New analysis may change our understanding of how plate actions fashioned the continents hundreds of thousands of years in the past.
The examine out of China suggests hundreds of thousands of years in the past India was about twice as large as it’s now, nevertheless it subsided underneath and pushed up, the Tibetan plateau.
The Earth’s floor hasn’t all the time seemed prefer it does at present —a whole lot of hundreds of thousands of years in the past there have been solely two supercontinents: Laurasia and Gondwana.
The continents and oceanic rock that make up Earth’s crust, or lithosphere, sit atop molten rock referred to as the mantle and transfer very slowly over it. The current Indian subcontinent was initially a part of Gondwana, which broke up about 150 million years in the past.
In some locations on Earth the continents crush into one another and trigger mountain ranges to rise. The Himalayas have been thought to have fashioned when the Indian Plate collided with the Asian Plate about 55 million years in the past (mya).
We all know {that a} portion of the Indian Plate subducted beneath the Himalayas and the Tibetan Plateau throughout this course of. Nonetheless, the scale of this “misplaced” a part of the continent, referred to as Larger India, has remained unsure.
Now new analysis has discovered that Larger India was a single plate, extending 2,000 to three,000 km to the north of the present day Indian subcontinent, earlier than it subducted underneath Asia.
Understanding the unique extent Larger India is essential to resolving a number of key questions surrounding the age of the India–Asia collision, and answering how and when the Tibetan Plateau fashioned.
Professor Jun Meng of China College of Geosciences, Beijing (CUGB), first creator of the examine printed in PNAS, explains that there are two major fashions for the India–Asia collision.
“The primary is a multistage collision mannequin that subdivides the oceanic basin at the forefront of India into smaller plates that have been later integrated into the Asian plate,” he says.
This historical oceanic basin is called the Tethys Ocean.
“The second mannequin says that India and Larger India existed as a single plate within the Early Cretaceous interval, with the higher crust of the northern margin of Larger India forming the Himalayan thrust belt and the decrease crust being subducted underneath Asia.”
His colleague from CUGB, Professor Chengshan Wang provides, “Our objective was to grasp which of those fashions was extra correct.”
Their findings help the second mannequin.
The group studied the Sangdanlin part, in southern Tibet, that was initially a part of the Larger India area that fashioned the Himalayas. They tracked the geographical place of the northern sector of the Indian Plate via time and estimated the minimal dimension for Larger India.
In response to the researchers, the quantity of lithosphere consumed by the subduction for the reason that begin of the collision 55 mya was bigger than the Indian subcontinent because it exists at present. Nearly 5 million km² of lithosphere has been subducted underneath the Asian Plate, which should have contributed to the rise of the Tibetan Plateau.
“Our findings problem established notions of the formation of Asia’s southern margin via the coalescence of impartial tectonic blocks within the Tethys Ocean,” says Professor Stuart A. Gilder of Ludwig Maximilians College, Germany.
“They might assist us fill the hole within the information concerning the scale of the Indian plate in a Gondwana configuration and the tectonic historical past of India up till its collision with Asia.”
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