A tectonic shift in our understanding of the India-Asia collision
New research could change our understanding of how moving plates formed continents millions of years ago.
This study from China suggests that millions of years ago, India was about twice the size it is now, but the Tibetan Plateau sank beneath it, pushing it up.
The Earth’s surface did not always look like it does today. Hundreds of millions of years ago, there were only her two supercontinents: Laurasia and Gondwana.
The continental and oceanic rocks that make up the Earth’s crust, or lithosphere, sit on top of the mantle, a molten rock over which they move very slowly. What is now the Indian subcontinent was originally part of Gondwana, which broke up about 150 million years ago.
In some places on Earth, continents collide with each other and form mountain ranges. The Himalayas are believed to have formed when the Indian plate collided with the Asian plate about 55 million years ago (mya).
During this process, part of the Indian plate is known to have subducted beneath the Himalayas and the Tibetan Plateau. However, the scale of this “lost” part of the continent, known as “Greater India”, remains unclear.
A new study reveals that Greater India was a single plate that extended 2,000 to 3,000 kilometers north of what is now the Indian subcontinent before it was subducted beneath Asia.
Understanding the original extent of Greater India is important for clarifying some important questions surrounding the era of Indo-Asia conflict and for answering how and when the Tibetan Plateau was formed.
Professor Jun Meng of the China University of Geosciences, Beijing (CUGB), lead author of the study published in PNAS, explains that there are two main models for the India-Asia collision.
“The first is a multi-stage impact model that splits the oceanic basins on India’s leading edge into smaller plates that are later integrated into the Asian plate,” he says.
