Snowball Earth again
A second round of ice all the way to the tropics
See it on the timeline →In depth
The Marinoan glaciation is better dated than the preceding Sturtian, and ends sharply at 635.5 million years. The Elatina Formation in the Flinders Ranges carries the classic evidence: glacially deposited sediments with palaeomagnetic signatures showing low latitude. That two snowballs occur back to back strengthens the explanation: the break-up of Rodinia exposed vast quantities of basalt in the tropics, where weathering is fastest, and basalt weathering draws CO₂ out of the atmosphere. The climate system was pushed over a threshold twice by the same cause.
For children
Earth had barely thawed before it froze again. This time it lasted "only" 15 million years, but the ice reached just as far towards the equator. In Australia lie rocks scratched by glaciers — laid down in what was then the tropics.
Connects to
Part of Terra Saga — the story of Earth on a timeline. terrasaga.org