View source for Lake Agassiz

{{Short description|Large lake in central North America at the end of the last glacial period}}
{{Use dmy dates|date=June 2019}}

{{Infobox body of water
| name = Lake Agassiz
| image = Agassiz.jpg
| image_size = 255
| caption = Map of the extent of Lake Agassiz in central North America, by 19th century geologist [[Warren Upham]]. The regions covered by the lake were significantly larger than shown here.
| alt = Map of the extent of Lake Agassiz in central North America, by 19th century geologist [[Warren Upham]]. The regions covered by the lake were significantly larger than shown here.
| coords = {{Coord|51|N|97|W|region:CA_type:waterbody_scale:1500000|display=inline,title}}
| location = [[Manitoba]], [[Ontario]], and [[Saskatchewan]] in Canada; 
[[Minnesota]] and [[North Dakota]] in the U.S.
| group = 
| lake_type = [[proglacial lake]]
| etymology = [[Louis Agassiz]]
| inflow = [[Laurentide Ice Sheet]]
| outflow = [[Glacial River Warren]], the [[Vermilion River (Manitoba)|Vermilion River]], the [[Wanapitei River]], and the [[Montreal River (Saskatchewan)|Montreal River]] valley<ref name="Michalek">{{cite web|last=Michalek
|first=Michael J|year=2013|title=Examining the progression and termination of Lake Agassiz|url = https://www.msu.edu/~michal76/research/407_Geomorphology_Lake%20Agassiz2.pdf|publisher = Michigan State University|archive-url = https://web.archive.org/web/20140505231346/https://www.msu.edu/~michal76/research/407_Geomorphology_Lake%20Agassiz2.pdf|access-date=2 May 2014|archive-date=5 May 2014}}</ref>
| basin_countries = Canada, United States 
| date-flooded =  12,875 years before present
| length = {{cvt|475|mi|km}}<ref name=Michalek/>
| width = {{cvt|296|mi|km}}<ref name=Michalek/>
| area = {{cvt|260,000|km2|sqmi}}<ref name=Michalek/>
| depth = 
| max-depth = 
| volume = 
| residence_time =
| shore = 
| elevation = {{ubl|{{convert|335|m|ft}}|
{{convert|258|m|ft}}|
{{convert|325|m|ft}}|
{{convert|310|m|ft}}<ref name=Michalek/>}}
| islands = 
| islands_category = 
| cities = 
| pushpin_map = North America
| pushpin_label_position = "right"
| pushpin_map_caption = Location in North America
}}

'''Lake Agassiz''' ({{IPAc-en|ˈ|æ|g|ə|s|i}} {{respell|AG|ə|see}}) was a large [[proglacial lake]] that existed in central [[North America]] during the late [[Pleistocene]], fed by [[meltwater]] from the retreating [[Laurentide Ice Sheet]] at the end of the [[last glacial period]]. At its peak, the lake's area was larger than all of the modern [[Great Lakes]] combined.<ref name="Perkins"/> It eventually drained into what is now [[Hudson Bay]], leaving behind [[Lake Winnipeg]], [[Lake Winnipegosis]], [[Lake Manitoba]], and [[Lake of the Woods]].

First postulated in 1823 by [[William H. Keating]],<ref>{{cite book |last1=Keating |first1=William H. |title=Narrative of an Expedition to the Source of St. Peter's River, Lake Winnepeek, Lake of the Woods, … |date=1824 |publisher=H.C. Cary & I. Lea |location=Philadelphia, Pennsylvania, U.S.A. |volume=2 |page=7 |url=https://www.biodiversitylibrary.org/item/48506#page/17/mode/1up}}  From p. 7:  "In some places pebbles were as abundant as if we had been travelling upon the bed of some former river or lake; the mind endeavours in vain to establish limits to the vast expanse of water which certainly at some former day overflowed the whole of that country."</ref> it was named by [[Warren Upham]] in 1879 after [[Louis Agassiz]], the then recently deceased (1873) founder of [[glaciology]], when Upham recognized that the lake was formed by glacial action.<ref>{{cite book |last1=Upham |first1=Warren |title=The Geology of Central and Western Minnesota. A Preliminary Report. [From the General Report of Progress for the Year 1879.] |date=1880 |publisher=The Pioneer Press Co. |location=St. Paul, Minnesota, U.S.A. |page=18 |url=https://babel.hathitrust.org/cgi/pt?id=uc1.b4170421;view=1up;seq=28}}  From p. 18:   "Because of its relation to the retreating continental ice-sheet it is proposed to call this ''Lake Agassiz'', in memory of the first prominent advocate of the theory that the drift was produced by land-ice."</ref>

== 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 |url-access=subscription }}</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>

