PARIS: The Himalayas and Tibetan plateau formed when a “supercontinent” broke up and the Indian sub-continent smashed at high speed into Eurasia, a study published in the British journal Nature says.
Until 140 million years ago, modern-day India formed part of a supercontinent called Gondwanaland, which broke apart to form what, today, is Africa, India, Australia, Antarctica and South America, it says. India moved at much higher speed than the other parts — at between 18 and 20 centimetres per year, its German and Indian authors believe.
By comparison, Australia and African plates moved at just four centimetres (1.6 inches) per year or less, and also travelled much smaller distances, while Antarctica remained almost stationary.
Zipping up to the north, India smashed into the continent of Eurasia about 50 million years ago, and the mighty collision caused land to crumple and rear up, creating the world’s highest mountain range. The theory about Earth’s structure is that the planet comprises a brittle outer crust, called the lithosphere, which lies atop the mantle, the hot, elastic layer that is sandwiched between the crust and the scorching iron-rich core.
The researchers, at the Geo Forschungs Zentrum (GFZ, Germany’s national lab for geoscience) in Potsdam believe Gondwanaland fractured apart because of a “plume” of intense heat that spewed from the mantle. India may have been on top of, or near, this plume, with the result that its lithospheric roots were literally burned away, leaving the sub-continent rather like a plate floating on a fluid.
Using a method called the shear-wave receiver function technique to measure the thickness of lithospheric plates, the GFZ team calculate the Indian plate to be only about 100 kilometres thick.
That compares with between 180 and 300 kilometres of thickness for the other parts of Gondwanaland, which suggests that these parts kept some roots in the mantle, thus limiting their ability to move.
Shorn of its anchor, India was transformed “from a sloth to a cheetah,” making it able to roam far and fast, said Dietmar Mueller, a University of Sydney geoscientist, in a review of the study.—AFP
