Timeline of glaciation

[[File:Phanerozoic Climate Change.png|thumb|350px|Climate history over the past 500 million years, with the last three major ice ages indicated,

Hirnantian (450 Mya), Late Paleozoic (300 Mya), and the Late Cenozoic. A less severe cold period or ice age is shown during the Jurassic-Cretaceous (150 Mya).]]

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 around 33.9 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 conditions, 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 around 11,700 years ago. The current interglacial is known as the Holocene epoch.

Based on climate proxies, paleoclimatologists study the different climate states originating from glaciation.

Known ice ages

900px|Major known ice ages shown in blue.

{| class="wikitable"

! Name of ice age

! Years ago

! Period

! Era

| Pongola

| 2.985-2.837 Bya

| Mesoarchean

| Huronian

| 2.4–2.1 Bya

| Siderian Rhyacian

| Paleoproterozoic

|Sturtian

|717–660 Mya

| rowspan="2" |Cryogenian

| rowspan="5" |Neoproterozoic

| rowspan="2" |Marinoan

| rowspan="2" |654.5–632.3 Mya

| rowspan="3" |Ediacaran

|Gaskiers

|579.88–579.63 Mya

| Baykonurian

| 547–540 Mya

| Hirnantian

| 460–420 Mya

| Ordovician Silurian

| rowspan="2" | Paleozoic

| Late Paleozoic icehouse

| 360–255 Mya

| Carboniferous Permian

| Late Cenozoic Ice Age (incl. Quaternary glaciation)

| 34 Mya–Present

| Late Paleogene Neogene Quaternary

| Cenozoic

Descriptions

The third ice age, and possibly most severe, is estimated to have occurred from 717 to 660 million years ago, in the Cryogenian Period, and it has been suggested that it produced a second "Snowball Earth", i.e. a period during which Earth was completely covered in ice. It has also been suggested that the end of that second cold period though is gaining credence among researchers, as evidence in its favour has mounted.

A minor series of glaciations occurred from 460 to 430 million years ago, and there were extensive glaciations from 350 to 289 million years ago.

The Late Cenozoic Ice Age has seen extensive ice sheets in Antarctica for the last 34 million years. During the last 3 million years, ice sheets have also developed on the northern hemisphere. That phase is known as the Quaternary glaciation, and was marked by more or less extensive glaciation. They first appeared with a dominant frequency of 41,000 years, but after the Mid-Pleistocene Transition that changed to high-amplitude cycles, with an average period of 100,000 years.

Nomenclature of Quaternary glacial cycles

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. 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. It is now more common for researchers to refer to the periods by their marine isotopic stage number. For example, there are five Pleistocene glacial/interglacial cycles recorded in marine sediments during the last half million years, but only three classic glacials were originally recognized on land during that period (Mindel, Riss and Würm).

Land-based evidence works acceptably well back as far as MIS 6 (see Marine isotope stages, Stages), 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.

Bavelian
Cromerian complex (MIS 21-13 ?)
Elster glaciation (MIS 12)
Holstein interglacial (MIS 11)
Saale glaciation (MIS 10-6)
Eem interglacial (MIS 5e)
Weichsel glaciation (MIS 5d-2)

Historical nomenclature in North America

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 6)
Sangamonian (MIS 5e, sometimes also 5d-5a)
Wisconsin glaciation (MIS 4-2, sometimes also 5d-5a)

Historical nomenclature in South America

Caracoles (Río Frío) glaciation

{| class="wikitable"

! rowspan=2|Marine isotope stage

! rowspan=2|Time ago (ka)

! colspan=6|Regional names

! rowspan=2|Global age / epoch

! Alpine region

! Great Britain

! N. Europe

! E. Europe

! N. America

! S. America

| MIS 103-64

| 2600–1800

| Biber

| Verkhodon

| Eburon

| Cromer

| Pre-illinois F

| Cromer

| Don

| Pre-illinois D

| Pre-illinois

|- BGCOLOR="#ddffdd"

| MIS 14

| 563–533

| Günz

| Anglia

| Pre-illinois

|- BGCOLOR="#ffffff"

| MIS 10

| 374–337

| Mindel?

| Holstein?

| AC

| Pre-illinois

|- BGCOLOR="#ffffff"

| MIS 6

| 191–130

| Riss

| Santa María Casma?

| Weichsel/Herning

| Valdai