A new international study suggests that a geological theory accepted for over a century, which explains how Asia manages to support the huge weight of the Himalaya chain and the Tibetan plateau could be wrong.
The research, published on August 26 in Tectonics magazine, shows that under the highest mountain range on Earth there is a layer that fundamentally changes the way the structure of the region is understood.
Himalayas formed about 50 million years ago, following the collision between Indian and Eurasian tectonic plates. The theory formulated in 1924 by the Swiss geologist Émile argand claimed that the bark of the two continents were overlapping, reaching a thickness of 70-80 km and thus explaining the lifting of the mountains. But the new research shows that this explanation does not match the geological reality. At depths greater than 40 km, the rocks become ductile, “like yogurt”, and could not support the weight of such a mountain formation, explains Pietro Sternai, a geophysical professor at Milan-Bicocca, the main author of the study.
The computer simulations made by the international team showed that, during the collision, fragments of the Indian plate did not stick to the bottom of the Eurasian bark, but the base of the lithosphere-the rigid layer that combines the bark and the upper part of the coat. Thus, between the two bark is a solid layer of mantle, which ensures the mechanical resistance necessary for the Himalaya and the Tibetan plateau to remain at impressive altitudes.
“You have all the necessary ingredients to lift the topography and support the weight of the Himalayas and the Tibetan plateau,” says Sternai. The results match the seismic data and observations on the rocks, providing an explanation for a series of geological abnormalities that the classic theory could not justify.
The study has attracted the attention of the scientific community. “It is an interesting new discovery and an elegant interpretation,” says Douwe Van Hinsbergen, a professor at Utrecht University in the Netherlands. Other experts, such as Adam Smith of the University of Glasgow, believe that the theory remains controversial, but I admit that the new models are plausible and well supported by evidence.
This research opens the path to rewrite a fundamental theory of modern geology and could change how we understand tectonic processes that shape the surface of the earth.
