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There have been four major periods of glaciation in the Earth's past. The first, and possibly most severe, may have occurred from 800 to 600 million years ago (the late Proterozoic Age) and it has been suggested that it produced a Snowball Earth in which the earth iced over completely. It has been suggested also that the end of this cold period was responsible for the subsequent Cambrian Explosion — this theory is recent and controversial.
A minor series of glaciations occurred from 460 to 430 million years ago. There were extensive glaciations from 350 million years before present to 250 million. The present Pleistocene ice age has seen more or less extensive glaciation on 40,000 and 100,000 year cycles. The last glacial period ended about 10,000 years ago.
The last glacial and interglacial phases of the Pleistocene are named, from most recent to most distant, as follows (names before the '/' are North America, names after it Northern European, dates in thousand years BCE. In the UK, Eastern Europe and the Alps yet other names are used; see Geology of the United Kingdom for UK names).
Originally, the periods were named after characteristic geological features, and these names vary from region to region. It is now perhaps more common (before the previous interglacial, the Eemian) to refer to periods by their Marine isotopic stage number. The marine record preserves all the past glaciations; the land-based evidence is less complete because successive glaciations may wipe out evidence of their predecessors. Hence the "names" system is incomplete: the Pastonian glaciation is MIS63, ie the 30th interglacial before present.
The Brunhes-Matuyama reversal occurred 780 kyr ago, approximately coincident with MIS19, the "Cromerian Complex" interglacial I, and can be used to date sediment cores.
| Name | Inter/Glacial | Period / MIS | Geologic period |
| Holocene | interglacial | present – 12 / MIS1 | |
| Wisconsinan / Weichsel or Vistula | glacial period, | 15 – 70 / MIS2-4 & 5a-d | Pleistocene |
| Sangamon / Eemian | interglacial, | 110 – 130 / MIS5e | |
| Illinoian / Saale | glacial, | 130 – 180 / MIS6 | |
| Yarmouth / Holstein | interglacial, | 180 – 230 / MIS7 | |
| Kansan / Elster | glacial, | 230 – 300 | |
| Aftonian / Cromer | interglacial, | 300 – 330 | |
| Nebraskan / Gunz | glacial, | 330 – 470 | |
| — / Waalian | interglacial | 470 – 540 | |
| — / Donau II | glacial | 540 – 550 | |
| — / Tiglian | interglacial | 550 – 585 | |
| — / Donau I | glacial | 585 – 600 | |
| / Pastonian interglacial | interglacial | 600 – 800 | |
| / Pre-Pastonian glaciation | glacial | 800 – 1.3 mill | |
| Bramertonian Interglacial | interglacial | 1.3 mill – 1.55 mill | |
| glacial | 250-350 Myr | Devonian, Carboniferous, Permian | |
| glacial | 430-460 Myr | Ordovician | |
| Cryogenian (or Sturtian-Varangian) | glacial | 650-900 Myr | late Proterozoic |
References
editSee also
edit[[Category:Climate change]] [[Category:Glaciology]] [[Category:History of climate]]