Snowball Earth or open oceans?
According to the ’Snowball Earth’ concept, the entire globe was frozen for extended intervals more than 600 million years ago. Not so, concludes a review article online in Nature Geoscience that examines earlier work on the topic.
Philip Allen and James Etienne evaluate earlier studies that investigated the Cryogenian period, approximately 840 to 635 millions of years ago, which was characterized by exceptionally severe periods of icehouse climate when low-altitude glaciers reached the low latitudes. The researchers conclude that, contrary to the Snowball Earth concept, the sedimentary evidence from this time points to a continuously active water cycle on Earth, which is inconsistent with the idea of oceans that were completely sealed by ice.
Determining whether substantial parts of the oceans remained ice-free has important consequences for our understanding of the survival and diversification of life and Earth’s carbon cycle.