Editing Lake Agassiz (section)

== Geological progression ==
During the [[Last Glacial Period|last glacial maximum]], northern North America was covered by an [[ice sheet]], which alternately advanced and retreated with variations in the climate. This continental ice sheet formed during the period now known as the [[Wisconsin glaciation]], and covered much of central North America between 30,000 and 10,000 years ago. As the ice sheet disintegrated,<ref>The "retreat" of glacial margins is not caused by a reversal of the glacier's flow, but rather from melting of the ice sheet.</ref> its meltwaters created an immense [[proglacial lake]].<ref name=Ojakangas>{{cite book|vauthors=Ojakangas RW, Matsch CL |title=Minnesota's Geology|url=https://archive.org/details/minnesotasgeolog00ojak |url-access=limited |year=1982|publisher=University of Minnesota Press|location=Minnesota|isbn=978-0816609536|pages=[https://archive.org/details/minnesotasgeolog00ojak/page/n116 106]–110}}</ref>

Around 13,000 years ago, this lake came to cover much of what are now southeastern [[Manitoba]], northwestern [[Ontario]], northern [[Minnesota]], eastern [[North Dakota]], and [[Saskatchewan]]. At its greatest extent, it may have covered as much as {{convert|440000|km2|sqmi|abbr=on}},<ref>{{cite journal| last1 = Fisher| first1 = Timothy G.| last2 = Smith| first2 = Derald G.| last3 = Andrews| first3 = John T.| title = Preboreal oscillation caused by a glacial Lake Agassiz flood| journal = Quaternary Science Reviews| volume = 21| issue = 2002| pages = 873–78| year = 2002| url = http://www.eeescience.utoledo.edu/Faculty/fisher/Fisher/Publications_files/Fisher_etal_QSR02.pdf| doi = 10.1016/S0277-3791(01)00148-2| access-date = 2018-04-07| url-status = dead| archive-url = https://web.archive.org/web/20140222170725/http://www.eeescience.utoledo.edu/Faculty/fisher/Fisher/Publications_files/Fisher_etal_QSR02.pdf| archive-date = 22 February 2014| df = dmy-all| bibcode = 2002QSRv...21..873F}}, at page 874. This is the extreme figure of the ranges cited there.</ref> larger than any currently existing lake in the world (including the [[Caspian Sea]]) and approximately the area of the [[Black Sea]].

At times the lake drained south through the [[Traverse Gap]] into [[Glacial River Warren]] (parent to the [[Minnesota River]], a tributary of the [[Mississippi River]]),<ref name = Chrono/> east through Lake Kelvin (modern [[Lake Nipigon]]) to what is now [[Lake Superior]],<ref>{{cite journal | last = Leverington | first = DW
  |author2=Teller JT | title = Paleotopographic reconstructions of the eastern outlets of glacial Lake Agassiz |journal=[[Canadian Journal of Earth Sciences]] |volume = 40 | issue = 9 | pages = 1259–78 | year = 2003 | doi = 10.1139/e03-043| bibcode = 2003CaJES..40.1259L | citeseerx = 10.1.1.468.8518
  }}</ref> and northwest through the [[Clearwater River (Saskatchewan)#Geology|Clearwater Spillway]] to the [[Mackenzie River|Mackenzie River System]] and the Arctic Ocean about 13,000 years ago.<ref name=Perkins>{{cite journal|author=Perkins S |title=Once Upon a Lake |journal=Science News |volume=162 |issue=18 |pages=283–284 |year=2002 |doi=10.2307/4014064 |url=http://cgrg.geog.uvic.ca/abstracts/PerkinsOnceDuring.html |access-date=2012-09-29 |url-status=dead |archive-url=https://web.archive.org/web/20090228144357/http://cgrg.geog.uvic.ca/abstracts/PerkinsOnceDuring.html |archive-date=28 February 2009 |jstor=4014064 }}</ref><ref>{{cite journal|author=Murton, J. B., Bateman MD, Dallimore SR, Teller JT, Yang Z |date=2010-04-01|title=Identification of Younger Dryas outburst flood path from Lake Agassiz to the Arctic Ocean|journal=[[Nature (journal)|Nature]] |volume=464|issue=7289|pages=740–743|doi=10.1038/nature08954 |pmid= 20360738 |bibcode=2010Natur.464..740M|s2cid=4425933}}</ref><ref>{{cite journal|title=River reveals chilling tracks of ancient flood |last=Schiermeier |first=Quirin |date=31 March 2010|journal=Nature|volume=464 |issue=7289 |pages=657 |doi=10.1038/464657a |pmid=20360702 |doi-access=free }}</ref><ref name="folio"/>

