Science

Earth was flat and almost entirely covered in water 4.4 billion years ago, new research suggests

Scientists came to the conclusion after analysing mineral grains from the oldest rocks ever found.

Earth 4.4 billion years ago was flat and almost entirely covered in water, with just a few small islands, if the latest research is anything to go by.

Scientists came to the conclusion after analysing tiny zircon mineral grains from a region of Western Australia containing the oldest rocks ever found.

Lead researcher Dr Antony Burnham, from the Australian National University, said: “The history of the Earth is like a book with its first chapter ripped out with no surviving rocks from the very early period, but we’ve used these trace elements of zircon to build a profile of the world at that time.

Dr Antony Burnham
Dr Antony Burnham (Stuart Hay/Australian National University)

“Our research indicates there were no mountains and continental collisions during Earth’s first 700 million years or more of existence – it was a much more quiet and dull place.

“Our findings also showed that there are strong similarities with zircon from the types of rocks that predominated for the following 1.5 billion years, suggesting that it took the Earth a long time to evolve into the planet that we know today.”

The team conducted a forensic study of the grains looking for clues to their formation and found that the zircon was created by melting old igneous rocks rather than sediments.

Zircon crystals.
Zircon crystals (Stuart Hay/Australian National University)

“Sediment melting is characteristic of major continental collisions, such as the Himalayas, so it appears that such events did not occur during these early stages of Earth’s history,” said Burnham.

The zircon grains, preserved in sandstone rocks in the Jack Hills, date back to when the Earth was only 160 million years old.

The new research fits in with the Cool Early Earth theory that suggests a cool, quiet period followed the extreme conditions of Earth’s earliest history.

Sandstone from the Jack Hills in Western Australia
Sandstone from the Jack Hills in Western Australia (Stuart Hay/Australian National University)

It pre-dated the Late Heavy Bombardment 4.1 to 3.8 billion years ago when the Earth was pummelled by comets and asteroids.

Bacterial life is thought to have emerged on Earth at the end of the bombardment around 3.8 billion years ago.

The study is published in the journal Nature Geoscience.

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