Concepts
Snowball Earth
Also Known As Snowball Earth Hypothesis
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The geohistorical hypothesis that during one or more of Earth's icehouse climates the planet's surface was nearly entirely frozen, with little or no liquid water exposed. It is most commonly associated with the Cryogenian period's two major glacial episodes, the Sturtian at roughly 717 to 660 million years ago and the Marinoan at roughly 650 to 635 million years ago, and its proposed episodes precede the sudden radiations of multicellular life known as the Avalon and Cambrian explosions; whether Earth was a full snowball or a slushball with an open equatorial band remains unresolved.
Facts
Origin YearThe term was coined by Joseph Kirschvink in 1992; the broader glaciation hypothesis had earlier antecedents. Cross-Tradition Connections
Associated With
Most commonly associated with the Cryogenian period's Sturtian and Marinoan glacial episodes.
In Discipline
A geohistorical hypothesis about Earth's icehouse climates.
Sources
1. Snowball Earth (Wikipedia)
Wikimedia FoundationLead sectionQuote, Lead section
The snowball Earth hypothesis was originally devised to explain geological evidence for the apparent presence of glaciers at tropical latitudes.
1. Snowball Earth (Wikipedia)
Wikimedia FoundationGlobal glaciation proposedQuote, Global glaciation proposed
The term "snowball Earth" was coined by Joseph Kirschvink in a short paper published in 1992.
Open Questions (1 open question)
Was Snowball Earth a full snowball or a slushball with an open equatorial band?
Proponents argue that near-total glaciation best explains glacial deposits at tropical palaeolatitudes and other enigmatic features of the Cryogenian record, while opponents contest the geological evidence for global glaciation and the geophysical feasibility of an ice-covered or slush-covered ocean, and emphasize the difficulty of escaping an all-frozen state. Whether an equatorial band of open or seasonally open water persisted remains one of the hypothesis's named unanswered questions.
What would resolve this Sedimentary or geochemical evidence that settles whether open water persisted at the Cryogenian equator during the Sturtian and Marinoan episodes, tested against climate models able to reproduce both entry into and escape from the frozen state.
Paleoclimatology, Geology, GeochemistrySnowball Earth (Wikipedia)
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