Move Over, Atlantis!

From the Now-I’ve-Heard-Everything department —

Mythology likes to rhapsodize about the lost continent of Atlantis, but there may be another loss we’ve completely overlooked.  It’s in the Indian Ocean beneath the island of Mauritius.

Although Mauritius is only 790 square miles, it has long interested scientists because of an unusually strong gravitational pull.  You may be surprised to learn that Earth’s gravity varies from place to place.  For example, if a large, iron-rich meteor strikes, the crust in that area will be slightly denser.  These spots are called “mascons” for mass concentrations.

Is Mauritius atop such a mascon?  If so, it was probably because an existing landmass shattered and sank due to crustal motion, with the island rising to the top.  This is what geoscientist Lewis Ashwal of the University of Witwatersrand in Johannesburg believes.  In a paper recently published in Nature Communications, Ashwal presents his case based on a study of (really!) 13 small grains of zircon.

Mauritius tests out at only eight million years old, which means its overall geology should be about the same age.   But two-billion-year-old samples of  zircon have been gathered from its beaches.  Ashwal and his colleagues used uranium-lead dating techniques, which measures the concentration of those elements in the zircon to determine its age, and found the samples were about three billion years old.  The zircon had to have been formed separately from the island, probably being blown up onto land when undersea volcanoes ejected older rocks from subsurface crust.

Ashwal and his colleagues now think a large area of land once existed between India and Madagascar as part of the ancient supercontinent of Gondwanaland, which broke up about 200 million years ago.  When it did, this part of the landmass probably fractured into ribbons, compressed and sank underneath the ocean, creating the mass concentrations.  Later volcanoes formed Mauritius, and still later eruptions deposited the zircon.  Thus their conclusion — “Our findings confirm the existence of continental crust beneath Mauritius.”

The complete account is at  http://time.com/4657836/lost-continent-mauritius/?xid=newsletter-brief.

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