Snowball Earth

The name given to the hypothesis that the Earth was almost completely covered by glacier ice in late Precambrian time (c. 1000 to 542 million years ago).

Boulders dropped by icebergs into laminated marine sediment in late Precambrian time, Narachaampspos, Kaokoveld, Namibia. The chief proponent of the Snowball Earth hypothesis, Paul Hoffman, points to the transition to carbonate rocks which indicate the sudden termination of this frigid event. Photo M. J. Hambrey.