Friday, 28 Nov, 2008 Science

Billions of Years Ago Earth Looked Like Hell


According to Australian scientists, a layer of rock located inside the earth's mantle appeared as a result of Earth being roofed by a sea of lava, which was several kilometers thick 3.5 billion years ago.

Researchers used computer models of the planet's interior. After analyzing the models Dr Geoff Davies of the Australian National University, located in Canberra, said that these events could bring light on the formation of continents. The study and its results were published in the journal "Earth and Planetary Science Letters."

"We do know that the continents formed in several bursts. The biggest one occurred 2.7 billion years ago, earlier ones at 3 and 3.3 billion years ago," says Davies. He mentioned that it is yet not clear why things occurred in burst.

The scientist says that the heat produced under the crust of the planet appeared because of natural radioactive decay. The heat pushes convention currents in the layer, which drives against the tectonic plates that lead to the creation of the crust. One plate slides under another spontaneously, such process is known as subduction, reports ABC News.

The lead researcher created a computer model of the planet's interior in order to study the correlation between the subduction process and the mantle. The model of Dr Davies shows that throughout the first billion years on our planet, rock from the crust drops down to an area, where it gathers and later turns into a basaltic barrier.

"Once that blocking layer is there, there's no way for the heat from the deep mantle to escape to the surface," Davies says.

The temperature of the heat continuously increases till it breaks through the barrier arriving to the surface. Davies says that the heat melts while reaching the lower pressure next to the top of the mantle and afterwards the melted rock erupts as lava flows.

"The lava flows could pile up to a thickness of ten to fifteen kilometers over much of the earth," he said. Davies' model states that the volcanic events that take place on our planet may last for a period of 1 million years. The model also shows that these events occur once in very 100 million years.

Davies added that the volcanic events released huge amounts of carbon dioxide and sulfur dioxide, both having a serious impact on earth's oceans and atmosphere. Thus only the hardiest bacteria were able to survive.

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