Missouri River-Missouri Escarpment drainage divide area landform origins along the North Dakota-South Dakota border, USA

Authors

A geomorphic based on topographic map evidence

Abstract:

The Missouri River-Missouri Escarpment drainage divide area along the North Dakota-South Dakota border includes areas in Emmons, McIntosh, and Dickey Counties, North Dakota and areas in Campbell and McPherson Counties, South Dakota. Between the south-oriented Missouri Coteau and the east-facing Missouri Escarpment is the Missouri Coteau, which is a region underlain by thick deposits of glacially-transported debris. The Missouri Escarpment is here interpreted to have formed as the west wall of a large south-oriented ice-walled and bedrock-floored valley sliced by an immense south-oriented melt water river into the surface of a thick North American ice sheet. The Missouri River valley was eroded by south-oriented ice-marginal floods moving along the thick ice sheet’s west margin. The Missouri Coteau represents where the thick ice sheet’s detached southwest margin slowly melted and deposited whatever debris it contained.

Preface:

The following interpretation of detailed topographic map evidence is one of a series of essays describing similar evidence for all major drainage divides contained within the Missouri River drainage basin and for all major drainage divides with adjacent drainage basins. The research project is interpreting evidence in the context of a previously unexplored deep glacial erosion paradigm, which is fundamentally different from most commonly accepted North American glacial history interpretations. Project essays are listed on the sidebar category list under their appropriate Missouri River tributary drainage basin, Missouri River segment drainage basin (by state), and/or state in which the Missouri River drainage basin is located.    

Introduction:

  • The purpose of this essay is to use topographic map interpretation methods to explore Missouri River-Missouri Escarpment drainage divide area landform origins along the North Dakota-South Dakota border, USA. Map interpretation methods can be used to unravel many geomorphic events leading up to formation of present-day drainage routes and development of other landform features. While each detailed topographic map feature provides detailed evidence to be explained, the solution must be consistent with explanations for adjacent area map evidence as well as solutions to big picture map evidence puzzles. I invite readers to improve upon my solutions and/or to propose alternate solutions that better explain evidence and are also consistent with adjacent map area and big picture evidence. Readers may do so either by making comments here or by writing and publishing their own essays and then by leaving a link to those essays in a comment here.
  • This essay is also exploring a new geomorphology paradigm in which erosional landforms are interpreted as evidence left by immense glacial melt water floods. Implied in that interpretation is the immense floods were derived from a thick North American ice sheet that created a deep “hole” in the North American continent and also melted fast. The previously unexplored paradigm being tested in this and other Missouri River drainage basin landform origins research project essays is a thick North American ice sheet, comparable in thickness to the Antarctic ice sheet, occupied the North American region usually recognized to have been glaciated, and through its weight and erosive actions created a deep North American “hole”. The southwestern rim of that deep “hole” is today preserved in the high Rocky Mountains. The ice sheet through its weight and deep erosion (and perhaps deposition along major south-oriented melt water flow routes) caused significant crustal warping and tectonic change, through its action of melting fast produced immense floods that flowed across the continent, and through its action of melting fast systematically opened up space in the ice sheet created “hole” so headward erosion of newly developed north-oriented drainage systems captured immense south-oriented melt water floods and diverted immense melt water floods north into space the ice sheet had once occupied.
  • If this previously unexplored paradigm is correct the geographic region explored by this essay should contain evidence of immense floods that were captured by headward erosion of new valley systems so as to cause the floods to flow in a different direction. Ability of this previously unexplored paradigm to explain Missouri River-Missouri Escarpment drainage divide area landform evidence along the North Dakota-South Dakota border will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm. This essay is included in the Missouri River drainage basin landform origins research project essay collection.

Missouri River-Missouri Escarpment drainage divide area along North Dakota-South Dakota border location map

Figure 1: Missouri River-Missouri Escarpment drainage divide area along North Dakota-South Dakota border location map (select and click on maps to enlarge). National Geographic Society map digitally presented using National Geographic Society TOPO software.

