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Forever young: Earth’s crust recycles faster than we thought

Scientists from Max Planck Institute for Chemistry say Earth’s crust may be recycled in only half a billion years, based on data from volcano Mauna Loa.

Scientists from the Max Planck Institute for Chemistry in Berlin, Germany have obtained data from the Mauna Loa volcano in Hawaii suggesting that Earth’s crust might be recycled in as little as half a billion years. Previously, geologists assumed that the recycling process would take approximately two billion years.

The recycling of Earth’s crust is initiated by tectonic forces from deep within Earth – the same forces that push up mountain ranges, for example. The recycling happens at Earth’s subduction zones, where one of Earth’s great land plates moves beneath another. During the geological process of subduction, the edge of a crustal plate is forced downward, below another plate, into Earth’s mantle – a magma-filled layer of Earth between the crust and our world’s core. Eventually, the subducted material melts into the mantle. Later, it’s recycled back to the crust, emerging through volcanic eruptions.

Alexander Sobolev and his team calculated the rate of crustal recycling by the Mauna Loa volcano in Hawaii through a geological dating technique based on strontium isotopes. Isotopes are elements that decay at predictable rates and are often referred to as “clocks in rocks.” Specifically, the scientists measured the amount of strontium isotopes contained within olivine crystals isolated from the lava.

Olivine crystals obtained from Mauna Loa, Hawaii. The brown ovals are inclusions trapped as melt by the growing crystal and contain strontium isotopes inherited from 500 million year old seawater. Image Credit: Sobolev, Max Planck Institute for Chemistry.

The scientists were surprised to discover that inclusions in the olivine crystals matched the age of 200 to 650 million year old seawater. In a press release, co-author Klaus Peter Jochum commented:

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. This discovery was a huge surprise for us.

Mauna Loa is the largest volcano on Earth. While the volcano only rises 4,000 meters (about 2.5 miles) above sea level, its height from its actual base in a deep depression in the sea floor is 17,000 meters (about 10.5 miles). Mauna Loa is also one of the most active volcanoes on Earth. It has erupted 33 times since historical recordkeeping began in 1843.

Satellite image of Mauna Loa on the island of Hawaii. Image Credit: NASA.

Lead author Alexander Sobolev and his colleagues are hoping to evaluate more volcanoes in the future. Such research could help to improve estimates of the recycling age of Earth’s crust.

The study describing the faster-than-expected recycling rate of Earth’s crust by the Mauna Loa volcano was published in the August 25, 2011 issue of the journal Nature.

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