The sands of Mauritius are hiding a secret: deep beneath them lurks an ancient continent.

Trond Torsvik and colleagues at the University of Oslo, Norway, analysed grains of zircon found on the island’s beaches, measuring the balance of lead and uranium isotopes to work out their age. This showed some formed almost 2 billion years ago – although the volcanic island is no more than 65 million years old.

So where did the grains come from? Torsvik thinks they are from fragments of continental crust beneath Mauritius that melted as the volcanic island formed. The team have named the proposed continent Mauritia.

It’s a reasonable idea, says Michael Wysession at Washington University in St. Louis, Missouri. “It’s hard to imagine how zircons could be there any other way.”

Journal reference: Nature Geoscience, DOI: 10.1038/ngeo1736