== Glacial River Warren outlet ==
[[File:Browns Valley flood 07.jpg|thumb|upright=1.3|right|[[Traverse Gap]] in the riverbed of [[Glacial River Warren]]. The former southern outlet of Lake Agassiz and source of River Warren is at [[Lake Traverse]] at the bottom of the photo; the flooded valley in the center (now [[Browns Valley, Minnesota|Browns Valley]]) and [[Big Stone Lake]] in the distance are relics of the river.]]
The lowest point between the drainage of [[Hudson Bay]] and the [[Gulf of Mexico]] is in the [[Traverse Gap]] between the U.S. states of [[Minnesota]] and [[South Dakota]]. It lies between [[Lake Traverse]] and [[Big Stone Lake]].<ref name = Sansome>{{cite book | last = Sansome | first = Constance Jefferson | title = Minnesota Underfoot: A Field Guide to the State's Outstanding Geologic Features | publisher = Voyageur Press | year = 1983 | location = Stillwater, MN | pages = 174–79 | isbn = 978-0-89658-036-7 }}</ref> This continental divide is about {{convert|300|m|ft}} above sea level.<ref name=Spading2>{{cite web|last=Spading|first=Kenton |title=Memorandum for Record: Interbasin Flow, Browns Valley Dike, Browns Valley, Minnesota, 2001 Flood and Historical Information |work=Memorandum for Record |publisher=U.S. Army Corps of Engineers |date=23 August 2001 |url=http://www2.mvr.usace.army.mil/WaterControl/Districts/MVP/Reports/projects/docs/BrownsValleyMFR2001.pdf |access-date=2014-05-15 |url-status=dead |archive-url=https://web.archive.org/web/20110811151743/http://www2.mvr.usace.army.mil/WaterControl/Districts/MVP/Reports/projects/docs/BrownsValleyMFR2001.pdf |archive-date=11 August 2011}} A [http://www.johnweeks.com/river_minnesota/pages/mnD20.html sign] at the dike however gives the elevation of the continental divide as {{convert|977|ft|m}}.</ref> When Lake Agassiz existed, the gap was the [[Glacial River Warren|outlet to River Warren]]. The outflow from the melting glaciers filled Lake Agassiz and then drained through the gap to the Gulf of Mexico. This mass of moving water eroded a valley {{convert|2-5|km|mi}} wide and from {{convert|100|to|125|ft|m}} deep.<ref name=Chrono>{{cite journal|last=Fisher|first=Timothy G. |title=Chronology of glacial Lake Agassiz meltwater routed to the Gulf of Mexico |journal=Quaternary Research |volume=59 |issue=2 |pages=271–76 |date=March 2003 |url=http://www.eeescience.utoledo.edu/Faculty/Fisher/Fisher-%20Chronology%20of%20glacial%20Lake%20Agassiz%20meltwater%20routed%20to%20the%20Gulf%20of%20Mexico.pdf |doi=10.1016/S0033-5894(03)00011-5 |access-date=2014-05-14 |url-status=dead |archive-url=https://web.archive.org/web/20080910132708/http://www.eeescience.utoledo.edu/Faculty/Fisher/Fisher-%20Chronology%20of%20glacial%20Lake%20Agassiz%20meltwater%20routed%20to%20the%20Gulf%20of%20Mexico.pdf |archive-date=10 September 2008 |bibcode=2003QuRes..59..271F |s2cid=130223046}}</ref><ref name=UphamII>The Glacial Lake Agassiz, Monographs of the United States Geological Survey, Volume XXV; Warren Upham; Government Printing Office, Washington; 1895; Chapter II</ref> Today, this valley contains the [[Minnesota River]], joined by the [[Upper Mississippi River]] at [[Fort Snelling, Minnesota]].

North of the gap, the [[Red River of the North]] flows from Lake Traverse north through the former lakebed of Lake Agassiz to [[Lake Winnipeg]].<ref name=UphamII/>

== Phases ==

=== Lockhart Phase: 12,875–12,560 [[Before Present|YBP]] ===
[[File:13,000 YBP Lockhart Phase.jpg|thumb|Lockhart Phase of Lake Agassiz, c. 13,000 [[Before Present|YBP]]. Teller and Leverington, 2004 (U.S. Geological Survey)]]
During the Lockhart Phase, water accumulated in the [[Red River of the North|Red River]] valley of [[North Dakota]] and [[Minnesota]]. As the water reached to the top of the divide to the south, the water drained into the ancestral [[Minnesota River|Minnesota]] and [[Mississippi River]] systems. This occurred while the Laurentian Ice Sheet was at or south of the current Canada–US border.<ref name=Michalek/> As the ice sheet melted northward, an early Lake Agassiz covered southern [[Manitoba]], the Minnesota and [[Ontario]] boundary country, and along the Red River south of [[Fargo, North Dakota]]. The Lockhart Phase is associated with the Herman lake stage ({{convert|335|m|ft}}), the highest shoreline of Lake Agassiz. The [[Big Stone Moraine]] formed the southern boundary of the lake. During the Lockhart Phase the lake is estimated to have been {{convert|231|m|ft}} deep, with greater depths near the glacier.<ref name=Michalek/>

