Lake Eyre will not exist in 30 million years image

Geologists predict Lake Eyre will not exist in 30 million years.

One day Lake Eyre and the Murray-Darling Basin will cease to exist.

Whether humans will be around to deal with the consequences is harder to predict.

Scientists have discovered how Australia’s two largest basins formed. Their research also suggests that in 30 million years neither will exist.

Geologist Wouter Schellart and a colleague’s research has found that sitting more than 800 kilometres below the two basins is a large mass of oceanic plate sinking deep into the Earth’s mantle.

Dr Schellart thought that given the rate the plate was sinking it was likely pulling down on the Australian continent’s surface.

Lake Eyre is the lowest natural point in Australia, sitting 15 metres below sea level image

Lake Eyre is the lowest natural point in Australia, sitting 15 metres below sea level.

“It could be the cause of these basins,” said Dr Schellart, an associate professor at Monash University.

How this oceanic plate came to sit underneath these famous Australian basins starts 70 million years ago, when two tectonic plates collided and created a subduction zone, where one plate sinks beneath the other into the Earth’s mantle.

While the subduction zone is no longer active, Dr Schellart used supercomputers to reconstruct its life cycle. He discovered it had been active between 70 and 50 million years ago and was located “where we currently have the Lake Eyre and Murray-Darling Basins.”

At that time, as this huge stretch of ocean plate was disappearing into the mantle, the Australian continent was much further south than where it sits today, he said.

Then, about 40 million years ago, the Australian continental plate started moving northward directly over the top of the sinking mass.

With seismologist colleague Professor Wim Spakman from Utrecht University in the Netherlands, Dr Schellart used technology that tracks earthquakes to pinpoint the exact location of this subducted plate.

“We found it, more or less, in the place we predicted it to be,” he said.

They also figured out how hard it was likely pulling on the Australian continent, using that information to predict that the sinking plate would have drawn down the continent by about 200 metres.

“That fits very nicely with the depth of Lake Eyre and the Murray-Darling basin compared to the surrounding topography,” said Dr Schellart, whose research is published in the international journal Earth and Planetary Science Letters.

But as the Australian plate continues to move north, about five centimetres a year, there will come a point when Lake Eyre and the Murray-Darling Basins no longer sit over the sinking plate.

In about 30 million years Australia will be 1500 kilometres closer to the equator, he said.

“If the [ocean plate] is no longer pulling Australia down at those positions, Lake Eyre and the Murray-Darling Basin will come up again. There won’t be any basins there,” he said.


Henry Sapiecha

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