Last updated on April 18, 2014 at 12:48 EDT
Global Glaciations
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Global Glaciations

February 21, 2011
A diagram showing two theories on glaciation on early Earth (from 716.5 to 630 million years ago).

Two ideas exist on the progression of glaciation on Earth from 716.5 to 630 million years ago. Current evidence suggests the top version: a dynamic snowball Earth in which at least two long-lived glaciations happened during which communication between the ocean and the atmosphere was cut off. In this scenario, as CO2 built up, a hot-house effect ensued resulting in an ice-free planet at 670 and 630 million years ago.