=== Moorhead Phase: 12,560–11,690 YBP ===
As the ice sheet melted northward, Lake Agassiz found a lower outlet through the [[Kaministiquia River|Kaministikwia]] route along the modern Minnesota–Ontario border. This moved water to [[Lake Duluth]], a proglacial lake in the [[Lake Superior]] basin. From there the water drained south via an ancestral [[St. Croix River (Wisconsin–Minnesota)|St. Croix]] and [[Mississippi River]] systems. The lake drained below the Herman lake beaches until [[isostatic rebound]] and glacial advances closed the Kaministikwia route. This stabilized the lake at the Norcross lake stage ({{convert|325|m|ft}}).<ref name=Michalek/><ref>(Thorleifson, 1996).</ref> The average depth of Lake Agassiz during the late Moorhead Phase was {{convert|258|m|ft}}. Drainage from Lake Agassiz continued to flow southward out of the ancient Minnesota and Mississippi River systems into the Gulf of Mexico.<ref name=Michalek/>

=== Emerson Phase: 11,690–10,630 YBP ===
During the Emerson Phase, lake levels and drainage patterns continually fluctuated. The lake switched from a southward outlet to a northwestern outlet, and may have been static without a significant outlet during this phase. Isostatic rebound changed the elevation of the land, and this, combined with changes in the volume of meltwater from the ice margin and the closure of the Kaministikwia outlet in the east increased the size of the northern end of the lake.<ref name=Michalek/> One hypothesis postulates that the lake was a '[[Endorheic lake|terminal lake]]' with water inflows and [[evapotranspiration]] being equal. Dating of the glacial moraines shows that the [[Clearwater River (Saskatchewan)|Clearwater]] and [[Athabasca River]] system and [[Lake Nipigon]] and Minong basin were still ice-covered. A period of precipitation and meltwater input balance with the rate of evapotranspiration may have existed for a short period of time.<ref name=Michalek/> During this phase, the Clearwater and Athabasca River system outlet opened. Isostatic rebound opened the southern outlet for a time, creating the Norcross ({{convert|325|m|ft}}), Tintah ({{convert|310|m|ft}}), and Upper Campbell ({{convert|299|m|ft}}) beaches. The south outlet was permanently closed at the end of Emerson Phase.<ref name=Michalek/>

=== Nipigon Phase: 10,630–9,160 YBP ===
The opening of the [[Kaministiquia River|Kaministiquia outlet]] to the east initiated the onset of the Nipigon Phase. The lower lake level ended the southern outlet through the ancestral Minnesota and Mississippi River systems.<ref name=Michalek/>  The ice sheets advanced and blocked the northwestern outlet through the Clearwater and Athabasca systems. There were several other low level outlets into the [[Lake Minong]] basin, including the Kaministiquia and the Lake Nipigon outlet. These allowed large amounts of water to flow from Lake Agassiz into Lake Minong. A series of ice advances and retreats between 10,500 and 9,500 [[Before Present|YBP]] blocked the Lake Nipigon outlet and the other low level outlets, creating intermittent catastrophic outbursts of water into the Lake Minong basin.<ref name=Michalek/>

These large inflows of water raised Lake Minong lake levels and flowed into Lake Algonquin in the Lake Michigan and Huron basins.<ref name=Michalek/> These outbursts refilled the Lake Michigan and Huron basins, which are extreme low water levels of [[Lake Chippewa]] (Lake Michigan basin) and [[Glacial Lake Stanley|Lake Stanley]] (Lake Huron basin). This was due to isostatic rebound of the northern shorelines combined with the opening of the [[North Bay, Ontario|North Bay]] outlet of the Lake Huron basin.<ref name=Michalek/> These repetitive outbursts from Lake Agassiz flooded the Lake Minong basin, then flowed over into the Lake Stanley basin, and then flowed through the North Bay drainage route into the [[Champlain Sea]] (present day [[St. Lawrence River|St. Lawrence]] lowland).<ref name=Michalek/> The shifting ice sheet created fluctuating drainage channels into the Lake Nipigon and Superior basins. A dozen beaches were created during short periods of stability. Towards the end of the Nipigon Phase, Lake Agassiz reached its largest geographical size as it joined with [[Lake Ojibway]] in the east.<ref name=Michalek/>

