Pleistocene

Pleistocene

Overview
The Pleistocene (symbol PS) is the epoch
Epoch (geology)
An epoch is a subdivision of the geologic timescale based on rock layering. In order, the higher subdivisions are periods, eras and eons. We are currently living in the Holocene epoch...

 from 2,588,000 to 11,700 years BP
Before Present
Before Present years is a time scale used in archaeology, geology, and other scientific disciplines to specify when events in the past occurred. Because the "present" time changes, standard practice is to use AD 1950 as the origin of the age scale, reflecting the fact that radiocarbon...

 that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek (pleistos "most") and (kainos "new").

The Pleistocene Epoch follows the Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...

 Epoch and is followed by the Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...

 Epoch
Geologic time scale
The geologic time scale provides a system of chronologic measurement relating stratigraphy to time that is used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth...

. The Pleistocene is the first epoch of the Quaternary
Quaternary
The Quaternary Period is the most recent of the three periods of the Cenozoic Era in the geologic time scale of the ICS. It follows the Neogene Period, spanning 2.588 ± 0.005 million years ago to the present...

 Period or 6th epoch of the Cenozoic
Cenozoic
The Cenozoic era is the current and most recent of the three Phanerozoic geological eras and covers the period from 65.5 mya to the present. The era began in the wake of the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and...

 Era.
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Encyclopedia
The Pleistocene (symbol PS) is the epoch
Epoch (geology)
An epoch is a subdivision of the geologic timescale based on rock layering. In order, the higher subdivisions are periods, eras and eons. We are currently living in the Holocene epoch...

 from 2,588,000 to 11,700 years BP
Before Present
Before Present years is a time scale used in archaeology, geology, and other scientific disciplines to specify when events in the past occurred. Because the "present" time changes, standard practice is to use AD 1950 as the origin of the age scale, reflecting the fact that radiocarbon...

 that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek (pleistos "most") and (kainos "new").

The Pleistocene Epoch follows the Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...

 Epoch and is followed by the Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...

 Epoch
Geologic time scale
The geologic time scale provides a system of chronologic measurement relating stratigraphy to time that is used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth...

. The Pleistocene is the first epoch of the Quaternary
Quaternary
The Quaternary Period is the most recent of the three periods of the Cenozoic Era in the geologic time scale of the ICS. It follows the Neogene Period, spanning 2.588 ± 0.005 million years ago to the present...

 Period or 6th epoch of the Cenozoic
Cenozoic
The Cenozoic era is the current and most recent of the three Phanerozoic geological eras and covers the period from 65.5 mya to the present. The era began in the wake of the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and...

 Era. The end of the Pleistocene corresponds with the end of the last glacial period. It also corresponds with the end of the Paleolithic
Paleolithic
The Paleolithic Age, Era or Period, is a prehistoric period of human history distinguished by the development of the most primitive stone tools discovered , and covers roughly 99% of human technological prehistory...

 age used in archaeology
Archaeology
Archaeology, or archeology , is the study of human society, primarily through the recovery and analysis of the material culture and environmental data that they have left behind, which includes artifacts, architecture, biofacts and cultural landscapes...

.

In the ICS
International Classification for Standards
International Classification for Standards is an international classification system for technical standards. It is designed to cover every economic sector and virtually every activity of the humankind where technical standards may be used....

 timescale, the Pleistocene is divided into four stages or ages, the Gelasian
Gelasian
The Gelasian is an age in the international geologic timescale or a stage in chronostratigraphy, being the earliest or lowest subdivision of the Quaternary period/system and Pleistocene epoch/series. It spans the time between 2.588 ± 0.005 Ma and 1.806 ± 0.005 Ma...

, Calabrian, Ionian
Middle Pleistocene
The Middle Pleistocene, more specifically referred to as the Ionian stage, is a period of geologic time from ca. 781 to 126 thousand years ago....

 and Tarantian. All of these stages were defined in southern Europe. In addition to this international subdivision, various regional subdivisions are often used.

