«Al Jazeera» – Agencies:
An international team of scientists has discovered that below the Andes mountain range in South America, the Earth’s crust collapses into the mantle over millions of years. According to the study, recently published in the journal Communications Earth Island Environment, this phenomenon is known as ‘lithospheric dripping’, a name derived from the fragmentation of the rocky material that makes up the Earth’s crust and upper mantle. This long geological process, as it has been going on for millions of years, has led to the appearance of large surface deformations such as basins, crustal folding and irregular elevations. It is a geological phenomenon in which a relatively cold, dense mass of lithosphere sinks into the more malleable upper mantle. Although this process is a relatively new concept in the decades-old field of plate tectonics, numerous examples of ‘lithosphere dripping’ have been identified around the world, including the Central Anatolian Plateau in Turkey and the Great Basin in the western United States, on the other. But not limited to. Now, a research team led by geoscientists at the University of Toronto has confirmed that several regions in the Central Andes of South America were formed in the same way. “We confirmed that deformation on the surface of an area of the Andes led to the absorption of a large part of the lithosphere below,” said lead study author Julia Andersen and a graduate student in geology at the University of Toronto in Canada. The “deformation” that Andersen refers to was found in the Arezarro Basin and consists of wrinkles that were forming on the surface as the crust disappears below. “Given its high density, it drips like cold syrup or honey deep into the planet’s interior and may be responsible for two major tectonic events in the central Andes: changing the topography of the region by hundreds of kilometers, and crushing and stretching the surface crust itself,” Andersen explained. To reach this conclusion, the scientists recreated the process in the lab, using a tank and layered materials as backup units for the lower mantle, upper mantle and crust. “It was like creating and destroying mountain tectonic belts in a sandbox, floating in a simulated magma pool, all under incredibly accurate measurement conditions,” Andersen revealed. The results of the model were then compared with geophysical and geological studies conducted in the central Andes, particularly in the Isaro Basin, and the team found that changes in crustal elevation caused by drip in the laboratory “strongly follow changes in the height of the Arizaro”. “We also observed shortening of the folded crust in the model, as well as trough-like depressions at the surface, so we are confident that the droplets are very likely to be the cause of the deformations observed in the Andes,” Andersen added. Experiments have also shown other ways in which distillation of the lithosphere can distort the Earth’s crust. Not all of this has been observed in the Andes, which suggests that there may be other regions of the world where different types of drip can be observed, if we can identify them.