=== Ojibway Phase: 9,160–8,480 YBP ===
[[File:7,900 Glacial Lake Agassiz & Glacial Lake Ojibway (7900) use fileTeller and Leverington, 2004.jpg|thumb|Map of Glacial Lake Agassiz and Lake Ojibway c. 7900 YBP. Designed from Teller and Leverington, 2004 (U.S. Geological Survey)]]
The Ojibway Phase is named for the glacial lake along the ice front in northern [[Ontario]]. [[Lake Ojibway]] merged with Lake Agassiz at this time. Isostatic rebound of glaciated lands that were south of the ice sheet created a long linear lake from the [[Saskatchewan]]–[[Manitoba]] border to [[Quebec]]. This long lake drained through the eastern outlet at {{ill|Kinojevis River|fr|Rivière Kinojévis}}, into the [[Ottawa River]] valley.<ref name=Michalek/>  Lake Agassiz-Ojibway drainage raised sea levels. The results can be seen in [[Nova Scotia]], [[New Brunswick]], and eastern [[Maine]]. Marine records from the North Atlantic have identified two separate episodes, linked to northern hemisphere cooling in 8,490 YBP and 8,340–8,180 YBP. These may be linked with the Ojibway Phase of Lake Agassiz and may indicate large amounts of drainage from the Ottawa River valley and the [[Tyrrell Sea]] (ancestral Hudson Bay).<ref name=Michalek/>

The Laurentide Ice Sheet continued to recede. Continued warming shrank the ice front towards present day Hudson Bay. Here, the Lake Agassiz northward outlet drained into the Tyrrell Sea. This breach dropped the water level below the eastern Kinojevis outlet. The drainage was followed by the disintegration of the adjacent ice front at about 8,480 YBP. This brought on the end of Lake Agassiz. The ice sheet continued its northward retreat to [[Baffin Island]], leaving the North American mainland around 5,000 YBP.<ref name=Michalek/>

== Lakes of the Lake Agassiz basin ==
Numerous lakes have formed in this glacial lake basin. The best known are the ''Great Lakes of Manitoba''; [[Lake Winnipeg]], [[Lake Manitoba]], and [[Lake Winnipegosis]]. A cluster of smaller lakes surround these, including: [[Cedar Lake (Manitoba)|Cedar Lake]], through which the [[Saskatchewan River]] flows; [[Lake Dauphin]], south of Lake Winnipegosis and tributary to it; and [[Lake St. Martin]], on the Fairford or [[Little Saskatchewan River]], the outlet of lakes Manitoba and Winnipegosis.<ref name=UphamII/> In northern Minnesota, there are [[Roseau Lake (Manitoba)|Roseau]], [[Thief Lake (Manitoba)|Thief]], [[Mud Lake (Manitoba)|Mud]], and [[Maple Lake (Manitoba)|Maple lakes]], besides three large lakes of that state, [[Rainy Lake]], the [[Lake of the Woods]], and [[Red Lake (Minnesota)|Red Lake]].<ref name=UphamII/>
{| class="wikitable"
|-
! scope="col" ! scope="col" | Lake
! scope="col" | Length 
! scope="col" | Width 
! scope="col" | Area 
! scope="col" | Comments
! scope="col" | Elevation<br/>({{abbr|ASL|above sea level}}) 
! scope="col" | {{abbr|Max.|Maximum}} depth
! scope="col" | Outlet
|-
| [[Lake Winnipeg]]
| {{convert|400|km|mi|abbr=off}}
| The southern area is {{convert|40|km|mi|abbr=on}} wide. The northern area is {{convert|97|km|mi|abbr=on}} wide.
| {{convert|9465|sqmi|km2}}
| 85 miles to a strait {{convert|2|to|4|mi|km|0}} wide, which extends  {{convert|12|mi|km}} to Cape Dog. The narrowest is about {{convert|1|mi|km}} wide with five-sixths of the lake north of the cape, and one-sixth south. 
| {{convert|216|m|ft|abbr=off}} above sea level.
| Max. depth < {{convert|65|ft|m}}. Much is {{convert|1.8|-|2.1|m|ft}} deep<ref name=UphamII/>
| [[Nelson River]]
|- 
| [[Lake Manitoba]] 
| {{convert|200|km|mi}}
| {{convert|45|km|mi}} (south end)
| {{convert|1,785|mi2|km2}}
| Narrows to a strait of {{convert|3|km|mi|abbr=off}} width, becoming irregular to the north
| {{convert|247|m|ft}}
| {{convert|7|m|ft}}
| [[Fairford River]] to [[Lake Winnipeg]]
<ref name=UphamII/>
|-
| [[Lake Winnipegosis]]
| {{convert|240|km|mi}} with the northern portion bent towards the west
| {{convert|8|to|24|km|mi}}
| {{convert|2,070|mi2|km2}}
| Lies in the same valley as Lake Manitoba, parallel to [[Lake Winnipeg]]
| {{convert|254|m|ft}}
| {{convert|12|m|ft}}
| Water Hen River and Lake to [[Lake Manitoba]]<ref name=UphamII/>
|-
| [[Rainy Lake]]
| {{convert|80|km|mi}}, with the northern portion bent towards the west
| {{convert|8|km|mi}}
| {{convert|360|mi2|km2}}
| Numerous bays, narrows and islands.
| {{convert|340|m|ft}}
| {{convert|50|m|ft}}
| [[Rainy River (Minnesota–Ontario)|Rainy River]] to [[Lake of the Woods]]<ref name=UphamII/>
|-
| [[Lake of the Woods]]
| {{convert|100|km|mi}}, with the northern portion bent towards the west
| {{convert|100|km|mi}}
| {{convert|1,679|mi2|km2}}
| Irregularly shaped with a substantial peninsula on the west side
| {{convert|323|m|ft}}
| {{convert|64|m|ft}}
| [[Winnipeg River]] to [[Lake Winnipeg]]<ref name=UphamII/>
|-
| [[Red Lake (Minnesota)|Red Lake]]
| {{convert|32|km|mi}} for each lobe with a total of {{convert|50|km|mi}} across both
| {{convert|16|km|mi}} for each lobe
| {{convert|427|mi2|km2}}
| Divided into two equal areas by a strait 1,200 metres (3/4 of a mile) wide.<ref name=UphamII/>
| {{convert|357|m|ft}}
| {{convert|25.6|m|ft}}
| [[Red Lake River]] to the [[Red River of the North]] and Lake Winnipeg<ref name=UphamII/>
|}

