Editing Timeline of glaciation (section)

==Descriptions==
{{Life timeline}}
The third ice age, and possibly most severe, is estimated to have occurred from 720 to 635&nbsp;[[year|Ma]] (million years) ago,<ref name="SG-20170113">{{cite web|url=http://www.stratigraphy.org/index.php/ics-chart-timescale |title=Chart |publisher=International Commission on Stratigraphy |access-date=2017-02-14 |url-status=dead |archive-url=https://web.archive.org/web/20170113013553/http://www.stratigraphy.org/index.php/ics-chart-timescale |archive-date=2017-01-13 }}</ref> in the [[Neoproterozoic]] Era, and it has been suggested that it produced a second<ref name="2nd of two">Miracle Planet: Snowball Earth, (2005) documentary, Canadian Film Board, rebroadcast 25 April 2009 on the Science Channel (HD).</ref> "[[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<ref name="2nd of two"/> was responsible for the subsequent [[Cambrian explosion]], a time of rapid diversification of multi-cellular life during the [[Cambrian]] Period. The hypothesis is still controversial,<ref>{{cite book |last=van Andel |first=Tjeerd H. |title=New Views on an Old Planet: A History of Global Change |publisher=Cambridge University Press |location=Cambridge UK |year=1994 |isbn=978-0-521-44755-3 |edition=2nd }}</ref><ref>{{cite journal |author=Rieu, Ruben|title=Climatic cycles during a Neoproterozoic "snowball" glacial epoch |journal=Geology |volume=35 |issue=4 |pages=299–302 |year=2007 |doi=10.1130/G23400A.1|display-authors=etal|bibcode=2007Geo....35..299R }}</ref> though is gaining credence among researchers, as evidence in its favour has mounted.<ref>{{Cite web |title=The Cambrian Period |url=https://ucmp.berkeley.edu/cambrian/cambrian.php |access-date=2024-02-26 |website=ucmp.berkeley.edu}}</ref>

A minor series of [[wiktionary:glaciation|glaciations]] occurred from 460 to 430&nbsp;Ma, and there were extensive glaciations from 350 to 289&nbsp;Ma.

The [[Late Cenozoic Ice Age]] has seen extensive ice sheets in [[Antarctica]] for the last 34&nbsp;Ma. During the last 3&nbsp;Ma, 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-year problem|100,000 years]].<ref name="Willeit">{{cite journal|title=Mid-Pleistocene transition in glacial cycles explained by declining CO2 and regolith removal &#124; Science Advances|journal=Science Advances|date=April 2019 |volume=5 |issue=4 |pages=eaav7337 |doi=10.1126/sciadv.aav7337 |last1=Brovkin| first1=V.| last2=Calov| first2=R.|last3=Ganopolski| first3=A. |last4=Willeit |first4=M. |pmid=30949580 |pmc=6447376}}</ref>