Even when Earth was locked in its most extreme deep freeze, the planet’s climate may not have been as silent and still as ...

Earth froze over 717 million years ago. Ice crept down from the poles to the equator, and the dark subglacial seas suffocated ...

Ancient rocks once beneath the ocean hold clues of severe conditions unimaginable on today's planet. Artwork showing the Earth during the Cryogenian period. This geologic period lasted from 850 to 635 ...