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Lightning are changing Rocks at Atomic Level..

Lightning changes chemical composition of rocks
In the south of France, there’s a strange-looking rock outcropping, where a jagged fracture runs through granite. The surface in and around the crevice is discolored black, as if wet or covered in algae. But the real cause of the rock’s odd appearance is that it was struck by lightning.

We think of lightning as something that starts fires, knocks down trees, and in rare instances strikes an unlucky or unwary person. But as a team of researchers who examined the French rock outcropping with an electron microscope discovered, electrical discharges from the sky can alter rock in both obvious and subtle ways as well.

In this instance, lightning melted the rock’s surface, resulting in a distinctive black glaze.

But that’s not all. The lightning strike transferred enough pressure to deform a thin layer of quartz crystals beneath the surface, resulting in distinct atomic-level structures called shock lamellae — an effect that prior to this, scientists believed was caused only by the impact of meteorites.

“I think the most exciting thing about this study is just to see what lightning can do,” said Reto Gieré, a professor and chairman of the Department of Earth and Environmental Science in the University of Pennsylvania. “To see that lightning literally melts the surface of a rock and changes crystal structures, to me, is fascinating.”

Gieré, who described the research in a press release, and colleagues in Germany and Australia published their findings in American Mineralogist.

Previously, scientists had known that lightning could cause some changes in rocks, in part by increasing their temperature. When lightning hits sand, for example, it melts the grains, which fuse and form glass tubes known as fulgurites.
Gieré and colleagues took samples from the rock, cut and polished them, and then examined them under an optical microscope. They found that the black outer layer of the fulgurite had a black, ceramic-like glaze that was extremely porous, due to the lightning’s heat when it vaporized the rock surface.

A chemical analysis of the fulgurite layer showed elevated levels of sulfur dioxide and phosphorous pentoxide, which the researchers believe came from lichen living on the rock’s surface at the time of the lightning strike.

In an extremely thin layer — less than 4 percent of the width of a human hair — beneath the fulgurite, the scientists found shock lamellae, which are created when a crystal structure deforms in response to pressure.

“It’s like if someone pushes you, you rearrange your body to be comfortable,” Gieré said. “The mineral does the same thing.”

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