For ages now, Mauritia has been hiding. The small, precambrian continent once resided between Madagascar and India, before splitting off and disappearing beneath the ocean waves in a multi-million-year breakup spurred by tectonic rifts and a yawning sea-floor. But now, volcanic activity has driven remnants of the long-lost continent right through to the Earth's surface. After millions of years, and some incredible geologic sleuthing, it seems Mauritia has been found.
The news comes from a team of researchers led by University of Oslo geologist Bjørn Jamtveit. In the latest issue of Nature Geoscience Jamtveit and his colleagues present the result of a study
that examined the beaches of Mauritius, a volcanic island off the coast of Madagascar (pictured up top). The lava sands of Mauritius are laced with very interesting particles called — and this is probably the coolest scientific term I've come across in weeks — "zircon xenocrysts."
The vast majority of Mauritius's volcanic lava sands date to around 9 million years ago. But a grain-by-grain analysis revealed the sparsely distributed xenocrysts to be anywhere from 660 million to 1.97 billion years old. A strange find, to be sure, but Jamtveit and his colleagues have a compelling explanation for the anachronistic crystals.
The zircons, write the researchers, likely originated in fragments of ancient continental crust situated beneath Mauritius, and were in fact pushed up through to the planet's surface through volcanic activity. How far were they pushed? Geologist Trond Torsvik, first author on the paper, told the BBC he thinks pieces of long-lost Mauritia are likely situated 10km beneath the island and a chunk of the Indian Ocean. Analyses of Earth's gravitational field corroborate his claims, revealing several regions of the sea floor where the crust is significantly thicker than normal (around 30 kilometers thick, where it should be closer to 5 or 10).
Torsvik says the researchers will need seismic data to image the seafloor structures more accurately — either that, or deep drilling. But a 2-billion-year old zircon xenocryst on a beach covered in 9-million-year-old volcanic sands is a hell of a geological riddle, and right now, fragments of an ancient precambrian microcontinent, coaxed surfaceward particle-wise by volcanism, seem a rather compelling explanation. Then again, they are called zircon xenocrystals. So aliens and timetravel seem as good an explanation as any, right?
Top image: Mauritius, by Jack Abuin via Nature News.