The tiny nation of Mauritius lives on a beautiful volcanic island in the Indian Ocean. Once, it was a strategic colony for trade routes between Europe and the Far East. These days it’s a tropical tourist destination with postcard beaches.
And now geologists have figured out that there’s far more to Mauritius than meets the eye.
In a study published last week in Nature Communications, a team of South African researchers have described the discovery of 3-billion-year-old zircon crystals on Mauritius. But the volcanic island itself is only some 8 million years old, so how is that possible?
The ancient minerals, found on the island’s beaches, were likely ejected by volcanic eruptions from far below. Their age suggests the zircons once belonged to a continental crust much older than the recently formed island itself.
This means that deep underneath the surface of the Indian Ocean and right under Mauritius, there was once a small continent.
Mauritia, as the researchers have proposed to name it, was only a quarter of the size of Madagascar and has been buried under volcanic material for millions of years.
“It’s a continent in the geological sense, not in the geographical one,” lead author Lewis D. Ashwal from the University of Witwatersrand told the New York Times. Researchers have been suspecting this for a while, because there are areas in the Indian Ocean with a stronger gravitational pull than the land surface would suggest.
Indian Ocean topography showing the location of Mauritius as part of a chain of progressively older volcanoes extending from the presently active hot-spot of Réunion toward the 65-million-year-old Deccan traps of northwest India.
Originally published in: Ashwal et al. (2016) A mantle-derived origin for Mauritian trachytes.
“Mauritia acted as a buffer zone between the western Indian subcontinent and eastern Madagascar, and was fragmented by numerous tectonic and volcanic events that occurred in that region since the early Cretaceous,” the authors write in the paper.
Scientists found the clues to this geological history in tiny zircon crystals from Mauritius’ pristine volcanic sand. The extremely sturdy minerals contain traces of uranium and thorium, making them a great material for a method called radiometric dating.
The early Cretaceous happened some 146-100 million years ago. Dinosaurs like Tyrannosaurus rex and sauropods were wandering around the early continent of Gondwana—now South America, Africa, India, Antarctica, and Australia.
As Gondwana changed shape, causing India and Madagascar to move apart some 180 million years ago, Mauritia broke into smaller and thinner pieces.
These bits of continental crust sunk deep underwater and became precursors to many of the small volcanic islands now littering the Indian Ocean. Evidence of their billion-year-history is right there in the beach sand.
Want more lost continents? Tune in to James Cameron’s Atlantis Rising
at 7.30pm on 19 February on National Geographic Channel.