== Glacial lakes draining into Lake Agassiz ==
Glacial [[Lake Souris]] formed along the [[Manitoba]] and [[North Dakota]] border, forming a crescent around the west side of the [[Turtle Mountain Provincial Park|Turtle Mountains]]. Lake Souris had three successive outlets: the [[Sheyenne River]], the Pembina River, and finally the Assiniboine River.<ref>(Upham, 1895), pp. 267; 270–272.</ref><ref>The land around former Lake Souris inclines downhill along a northeast direction; thus, as the ice sheet retreated northwards, it exposed outlets of successively lower elevation. (Upham, 1895), pp. 270–272.</ref>  Initially, Lake Souris' southern bay drained into the Sheyenne River, a tributary of the Red River, which in turn flowed into Lake Agassiz.<ref>(Upham, 1895), p. 268.</ref>  However, after the ice sheet had retreated enough to uncover Turtle Mountain, the northern bay of Lake Souris found an outlet at the "elbow" of the modern [[Souris River]]; the elbow is about {{convert|18|mi|km}} southwest of the present mouth of the Souris River.<ref name=UphamII/>{{rp|57}} From this elbow, the lake's waters flowed southeast and entered the [[Pembina River (Manitoba – North Dakota)|Pembina River]], now a tributary of the [[Red River of the North|Red River]],<ref name=UphamII/>{{rp|57–58,268}} and the Pembina, in turn, entered Lake Agassiz at its [[Assiniboine River|Assiniboine]] embayment.<ref>(Upham, 1895), Plate IX (following p. 36).</ref> When the ice sheet retreated north of the Assiniboine River, Lake Souris drained via that river into Lake Agassiz.<ref>(Upham, 1895), pp. 271–272; see also Plate XXI (following p. 268).</ref>  ([[Pelican Lake (Manitoba)|Pelican Lake]] in Langs Valley of Manitoba occupies what was once the northern shore of Lake Souris.<ref>(Upham, 1895), see Plate XXI (following p. 268).</ref>)

The lower part of the [[Saskatchewan River]] basin near the river's mouth at Cedar Lake was clear of the ice-sheet before Lake Agassiz began to drain to northeast.<ref name=UphamII/>  Lake Saskatchewan existed on about {{convert|135|mi|km}} of the [[North Saskatchewan River]] between [[Saskatoon]] and [[Prince Albert, Saskatchewan|Prince Albert]], Saskatchewan. A few miles east of Lake Saskatchewan's outlet, near the modern junction of the north and south branches, it entered Lake Agassiz. This Saskatchewan embayment extended for {{convert|400|mi|km}} along the modern Saskatchewan River route.<ref name=UphamII/>

== Formation of beaches ==
[[Raised beach]]es, many kilometres from any current water, mark the former boundaries of the lake. While the Red River gradually descends from south to north, these old [[High water mark|strandlines]] ascend as one goes north, due to [[isostatic rebound]] since glaciation.<ref name=Ojakangas/>