Figure 1 provides a Missouri River-Missouri Escarpment drainage divide area along the North Dakota-South Dakota border location map. The west-to-east oriented North Dakota-South Dakota border is located just south of the figure 1 center. North Dakota is the state north of the purple boundary and South Dakota is the state south of the red boundary. The Missouri River flows south-southeast in North Dakota past Bismarck and then flows south into South Dakota. Lake Oahe is a large reservoir flooding the Missouri River valley. The dam responsible for Lake Oahe is located south of the figure 1 map area. The Missouri River in this region has extensive and long tributaries entering from the west. Note the Heart River and Cannonball River in North Dakota and the Grand River and Moreau River in South Dakota. Missouri River tributaries from the east are much shorter and with the exception of Beaver Creek (flowing trough Linton, North Dakota) are not even named on figure 1. Also note barbed tributaries on both sides of the south-oriented Missouri River. In North Dakota the Heart River and Cannonball River flow in a northeast direction to enter the south-oriented Missouri River. In South Dakota the Moreau River also flows northeast to enter the south-oriented Missouri River. These barbed tributaries provide evidence the Missouri River valley eroded headward to capture northeast-oriented drainage routes, which maybe once extended northeast of the present day Missouri River valley. Barbed tributaries are also located on the east side of the Missouri River. Note in particular tributaries flowing in a northwest direction to enter the south-oriented Missouri River near the North Dakota-South Dakota state line. These tributaries are studied in the detailed maps and discussion below. The major drainage system in the figure 1 east half is the south-oriented James River. The James River has a number of east and southeast-oriented tributaries. These east and southeast-oriented James River tributaries originate along the east-facing Missouri Escarpment, which is not identified or otherwise shown on figure 1. Between the Missouri Escarpment and the west-oriented Missouri River tributaries is a region with no integrated drainage. That undrained region is the Missouri Coteau and in more detailed maps is a region of hummocky topography with numerous small interior drainage basins, often partially filled with water. The Missouri Coteau is underlain by thick glacial moraines, suggestive of a region where an ice sheet containing large amounts of debris slowly melted.

Missouri River-Missouri Escarpment drainage divide area along North Dakota-South Dakota border detailed location map

Figure 2: Missouri River-Missouri Escarpment drainage divide area along North Dakota-South Dakota border detailed location map. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 2 provides a somewhat more detailed map of the Missouri River-Missouri Escarpment drainage divide area along the North Dakota-South Dakota border. McIntosh County is located in North Dakota. The unnamed (in figure 2) North Dakota county west of McIntosh County is Emmons County. Campbell, McPherson, Walworth, and Edmunds Counties are located in South Dakota. Red shaded areas west of the Missouri River represent Standing Rock Indian Reservation lands. Lake Oahe floods the south-southeast oriented Missouri River valley in the figure 2 west half. Note in the figure 2 southeast corner how the northeast oriented Moreau River turns southeast to enter the Missouri River valley. Further north in South Dakota the northeast oriented Grand River makes a similar turn to the southeast. East of the Missouri River note how Spring Creek flows west, southwest, west and northwest to the Pocasse National Wildlife Refuge Area (located just south of the state line) and hen turns southwest to enter the south-oriented Missouri River valley. Also note the unnamed northeast and northwest oriented tributary immediately south of the Pocasse National Wildlife Refuge. North of the state line note how Cattail Creek flows in a northwest direction to enter the south-oriented Missouri River. Also, along the figure 2 north edge note west-oriented Beaver Creek, which flows to the south-oriented Missouri River. Near the figure 2 east edge are headwaters of numerous east and southeast-oriented James River tributaries. The east and southeast-oriented James River tributaries all originate on the east facing Missouri Escarpment slope, and while the Missouri Escarpment is not shown or otherwise identified on figure 2, its location can be identified by the location of the headwaters of the east and southeast-oriented James River tributaries. East of the Missouri Escarpment the landscape is generally 100-200 meters lower than it is to the west. The south-oriented Missouri River valley has been eroded into the higher level topographic surface west of the Missouri Escarpment. The region between the west-oriented Missouri River tributaries and the Missouri Escarpment is the previously mentioned Missouri Coteau. Figure 2 shows numerous small lakes in the Missouri Coteau region, which is due to the presence of many small interior drainage basins. This essay attempts to address origins of the Missouri River valley, barbed Missouri River tributaries from the east, the Missouri Coteau, and the Missouri Escarpment. These origins are interpreted from the context of a “thick ice sheet that melted fast” geomorphology paradigm, which differs from most if not all previously published interpretations. For additional background on this previously untested geomorphology paradigm see the “About the thick ice sheet that melted fast geomorphology paradigm” essay (see menu at top of this page).