Before a change finally confirmed in 2009 by the International Union of Geological Sciences
International Union of Geological Sciences
The International Union of Geological Sciences is an international non-governmental organization devoted to international cooperation in the field of geology.-About:...

, the boundary between the Pleistocene and the preceding Pliocene was regarded as being at 1.806 not 2.588 million years BP; publications from the preceding years may use either definition of the period.

Dating


The Pleistocene has been dated from 2.588 million (±5,000) to 12,000 years before present
Before Present
Before Present years is a time scale used in archaeology, geology, and other scientific disciplines to specify when events in the past occurred. Because the "present" time changes, standard practice is to use AD 1950 as the origin of the age scale, reflecting the fact that radiocarbon...

 (BP), with the end date expressed in radiocarbon years as 10,000 carbon-14 years BP. It covers most of the latest period of repeated glaciation, up to and including the Younger Dryas
Younger Dryas
The Younger Dryas stadial, also referred to as the Big Freeze, was a geologically brief period of cold climatic conditions and drought between approximately 12.8 and 11.5 ka BP, or 12,800 and 11,500 years before present...

 cold spell. The end of the Younger Dryas has been dated to about 9640 BC (11,590 calendar years BP).

In 2009 the International Union of Geological Sciences
International Union of Geological Sciences
The International Union of Geological Sciences is an international non-governmental organization devoted to international cooperation in the field of geology.-About:...

 (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 of the Gelasian
Gelasian
The Gelasian is an age in the international geologic timescale or a stage in chronostratigraphy, being the earliest or lowest subdivision of the Quaternary period/system and Pleistocene epoch/series. It spans the time between 2.588 ± 0.005 Ma and 1.806 ± 0.005 Ma...

 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
Global Boundary Stratotype Section and Point
A Global Boundary Stratotype Section and Point, abbreviated GSSP, is an internationally agreed upon stratigraphic section which serves as the reference section for a particular boundary on the geologic time scale. The effort to define GSSPs is conducted by the International Commission on...

 (GSSP), for the upper Pleistocene/Holocene boundary (i.e. the upper boundary). The proposed section is the North Greenland Ice Core Project ice core 75° 06' N 42° 18' W. The lower boundary of the Pleistocene Series is formally defined magnetostratigraphically
Magnetostratigraphy
Magnetostratigraphy is a geophysical correlation technique used to date sedimentary and volcanic sequences. The method works by collecting oriented samples at measured intervals throughout the section. The samples are analyzed to determine their characteristic remanent magnetization , that is, the...

 as the base of the Matuyama (C2r) chronozone
Chronozone
A chronozone or chron is a slice of time that begins at a given identifiable event and ends at another. In the fossil record such tracer events are usually keyed to disappearance of a widely distributed and rapidly changing species or the appearance of such a species in the geological record...

, isotopic stage 103. Above this point there are notable extinctions of the calcareous nanofossils: Discoaster pentaradiatus and Discoaster surculus
Discoaster
Discoaster is a genus of fossil haptophytes.- Species :Some species in this genus include:*D. asymmetricus Gartner*D. bellus Bukry and Percival*D. berggrenii Bukry*D. bollii Martini and Bramlette...

.

The Pleistocene covers the recent period of repeated glaciations. The name Plio-Pleistocene has in the past been used to mean the last ice age. The revised definition of the Quaternary
Quaternary
The Quaternary Period is the most recent of the three periods of the Cenozoic Era in the geologic time scale of the ICS. It follows the Neogene Period, spanning 2.588 ± 0.005 million years ago to the present...

, by pushing back the start date of the Pleistocene to 2.58 Ma, results in the inclusion of all the recent repeated glaciations within the Pleistocene.

Paleogeography and climate



The modern continent
Continent
A continent is one of several very large landmasses on Earth. They are generally identified by convention rather than any strict criteria, with seven regions commonly regarded as continents—they are : Asia, Africa, North America, South America, Antarctica, Europe, and Australia.Plate tectonics is...

s 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.

