The Himalayan mountain range originated from plate tectonics. Billions of years ago, the Indian subcontinent’s tectonic plate collided with the Eurasian plate. This collision caused one plate to slide beneath the other, sinking the Indian plate while raising the Eurasian plate. This process created some of the world’s highest peaks, including the Himalayas and the Alps.
However, the uplift resulting from this collision isn’t a simple overlap of two plates. The dynamics are much more complex.
Destroying Earth’s crust. A recent study published in Earth and Planetary Science Letters explores what happens to the section of Earth’s crust located beneath the colliding tectonic plates. Researchers estimated that the collision that caused Mount Everest to rise destroyed around 30% of the crustal mass involved in this event.
Beyond the Himalayas. Many of the world’s major mountain ranges were formed (and some are still growing) through similar subduction processes. For instance, the Himalayas are rising at a rate of about 0.40 inches per year. Other examples include the Alps in Europe and the Zagros Mountains in Iran and Turkey.
During these subduction processes, when two tectonic plates collide, one slides beneath the other. As the second plate “folds” and rises, it forms vast mountain systems. Matter from the first plate becomes trapped between the Earth’s mantle and the new mountain range, where it may melt and migrate into deeper layers of the Earth.
Between 30% and 64%. The research team estimates that the crust loss in the Alps could be around 50% of its initial volume. The estimated loss is about 30% for the Himalayas and Zagros Mountains. However, in the case of the Zagros, the upper estimate could reach 64%.
According to co-author Ziyi Zhu, this process could explain the rapid rise of mountain ranges like the Himalayas. “Imagine a piece of floating wood with an iron layer attached beneath it, which partially submerges it; if the iron layer detaches and sinks, the wood will pop up to the surface,” Zhu told Phys.org.
Theoretical models. To estimate the changes in the continental crust, Zhu and her team developed a theoretical model that assessed the mass/volume balance of the crust. They compared this model to the thickness of the crust in the area, its lateral movement, and the erosion at the surface.
Up and down. To make their estimates, researchers also calculated how erosion impacted changes in the thickness of the crust. They measured the volume of sediment accumulated around the mountains. They found that the amount of material removed by erosion was significantly less than what was lost from the inner layers of the crust.
A “flat-slab” subduction. The results of the latest study align with findings from another geological analysis of the region, which described a “flat-slab” subduction process. In this scenario, the collision of tectonic plates wasn’t characterized by one plate simply folding over the other. Instead, one plate was effectively sliced through by the other.
Image | Katyayan Gauniyal
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