=== When Lake Agassiz outflowed to the south ===
The highest shore of Lake Agassiz is called the [[Herman Beach]]. It is named for [[Herman, Minnesota]], in [[Grant County, Minnesota|Grant County]]. The Herman Beach is the highest shoreline and can be traced from the historic outlet at [[Traverse Gap|Lake Traverse]] on the border of Minnesota and South Dakota. The beach fluctuates between {{convert|973|and|976|ft|m|round=0.5}} above sea level. <!-- the following sentence doesn't make sense... -->The altitude of Lake Traverse at {{convert|971|ft|m}} above sea level at the [[Traverse Gap]] at [[Browns Valley, Minnesota|Brown's Valley]] is at {{convert|980|ft|m}}.<ref name=UphamVII/>  This was the south outlet of Lake Agassiz.<ref name=UphamVI>The Glacial Lake Agassiz;, Monographs of the United States Geological Survey, Volume XXV; Warren Upham; Government Printing Office, Washington; 1895; Chapter VI</ref>

The Herman Beach displays numerous deltas from the major rivers that entered Lake Agassiz. In Minnesota and North Dakota, these include the Buffalo River Delta, Sand Hill River Delta, Sheyenne River Delta, Elk Valley Delta, and the Pembina River Delta. In Manitoba, there is the Assiniboine River Delta.<ref name=UphamVI/><!-- is this to be part of the following list? -->
* ''Beaches of the Norcross'' stages: The Norcross shoreline lies near the Herman shore on the slope of eroded till.<ref name=UphamVII>The Glacial Lake Agassiz;, Monographs of the United States Geological Survey, Volume XXV; Warren Upham; Government Printing Office, Washington; 1895; Chapter VII</ref>
* ''Beaches of the Tintah'' Stage: The Tintah beaches are {{convert|1040|to|1055|ft|m}} above sea level.<ref name=UphamVII/>
* ''Beaches of the Campbell'' Stage: These have a well developed profile and are useful in establishing the boundary of the lake when it ceased to flow south into the River Warren.<ref name=UphamVII/>
*  ''Beaches of the McCauleyville'' Stage: The channel of the River Warren, flowing out of Lake Agassiz, eroded the channel below the level of Traverse Lake and [[Big Stone Lake]], down to {{convert|935|ft|m}}, the deepest part of Lake Traverse. The southern portions of the McCauleyville shoreline coincides with the levels of high and low water in Lake Traverse, which are {{convert|976|to|970|ft|m}} above sea level.<ref name=UphamVII/>

=== When Lake Agassiz outflowed to the northeast ===
Fourteen shorelines of Lake Agassiz have been identified, which lie below the McCauleyville beaches. These formed when the River Warren could no longer receive the outflow of the lake. This occurred when a lower outlet was found and the lake shrank with the release of the lake's waters.<ref name=UphamVIII>The Glacial Lake Agassiz;, Monographs of the United States Geological Survey, Volume XXV; Warren Upham; Government Printing Office, Washington; 1895; Chapter VIII</ref> The three highest shorelines are named the Blanchard beaches, and the next five in descending order are the Hillsboro, the two Emerado, and the two Ojata beaches, from towns on or near their course in North Dakota.<ref name=UphamVIII/>

* ''Beaches of the Blanchard'' Stage (Hillsboro Beach): Three successive levels of the lake pass near [[Blanchard, North Dakota]]. They are indicated by sand and gravel deposits {{convert|5|to|7|mi|km}} southeast of [[Euclid, Minnesota]]., and near [[Midway station, Manitoba]]<ref name=UphamVIII/> The next lower beach is called the Hillsboro Beach and is visible near [[Glyndon, Minnesota]], and {{convert|5|to|15|mi|km}} north of [[Crookston, Minnesota]].<ref name=UphamVIII/>
* ''Beaches of the Emerado'' Stage: The Emerado shoreline is approximately {{convert|885|ft|m}} above sea level. Its southern tip is across the Red River between [[Kragnes, Minnesota]], and [[Harwood, North Dakota]]. This single shoreline, clearly shows that it belongs to a period when the lake flowed northeastward to its outlet. Crustal rebound was greater to the north, where the Emerado Beach, in Manitoba, is {{convert|10|to|20|ft|m}} higher.<ref name=UphamVIII/>
* ''Beaches of the Ojata'' Stage: The upper Ojata shoreline is between {{convert|870|and|875|ft|m}} above sea level near [[Perley, Minnesota]], and [[Noble, North Dakota]]. In Minnesota it is {{convert|2|to|6|mi|km}} east of the Red River. Some of the shore is marked by a beach ridge, especially to the north, where the surface is till.<ref name=UphamVIII/>
* ''Gladstone Beach'': The southern tip of Lake Agassiz when <!-- this sentence is also not making sense...  -->Gladstone beach formed is near [[Belmont, North Dakota]], {{convert|20|m|km}} south of [[Grand Forks, North Dakota|Grand Forks]], it lies {{convert|845|ft|m}} above sea level. It runs northward about {{convert|10|mi|km}} east of the Red River.<ref name=UphamVIII/>
* ''Burnside Beach'': <!-- also super confusing?!? too many directions -->The Burnside Beach crosses the Red River at Grand Forks, North Dakota, and to the northeast, then north, paralleling the Red River  {{convert|10|to|13|m|km}} to the east. This beach is indistinct south of the international border. The beach lies {{convert|835|to|840|ft|m}} above sea level.<ref name=UphamVIII/>
* ''Ossowa Beach'': The Ossowa Beach lies only a few miles south of the international boundary. The beach lies {{convert|815|to|820|ft|m}} above sea level.<ref name=UphamVIII/>
* ''Stonewall Beach'': In [[Stonewall, Manitoba]], there is a conspicuous beach ridge {{convert|0.33|mi|km}} or more. Its crest is {{convert|820|to|825|ft|m}} above sea level and about {{convert|10|ft|m}} deep. Beach deposits belonging to this stage were not observed elsewhere in southern Manitoba. It is believed that they are buried for most of their length from the U.S. side of the border, north to [[Winnipeg]]<ref name=UphamVIII/>
* ''Beaches of the Niverville'' Stage: About {{convert|0.5|mi|km|1}} southeast of [[Niverville, Manitoba|Niverville]] the road crosses this beach. Its crest is {{convert|777|to|778|ft|m}} above sea level. It stands {{convert|4|ft|m}} above the surrounding surface. Beginning near Niverville station, it extends southeasterly at least a mile. About {{convert|0.33|mi|km}} south, a similar beach ridge crest is at {{convert|780|ft|m}} above sea level. It rises {{convert|2|to|4|ft|m}} above the land. Much of it [[Slough (hydrology)|sloughs]], with water throughout the year, the elevation of the beach crest is {{convert|782|to|784|ft|m}} above sea level.<ref name=UphamVIII/>

