The Snowball Earth is a geohistorical hypothesis that proposes during one or more of Earth's icehouse climates, the planet's surface became entirely or nearly entirely frozen with no liquid oceanic or surface water exposed to the atmosphere. The most academically referred period of such global glaciation is believed to have occurred sometime before 650 mya during the Cryogenian period.
Artist's rendition of a fully-frozen Snowball Earth with no remaining liquid surface water.
Diamictite of the Neoproterozoic Pocatello Formation, a "snowball Earth"-type deposit
Elatina Fm diamictite below Ediacaran GSSP site in the Flinders Ranges NP, South Australia. A$1 coin for scale.
2.1 billion-year-old rock with black-band ironstone
The Cryogenian is a geologic period that lasted from 720 to 635 million years ago. It forms the second geologic period of the Neoproterozoic Era, preceded by the Tonian Period and followed by the Ediacaran.
Diamictite of the Elatina Formation in South Australia, formed during the Marinoan glaciation of the late Cryogenian