Editing Ice age (section)

===Volcanism===
Volcanic eruptions may have contributed to the inception and/or the end of ice age periods. At times during the paleoclimate, carbon dioxide levels were two or three times greater than today. Volcanoes and movements in continental plates contributed to high amounts of CO<sub>2</sub> in the atmosphere. Carbon dioxide from volcanoes probably contributed to periods with highest overall temperatures.<ref>{{cite web|last=Rieke|first=George|title=Long Term Climate|url=http://ircamera.as.arizona.edu/NatSci102/NatSci102/lectures/climate.htm|access-date=25 April 2013|archive-date=2 June 2015|archive-url=https://web.archive.org/web/20150602033750/http://ircamera.as.arizona.edu/NatSci102/NatSci102/lectures/climate.htm|url-status=dead}}</ref> One suggested explanation of the [[Paleocene–Eocene Thermal Maximum]] is that undersea volcanoes released [[methane]] from [[clathrate]]s and thus caused a large and rapid increase in the [[greenhouse effect]].<ref>{{Cite web|url=https://www.wunderground.com/climate/PETM.asp|title=PETM: Global Warming, Naturally |website=Weather Underground |access-date=2016-12-02|url-status=dead|archive-url=https://web.archive.org/web/20161202234346/https://www.wunderground.com/climate/PETM.asp|archive-date=2016-12-02}}</ref>  There appears to be no geological evidence for such eruptions at the right time, but this does not prove they did not happen.