== Soils ==
The fertile soils of the [[Red River Valley]], now drained by the [[Red River of the North]], were formed from [[Lacustrine plain|lacustrine]] deposits of [[silt]] from Lake Agassiz.<ref name=Ojakangas/><ref>{{Cite book| last = Sansome| first = Constance Jefferson | title = Minnesota Underfoot: A Field Guide to the State's Outstanding Geologic Features | publisher = Voyageur Press| year = 1983| location = Stillwater, MN | isbn = 978-0-89658-036-7|pages=174–181}}</ref>

== See also ==
{{Div col|small=yes}}
* [[Glacial history of Minnesota]] 
* [[Glacial lake outburst flood]]
* [[Lake Algonquin]] 
* [[Lake Chicago]]
* [[Lake Maumee]]
* [[Lake McConnell]]
* [[List of prehistoric lakes]]
{{Div col end}}
{{Portal inline|Wetlands}}

== References ==
{{Reflist}}

== Sources ==
* {{cite journal
 |last=Fisher 
 |first=Timothy G. 
 |title=River Warren boulders, Minnesota, USA: catastrophic paleoflow indicators in the southern spillway of glacial Lake Agassiz 
 |journal=Boreas 
 |volume=33 
 |issue=4 
 |pages=349–58 
 |date=December 2004 
 |doi=10.1111/j.1502-3885.2004.tb01245.x
 |doi-access=free
 |bibcode=2004Borea..33..349F 
 |issn=0300-9483 
}}
* {{cite journal |last1=Hostetler |first1=S. W. |year=2000 |title=Simulated influences of Lake Agassiz on the climate of central North America 11,000 years ago |journal=Nature |volume=405 |issue=6784 |pages=334–337 |doi=10.1038/35012581 |pmid=10830959 |display-authors=1 |last2=Bartlein |first2=P. J. |last3=Clark |first3=P. U. |last4=Small |first4=E. E. |last5=Solomon |first5=A. M. |bibcode=2000Natur.405..334H |s2cid=205006564 }}
* {{cite web
| last = Lusardi
| first = B. A.
| year = 1997
| url = http://www.winona.edu/geology/MRW/MNglance/Mn_Quaternary.pdf
| title = Quaternary Glacial Geology
| work = Minnesota at a Glance
| publisher = Minnesota Geological Survey, University of Minnesota
| access-date =22 September 2007
|archive-url = https://web.archive.org/web/20070928060129/http://www.winona.edu/geology/MRW/MNglance/Mn_Quaternary.pdf |archive-date = 28 September 2007}}
* {{cite web
| last =  Michalek
| first = Michael J.
| year = 2013
| title = Examining the progression and termination of Lake Agassiz 
| url = https://www.msu.edu/~michal76/research/407_Geomorphology_Lake%20Agassiz2.pdf
| publisher = Michigan State University
| archive-url = https://web.archive.org/web/20140505231346/https://www.msu.edu/~michal76/research/407_Geomorphology_Lake%20Agassiz2.pdf
| access-date = 2 May 2014
| archive-date = 5 May 2014
}} 
* Pielou, E. C. (1991). ''After the Ice Age: The Return of Life to Glaciated North America'', Chicago: University of Chicago Press, {{ISBN|0-226-66812-6}}
* Thorleifson, L.H. (1996).  [http://www.esci.umn.edu/sites/www.esci.umn.edu/files/REVIEW%20OF%20LAKE%20AGASSIZ%20HISTORY.pdf "Review of Lake Agassiz History"],  ''Sedimentology, Geomorphology, and History of the Central Lake Agassiz Basin'', Geological Association of Canada Field Trip Guidebook for GAC/MAC Joint Annual Meeting, pp.&nbsp;55–84.
* {{cite journal
 |last         = Upham
 |first        = Warren
 |title        = The Glacial Lake Agassiz
 |journal      = Monographs of the United States Geological Survey
 |volume       = XXV
 |date         = 1895
 |url          = https://babel.hathitrust.org/cgi/pt?id=ucw.ark:/13960/t71v6307j;view=1up;seq=19
 |access-date  = 16 April 2009
 |url-status   = dead
 |archive-date = 20 May 2021
 |df           = dmy-all
 |archive-url  = https://web.archive.org/web/20210520232728/https://babel.hathitrust.org/cgi/pt?id=ucw.ark%3A%2F13960%2Ft71v6307j;view=1up;seq=19
}}  Archived at:  [https://web.archive.org/web/20090523133424/http://library.ndsu.edu/exhibits/text/lakeagassiz/ Wayback Machine]
* {{cite web
| date = 15 November 2004
| url = http://mrbdc.mnsu.edu/mnbasin/fact_sheets/valley_formation.html
| title = Valley Formation
| work = Fact Sheets
| publisher = Minnesota River Basin Data Center (MRBDC, Minnesota State University, Mankato
| access-date =22 September 2007
}}