According to Mark Lynas
Mark Lynas
Mark Lynas is a British author, journalist and environmental activist who focuses on climate change. He is a contributor to New Statesman, Ecologist, Granta and Geographical magazines, and The Guardian and The Observer newspapers in the UK; he also worked on the film The Age of Stupid...

 (through collected data), the Pleistocene's overall climate could be characterized as a continuous El Niño with trade winds in the south Pacific
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

 weakening or heading east, warm air rising near Peru
Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....

, warm water spreading from the west Pacific and the Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...

 to the east Pacific, and other El Niño markers.

Glacial features


Pleistocene climate was marked by repeated glacial cycles where continental glacier
Continental Glacier
Continental Glacier is located in Bridger-Teton and Shoshone National Forests, in the U.S. state of Wyoming and straddles the Continental Divide in the northern Wind River Range. Continental Glacier is in both the Bridger and Fitzpatrick Wildernesses, and is part of the largest grouping of glaciers...

s pushed to the 40th parallel in some places. It is estimated that, at maximum glacial extent, 30% of the Earth's surface was covered by ice. In addition, a zone of permafrost
Permafrost
In geology, permafrost, cryotic soil or permafrost soil is soil at or below the freezing point of water for two or more years. Ice is not always present, as may be in the case of nonporous bedrock, but it frequently occurs and it may be in amounts exceeding the potential hydraulic saturation of...

 stretched southward from the edge of the glacial sheet, a few hundred kilometres in North America, and several hundred in Eurasia. The mean annual temperature at the edge of the ice was -6 °C; at the edge of the permafrost, 0 °C (32 °F).

Each glacial advance tied up huge volumes of water in continental ice sheets 1500 to- thick, resulting in temporary sea level drops of 100 metres (328.1 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. Antarctica was ice-bound throughout the Pleistocene as well as the preceding Pliocene. The Andes
Andes
The Andes is the world's longest continental mountain range. It is a continual range of highlands along the western coast of South America. This range is about long, about to wide , and of an average height of about .Along its length, the Andes is split into several ranges, which are separated...

 were covered in the south by the Patagonia
Patagonia
Patagonia is a region located in Argentina and Chile, integrating the southernmost section of the Andes mountains to the southwest towards the Pacific ocean and from the east of the cordillera to the valleys it follows south through Colorado River towards Carmen de Patagones in the Atlantic Ocean...

n ice cap. There were glaciers in New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

 and Tasmania
Tasmania
Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...

. The current decaying glaciers of Mount Kenya
Mount Kenya
Mount Kenya is the highest mountain in Kenya and the second-highest in Africa, after Kilimanjaro. The highest peaks of the mountain are Batian , Nelion and Point Lenana . Mount Kenya is located in central Kenya, just south of the equator, around north-northeast of the capital Nairobi...

, Mount Kilimanjaro
Mount Kilimanjaro
Kilimanjaro, with its three volcanic cones, Kibo, Mawenzi, and Shira, is a dormant volcano in Kilimanjaro National Park, Tanzania and the highest mountain in Africa at above sea level .-Geology:...

, and the Ruwenzori Range
Ruwenzori Range
The Rwenzori Mountains, previously called the Ruwenzori Range , and sometimes the Mountains of the Moon, is a mountain range of central Africa, often referred to as Mt...

 in east and central Africa were larger. Glaciers existed in the mountains of Ethiopia
Ethiopia
Ethiopia , officially known as the Federal Democratic Republic of Ethiopia, is a country located in the Horn of Africa. It is the second-most populous nation in Africa, with over 82 million inhabitants, and the tenth-largest by area, occupying 1,100,000 km2...

 and to the west in the Atlas mountains
Atlas Mountains
The Atlas Mountains is a mountain range across a northern stretch of Africa extending about through Morocco, Algeria, and Tunisia. The highest peak is Toubkal, with an elevation of in southwestern Morocco. The Atlas ranges separate the Mediterranean and Atlantic coastlines from the Sahara Desert...

