Australia - Kiwi 100 mln yr old break-up indicates similar fate for South America

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Sydney, March 22 (ANI): A team of geoscientists have created a mathematical model that accurately predicts how Australia and New Zealand broke apart 100 million years ago, and indicates that a similar process could be happening under South America.

According to a report in ABC Science, Australian geoscientists Associate Professor Patrice Rey and Professor Deitmar Muller from the University of Sydney, studied changes in magnetism on the ocean floor, which maps the movement of the plates.

Rey then modelled scenarios of the break up looking at aspects such as how changes in heat and density affected how the continents split apart.

The theory is relevant to the South American area, which may be undergoing the same, slow process of continental fragmentation, according to the researchers.

Between 105 to 90 million years ago Australia and New Zealand were joined at the hip along with Antarctica in a massive land mass called Gondwana.

The Pacific plate, which is denser and thinner than continental crust, dove under the supercontinent's east coast at the rate of 7 to 8 centimetres per year, which is about the same rate it currently sinks beneath South America.

"As the plates slowed down, contact between the two plates (the Pacific and Gondwanan) got smaller and smaller and the mountain belt along East Gondwana began to collapse, spreading under its own weight," said Rey.

At the same time, the rate of the Pacific plate's descent slowed. s it did, the mantle became more buoyant, and stretched instead of shortening.

This buoyant mantle exerted a force that pushed on the crust above, causing it to fracture.

The telltale cracks were the first wedges driving Australia and New Zealand apart, and also tore off the continental fragments that eventually became Lord Howe Island and the Challenger Rise, a submerged lump of continental crust off Australia's east coast.

"As the mantle pushed up, the nature of the plate boundary changed from a push to a pull," said Rey.

According to Rey, a similar situation is being played out at the other side of the Pacific.

During the last 20 million years the Pacific plate's descent under South America has slowed from 25 centimetres per year to about 7 centimetres per year.

"We can predict that if the velocity of the Pacific plate and the South American plate continues to decrease then the (Andes) will start to collapse and parts of South America will move away from the mainland," said Rey. (ANI)

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