Study: Early Earth was flat and almost fully underwater
In its early life, the Earth was likely flat, barren and almost completely underwater with only a few small islands, according to new study.
The findings by Australian National University were based on analysis of tiny mineral grains as old as 4.4 billion years. The zircon mineral grains were preserved in sandstone rocks in the Jack Hills of Western Australia, the oldest fragments of the Earth ever found, the 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,” said lead researcher Antony Burnham.
The research indicates there were no mountains or continental collisions during Earth’s first 700 million years or more of existence.
“It was a much more quiet and dull place,” said Burnham.
There are strong similarities between zircon and 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, Burnham said.
Zircon grains that eroded out of the oldest rocks were like skin cells found at a crime scene, he said.
“We used the granites of southeast Australia to decipher the link between zircon composition and magma type, and built a picture of what those missing rocks were,” he said.
The first known form of life emerged some time later, around 3.8 billion years ago, Burnham said.
The samples of zircon from Jack Hills have been collected over the course of several decades by many people, while chemical analyses carried out by an ANU research group 20 years ago have proved invaluable,” he said.
The study was published in Nature Geoscience.
Source: Australian National University