The course of the Minnesota River follows the valley carved by Glacial River Warren

The valley of River Warren shows in this shaded relief image. At the upper left (northwest) is the bed of Lake Agassiz; its outflow breached the U-shaped Big Stone Moraine at Traverse Gap and became the source of River Warren. Lake Agassiz was an immense Glacial lake located in the center of North America. The Traverse Gap is an ancient river channel occupied by Lake Traverse and Big Stone Lake and the valley connecting them at Browns Valley Minnesota. At the extreme right, the northernmost oxbow loop is the Mississippi at downtown Saint Paul. A meander in general is a bend in a sinuous watercourse also known as an oxbow loop or simply an Oxbow. Mississippi ( is a state located in the Deep South of the United States Saint Paul ( abbreviated St Paul) is the capital and second most populous city in the U Just to its west and almost invisible is the valley of the Mississippi above its confluence with River Warren at Fort Snelling. Mississippi ( is a state located in the Deep South of the United States Fort Snelling, originally known as Fort St Anthony, is a former Military Fortification located at the confluence of the Minnesota

This shaded relief image shows the area of Minneapolis-St. Paul. The wide channel of River Warren enters from the southwest. The Mississippi enters from the north near the left side and the St. Croix enters from the north at the right. The present rivers are grossly underfit for their valleys; the widening of the Mississippi to the southeast is the slackwater pool from Lock and Dam No. 2. A misfit stream (or underfit stream) is a Stream that is far too small to have eroded the Valley which the stream occupies A reservoir is most broadly a place or hollow vessel where Fluid is kept in Reserve, for later use The first lock and dam to be built on the Mississippi was also called Lock and Dam No

Glacial River Warren or River Warren was a prehistoric river that drained Lake Agassiz in central North America between 11,700 and 9,400 years ago. Lake Agassiz was an immense Glacial lake located in the center of North America. The enormous outflow from this lake carved a mighty valley now occupied by the much-smaller Minnesota River and the Upper Mississippi River. The Minnesota River is a Tributary of the Mississippi River, approximately 332 miles (534 km long in the U WikipediaCiting sources --> See also Mississippi River The Upper Mississippi

Creation

Lake Agassiz was formed from the meltwaters of the Laurentide Ice Sheet during the Wisconsonian glaciation of the last ice age. The Laurentide Ice Sheet was a massive sheet of ice that covered hundreds of thousands of square miles including most of Canada and a large portion of the northern "Last glacial" redirects here For the period of maximum glacier extent during this time see Last Glacial Maximum The last glacial period An ice age is a period of long-term reduction in the Temperature of the Earth 's surface and atmosphere resulting in an expansion of continental Ice sheets Agassiz was a huge body of water, up to 600-700 feet (~200 m) deep, and at various times covering areas totaling over 110,000 square miles (~300,000 km²). ^[1] Blocked by an ice sheet to the north, the lake water rose until about 9,700 years Before Present (BP), when it overtopped the Big Stone Moraine, a ridge of glacial drift left by the receding glacier, at the location of Browns Valley, Minnesota. Before Present (BP years are a time scale used in Archaeology, Geology, and other scientific disciplines to specify when events in the past occurred Moraine refers to any glacially formed accumulation of unconsolidated glacial debris (soil and rock which can occur in currently glaciated and formerly glaciated regions such as those Browns Valley is a city in Traverse County, Minnesota, United States, adjacent to the South Dakota border The lake's outflow was catastrophic at times,^[2] and carved a gorge through the moraine a mile (1. 6 km) wide and 130 feet (~40 m) deep, which is now known as the Traverse Gap. The Traverse Gap is an ancient river channel occupied by Lake Traverse and Big Stone Lake and the valley connecting them at Browns Valley Minnesota. ^[3]

From the gap issued the Glacial River Warren. From its inception until final abandonment of Agassiz' southern outlet, this stream drained the meltwater of that lake to the Mississippi valley. The drainage was not however continuous, as Lake Agassiz periodically had other outlets. The Laurentide ice sheet retreated and advanced with climatic variations and these changes in ice cover contributed to isostatic adjustments in the level of the land over which the watercourses ran. Isostasy (Greek isos = "equal" stásis = "standstill" is a term used in Geology to refer to the state of gravitational equilibrium between the These changes in turn uncovered or blocked the lake's other outlets to the sea. ^[4]