Missouri River-Cattail Creek drainage divide area

Figure 3: Missouri River-Cattail Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 illustrates the Missouri River-Cattail Creek drainage divide area in southern Emmons County (just north of the North Dakota-South Dakota state line). Lake Oahe is a reservoir flooding the south oriented Missouri River valley. Cattail Creek is a northwest-oriented stream flowing to the south oriented Missouri River as a barbed tributary. How does a major south oriented river obtain a northwest-oriented tributary? Note the size of the northwest-oriented Cattail Creek valley. At one time large volumes of water flowed in the Cattail Creek valley, although the water was moving to the southeast. Figure 4 below illustrates the Cattail Creek valley south of the figure 3 map area. The Missouri River valley eroded headward along what was the approximate southwest margin of a rapidly melting thick ice sheet. Headward erosion of the Missouri River valley in this North Dakota-South Dakota border region occurred late during the ice sheet melt down. Because the ice sheet was located in a deep “hole”, created in part by crustal warping caused by ice sheet weight, areas adjacent to the ice sheet were generally lower than areas further away. Also, as the ice sheet melted elevations of the ice sheet surface (at least at the south end) eventually became lower than elevations of adjacent ice sheet rim areas. As a result melt water floods moved along the ice sheet margin and where possible even flowed out onto the ice sheet surface. In the case of the figure 3 map area the evidence suggests melt water floods were moving south and southeast along the ice sheet margin. Very large floods typically erode ever-changing anastomosing channel complexes, at least until a deep valley, such as the Missouri River valley, erodes up flood to capture and consolidate the flood flow. The Cattail Creek valley probably was initiated as one of several south- and southeast-oriented flood flow anastomosing channels. It is possible southeast-oriented flood flow in the Cattail Creek valley was moving to a breach in what was then the detached thick ice sheet southwest margin and then moving east to lower elevation areas east of the Missouri Escarpment. However, it is possible the water was simply moving along the ice sheet margin to wherever the actively eroding Missouri River valley head was at that time. In either case, as the deep Missouri River valley eroded north into the figure 3 map area, it beheaded southeast-oriented flood flow in the Cattail Creek valley. Flood waters on the northwest end of the beheaded flood flow channel reversed flow direction to flow northwest to newly eroded and deeper south-oriented Missouri River valley (and to create a northwest-oriented valley).

