Was the Earth once a massive global ocean?

Scientists in the US have found evidence that Earth used to be a water world billions of years ago.

It is widely believed that the continents - or land - used to be a supercontinent which broke apart 175 million years ago, but a new study in Nature Geoscience magazine gives more of an idea of what Earth looked like even further back.

Researchers from the Universities of Colorado and Iowa studied a 3.2 billion-year-old chunk of ocean crust.

The crust, which is found in the Panorama district in Australia's outback, has been turned on its side so scientists can see the layers.

By studying the different layers scientists worked out what happened to each layer throughout ancient history.

They discovered that around three billion years ago there were clay-rich soils present but not big soil-rich areas of land.

Scientists analysed the ancient rock layers and found that the Earth was mainly water and much smaller bits of land

This points to the Earth being covered in 'super oceans' and very small areas of clay-rich land - a very different planet compared to ours today.

"I imagine... vast expanses of ocean waters to the north and south with small volcanic rocky islets barely poking above the ocean surface," said Boswell Wing, of the University of Colorado.

The next mystery for researchers is to find out when the continents we know today were formed.