2023-06-27 09:41:17
Thanks to the development of a new method, researchers from the University of Copenhagen may be able to answer several geological questions that are still unanswered and learn more regarding the great mysteries of our planet and its evolution. Before getting there, they first focused on the geological evolution of the longest mountain range in the world: the Andes. It was by using this new method of geological research that they were able to determine how this immense mountain range was formed…
Indeed, using a new method developed by one of the researchers from the University of Copenhagen, the team began to closely study the tectonic plate on which the Andes Mountains lie. They then discovered new elements explaining how this colossal mountain range might emerge from the interior of the Earth. The results of the study are published in the journal Earth and Planetary Science Letters.
The Andes – the world’s longest continental mountain range – stretches 8,900 kilometers along the western edge of South America and is up to 700 kilometers wide. It crosses a total of seven countries, starting in Venezuela, passing through Colombia, Ecuador, Peru, Bolivia and ending its route in Patagonia, southern Chile and Argentina.
The tectonic plates, which cover the surface of the Earth, move a few centimeters each year (regarding the same rate as our fingernails grow). These plates can sometimes speed up or slow down suddenly. Using their new method, the researchers were able to obtain more accurate estimates of the magnitude and frequency of plate velocity changes in the past.
The lithosphere, Earth’s outermost mobile layer, is divided into a small number of rigid moving plates on the asthenosphere, the part of the Earth’s mantle immediately below. This structuring controls geological phenomena such as earthquakes or volcanism. It also influences the climate of our planet (in particular via the mountain ranges and the long carbon cycle) and has played an essential role in the appearance and evolution of life (modification of the atmosphere, creation and drift of continents ).
By taking a close look at the case of the Andes Cordillera, the researchers’ new calculations show that the south american plate has suddenly and dramatically shifted gears and slowed down twice significantly in the past 15 million years. This slowdown may then have contributed to the widening of this immense mountain range.
“In the periods up to the two downturns, the plate immediately to the west, the Nazca Plate, pushed into the mountains and compressed them, causing them to grow. This result might indicate that part of the preexisting range acted as a brake on both the Nazca plate and the South American plate. As the plates slowed their speed, the mountains widened instead”explains Valentina Espinoza, lead author and doctoral student in the Department of Geosciences and Natural Resource Management.
How to explain the slowdown of the South American plate?
3D representation of South America with the Andes mountain range
© Saylowe / Pixabay – License: Pixabay
According to the results of the study, the South American plate slowed down by 13% during a period that occurred 10 to 14 million years ago, and by 20% during another period 5 to 9 million years ago. On the geological time scale, these changes are very rapid and abrupt.
There would be two main reasons for these sudden slowdowns. On the one hand, the researchers propose the hypothesis that the interaction between the expansion of the mountains and the lower velocity of the plates is due to a phenomenon called delamination. This means that much of the unstable material below the Andes broke off and sank into the Earth’s mantle, causing major readjustments in plate configuration.
So, according to this assumption, the Andes were caused to change shape and grew laterally. It was during these periods that the mountain range extended 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 regarding how this huge mountain range came to be. But there’s still a lot we don’t know. Why did it get so big? How fast did it form? How does the mountain range hold together? And will it eventually collapse?”asks Valentina Espinoza.
On the other hand, the researchers put forward a second possible hypothesis that the slowing of the plate might be caused by a change in the heat flux from the Earth’s interior – known as convection – which moved in the highest viscous layer of the mantle on which float tectonic plates.
A new standard method?
This new method of calculating changes in the motion of tectonic plates provides estimates with unprecedented precision. She uses high resolution geological data, generally used to calculate the motion of plates relative to each other. However, in this new method, that same data is used to calculate changes in plate motion relative to the planet itself.
The research team thinks it might become a standard method. “This method can be used for all plates, as long as high-resolution data are available. I hope that such a method will be used to refine historical models of tectonic plates and thus improve the chances of reconstructing geological phenomena that remain unclear to us”assures Giampiero Iaffaldano, while adding that: “If we can better understand the changes that have taken place in plate motions over time, we may have a chance to answer some of the greatest mysteries of our planet and its evolution. We still know so little regarding , for example, the temperature of the Earth’s interior, or roughly when the plates started moving. Our method can most likely be used to find pieces for this large puzzle.”
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