A team of geologists from the University of Copenhagen in Denmark has developed a new method of study to analyze the tectonic plate that underlies the Andes Mountains in South America. This method has made it possible to estimate with unprecedented accuracy how tectonic plate velocities have changed over the past millions of years. High-resolution geological data have shown that during the last 15 million years, the South American plate has suddenly shifted gears and slowed down on two significant occasions, which has contributed to the widening of the mountain range and its growth in height.
Calculations made by the researchers indicate that the South 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, which are very rapid and abrupt changes in geological terms. In the periods prior to the two slowdowns, the Nazca Plate sank into the mountains and compressed them, which caused the mountains to grow taller. As the plates slowed, the mountains widened.
To explain the causes of the abrupt braking of the South American plates, researchers have proposed two hypotheses. The first hypothesis suggests that a large amount of unstable material beneath the Andes broke loose and sank into the mantle, causing the plate to accumulate more material and become heavier, thus slowing its movement. The second hypothesis posits that a change in convection, or the pattern of heat flow from the Earth’s interior, caused a change in the upper viscous layer of the mantle, impacting the movement of the plate floating on it.
The researchers hope that this method of study can be used to refine historical models of plate tectonics and improve the possibility of reconstructing geological phenomena that are still unclear. The results of this study were recently published in the journal Earth and Planetary Science Letters.
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