The PLEISTOCENE ( /ˈplaɪstəˌsiːn, -toʊ-/ , often colloquially
referred to as the ICE AGE) is the geological epoch which lasted from
about 2,588,000 to 11,700 years ago, spanning the world's most recent
period of repeated glaciations . The end of the Pleistocene
corresponds with the end of the last glacial period and also with the
end of the
Before a change finally confirmed in 2009 by the International Union
of Geological Sciences , the time boundary between the
* 1 Etymology * 2 Dating
* 3 Paleogeography and climate
* 3.3 Palaeocycles
* 4 Fauna
* 4.1 Humans
* 5 Deposits * 6 See also * 7 References * 8 External links
Human timeline view • discuss • edit -10 — – -9 — –
-8 — – -7 — – -6 — – -5 — – -4 — – -3 — – -2
— – -1 — – 0 — Human-like
Nakalipithecus _ _
Ouranopithecus _ _
s Axis scale : millions of years . Also see: _Life timeline _ and _Nature timeline _
In 2009 the
International Union of Geological Sciences (IUGS)
confirmed a change in time period for the Pleistocene, changing the
start date from 1.806 to 2.588 million years BP, and accepted the base
Gelasian as the base of the Pleistocene, namely the base of the
Monte San Nicola GSSP . The IUGS has yet to approve a type section ,
Global Boundary Stratotype Section and Point (GSSP), for the upper
PALEOGEOGRAPHY AND CLIMATE
The maximum extent of glacial ice in the north polar area during
The modern continents were essentially at their present positions during the Pleistocene, the plates upon which they sit probably having moved no more than 100 km relative to each other since the beginning of the period.
Mark Lynas (through collected data), the Pleistocene's
overall climate could be characterized as a continuous
El Niño with
trade winds in the south Pacific weakening or heading east, warm air
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Each glacial advance tied up huge volumes of water in continental ice sheets 1,500 to 3,000 metres (4,900–9,800 ft) thick, resulting in temporary sea-level drops of 100 metres (300 ft) or more over the entire surface of the Earth. During interglacial times, such as at present, drowned coastlines were common, mitigated by isostatic or other emergent motion of some regions.
The effects of glaciation were global.
In the northern hemisphere, many glaciers fused into one. The
Cordilleran ice sheet covered the North American northwest; the east
was covered by the
Laurentide . The Fenno-Scandian ice sheet rested on
northern Europe , including
South of the ice sheets large lakes accumulated because outlets were
blocked and the cooler air slowed evaporation. When the
sheet retreated, north central
It has been estimated that during the Pleistocene, the East Antarctic
Ice Sheet thinned by at least 500 meters, and that thinning since the
Over 11 major glacial events have been identified, as well as many minor glacial events. A major glacial event is a general glacial excursion, termed a "glacial." Glacials are separated by "interglacials". During a glacial, the glacier experiences minor advances and retreats. The minor excursion is a "stadial"; times between stadials are "interstadials".
These events are defined differently in different regions of the glacial range, which have their own glacial history depending on latitude, terrain and climate. There is a general correspondence between glacials in different regions. Investigators often interchange the names if the glacial geology of a region is in the process of being defined. However, it is generally incorrect to apply the name of a glacial in one region to another.
For most of the 20th century only a few regions had been studied and
the names were relatively few. Today the geologists of different
nations are taking more of an interest in
The glacials in the following tables show _historical_ usages, are a simplification of a much more complex cycle of variation in climate and terrain, and are generally no longer used. These names have been abandoned in favor of numeric data because many of the correlations were found to be either inexact or incorrect and more than four major glacials have been recognized since the historical terminology was established.
Historical names of the "four major" glacials in four regions. REGION GLACIAL 1 GLACIAL 2 GLACIAL 3 GLACIAL 4
ALPS Günz Mindel Riss Würm
NORTH EUROPE Eburonian Elsterian Saalian Weichselian
MIDWEST U.S. Nebraskan Kansan Illinoian Wisconsinan
Historical names of interglacials. REGION INTERGLACIAL 1 INTERGLACIAL 2 INTERGLACIAL 3
ALPS Günz-Mindel Mindel-Riss Riss-Würm
NORTH EUROPE Waalian Holsteinian Eemian
BRITISH ISLES Cromerian Hoxnian Ipswichian
MIDWEST U.S. Aftonian Yarmouthian Sangamonian
Corresponding to the terms glacial and interglacial, the terms pluvial and interpluvial are in use (Latin: _pluvia_, rain). A pluvial is a warmer period of increased rainfall; an interpluvial, of decreased rainfall. Formerly a pluvial was thought to correspond to a glacial in regions not iced, and in some cases it does. Rainfall is cyclical also. Pluvials and interpluvials are widespread.