Cattail Creek-Spring Creek drainage divide area at Becker Lake

Figure 4: Cattail Creek-Spring Creek drainage divide area at Lake Becker. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 illustrates the Cattail Creek-Spring Creek drainage divide area at Becker Lake and is located southeast of the figure 3 map area. Becker Lake is located near the figure 4 center. Cattail Creek headwaters are northwest of Becker Lake and flow in a northwest direction to the figure 4 north edge. Headwaters of a southeast-oriented Spring Creek tributary originate southeast of Becker Lake and flow southeast to join the northwest and southwest-oriented Spring Creek at its elbow of capture (see figure 5 below). Note how the northwest-oriented Cattail Creek valley is really the northwest end of a northwest-southeast oriented through valley, with northwest-oriented Cattail Creek using the northwest end, the southeast-oriented Spring Creek tributary using a middle section, and northwest-oriented Spring Creek using the southeast end (see figure 5). Becker Lake is located near the present day drainage divide between the northwest-oriented Cattail Creek and the southeast-oriented Spring Creek tributary. Also note the south and west-oriented Cattail Creek tributaries located north of Becker Lake. Those tributaries provide evidence reversed flood flow in the newly beheaded Cattail Creek valley captured southeast flood flow moving northeast of the Cattail Creek valley and diverted that flood flow to the newly reversed Cattail Creek valley. Capture of the yet to be beheaded (by headward erosion of the deep Missouri River valley) southeast-oriented flood flow between the southeast-oriented Cattail Creek-Spring Creek through valley and the ice sheet southwest margin provided the water volumes required to erode the rather significant northwest-oriented Cattail Creek valley seen today. Reversal of flood flow to create the northwest-oriented Cattail Creek valley is typical of flood flow reversals that occurred throughout the entire Missouri River drainage basin as present day drainage routes were created. Barbed tributaries are a remarkably common landscape feature and provide evidence of such flood flow captures and reversals.

Missouri River-Spring Creek drainage divide area at Lake Pocasse

Figure 5: Missouri River-Spring Creek drainage divide area at Lake Pocasse. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the Missouri River-Spring Creek drainage divide area at Lake Pocasse and is located south and east of the figure 4 map area. A large meander in the flooded Missouri River valley can be seen in the figure 5 southwest corner. Spring Creek flows in a northwest direction from the figure 5 southeast corner to Lake Pocasse, which is a reservoir impounded behind a dam at Polock, South Dakota (Lake Pocesse is also a higher elevation arm of Lake Oahe, which floods the Missouri River valley and the southwest oriented Spring Creek valley downstream from Pollock). The unnamed southeast-oriented Spring Creek tributary referred to in the figure 4 discussion enters Lake Pocasse (the flooded Spring Creek valley) directly north of Pollock near the figure 5 north edge. Note how the alignment of the southeast-oriented tributary is the same as the alignment of the northwest-oriented Spring Creek valley segment. In other words, the northwest-oriented Spring Creek valley is an extension of the northwest-southeast oriented through valley drained further to the northwest by northwest-oriented Cattail Creek. Note how Spring Creek makes an abrupt turn from flowing in a northwest direction to flowing in a southwest direction to enter the south-oriented Missouri River valley. The elbow of capture was created when the deep Missouri River valley eroded headward into the figure 5 map region. At that time large volumes of ice marginal flood water were moving south and southeast along the decaying ice sheet’s southwest margin. The flood waters were moving south in ever-changing anastomosing (or interconnected) channels with the deep Missouri River valley probably eroding headward to capture flood flow from those channels. Just west of figure 5 the deep Missouri River valley eroded to the northwest (probably along what was then a higher volume flood flow route), although the present day southwest oriented Spring Creek valley eroded headward along what was probably a significant flood flow route linking the northwest-southeast oriented Cattail Creek-Spring Creek flood flow channel with the channel the deep Missouri River valley was eroding. Headward erosion of the deep southwest oriented Spring Creek valley segment beheaded southeast-oriented flood flow in what was the southeast-oriented Cattail Creek-Spring Creek channel. Flood waters on the northwest end of the beheaded flood flow route then reversed flow direction to flow northwest to the deeper southwest-oriented Spring Creek valley and south-oriented Missouri River valley. Headward erosion of the deeper northwest-oriented Spring Creek valley was able to capture significant yet to be beheaded southeast-oriented flood flow routes further to east (see figure 6 below and southwest- and west-oriented Spring Creek headwaters in figure 2). Capture of the yet to be beheaded flood flow provided the water volumes required to erode the large northwest-oriented Spring Creek valley.

