MELBOURNE: Himalayas were born about 47 million years ago when India and Eurasia initially smashed into each other, an international team of scientists who discovered the first oceanic microplate in the Indian Ocean has found.
Although there are at least seven microplates known in the Pacific Ocean, this is the first ancient Indian Ocean microplate to be discovered, researchers said.
Radar beam images from an orbiting satellite have helped put together pieces of this plate tectonic jigsaw and pinpointed the age for the collision, whose precise date has divided scientists for decades.
The team of Australian and US scientists believe the collision occurred 47 million years ago when India and Eurasia initially smashed into each other.
Researchers led by the University of Sydney School of Geosciences discovered that crustal stresses caused by theinitial collision cracked the Antarctic Plate far away from the collisional zone and broke off a fragment the size of Australia's Tasmania in a remote patch of the central Indian Ocean.
The authors, comprising Professor Dietmar Muller and Kara Matthews from the University of Sydney and Professor David Sandwell from the Scripps Institution of Oceanography, have named the ancient Indian microplate the Mammerickx Microplate, after Jacqueline Mammerickx, a pioneer in seafloor mapping.
The Mammerickx Microplate rotation is unveiled by a rotating pattern of grooves and hills that turn the topography of the ocean floor into a jagged landscape.
These so-called "abyssal hills" record a sudden increase in crustal stress, dating the birth of the Himalayan Mountain Range to 47 million years ago, researchers said.
The ongoing tectonic collision between the two continents produces geological stresses that build up along the Himalayas and leads to numerous earthquakes every year - but this latest finding indicates how stressed the Indian Plate became when its northern edge first collided with Eurasia.
The new research shows that 50 million years ago, India was travelling northwards at speeds of some 15 centimetres a year - close to the plate tectonic speed limit.
Soon after it slammed into Eurasia crustal stresses along the mid-ocean ridge between India and Antarctica intensified to breaking point.
A chunk of Antarctica's crust broke off and started rotating like a ball bearing, creating the newly discovered tectonic plate.
The discovery was made using satellite radar beam mapping from space, which measures the bumps and dips of the sea surface caused by water being attracted by submarine mountains and valleys, combined with conventional marine geophysical data.
"The age of the largest continental collision on Earth has long been controversial, with age-estimates ranging from at least 59 to 34 million years ago," said lead author Matthews.
The research was published in the journal Earth and Planetary Science Letters.