Timeline of glaciation
There have been five or six major ice ages in the history of Earth over the past 3 billion years. The Late Cenozoic Ice Age began 34 million years ago, its latest phase being the Quaternary glaciation, in progress since 2.58 million years ago.
Within ice ages, there exist periods of more severe glacial conditions and more temperate referred to as glacial periods and interglacial periods, respectively. The Earth is currently in such an interglacial period of the Quaternary glaciation, with the last glacial period of the Quaternary having ended approximately 11,700 years ago, the current interglacial being known as the Holocene epoch. Based on climate proxies, paleoclimatologists study the different climate states originating from glaciation.
Known ice agesEdit
|Name of ice age||Years BP (Ma)||Geological period||Era|
|Pongola||2900 – 2780||Mesoarchean|
|Huron||2400 – 2100||Siderian
|715 – 680
650 – 635
(incl. Hirnantian and
Late Ordovician glaciation)
|450 – 420||Late Ordovician
|Karoo||360 – 260||Carboniferous
|Late Cenozoic Ice Age
(incl. Quaternary glaciation)
|34 – present||Late Paleogene
The third ice age, and possibly most severe, is estimated to have occurred from 720 to 635 Ma (million years) ago, in the Neoproterozoic Era, and it has been suggested that it produced a second "Snowball Earth", in which the Earth iced over completely. It has been suggested also that the end of this second cold period was responsible for the subsequent Cambrian Explosion, a time of rapid diversification of multicelled life during the Cambrian Period. However, this hypothesis is still controversial, though is growing in popularity among researchers, as evidence in its favor has mounted.[who?]
A minor series of glaciations occurred from 460 Ma to 430 Ma. There were extensive glaciations from 350 to 250 Ma.
The Late Cenozoic Ice Age has seen extensive ice sheets in Antarctica for the last 34 Ma. During the last 3 Ma ice sheets have also developed on the northern hemisphere. This phase is known as the Quaternary glaciation, and has seen more or less extensive glaciation on 40,000 and later, 100,000 year cycles.
Nomenclature of Quaternary glacial cyclesEdit
Whereas the first 30 million years of the Late Cenozoic Ice Age mostly involved Antarctica, the Quaternary has seen numerous ice sheets extending over parts of Europe and North America that are currently populated and easily accessible. Early geologists therefore named apparent sequences of glacial and interglacial periods of the Quaternary Ice Age after characteristic geological features, and these names varied from region to region. It is now more common for researchers to refer to the 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. Ice cores from continental ice accumulations also provide a complete record, but do not go as far back in time as marine data. Pollen data from lakes and bogs as well as loess profiles provided important land-based correlation data. The names system has mostly been phased out by professionals, who instead use the marine isotopic stage indexes for all technical discussions. For example, there are five Pleistocene glacial/interglacial cycles recorded in marine sediments during the last half million years, but only three classic interglacials were originally recognized on land during that period (Mindel, Riss and Würm).
Land-based evidence works acceptably well back as far as MIS 6, but it has been difficult to coordinate stages using just land-based evidence before that. Hence, the "names" system is incomplete and the land-based identifications of ice ages previous to that are somewhat conjectural. Nonetheless, land based data is essentially useful in discussing landforms, and correlating the known marine isotopic stage with them.
Historical nomenclature in the AlpesEdit
- Biber-Danube interglacial
- Danube-Gunz interglacial
- Günz-Haslach interglacial
- Haslach-Mindel interglacial
- Mindel (MIS 10 ?)
- Mindel-Riss interglacial (MIS 9 ?)
- Riss (ended with MIS 6)
- Riss-Würm interglacial (MIS 5e)
- Würm (MIS 5d-2)
Historical nomenclature in Great Britain and IrelandEdit
- Bramertonian Stage
- Baventian Stage/Pre-Pastonian
- Pastonian Stage
- Beestonian stage
- Cromerian Stage (MIS 21-13 ?)
- Anglian Stage (MIS 12, perhaps also MIS 10 ?)
- Hoxnian Stage (MIS 11, perhaps also MIS 9 ?)
- Wolstonian Stage (MIS 8-6, perhaps also MIS 10-9 ?)
- Ipswichian interglacial (MIS 5e)
- Devensian glaciation (MIS 5d-2)
- Flandrian interglacial (MIS 1)
Historical nomenclature in Northern EuropeEdit
- Tegelen/Tiglian interglacial
- Waalian interglacial
- Menapian glacial stage
- Cromerian complex (MIS 21-13 ?)
- Elster glaciation (MIS 10, perhaps also MIS 12 ?)
- Holstein interglacial (MIS 9 ?)
- Saale glaciation (ended with MIS 6)
- Eem interglacial (MIS 5e)
- Weichsel glaciation (MIS 5d-2)
Historical nomenclature in North AmericaEdit
- Nebraskan glaciation (replaced by Pre-Illinoian in modern scientific literature)
- Aftonian interglacial (replaced by Pre-Illinoian in modern scientific literature)
- Kansan glaciation (replaced by Pre-Illinoian in modern scientific literature)
- Yarmouthian (stage) (replaced by Pre-Illinoian in modern scientific literature)
- Illinoian stage (MIS 10, sometimes also MIS 8 ?)
- Sangamonian (MIS 5e, sometimes also 5d-5a)
- Wisconsin glaciation (MIS 4-2, sometimes also 5d-5a)
Historical nomenclature in South AmericaEdit
It has proved difficult to correlate the traditional regional names with the global marine and ice core sequences. The indexes of MIS often identify several distinct glaciations that overlap in time with a single traditional regional glaciation. Some modern authors use the traditional regional glacial names to identify such a sequence of glaciations, whereas others replace the word “glaciation” with “complex” to refer to a continuous period of time that also includes warmer stages. As shown in the table below, it is only during the last 200-300 thousand years that the time resolution of the traditional nomenclature allow for direct correspondence with MIS indexes.
|Historical regional names|
|Alpine region||Great Britain||N. Europe||N. America||S. America|
|MIS 5e||123 (peak)||Riss-Würm||Ipswich||Eem||Sangamon||Valdivia|
|MIS 5d||109 (peak)||AC||Devens/Early D.||Weichsel/Herning||AC||AC|
|MIS 5c||96 (peak)||AC||Devens/Early D.||Weichsel/Brørup||AC||AC|
|MIS 5b||87 (peak)||AC||Devens/Early D.||Weichsel/Rederstall||AC||AC|
|MIS 5a||82 (peak)||AC||Devens/Early D.||Weichsel/Odderade||AC||AC|
|MIS 4||71-57||Würm||Devens/Middle D.||Weichsel/Middle W.||Wisconsin||Llanquihue|
|MIS 3||57-29||Würm||Devens/Middle D.||Weichsel/Middle W.||Wisconsin||Llanquihue|
|Extensive interglacial (similar to Holocene)|
|Extensive glaciation (similar to LGM)|
|AC = Ambigous correlation|
For sources to the tables, see the individual linked articles.
- Brunhes–Matuyama reversal – The most recent geomagnetic reversal event (about 780,000 years ago)
- Geologic time scale – A system of chronological dating that relates geological strata to time
- Glacial history of Minnesota
- Glacial period
- Ice age – Period of long-term reduction in temperature of Earth's surface and atmosphere
- Last glacial period
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The dictionary definition of glaciation at Wiktionary
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