions between tectonic plates.

“This method can be used for all plates, as long as high-resolution data is available,” says geologist Giampiero Iaffaldano, from the University of Copenhagen.

“My hope is that such methods will be used to refine historic models of tectonic plates and thereby improve the chance of reconstructing geological phenomena that remain unclear to us.”

The staff additionally thought-about the query of why these two important slowdowns occurred within the first place. While a couple of million years is a very long time to us, it is a digital eye-blink in geological time scales.

One risk is convection currents within the mantle modified, shifting totally different densities of materials round. It’s additionally doable {that a} phenomenon known as delamination was accountable, the place important elements of a plate sink decrease into the mantle. Both occasions would’ve had knock-on results that influenced the speed of the plate’s motion.

Further analysis and extra information goes to be wanted to know for positive, and the brand new technique of evaluation will assist with that. Even as one query is (maybe) answered, there are lots extra to work by means of.

“If this explanation is the right one, it tells us a lot about how this huge mountain range came to be,” says Espinoza.

“But there is still plenty that we don’t know. Why did it get so big? At what speed did it form? How does the mountain range sustain itself? And will it eventually collapse?”

The analysis has been printed in Earth and Planetary Science Letters.

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