June 19, 2014

What's beneath our feet

Scientists See Earth's Most Abundant Mineral For The First Time Ever

Earth's most abundant mineral lies deep in the planet's interior, sealed off from human eyes.  Now, scientists for the first time have gotten a glimpse of the material in nature, enclosed inside a 4.5-billion-year-old meteorite. The result: They have characterized and named the elusive mineral,formerly known by its chemical components and crystal structure — silicate-perovskite as bridgmanite, after Percy Bridgman, a 1946 Nobel Prize-winning physicist

The mineral likely resides beneath Earth's surface in an area called the lower mantle, between the transition zone in the mantle and the core-mantle boundary, or between the depths of416 and 1,802 miles scientists said.
Researchers found the bridgmanite in a meteorite that had fallen to Earth near the Tenham station in western Queensland, Australia, in 1879.

 Bridgmanite-Mineral-Vein Bridgemante found in vein of meteor found in Australia

Earth may have underground 'ocean' three times that on surface

After decades of searching scientists have discovered that a vast reservoir of water, enough to fill the Earth’s oceans three times over, may be trapped hundreds of miles beneath the surface, potentially transforming our understanding of how the planet was formed.

The water is locked up in a mineral called ringwoodite about 400 miles beneath the crust of the Earth, researchers say. Geophysicist Steve Jacobsen from Northwestern University in the US co-authored the study published in the journal Science and said the discovery suggested Earth’s water may have come from within, driven to the surface by geological activity, rather than being deposited by icy comets hitting the forming planet as held by the prevailing theories.

Jacobsen and his colleagues are the first to provide direct evidence that there may be water in an area of the Earth’s mantle known as the transition zone. They based their findings on a study of a vast underground region extending across most of the interior of the US.
Jacobsen told the New Scientist that the hidden water might also act as a buffer for the oceans on the surface, explaining why they have stayed the same size for millions of years. "If [the stored water] wasn't there, it would be on the surface of the Earth, and mountaintops would be the only land poking out," he said.
Ringwoodite acts like a sponge due to a crystal structure that makes it attract hydrogen and trap water.

If just 1% of the weight of mantle rock located in the transition zone was water it would be equivalent to nearly three times the amount of water in our oceans, Jacobsen said.

 Ringwooditediamond A battered diamond that survived a trip from "hell" confirms a long-held theory: Earth's mantle is soaked.

"It's actually the confirmation that there is a very, very large amount of water that's trapped in a really distinct layer in the deep Earth," said Graham Pearson, lead study author and a geochemist at the University of Alberta in Canada. The findings were published on March 12 in the journal Nature.

The worthless-looking diamond encloses a tiny piece of an olivine mineral called ringwoodite, and it's the first time the mineral has been found on Earth's surface in anything other than meteorites or laboratories.

 Beneath Our Feet

Posted by Jill Fallon at June 19, 2014 11:18 AM | Permalink