== External links ==
=== Articles ===
* Bergh, Thor K., [https://webapps15.dnr.state.mn.us/volunteer_index_api/past_issues/article_pdf?id=4867 "Minnesota’s Sandy Soils"] {{Webarchive|url=https://web.archive.org/web/20221214125030/https://webapps15.dnr.state.mn.us/volunteer_index_api/past_issues/article_pdf?id=4867 |date=14 December 2022 }}, ''The Conservation Volunteer'', Minnesota Department of Conservation. September October 1944, pp.&nbsp;29–33.
* Coleman, Arthur Philemon, (1909), "Lake Ojibway; Last of the Great Glacial Lakes", in [http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/ARV18/ARV18.pdf Eighteenth Report of the Ontario Bureau of Mines], pp.&nbsp;284–293. Retrieved 14 December 2022.

=== Maps ===
* {{cite map
  |publisher= Minnesota River Basin Data Center
  |title= Valley Formation
  |url= http://mrbdc.mnsu.edu/mnbasin/fact_sheets/valley_formation.html
  |access-date=12 January 2009 }}
* {{cite web|publisher=Natural Resources Canada |title=Beach ridges of former Glacial Lake Agassiz, northwestern Manitoba |url=http://gsc.nrcan.gc.ca/landscapes/details_e.php?photoID=480 |access-date=2 September 2008 |url-status=dead |archive-url=https://web.archive.org/web/20060902145148/http://gsc.nrcan.gc.ca/landscapes/details_e.php?photoID=480 |archive-date=2 September 2006 }}
* {{cite web
  |title= Lake Agassiz Bathymetric Maps: Herman and Upper Campbell
  |url= http://www.webpages.ttu.edu/dleverin/quaternary_envs/quaternary_environments.html#agassiz
  |access-date=2 November 2009
}}

{{Continental Glaciations}}
{{Pleistocene Lakes and Seas}}
{{Greatlakes}}

{{Authority control}}

{{DEFAULTSORT:Agassiz, Lake}}
[[Category:Glacial lakes of the United States]]
[[Category:Glacial lakes of Canada]]
[[Category:Lakes of Manitoba]]
[[Category:Lakes of Ontario]]
[[Category:Lakes of Saskatchewan]]
[[Category:Shrunken lakes]]
[[Category:Geology of Manitoba]]
[[Category:Geology of Minnesota]]
[[Category:Geology of Saskatchewan]]
[[Category:Geology of North Dakota]]
[[Category:Lakes of the Mississippi River]]
[[Category:Bodies of water of Westman Region, Manitoba]]
[[Category:Paleogeography]]
[[Category:Proglacial lakes]]
[[Category:Former lakes of North America|agassiz]]
[[Category:Geology of Ontario]]
[[Category:Lakes of North Dakota]]
[[Category:Megafloods]]
[[Category:Glacial lakes of Manitoba]]
[[Category:Younger Dryas]]