.

In the northern hemisphere, many glaciers fused into one. The Cordilleran ice sheet
Cordilleran Ice Sheet
The Cordilleran ice sheet was a major ice sheet that covered, during glacial periods of the Quaternary, a large area of North America. This included the following areas:*Western Montana*The Idaho Panhandle...

 covered the North American northwest; the east was covered by the Laurentide. The Fenno-Scandian ice sheet rested on north Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

, including Great Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...

; the Alpine ice sheet on the Alps. Scattered domes stretched across Siberia
Siberia
Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...

 and the Arctic shelf. The northern seas were ice-covered.

South of the ice sheets large lakes accumulated because outlets were blocked and the cooler air slowed evaporation. When the Laurentide ice sheet retreated, north central North America was totally covered by Lake Agassiz
Lake Agassiz
Lake Agassiz was an immense glacial lake located in the center of North America. Fed by glacial runoff at the end of the last glacial period, its area was larger than all of the modern Great Lakes combined, and it held more water than contained by all lakes in the world today.-Conception:First...

. Over a hundred basins, now dry or nearly so, were overflowing in the American west. Lake Bonneville
Lake Bonneville
Lake Bonneville was a prehistoric pluvial lake that covered much of North America's Great Basin region. Most of the territory it covered was in present-day Utah, though parts of the lake extended into present-day Idaho and Nevada. Formed about 32,000 years ago, it existed until about 14,500 years...

, for example, stood where Great Salt Lake
Great Salt Lake
The Great Salt Lake, located in the northern part of the U.S. state of Utah, is the largest salt water lake in the western hemisphere, the fourth-largest terminal lake in the world. In an average year the lake covers an area of around , but the lake's size fluctuates substantially due to its...

 now does. In Eurasia, large lakes developed as a result of the runoff from the glaciers. Rivers were larger, had a more copious flow, and were braided. African lakes were fuller, apparently from decreased evaporation. Deserts on the other hand were drier and more extensive. Rainfall was lower because of the decrease in oceanic and other evaporation.

Major events



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 Pleistocene glaciology. As a consequence, the number of names is expanding rapidly and will continue to expand. Many of the advances and stadials remain unnamed. Also, the terrestrial evidence for some of them has been erased or obscured by larger ones, but evidence remains from the study of cyclical climate changes.

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
Beestonian stage
The Beestonian Stage is the name for an early Pleistocene stage used in the British Isles. It precedes the Cromerian Stage and follows the Pastonian Stage. This stage consists of alternating glacial and interglacial phases instead of being a continuous glacial epoch. It is equivalent to the...

Mindel Riss Würm
Last Glacial Maximum
The Last Glacial Maximum refers to a period in the Earth's climate history when ice sheets were at their maximum extension, between 26,500 and 19,000–20,000 years ago, marking the peak of the last glacial period. During this time, vast ice sheets covered much of North America, northern Europe and...

North Europe Eburonian Elsterian Saalian Weichselian
Last Glacial Maximum
The Last Glacial Maximum refers to a period in the Earth's climate history when ice sheets were at their maximum extension, between 26,500 and 19,000–20,000 years ago, marking the peak of the last glacial period. During this time, vast ice sheets covered much of North America, northern Europe and...

British Isles Beestonian
Beestonian stage
The Beestonian Stage is the name for an early Pleistocene stage used in the British Isles. It precedes the Cromerian Stage and follows the Pastonian Stage. This stage consists of alternating glacial and interglacial phases instead of being a continuous glacial epoch. It is equivalent to the...

Anglian Wolstonian Devensian
Midwest U.S. Nebraskan Kansan
Kansan glaciation
The Kansan glaciation or Kansan glacial was glacial stage and part of an early conceptual climatic and chronological framework composed of four glacial and interglacial stages.-History:...

