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
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.
M. de Wit