3.5 billion years ago, oceans were cool, not hot | Science News

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3.5 billion years ago, oceans were cool, not hot

Idea that Earth’s ancient seas were searing and inhospitable has hit an icy patch

2:09pm, February 26, 2016

 HOT IN SPOTS  Oxygen isotope data and field evidence from this chert in the Barberton Greenstone Belt in South Africa shows that, billions of years ago, the chert was altered and heated by localized hydrothermal activity on the ocean floor, not from a globally hot ocean. 

About 3.5 billion years ago, Earth’s oceans were cool, not inhospitably hot as previously thought. In fact, the entire planet at the time was probably locked in a cold snap that lasted at least 30 million years, a new study concludes. The findings, published online February 26 in Science Advances, could change the view of Earth’s ancient climate and life’s earliest years.

“This is the first evidence that over the entire [last] 3.5 billion years, Earth has operated within a temperature range that suits life,” says Maarten de Wit, a geologist at Nelson Mandela Metropolitan University in Port Elizabeth, South Africa.

Evidence for this big chill was found in South Africa’s Barberton Greenstone Belt, which contains some of the oldest, best preserved rocks on Earth. Along with Harald Furnes, a geologist at the University of Bergen in Norway, de Wit spent six

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