Meteorite hits mimic large volcanic eruptions

October 19th, 2011 - 4:06 pm ICT by IANS  

London, Oct 19 (IANS) Some aspects of giant meteorites that have struck the earth, often with devastating consequences, may mimic the behaviour of large volcanic eruptions, researchers say.

Mike Branney and Richard Brown, geologists from the universities of Leicester and Durham, respectively, reconstructed the impact of a meteorite hit with the help of forensics and how it hurled debris from the crater to devastate the surrounding region.

Meteorite impacts are more common than is popularly believed — but what happens when a meteorite hits?

Researchers picked through the still intact debris to reconstruct the catastrophic events.

Branney and Brown analysed an ejected layer derived from the impact of a huge meteorite and discovered that much of the ejected debris moved across the ground as rapid, dense, ground-hugging currents of gas and debris, according to a Leicester and Durham statement.

They are remarkably similar to the awesome pyroclastic density currents (PDC, made up of superheated gas and rocks) that flow outwards from explosive volcanoes, reaching temperatures of 1,000 degrees Celsius with speeds up to 700 kmph.

Branney said: “In particular, the way that ash and dust stick together seems identical. Moist ash from explosive volcanoes sticks together in the atmosphere to fall out as millimetre-sized pellets.

“These drop back into a hot pyroclastic density current. They grow into larger layered structures, known as accretionary lapilli.”

The researchers studied a finely preserved deposit in northwest Scotland from a huge impact that occurred a billion years ago.

It shows both types of these ‘volcanic’ particles - pellets and lapilli - are produced.

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