The Cryogenian (from Greek cryos "cold" and genesis "birth") is a geologic period that began 850 mya and ended 635 mya. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly The greatest ice ages known to have occurred on Earth at this time, the Sturtian and Marinoan glaciations, which may have covered the entire planet, occurred during this period. "Glacial" and "Glaciation" redirect here For the geological periods see Glacial period. It was the second geologic period of the Neoproterozoic Era, preceded by the Tonian Period and followed by the Ediacaran. Geology (from Greek γη gê, "earth" and λόγος Logos, "speech" lit The Neoproterozoic Era is the unit of geologic time from 1000 to 542 +/- 0 The Tonian (from Greek tonas, "stretch" is the first Geologic period in the Neoproterozoic Era and lasted from The Ediacaran Period (ˌiːdiˈækərən named after the Ediacara Hills of South Australia) is the last geological period of the Neoproterozoic These so-called 'snowball earth' events are the subject of much scientific controversy. The Snowball Earth Hypothesis as it was originally proposed]] Evidence The Snowball Earth hypothesis was originally devised to explain the apparent presence of The main debate involves whether these glaciation are truly global events or whether they are localised glaciations and not a worldwide event.

The period has not yet undergone the international ratification that all geological time periods undergo (the most recent being the Ediacaran Period which was ratified in 2004. The Ediacaran Period (ˌiːdiˈækərən named after the Ediacara Hills of South Australia) is the last geological period of the Neoproterozoic ) The period is defined only on the dates of the rocks and no observable and documented systematic global event. This is problematic as estimates of rock dates are variable and are subject to laboratory error. For instance, the Cambrian Period is marked not by rock younger than 543 million years old (this is the date generally given for the base of the Cambrian), but by the appearance of the world wide Phycodes pedum trace fossil assemblage. The Cambrian is a geologic period and system that began about Ma (million years ago at the end of the Proterozoic eon and ended about Ma with This means that rocks can be recognised as Cambrian when you are looking at them in the field and do not require extensive testing to be performed in a lab to find a date. As such the Cryogenian Period is best considered as a candidate period awaiting validation.

The name refers to the very cold global climate of the Cryogenian: characteristic glacial deposits indicate that Earth suffered the most severe ice ages in its history during this period. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 Glaciers extended and contracted in a series of rhythmic pulses, possibly reaching as far as the equator. "Glacial" and "Glaciation" redirect here For the geological periods see Glacial period. ^[1] It is generally considered to be divisible into at least two major worldwide glaciations. The Sturtian glaciation persisted from 750 million years ago to 700 Ma, and the Marinoan/Varanger glaciation terminated at circa 635 Ma. The deposits of glacial tillite also occur in places that were at low latitudes during the Cryogenian, a phenomenon which led to the hypothesis of deeply-frozen planetary oceans called "Snowball Earth". Till is unsorted glacial sediment Glacial drift is a general term for the coarsely graded and extremely heterogeneous Sediments of glacial origin The Snowball Earth Hypothesis as it was originally proposed]] Evidence The Snowball Earth hypothesis was originally devised to explain the apparent presence of ^[2]

During the Cryogenian, the supercontinent Rodinia broke up, and the supercontinent Pannotia began to form. For the Genus of Metalmark butterflies, see Rodinia (butterfly. Pannotia, first described by Ian W D Dalziel in 1997 is a hypothetical Supercontinent that existed from the Pan-African orogeny about 600 million years ago to the

References

1. ^ Dave Lawrence, "Microfossil lineages support sloshy snowball Earth" in Geotimes, April 2003. http://www.agiweb.org/geotimes/apr03/WebExtra041803.html, accessed Sept 18, 2007.
2. ^ Hoffman, P. F. 2001. Snowball Earth theory, accessed 15/Jun/2007, http://www.snowballearth.org

• Cryogenian Period. GeoWhen Database. Retrieved on January 5, 2006.
• James G. Ogg (2004). "Status on Divisions of the International Geologic Time Scale". Lethaia 37: 183–199.  

Proterozoic eon
Paleoproterozoic era				Mesoproterozoic era			Neoproterozoic era
Siderian	Rhyacian	Orosirian	Statherian	Calymmian	Ectasian	Stenian	Tonian	Cryogenian	Ediacaran

The Proterozoic (ˌproʊtərəˈzoʊɪk is a geological eon representing a period before the first abundant complex life on Earth. The Paleoproterozoic (ˌpeɪlɪoʊˌproʊtərəˈzoʊɪk also spelled Palaeoproterozoic) is the first of the three sub-divisions ( eras) of the The Mesoproterozoic Era is a geologic era that occurred between 1600 Ma and 1000 Ma (million years ago The Neoproterozoic Era is the unit of geologic time from 1000 to 542 +/- 0 The Siderian (saɪˈdɪəriən sideros meaning "iron" is the first Geologic period in the Paleoproterozoic Era and lasted from 2500 The Rhyacian (raɪˈeɪsiən Ρυαξ ( rhyax) meaning "stream of Lava " is the second Geologic period in the Paleoproterozoic The Orosirian (ˌɒroʊˈsɪəriən oroseira - ὀροσειρά, meaning "mountain range" is the third Geologic period in the The Statherian (stəˈθɪəriən statheros, meaning "stable firm" is the final Geologic period in the Paleoproterozoic Era The Calymmian (from Greek calymma, "cover" is the first Geologic period in the Mesoproterozoic Era and lasted The Ectasian (from Greek ectasis, "extension" is the second Geologic period in the Mesoproterozoic era and lasted The Stenian (from Greek stenos, "narrow" is the final Geologic period in the Mesoproterozoic Era and lasted The Tonian (from Greek tonas, "stretch" is the first Geologic period in the Neoproterozoic Era and lasted from The Ediacaran Period (ˌiːdiˈækərən named after the Ediacara Hills of South Australia) is the last geological period of the Neoproterozoic

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