Eruption 22 million years ago preserved traces of the Andes’ formation in Chile — Live Science
In northern Chile, an eruption about 22 million years ago covered the landscape with volcanic deposits and preserved a kind of “snapshot” of the early stage of the Andes’ formation. Analysis of the buried relief suggests that before the eruption, the area had more rolling foothills rather than steep mountain peaks.
Buried relief
The eruption originated from the Lauca caldera, located in what is now northern Chile. It produced ignimbrite — a rock that remains after a pyroclastic flow. Such a flow consists of rock fragments, volcanic gas and ash, and spreads across the surface over considerable distances.
According to Live Science, researchers cannot directly see the relief beneath the ignimbrite. However, the shape of the volcanic cover and knowledge of how rivers shape mountains allowed them to draw conclusions about the landscape that existed before the eruption.
More current news is available on the UA.News Telegram channel Telegram.
Rate of Andes uplift
The authors of the study, published in the journal Science Advances, determined that the original slope of the volcanic flow from the Lauca caldera was about 1.5 degrees. They also calculated landscape erosion to estimate the rate at which rocks were uplifted in the area.
Before the eruption, the Earth’s crust here was rising at a rate of no more than 0.26 kilometers per million years. The result is consistent with the hypothesis of the Andes forming slowly and gradually over 40–50 million years, rather than the mountains rising sharply only during the past 6–10 million years. The Andes formed as a result of the Nazca oceanic plate subducting beneath the continental crust of South America. The researchers noted that this method may also be useful for studying other mountain systems around the world.
