A group of scientists from Norway, Germany, South Africa and the U. K. have discovered a submerged continent in the Indian Ocean.
Their measurements predict that the continent, which they have named Mauritia, lies under Mauritius and its broken chunks today extend more than 1000 km northwards till Seychelles.
The discovery was sparked when they found crystals called zircons on Mauritian beaches. Zircons are resistant to erosion or chemical change and some of the ones they found were almost two billion years old, much older than any of the regular soil or sand samples found on nearby islands. Such old crystals, they thought, could only belong to a submerged continent, and may have perhaps been pushed up on the surface by underwater volcanoes.
To confirm whether these zircons indeed belonged to such a continent, they consulted satellite data which can help detect submerged land masses.
Nick Kusznir, professor of geophysics at the University of Liverpool in the U. K. and co-author of the paper that appeared this week in the journal Nature Geoscience, says: “We found that under Mauritius there were areas with an unusually thick Earth’s crust.”
In deep oceans the thickness of Earth’s crust, which forms the upper layer of the planet and protects us from the extremely hot magma underneath it, is about seven km.
But underneath Mauritius and leading to Seychelles, which is more than 1,000 km away, there were large chunks of the crust that were as thick as 30 km. “While we cannot be certain about the origins of the zircons, when combined with the evidence of thicker crusts in such big parts of the ocean floor, we can be quite certain that a small continent existed underneath Mauritius,” says Kusznir. There are a number of popular myths about submerged continents.
For instance, in the 19th century Lemuria, a large submerged continent in the Indian Ocean, was considered to extend from Antarctica to Kanyakumari. But its claimed existence did not stand the test of science. The Earth’s crust consists of seven or eight major “plates”, which are slowly but constantly moving relative to each other.
Over millions of years these have shaped how the world looks today. Some 140 million years ago, the Indian subcontinent split from a supercontinent called Gondwana, which also consisted of modern Africa, Australia, Antarctica and South America.
It eventually collided with the Eurasian plate some 50 million years ago, raising the Himalayas in the process.
Scientists predict that it was in between leaving Gondwana and colliding with the Eurasian plate that this continent Mauritia may have existed as an archipelago, a cluster of islands, squeezed in between Madagascar and the Indian subcontinent.
On the uses of finding such a submerged continent Kusznir says: “A better understanding of the sea floor and such submerged land masses can help us in better exploration of oil and gas in the oceans.”
First published in The Hindu.
Reference: Torsvik et al. Nature Geoscience 2013 http://dx.doi.org/10.1038/ngeo1736
Image from here.