Earth ‘recyles’ Itself Faster Than Thought
August 10, 2011 by UPI - United Press International, Inc.
MAINZ, Germany, Aug. 10 (UPI) — The volcanic recycling of crust that sinks due to the movement of Earth’s tectonic plates happens faster than previously thought, German researchers say.
Scientists at the Max Planck Institute for Chemistry in Mainz say sunken oceanic crust resurfaces from Earth’s mantle through volcanic eruptions after only 500 million years, a figure researchers had previously put at about 2 billion years.
Hot rock rises in cylindrical columns, so-called mantle plumes, from a depth of nearly 1,800 feet and near the surface it melts because the pressure is reduced and forms volcanoes.
The plumes originate from former ocean crust that sank to the bottom of the mantle early in the planet’s existence, and scientists had previously assumed this recycling required about 2 billion years.
Max Planck researchers found unexpected amounts of strontium isotopes in lava samples from Hawaiian volcanoes that allowed them to date the recycling process.
“Apparently strontium from sea water has reached deep in the Earth’s mantle, and reemerged after only half a billion years, in Hawaiian volcano lavas,” researcher Klaus Peter Jochum said. “This discovery was a huge surprise for us.”