Sunday, May 31, 2009

Discovery lead to historic volcanic eruption

A PREVIOUSLY unknown giant volcanic eruption that led to global mass extinctions 260m years ago has been "discovered" by scientists at the University of Leeds.
They say the eruption in the Emeishan province of south-west China unleashed around half a million cubic kilometres of lava, covering an area five times the size of Wales and triggering global annihilation of marine life.

Because the lava appears today as a distinctive layer of igneous rock containing easily datable fossilised marine life, the scientists were able to pinpoint the timing of the blast.

The fossilised rock shows mass extinction of different life forms, clearly linking the onset of the eruption with an environmental catastrophe.

The collision of fast-flowing lava with shallow sea water caused a violent explosion – throwing huge quantities of sulphur dioxide into the stratosphere.

"When fast-flowing, low-viscosity magma meets shallow sea it's like throwing water into a chip pan – there's a spectacular explosion producing gigantic clouds of steam," said Prof Paul Wignall, a palaeontologist at the University of Leeds, and the lead author of the paper.

The injection of sulphur dioxide into the atmosphere would have led to massive cloud formation spreading around the world – cooling the planet and ultimately resulting in acid rain. Scientists estimate from the fossil record that the disaster happened at the start of the eruption.

"The abrupt extinction of marine life we see in the fossil record firmly links giant volcanic eruptions with global environmental catastrophe," said Prof Wignall.

The work was done in collaboration with the Chinese University of Geosciences in Wuhan and funded by the Natural Environment Research Council, UK.

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