The ice returned to the south for a time, but as it again retreated north of the present [[Canada–United States border]] around 10,000 years ago, Lake Agassiz refilled. The last major shift in drainage occurred around 8,200 years ago. The melting of remaining [[Hudson Bay]] ice caused Lake Agassiz to drain nearly completely. This final drainage of Lake Agassiz has been associated with an estimated {{convert|0.8|to|2.8|m|ft|abbr=on}} [[sea level rise|rise in global sea levels]].<ref>{{cite journal|last=Lia|first=Yong-Xiang|author2=Torbjörn E. Törnqvist|author3=Johanna M. Nevitta |author4=Barry Kohla |title=Synchronizing a sea-level jump, final Lake Agassiz drainage, and abrupt cooling 8200 years ago|journal=Earth and Planetary Science Letters|date=January 2012|volume=315–316|pages=41–50|doi=10.1016/j.epsl.2011.05.034|bibcode=2012E&PSL.315...41L}}</ref>

Lake Agassiz's major drainage reorganization events were of such magnitudes that they significantly impacted climate, sea level, and possibly early [[human civilization]]. The lake's enormous freshwater release into the Arctic Ocean has been postulated to have disrupted oceanic circulation and caused temporary cooling. The draining of 13,000 years ago may be the cause of the [[Younger Dryas]] [[stadial]].<ref name = Perkins/><ref name=Broecker>{{cite journal |last=Broecker |first=Wallace S. |date=2006-05-26 |title=Was the Younger Dryas Triggered by a Flood? |journal=Science |volume=312 |issue=5777 |pages=1146–1148 |doi=10.1126/science.1123253 |pmid=16728622 |s2cid=39544213 }}</ref><ref>{{cite journal| last1 = Fisher| first1 = Timothy G.| last2 = Smith| first2 = Derald G.| last3 = Andrews| first3 = John T.| title = Preboreal oscillation caused by a glacial Lake Agassiz flood| journal = Quaternary Science Reviews| volume = 21| issue = 2002| pages = 873–78| year = 2002| url = http://www.eeescience.utoledo.edu/Faculty/fisher/Fisher/Publications_files/Fisher_etal_QSR02.pdf| doi = 10.1016/S0277-3791(01)00148-2| access-date = 2012-09-28| url-status = dead| archive-url = https://web.archive.org/web/20140222170725/http://www.eeescience.utoledo.edu/Faculty/fisher/Fisher/Publications_files/Fisher_etal_QSR02.pdf| archive-date = 22 February 2014| df = dmy-all| bibcode = 2002QSRv...21..873F}}</ref><ref name="folio">{{cite web |last1=Brown |first1=Michael |title=Massive ancient lake across Prairies emptied quickly enough to set off an ice age, study suggests |url=https://www.ualberta.ca/folio/2021/08/massive-ancient-lake-across-prairies-emptied-quickly-enough-to-set-off-an-ice-age-study-suggests.html |website=Folio |publisher=University of Alberta |access-date=3 September 2021 |date=5 August 2021}}</ref>  Although disputed,<ref>{{cite web|title=Polémique scientifique sur la disparition du lac Agassiz|url=http://www.journal.uqam.ca/archives/2007-2008/3417.pdf|author=Dominique Forget|website=Journal L'[[UQAM]]|pages=3–4 |date=12 May 2008}}</ref> the draining at 9,900–10,000 years ago may be the cause of the [[8.2-kiloyear event|8,200 yr climate event]]. A study by Turney and Brown links the 8,500-years-ago drainage to the expansion of agriculture from east to west across Europe; they suggest that this drainage may also account for various [[flood myth]]s of ancient cultures, including the [[Genesis flood narrative|Biblical flood narrative]].<ref>{{cite journal|vauthors=Turney CS, Brown H |year=2007|title=Catastrophic early Holocene sea level rise, human migration and the Neolithic transition in Europe|journal=Quaternary Science Reviews|volume=26|pages=2036–2041 |doi=10.1016/j.quascirev.2007.07.003 |issue=17–18|bibcode=2007QSRv...26.2036T}}</ref>