There is no systematic correspondence of pluvials to glacials, however. Moreover, regional pluvials do not correspond to each other globally. For example, some have used the term "Riss pluvial" in Egyptian contexts. Any coincidence is an accident of regional factors. Only a few of the names for pluvials in restricted regions have been strategraphically defined.
The sum of transient factors acting at the Earth's surface is
cyclical: climate, ocean currents and other movements, wind currents,
temperature, etc. The waveform response comes from the underlying
cyclical motions of the planet, which eventually drag all the
transients into harmony with them. The repeated glaciations of the
Main article: Milankovitch cycles
Milankovitch cycles cannot be the sole factor responsible for the
variations in climate since they explain neither the long term cooling
trend over the Plio-Pleistocene, nor the millennial variations in the
Greenland Ice Cores. Milankovitch pacing seems to best explain
glaciation events with periodicity of 100,000, 40,000, and 20,000
years. Such a pattern seems to fit the information on climate change
found in oxygen isotope cores. The timing of our present interglacial
interval (known as the
Main article: Oxygen isotope ratio cycle
In oxygen isotope ratio analysis, variations in the ratio of 18 O to 16 O (two isotopes of oxygen ) by mass (measured by a mass spectrometer ) present in the calcite of oceanic core samples is used as a diagnostic of ancient ocean temperature change and therefore of climate change. Cold oceans are richer in 18 O, which is included in the tests of the microorganisms (foraminifera ) contributing the calcite.
A more recent version of the sampling process makes use of modern glacial ice cores. Although less rich in 18 O than sea water, the snow that fell on the glacier year by year nevertheless contained 18 O and 16 O in a ratio that depended on the mean annual temperature.
Temperature and climate change are cyclical when plotted on a graph of temperature versus time. Temperature coordinates are given in the form of a deviation from today's annual mean temperature, taken as zero. This sort of graph is based on another of isotope ratio versus time. Ratios are converted to a percentage difference from the ratio found in standard mean ocean water (SMOW).
The graph in either form appears as a waveform with overtones . One
half of a period is a
Marine isotopic stage
According to this evidence, Earth experienced 102 MIS stages
beginning at about 2.588 Ma BP in the Early
By convention, stages are numbered from the Holocene, which is MIS1. Glacials receive an even number; interglacials, odd. The first major glacial was MIS2-4 at about 85–11 ka BP. The largest glacials were 2, 6, 12, and 16; the warmest interglacials, 1, 5, 9 and 11. For matching of MIS numbers to named stages, see under the articles for those names.
Both marine and continental faunas were essentially modern but with
many more large land mammals such as mammoths , mastodons ,
The severe climatic changes during the ice age had major impacts on
the fauna and flora. With each advance of the ice, large areas of the
continents became totally depopulated, and plants and animals
retreating southward in front of the advancing glacier faced
tremendous stress. The most severe stress resulted from drastic
climatic changes, reduced living space, and curtailed food supply. A
major extinction event of large mammals (megafauna ), which included
mammoths , mastodons , saber-toothed cats , _glyptodon _s, ground
Irish elk , cave bears , and short-faced bears , began late
The extinctions were especially severe in
* Asian land mammal ages (ALMA) include Zhoukoudianian , Nihewanian , and Yushean . * European land mammal ages (ELMA) include Gelasian (2.5—1.8 Ma ). * North American land mammal ages (NALMA) include Blancan (4.75–1.8), Irvingtonian (1.8–0.24) and Rancholabrean (0.24–0.01) in millions of years. The Blancan extends significantly back into the Pliocene. * South American land mammal ages (SALMA) include Uquian (2.5–1.5), Ensenadan (1.5–0.3) and Lujanian (0.3–0.01) in millions of years. The Uquian previously extended significantly back into the Pliocene, although the new definition places it entirely within the Pleistocene.
The evolution of anatomically modern humans took place during the
Pleistocene. In the beginning of the
According to mitochondrial timing techniques, modern humans migrated from Africa after the Riss glaciation in the Middle Palaeolithic during the Eemian Stage , spreading all over the ice-free world during the late Pleistocene. A 2005 study posits that humans in this migration interbred with archaic human forms already outside of Africa by the late Pleistocene, incorporating archaic human genetic material into the modern human gene pool.
HOMININ SPECIES DURING PLEISTOCENE
* ^ Jones, Daniel (2003) , Peter Roach, James Hartmann and Jane
Setter, eds., _English Pronouncing Dictionary_, Cambridge: Cambridge
University Press, ISBN 3-12-539683-2 CS1 maint: Uses editors
parameter (link )
* ^ "Gibbard, P. and van Kolfschoten, T. (2004) "The Pleistocene
* ^ "Pleistocene".
Online Etymology Dictionary .
* ^ "Major Divisions". _Subcommission on