Geologists figured out the origin of the Hindustan Peninsula
“The collision of the Indian and Eurasian plates not only set the shape of the future East Asia, but also caused some of the most powerful and deadly earthquakes in history. The presence of such breaks in the mantle explains why powerful earthquakes do not occur in all, but only in some regions of Tibet, ”says Xiaodong Song from the University of Illinois in Chicago (USA).
India, unlike many other regions of Eurasia, is a kind of geological "migrant". It was not part of the giant Eurasian tectonic plate initially, but joined our continent relatively recently, about 65–70 million years ago. Before that, it was part of Gondwana, the southern supercontinent, and its “neighbors” were Australia, Africa, Antarctica and South America.
The fact that India separated from the rest of Gondwana is not controversial - it happened about 100 million years ago, when the peninsula and Madagascar separated and Hindustan began his journey to the north, towards the future of Pakistan and India. On the other hand, when it was India that clashed with Asia and what happened during this clash, it causes heated debate among scientists.
The search for answers to this question, as noted by Song, is complicated by the fact that Tibet and the Himalayas remain one of the most inaccessible and almost untouched by civilization corners of the Earth, which prevents their detailed study. His team solved this problem and revealed some interesting details from the history of this cataclysm, analyzing and combining data obtained from observations of recent major earthquakes in Tibet.
Measurements of transverse and longitudinal seismic waves helped scientists create a virtual copy of the depths of Tibet with a depth of 160 kilometers, and understand where the line of contact of the tectonic plates is and how it is arranged.
Unexpectedly, it turned out that in the upper layers of the Earth's mantle under the Tibetan plateau there are four large gaps at once, in which the flows of the “sinking” Indian Plate crust do not move in the same way as in the neighboring regions of the planet’s bowels. It is different, as scientists note, not only the speed, but also the direction of movement of rock flows.
This, in turn, explains many oddities associated with the fact that earthquakes in the southern regions of Tibet often occur in the “wrong” corners of the plateau, where there are no faults in the crust and other points of seismic tension, as well as the strange nature of volcanic eruptions at the time of the formation of the “seam” »Between the Indian plate and Eurasia.
Scientists do not yet know exactly how these gaps occurred, but they assume that they arose because the edge of the Eurasian Plate was initially extremely heterogeneous. Part of its outskirts was noticeably stronger than other regions, which led to the "splitting" of relatively weak sections of the Indian Plate mantle into parts at the time of their collision with each other.
This led to a stretching of the crust and the appearance of additional faults inside it, which today periodically generate powerful earthquakes. Further observations of these gaps, scientists hope, will help reveal the history of the formation of the peninsula and allow better predictions of new shocks that are potentially dangerous for millions of people in China, India, Nepal and Bhutan.
The study is published in the journal PNAS.