Submission + - Long-lost continent found under the Indian Ocean (nature.com)
ananyo writes: "The drowned remnants of an ancient microcontinent may lie scattered beneath the waters between Madagascar and India, a new study suggests. Evidence for the long-lost land comes from Mauritius, a volcanic island about 900 kilometres east of Madagascar. The oldest volcanic rocks on the island date to about 8.9 million years ago. Yet grain-by-grain analyses of beach sand collected at two sites on the Mauritian coast revealed around 20 zircons — tiny crystals of zirconium silicate that are exceedingly resistant to erosion or chemical change — that were far older. One of these zircons was at least 1.97 billion years old.
The researchers that made the discovery think that geologically recent volcanic eruptions brought shards of the buried continent to the Earth’s surface, where the zircons eroded from their parent rocks to pepper the island’s sands. Analyses of Earth’s gravitational field reveal several broad areas where sea-floor crust at the bottom of the Indian ocean is much thicker than normal — at least 25 to 30 kilometres thick, rather than the normal 5 to 10 kilometres. Those crustal anomalies may be the remains of a landmass that researchers have now dubbed Mauritia, which they suggest split from Madagascar when tectonic rifting and sea-floor spreading sent the Indian subcontinent surging northeast millions of years ago."
The researchers that made the discovery think that geologically recent volcanic eruptions brought shards of the buried continent to the Earth’s surface, where the zircons eroded from their parent rocks to pepper the island’s sands. Analyses of Earth’s gravitational field reveal several broad areas where sea-floor crust at the bottom of the Indian ocean is much thicker than normal — at least 25 to 30 kilometres thick, rather than the normal 5 to 10 kilometres. Those crustal anomalies may be the remains of a landmass that researchers have now dubbed Mauritia, which they suggest split from Madagascar when tectonic rifting and sea-floor spreading sent the Indian subcontinent surging northeast millions of years ago."
