Recent scientific advancements may have overturned a 100-year-old theory regarding the geological forces that support the highest mountain range on Earth, the Himalayas. This groundbreaking study reveals new insights about the formation of the Himalayas, which arose from the collision between the Asian and Indian continents approximately 50 million years ago. The tectonic forces at play during this collision forced Tibet to crumple, resulting in a significant reduction of its area by nearly 620 miles (or 1,000 kilometers).
For decades, the dominant explanation for the towering heights of the Himalayas has been rooted in the idea that the doubling of the Earth's crust beneath this region is solely responsible for its elevation. This theory, initially proposed in 1924 by Swiss geologist Émile Argand, depicted the Indian and Asian crusts as stacked atop one another, extending to depths of approximately 45 to 50 miles (or 70 to 80 kilometers) beneath the Earth's surface. However, the latest research indicates that this model may not withstand scrutiny.
According to the lead researcher, Pietro Sternai, an associate professor of geophysics at the University of Milano-Bicocca, the theory fails to account for critical geological properties. He explained that at depths of around 25 miles (or 40 kilometers), the rocks in the crust become molten due to extreme temperatures. As Sternai noted, “If you've got 70 km of crust, then the lowermost part becomes ductile… it becomes like yogurt — and you can't build a mountain on top of yogurt.”
The newly published study, which appeared in the journal Tectonics on August 26, reveals that there exists a layer of mantle material between the Asian and Indian crusts. This finding provides a plausible explanation for the substantial height of the Himalayas and their ongoing uplift. The mantle, located directly beneath the crust, is denser and remains solid at higher temperatures compared to the crust. This characteristic allows the crust to behave like an iceberg, where increased thickness results in greater elevation above the Earth's surface.
In their research, Sternai and his team utilized computer simulations to model the collision between the Asian and Indian plates. The results demonstrated that as the Indian plate subducted beneath the Eurasian plate and began to liquefy, portions of the mantle material rose and adhered to the base of the lithosphere, which comprises the rigid outer layer of the planet. Sternai emphasized the importance of this finding, stating, “It means there is a rigid layer of mantle between the stacked crusts solidifying the whole structure beneath the Himalayas.”
By comparing their simulations with seismic data and geological samples, the researchers found that the newly proposed mantle sandwich effectively explains several geological anomalies that the previous model could not. Co-author Simone Pilia, an assistant professor of geoscience at King Fahd University of Petroleum and Minerals, remarked that the new model simplifies previously perplexing observations about the region.
Despite the compelling evidence presented, the study's challenge to Argand's long-accepted theory is not without controversy. Many in the geological community have traditionally accepted that all material beneath the Himalayas originated from the crust. Adam Smith, a postdoctoral research associate in numerical modeling, acknowledged the plausibility of the new findings but noted that they contradict a well-established paradigm.
However, not all experts view the findings as contentious. Douwe van Hinsbergen, a professor of global tectonics at Utrecht University, praised the research as an elegant interpretation of geological processes. He highlighted that the anticipated structure of the crust and mantle in such continental collisions aligns with the study's conclusions.
As this new research continues to unfold, it holds the potential to reshape our understanding of the geological forces that have shaped the Himalayas and the Tibetan Plateau. The implications extend beyond just mountain formation, influencing our broader comprehension of tectonic activity and Earth's geological history.