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
Yarmouthian Interglacial (Stage)
The Yarmouthian stage and the Yarmouth Interglacial were part of a now obsolete geologic timescale of the early Quaternary of North America.-Development:This climatic and chronological framework was composed of four glacial and interglacial stages...

Sangamonian
Sangamonian Stage
The Sangamonian Stage, also known as the Sangamon interglacial, is the name used by Quaternary geologists to designate the last interglacial period in North America from 125,000—75,000 years ago, a period of...



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.

Palaeocycles


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 Pleistocene were caused by the same factors.

Milankovitch cycles



Glaciation in the Pleistocene was a series of glacials and interglacials, stadials and interstadials, mirroring periodic changes in climate. The main factor at work in climate cycling is now believed to be Milankovitch cycles
Milankovitch cycles
Milankovitch theory describes the collective effects of changes in the Earth's movements upon its climate, named after Serbian civil engineer and mathematician Milutin Milanković, who worked on it during First World War internment...

. These are periodic variations in regional solar radiation caused by the sum of many repeating changes in the Earth's motion.

Milankovitch cycles cannot be the sole factor since they do not explain the start and end of the Pleistocene ice age, or of repeated ice ages. They seem to work best within the Pleistocene, predicting a glaciation once every 100,000, 40,000, and 20,000 years, based on his calculations of the Earth's orbital variation. 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 Holocene, Postglacial, or the Present Interglacial) to that of the previous interglacial beginning about 130,000 years ago (Sangamon), suggests that the next glacial will begin in about 3,000 years.

Oxygen isotope ratio cycles



In oxygen isotope ratio
Oxygen isotope ratio cycle
Oxygen isotope ratio cycles are cyclical variations in the ratio of the abundance of oxygen with an atomic mass of 18 to the abundance of oxygen with an atomic mass of 16 present in some substances, such as polar ice or calcite in ocean core samples. The ratio is linked to water temperature of...

 analysis, variations in the ratio of to (two isotopes of oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

) by mass
Mass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...

 (measured by a mass spectrometer) present in the calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...

 of oceanic core sample
Core sample
A core sample is a cylindrical section of a naturally occurring substance. Most core samples are obtained by drilling with special drills into the substance, for example sediment or rock, with a hollow steel tube called a core drill. The hole made for the core sample is called the "core hole". A...

s is used as a diagnostic of ancient ocean temperature change and therefore of climate change. Cold oceans are richer in , which is included in the tests of the microorganisms (foraminifera
Foraminifera
The Foraminifera , or forams for short, are a large group of amoeboid protists which are among the commonest plankton species. They have reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net...

) contributing the calcite.

A more recent version of the sampling process makes use of modern glacial ice cores. Although less rich in than sea water, the snow that fell on the glacier year by year nevertheless contained and 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
Waveform
Waveform means the shape and form of a signal such as a wave moving in a physical medium or an abstract representation.In many cases the medium in which the wave is being propagated does not permit a direct visual image of the form. In these cases, the term 'waveform' refers to the shape of a graph...

 with overtones. One half of a period is a Marine isotopic stage
Marine isotopic stage
Marine isotope stages , marine oxygen-isotope stages, or oxygen isotope stages , are alternating warm and cool periods in the Earth's paleoclimate, deduced from oxygen isotope data reflecting changes in temperature derived from data from deep sea core samples...

 (MIS). It indicates a glacial (below zero) or an interglacial (above zero). Overtones are stadials or interstadials.

According to this evidence, Earth experienced 102 MIS stages beginning at about 2.588 Ma BP
Before Present
Before Present years is a time scale used in archaeology, geology, and other scientific disciplines to specify when events in the past occurred. Because the "present" time changes, standard practice is to use AD 1950 as the origin of the age scale, reflecting the fact that radiocarbon...

 in the Early Pleistocene Gelasian
Gelasian
The Gelasian is an age in the international geologic timescale or a stage in chronostratigraphy, being the earliest or lowest subdivision of the Quaternary period/system and Pleistocene epoch/series. It spans the time between 2.588 ± 0.005 Ma and 1.806 ± 0.005 Ma...

