Editing Lake Agassiz (section)

== 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/>