The Himalayas’ towering peaks are engaged in a geological clash—a slow-motion collision between the Indian and Eurasian tectonic plates. This collision, initiated about 60 million years ago when India, then an island, collided with Eurasia, has resulted in the formation of Earth’s highest mountains. While the surface displays the dramatic effects of this clash, ongoing tectonic movements beneath the surface, spanning tens of kilometers, harbor mysteries.
Unlike dense oceanic plates, continental tectonic plates are thick and buoyant, resisting easy subduction into the mantle during collisions. The interaction between the Indian Plate and Tibet is a subject of scientific debate. Some propose that the Indian Plate resists sinking into the mantle and continues sliding horizontally under Tibet, while others suggest that a buoyant portion of the Indian Plate rumples along the collision’s front edge, facilitating subduction of the lower part.
A recent analysis of earthquake waves beneath Tibet and gases rising to the surface introduces a novel perspective. It suggests that a section of the Indian Plate may be undergoing “delamination” as it slides beneath the Eurasian Plate, with the denser bottom part peeling away from the top. The study also identifies evidence of a vertical fracture or tear at the boundary between the separated section of the slab and its intact counterpart.
This discovery challenges previous notions about continental behavior, offering fundamental insights into solid earth science. The research, presented in December 2023 at the American Geophysical Union conference, may contribute to a better understanding of Himalayan formation and potential earthquake hazards in the region.
While uncertainties remain, the study represents a crucial step in unraveling the processes shaping our modern landscape. Scientists have long speculated about the possibility of tectonic plates splitting, and this study captures such an event in action within a descending plate—a first of its kind. The Himalayan collision, with its varied plate thickness and composition before the collision, provides a unique context for investigating plate tearing.
The research, led by Simon Klemperer of Stanford University, relies on various clues, including isotope measurements of helium in Tibetan springs. Mapping these springs revealed a distinct line representing the farthest edge of the intact Indian Plate sliding under Tibet before subducting into the mantle. However, south of this line, near Bhutan’s eastern border, springs with mantle signatures hint at a potential section of the Indian Plate peeling apart.
Support for this hypothesis comes from the analysis of earthquake waves, indicating a lower slab detaching from its top. The proposed tear, located near the Cona-Sangri rift on the Tibetan Plateau, may influence earthquake hazards in Tibet today. Although the direct link remains uncertain, the study underscores the potential impact of plate tears on stress accumulation and earthquake occurrence.
Understanding these complex processes is crucial, as the collisions shaping Earth’s landmasses provide insights not only into our present landscape but also the earthquake hazards associated with ancient continental collisions. The study highlights the intricate history embedded in continents, presenting a challenge and excitement for scientists decoding a billion years of geological evolution.