Course

While active this turbulent stream cut and eroded a bed up to five miles (8 km) wide and 250 feet (80 m) deep. ^[5] This has left a valley which starts at Traverse Gap near Browns Valley, Minnesota, goes southeast to Mankato, then turns northeast to the Twin Cities. Browns Valley is a city in Traverse County, Minnesota, United States, adjacent to the South Dakota border River Warren was joined by the comparatively small Mississippi at Fort Snelling, from which the valley continues northeast to present-day Saint Paul, where the massive River Warren Falls once graced the landscape. Mississippi ( is a state located in the Deep South of the United States Fort Snelling, originally known as Fort St Anthony, is a former Military Fortification located at the confluence of the Minnesota Saint Paul ( abbreviated St Paul) is the capital and second most populous city in the U River Warren Falls was a massive waterfall on the Glacial River Warren initially located in present-day Saint Paul Minnesota, United States. Over 1700 years this waterfall retreated upstream and undercut the Mississippi at the site of Fort Snelling. Fort Snelling, originally known as Fort St Anthony, is a former Military Fortification located at the confluence of the Minnesota The falls then split. The Mississippi falls migrated upstream to form Saint Anthony Falls and create Minnehaha Falls in Minneapolis. Saint Anthony Falls, or the Falls of Saint Anthony, located northeast of downtown Minneapolis Minnesota, was the only natural major Waterfall on the Minnehaha Creek is a Tributary of the Mississippi River located in Hennepin County Minnesota that extends from Lake Minnetonka in the west The River Warren falls receded west in the Minnesota River valley until they reached an older buried river valley about two miles (3 km) west of the confluence, where the falls were extinguished. ^[6]

From Saint Paul the great valley goes southeast to Prescott, Wisconsin, where it is joined by the St. Croix River, itself once the outlet of another proglacial lake, Glacial Lake Duluth which occupied the western part of Lake Superior. Prescott is a city in Pierce County, Wisconsin at the confluence of the St The St Croix River is a Tributary of the Mississippi River, approximately 164 miles (264 km long in the U In Geology, a proglacial lake is a lake formed either by the Damming action of a Moraine or Ice dam during the retreat of a melting glacier or Glacial Lake Duluth was a Proglacial lake that formed in the Lake Superior drainage basin as the Laurentian Glacier retreated Lake Superior is the largest of the five Great Lakes of North America. From its confluence with the St. Croix the valley continues southeast along the Minnesota-Wisconsin border. River Warren's effects include the creation of bluffs along the valleys of the Minnesota and Mississippi Rivers, and contributed to the formation of Lake Pepin. Lake Pepin is a naturally occurring Lake, and the widest naturally occurring part of the Mississippi River. ^[7]

End

By about 9400 BP, the ice sheet finally retreated sufficiently far to the north that Lake Agassiz permanently took another outlet and receded below the level of Traverse Gap. River Warren then ceased to run. ^[8] The Lake Agassiz area watershed now feeds the Red River of the North which flows north, ultimately to Hudson Bay. A drainage basin is an extent of Land where Water from Rain or Snow melt drains downhill into a body of water such as a River, The Red River (rivière Rouge is a North American river Formed by the confluence of the Bois de Sioux and Otter Tail rivers in the United States River Warren's upper valley in the Traverse Gap is now occupied by the tiny Little Minnesota River, which flows into Big Stone Lake and the Minnesota River, which follows the greater river's ancient bed to its confluence with the Mississippi River. The Little Minnesota River is a Headwaters Tributary of the Minnesota River in northeastern South Dakota and west-central Minnesota Big Stone Lake is a long narrow Freshwater Lake and reservoir forming the border between western Minnesota and northeastern South Dakota These streams occupy only a small cross-section of River Warren's riverbed. ^[9]

Name

The hydrology of the oversized valley was first explained by General G. K. Warren in 1868. Gouverneur Kemble Warren ( January 8, 1830 &ndash August 8, 1882) was a Civil engineer and prominent general in the He made a detailed survey of the valley in his search for possible transcontinental railroad routes. The Pacific Railroad Surveys (1853-1855 explored possible routes for a Transcontinental railroad across North America ^[10] Posthumously, in appreciation of this work, the glacial river that was the outlet of Lake Agassiz was named River Warren. ^[11]

See also

• Geology of Minnesota
• Glacial history of Minnesota
• Laurentide ice sheet
• Proglacial lakes of Minnesota
• Wisconsin glaciation

References

Notes

Sources