. Early Pleistocene stages were shallow and frequent. The latest were the most intense and most widely spaced.

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.

Fauna



Both marine and continental faunas were essentially modern and many animals, specifically, mammals were much larger than their modern relatives .


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
Holocene extinction event
The Holocene extinction refers to the extinction of species during the present Holocene epoch . The large number of extinctions span numerous families of plants and animals including mammals, birds, amphibians, reptiles and arthropods; a sizeable fraction of these extinctions are occurring in the...

 of large mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s (megafauna
Megafauna
In terrestrial zoology, megafauna are "giant", "very large" or "large" animals. The most common thresholds used are or...

), which included mammoth
Mammoth
A mammoth is any species of the extinct genus Mammuthus. These proboscideans are members of Elephantidae, the family of elephants and mammoths, and close relatives of modern elephants. They were often equipped with long curved tusks and, in northern species, a covering of long hair...

s, mastodon
Mastodon
Mastodons were large tusked mammal species of the extinct genus Mammut which inhabited Asia, Africa, Europe, North America and Central America from the Oligocene through Pleistocene, 33.9 mya to 11,000 years ago. The American mastodon is the most recent and best known species of the group...

s, saber-toothed cats
Machairodontinae
Machairodontinae is an extinct carnivoran mammal subfamily of Felidae endemic to Asia, Africa, North America, South America, and Europe from the Miocene to Pleistocene living from c. 23 Ma until c...

, glyptodon
Glyptodon
Glyptodon was a large, armored mammal of the family Glyptodontidae, a relative of armadillos that lived during the Pleistocene Epoch. It was roughly the same size and weight as a Volkswagen Beetle, though flatter in shape...

s, ground sloth
Ground sloth
Ground sloths are a diverse group of extinct sloths, in the mammalian superorder Xenarthra. Their most recent survivors lived in the Antilles, where it has been proposed they may have survived until 1550 CE; however, the youngest AMS radiocarbon date reported is 4190 BP, calibrated to c. 4700 BP...

s, Irish elk
Irish Elk
The Irish Elk or Giant Deer , was a species of Megaloceros and one of the largest deer that ever lived. Its range extended across Eurasia, from Ireland to east of Lake Baikal, during the Late Pleistocene. The latest known remains of the species have been carbon dated to about 7,700 years ago...

, cave bear
Cave Bear
The cave bear was a species of bear that lived in Europe during the Pleistocene and became extinct at the beginning of the Last Glacial Maximum about 27,500 years ago....

s, and short-faced bears
Arctodus
Arctodus — known as the short-faced bear or bulldog bear — is an extinct genus of bear endemic to North America during the Pleistocene ~3.0 Ma.—11,000 years ago, existing for approximately three million years. Arctodus simus may have once been Earth's largest mammalian, terrestrial carnivore...

, began late in the Pleistocene and continued into the Holocene. Neanderthal
Neanderthal
The Neanderthal is an extinct member of the Homo genus known from Pleistocene specimens found in Europe and parts of western and central Asia...

s also became extinct during this period. At the end of the last ice age, cold-blooded
Poikilotherm
A poikilotherm is an organism whose internal temperature varies considerably. It is the opposite of a homeotherm, an organism which maintains thermal homeostasis. Usually the variation is a consequence of variation in the ambient environmental temperature...

 animals, smaller mammals like wood mice
Wood mouse
The wood mouse is a common murid rodent from Europe and northwestern Africa. It is closely related to the yellow-necked mouse but differs in that it has no band of yellow fur around the neck, has slightly smaller ears, and is usually slightly smaller overall: around 90 mm in length...

, migratory birds, and swifter animals like whitetail deer had replaced the megafauna and migrated north.

