News in Brief: Remnants of Earth's crust survive in the planet's interior
Slab unperturbed in the mantle for billions of years before resurfacing
Web edition: April 24, 2013
Slab unperturbed in the mantle for billions of years before resurfacing
By Erin Wayman
Web edition: April 24, 2013
Rocky Remains
Volcanic rocks in the Cook Islands have revealed that Earth?s crust can survive in the mantle for billions of years, as evidenced by sulfur isotopes trapped within crystals of the mineral olivine (blue, in this light-filtered image).
Credit: James M.D. Day
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.
The researchers suspect that the sulfur was originally part of a slab of oceanic crust that slid beneath another tectonic plate and plunged into the mantle more than 2.45 billion years ago. The crust sank so low in the mantle that it was effectively in a crustal graveyard, the team suggests, where convection was weak and the crust could stay intact. A couple billion years later, parts of that crust rose back to the surface in a plume of buoyant mantle material and fueled the volcanic eruptions that gave rise to the Cook Islands.
Citations
R.A. Cabral et al. Anomalous sulphur isotopes in plume lavas reveal deep mantle storage of Archean crust. Nature. Vol. 496, April 25, 2013, p. 490. doi: 10.1038/nature12020. [Go to]
Suggested Reading
A. Witze. Stop-and-go plate tectonics. Science News. Vol. 181, June 2, 2012, p. 11. [Go to]
A. Witze. Pacific volcanoes share split personality. Science News. Vol. 180, October 22, 2011, p. 8. [Go to]
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