Slab unperturbed in the mantle for billions of years before resurfacing
Earth’s crust is the ultimate survivor. Bits of crust that sink into the planet’s interior can last for billions of years, geologists report in the April 25 Nature.
Rita Cabral of Boston University and colleagues discovered traces of ancient crust in one of the South Pacific’s Cook Islands while analyzing lava that erupted 20 million years ago. The rock contains different forms, or isotopes, of sulfur in ratios that could have only originated in an atmosphere with little oxygen, sometime before 2.45 billion years ago.