The extinctions were especially severe in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 where native horse
Horse
The horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...

s and camel
Camel
A camel is an even-toed ungulate within the genus Camelus, bearing distinctive fatty deposits known as humps on its back. There are two species of camels: the dromedary or Arabian camel has a single hump, and the bactrian has two humps. Dromedaries are native to the dry desert areas of West Asia,...

s were eliminated.
  • Asian Land Mammal Ages
    Asian land mammal ages
    The Asian Land Mammal Ages establishes a geologic timescale for prehistoric Asian fauna beginning 58.7 Mya during the Paleogene and continuing through to the Middle Pleistocene...

     (ALMA) include Zhoukoudianian, Nihewanian, and Yushean.
  • European Land Mammal Ages
    European Land Mammal Ages
    The European Land Mammal Mega Zones are zones in rock layers that have a specific assemblage of fossils based on occurrences of fossil assemblages of European land mammals. These biozones cover most of the Neogene and Paleogene systems The European Land Mammal Mega Zones (abbreviation: ELMMZ,...

     (ELMA) include Gelasian
    Gelasian
    The Gelasian is an age in the international geologic timescale or a stage in chronostratigraphy, being the earliest or lowest subdivision of the Quaternary period/system and Pleistocene epoch/series. It spans the time between 2.588 ± 0.005 Ma and 1.806 ± 0.005 Ma...

     (2.5—1.8 Ma).
  • North American Land Mammal Ages
    North American Land Mammal Ages
    The North American Mammal Ages establishes a geologic timescale for prehistoric North American fauna beginning 66.5 Ma during the Paleocene and continuing through to the Late Pleistocene...

     (NALMA) include Blancan
    Blancan
    The Blancan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 4,750,000 to 1,808,000 years BP, a period of .. It is usually considered to start in the early-mid Pliocene epoch and end...

     (4.5–1.2), Irvingtonian
    Irvingtonian
    The Irvingtonian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 1,800,000 to 300,000 years BP, a period of . It is usually considered to overlap the Lower Pleistocene and Middle...

     (1.2–0.5) and Rancholabrean
    Rancholabrean
    The Rancholabrean North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from less than 240,000 years to 11,000 years BP, a period of . It is usually considered to overlap the Middle Pleistocene...

     (0.5–0.01) in millions of years. The Blancan extends significantly back into the Pliocene.
  • South American Land Mammal Ages (SALMA) include Uquian
    Uquian
    The Uquian age is a period of geologic time within the Pliocene epoch of the Neogene used more specifically with South American Land Mammal Ages. It follows the Montehermosan and precedes the Ensenadan age....

     (2.5–1.5), Ensenadan
    Ensenadan
    The Ensenadan age is a period of geologic time within the Early Pleistocene epoch of the Neogene used more specifically with South American Land Mammal Ages. It follows the Uquian and precedes the Lujanian age....

     (1.5–0.3) and Lujanian
    Lujanian
    The Lujanian age is a period of geologic time within the Pleistocene and Holocene epochs of the Neogene used more specifically with South American Land Mammal Ages...

     (0.3–0.01) in millions of years. The Uquian extends significantly back into the Pliocene.

Humans during the Pleistocene



Scientific evidence indicates that human
Human
Humans are the only living species in the Homo genus...

s evolved into their present form during the Pleistocene. In the beginning of the Pleistocene Paranthropus
Paranthropus
The robust australopithecines, members of the extinct hominin genus Paranthropus , were bipedal hominids that probably descended from the gracile australopithecine hominids...

species are still present, as well as early human ancestors, but during the lower Palaeolithic they disappeared, and the only hominid species found in fossilic records is Homo erectus
Homo erectus
Homo erectus is an extinct species of hominid that lived from the end of the Pliocene epoch to the later Pleistocene, about . The species originated in Africa and spread as far as India, China and Java. There is still disagreement on the subject of the classification, ancestry, and progeny of H...

for much of the Pleistocene. The Middle and late Palaeolithic saw the appearance of new types of humans, as well as the development of more elaborate tools than found in previous eras. 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. Humans in this migration interbred with archaic human forms already outside of African by the late Pleistocene, incorporating archaic human genetic material into the modern human gene pool.

