Think you have a pretty good grasp on the world’s continents? You may want to think again.
A ‘lost continent’ that was once sandwiched between India and Madagascar now lies under the Indian Ocean island nation of Mauritius.
The continent, called ‘Mauritia’, formed part of present-day Madagascar and India and was likely part of the gigantic supercontinent Gondwana, which broke up to become Antarctica, Africa, Australia and South America.
By studying zircon, a mineral found in rocks spewed up by lava during volcanic eruptions, on Mauritius, Professor Lewis Ashwal, lead author on the study, and his colleagues found that remnants of this mineral were much too old to belong on the island.
Earth is made up of two parts – continents, which are old, and oceans, which are ‘young’. On the continents you find rocks that are over four billion years old, but you find nothing like that in the oceans, as this is where new rocks are formed.
Mauritius is an island, and there is no rock older than 9 million years old on the island. However, by studying the rocks on the island, we have found zircons that are as old as 3 billion years.
The fact that we have found zircons of this age proves that there are much older crustal materials under Mauritius that could only have originated from a continent.
Ashwal suggests that there are likely many pieces of various sizes of undiscovered continent, collectively called ‘Mauritia’, left over by the breakup of Gondwanaland and spread over the Indian Ocean.
According to the new results, this break-up did not involve a simple splitting of the ancient super-continent of Gondwana, but rather, a complex splintering took place with fragments of continental crust of variable sizes left adrift within the evolving Indian Ocean basin.
This isn’t the first time that billion year old zircons have been found on the island though. A 2013 study found traces of the mineral in beach sand. However, the research received criticism, including that the mineral could have been blown in by the wind. But Ashwal’s new study contradicts this.
“The fact that we found the ancient zircons in rock (6-million-year-old trachyte), corroborates the previous study and refutes any suggestion of wind-blown, wave-transported or pumice-rafted zircons for explaining the earlier results,” says Ashwal.
The study appeared in the peer-reviewed British journal Nature Communications.