Озеро Агáссиз: Древнее ледниковое озеро Северной Америки

Large lake in central North America at the end of the last glacial period

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, the Wanapitei River, and the Montreal River valley
| basin countries = Canada, United States
| date flooded = 12,875 years before present
| length = 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.

During the 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, its meltwaters created an immense proglacial lake. 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 , 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), and northwest through the Clearwater Spillway to the Mackenzie River System and the Arctic Ocean about 13,000 years ago. 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. Although disputed, the draining at 9,900–10,000 years ago may be the cause of the 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 may also account for various flood myths of ancient cultures, including the Biblical flood narrative.

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. This continental divide is about above sea level. When Lake Agassiz existed, the gap was the 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 wide and from deep. 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. The average depth of Lake Agassiz during the late Moorhead Phase was Drainage from Lake Agassiz continued to flow southward out of the ancient Minnesota and Mississippi River systems into the Gulf of Mexico. Initially, Lake Souris' southern bay drained into the Sheyenne River, a tributary of the Red River, which in turn flowed into Lake Agassiz. 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 18 mile (29 km) southwest of the present mouth of the Souris River. When the ice sheet retreated north of the Assiniboine River, Lake Souris drained via that river into Lake Agassiz. (Pelican Lake in Langs Valley of Manitoba occupies what was once the northern shore of Lake Souris.) 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. 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. Beaches of the Tintah Stage: The Tintah beaches are above sea level. 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.

Bergh, Thor K., "Minnesota’s Sandy Soils" , The Conservation Volunteer, Minnesota Department of Conservation. September October 1944, pp. 29–33. Coleman, Arthur Philemon, (1909), "Lake Ojibway; Last of the Great Glacial Lakes", in Eighteenth Report of the Ontario Bureau of Mines, pp. 284–293. Retrieved 14 December 2022.