Deposits


Pleistocene non-marine sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....

s are found primarily in fluvial deposits, lakebeds, slope and loess
Loess
Loess is an aeolian sediment formed by the accumulation of wind-blown silt, typically in the 20–50 micrometre size range, twenty percent or less clay and the balance equal parts sand and silt that are loosely cemented by calcium carbonate...

 deposits as well as in the large amounts of material moved about by glaciers. Less common are cave
Cave
A cave or cavern is a natural underground space large enough for a human to enter. The term applies to natural cavities some part of which is in total darkness. The word cave also includes smaller spaces like rock shelters, sea caves, and grottos.Speleology is the science of exploration and study...

 deposits, travertine
Travertine
Travertine is a form of limestone deposited by mineral springs, especially hot springs. Travertine often has a fibrous or concentric appearance and exists in white, tan, and cream-colored varieties. It is formed by a process of rapid precipitation of calcium carbonate, often at the mouth of a hot...

s and volcanic deposits (lavas, ashes). Pleistocene marine deposits are found primarily in shallow marine basins mostly (but with important exceptions) in areas within a few tens of kilometers of the modern shoreline. In a few geologically active areas such as the Southern California
Southern California
Southern California is a megaregion, or megapolitan area, in the southern area of the U.S. state of California. Large urban areas include Greater Los Angeles and Greater San Diego. The urban area stretches along the coast from Ventura through the Southland and Inland Empire to San Diego...

 coast, Pleistocene marine deposits may be found at elevations of several hundred meters.

See also

  • Abbassia Pluvial
    Abbassia Pluvial
    The Abbassia Pluvial was an extended wet and rainy period in the climate history of North Africa. It began c. 120,000 years before the present , lasted approximately 30,000 years, and ended c. 90,000 ybp...

  • Geologic time scale
    Geologic time scale
    The geologic time scale provides a system of chronologic measurement relating stratigraphy to time that is used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth...

  • Glacial history of Minnesota
    Glacial history of Minnesota
    The glacial history of Minnesota is most defined since the onset of the last glacial period, which ended some 10,000 years ago. Within the last million years, most of the Midwestern United States and much of Canada were covered at one time or another with an ice sheet. This continental glacier had...

  • Ice age
    Ice age
    An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...

  • List of fossil sites (with link directory)
  • Mousterian Pluvial
    Mousterian Pluvial
    The Mousterian Pluvial was an extended wet and rainy period in the climate history of North Africa. It occurred during the Upper Paleolithic era, beginning around 50,000 years before the present , lasting 20,000 years, and ending around 30,000 ybp .During the Mousterian Pluvial, the now-desiccated...

  • Paleontological Museum in Tocuila
    Paleontological Museum in Tocuila
    The Paleontological Museum in Tocuila displays part of one of the richest deposits of Late Pleistocene fauna in America...

  • Pleistocene megafauna
    Pleistocene megafauna
    Pleistocene megafauna is the set of species of large animals — mammals, birds and reptiles — that lived on Earth during the Pleistocene epoch and became extinct in a Quaternary extinction event. These species appear to have died off as humans expanded out of Africa and southern Asia,...

  • Pleistocene Park
    Pleistocene Park
    Pleistocene Park is a nature reserve south of Chersky in the Sakha Republic in northeastern Siberia, where an attempt is being made to recreate the northern steppe grassland ecosystem that flourished in the area during the last ice age.-Goals:...

  • Terasecond and longer
    Terasecond and longer
    A terasecond is 1 trillion seconds, or roughly 31,700 years. This page lists time-spans above 1 terasecond. 1 thousand teraseconds is called a petasecond...


External links



style="font-size:larger;"| Hominin
Hominini
Hominini is the tribe of Homininae that comprises Homo, and the two species of the genus Pan , their ancestors, and the extinct lineages of their common ancestor . Members of the tribe are called hominins...

species during Pleistocene