Earth 'recycles' itself four times faster than thought

The volcanic recycling of the Earth's crust that sinks deep into the earth due to the movement of tectonic plates happens much faster than scientists had previously thought, a new research has found.

Researchers from the Max Planck Institute for Chemistry in Mainz say that the rock of the oceanic crust reemerges through volcanic eruptions after around 500 million years. Previously, geologists thought this process would take about two billion years.

Hot rock rises in cylindrical columns, the so-called mantle plumes, from a depth of nearly 3000 kilometres. Near the surface, it melts, because the pressure is reduced, and forms volcanoes.

The plume originates from former ocean crust, which early in the Earth’s history, sank to the bottom of the mantle. Previously, scientists had assumed that this recycling took about two billion years.

The chemical analysis of tiny glassy inclusions in olivine crystals from basaltic lava on Mauna Loa volcano in Hawaii has now surprised geologists: the entire recycling process requires at most half a billion years, four times faster than previously thought.

Researchers found residues of seawater with an unexpected strontium isotope ratio in lava samples from Hawaiian volcanoes, which suggested an age of less than 500 million years for the inclusions.

“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,” says Klaus Peter Jochum, co-author of the publication.

“This discovery was a huge surprise for us,” he added.