West-oriented Spring Creek headwaters

Figure 6: West-oriented Spring Creek headwaters. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 illustrates the southwest-oriented Spring Creek headwaters west of the figure 5 map area. Spring Creek originates in the figure 6 southeast quadrant and flows in a generally west oriented direction to the figure 6 west edge. From the figure 6 map area Spring Creek turns to flow southwest before turning to flow in a northwest direction as seen in figure 5. The west-to-east oriented North Dakota-South Dakota boundary separates the figure 6 north and south halves. Venturia, North Dakota is the town in the figure 6 north center area. Spring Creek headwaters are about as far east into the Missouri Coteau region as any Missouri River tributaries in this North Dakota-South Dakota border region reach. The only other Missouri River tributary to reach this far east is Beaver Creek, which is located in North Dakota and which is illustrated in figure 7 below. The figure 6 landscape (away from the Spring Creek valley and its tributary valleys) is characteristic of the Missouri Coteau region, with some small lakes and interior drainage basins. The Missouri Coteau as previously mentioned is underlain by thick glacial moraines and is here interpreted to be the location where the detached southwest margin of a thick North American ice sheet slowly melted and deposited whatever debris it contained. Also, as previously mentioned, late during the ice sheet’s melt down history large south and southeast oriented floods moved along the ice sheet’s southwest (and west) margin as the deep Missouri River valley was eroding north. Previous figures have illustrated areas close to the Missouri River valley and provided evidence of those south and southeast oriented floods. Figures 6 and 7 illustrate headwaters of two of the west-oriented Missouri River tributaries to show evidence of how the southeast and south-oriented floods were interacting with the decaying ice sheet margin. The fact the Spring Creek valley has eroded headward into this figure 6 region suggests flood waters may have been eating into the decaying ice sheet’s western margin. Flood waters moved southeast into the figure 6 map area and were captured by headward erosion of the Spring Creek valley. The Spring Creek valley as seen in figure 5 eroded headward from what was originally a southeast-oriented flood flow channel, so the west- and southwest-oriented Spring Creek valley segments may predate headward erosion of the deep Missouri River valley into the figure 5 map area. However the sequence occurred, at the time the Spring Creek valley eroded west into the figure 6 map area flood waters had not yet been beheaded by headward erosion of the Beaver Creek valley to the north (or by headward erosion of the deep Missouri River valley still further to the north).

Beaver Creek-South Branch Beaver Creek drainage divide area

Figure 7: Beaver Creek-South Branch Beaver Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the Beaver Creek headwaters area north and slightly east of the figure 6 map area. The town in the figure 7 west center (on the red highway) is Wishek, North Dakota. Burnstad, North Dakota is located just west of the southern tip of a lake along the figure 7 north edge (north of Wishek). The lake is Beaver Lake where Beaver Creek originates. Beaver Creek flows west along the figure 7 north edge area and then turns south and southwest to flow to the figure 7 west edge (south of the west-to-east red highway). From the figure 7 map area Beaver Creek generally flows west to the south-oriented Missouri River (see figure 1). The southwest and north-northwest oriented stream in the figure 7 southwest quadrant is the South Branch Beaver Creek. The eastern half of figure 7 is typical Missouri Coteau landscape, with numerous small interior drainage basins, many partially filled with water. The sequence of events in figures 6 and 7 is closely related to what happened further west as the deep Missouri River valley eroded north. The west-oriented Spring Creek valley eroded east to the decaying ice sheet margin first to capture the ice marginal flood flow and to divert the flood waters west probably to the newly eroded deep Missouri River valley (although possibly to a south-oriented flood flow channel). When the deep Missouri River valley did erode headward into southern North Dakota the west-oriented Beaver Creek valley was able to erode east to capture the south-oriented ice marginal floods. The north-northwest oriented South Branch Beaver Creek valley segment probably originated as a south-southeast oriented flood flow route that was beheaded by headward erosion of the west-oriented Beaver Creek valley. Flood waters on the north-northwest end of the beheaded flood flow route reversed flow direction to flow to the newly eroded and deeper Beaver Creek valley while the southwest-oriented South Branch Beaver Creek valley eroded northeast to capture additional southeast-oriented flood flow. At the same time the Beaver Creek valley eroded northeast and east to behead flood flow to the newly eroded South Branch Beaver Creek valley. The valleys did not erode further east because at that time the area further east was still covered by remnants of the decaying ice sheet’s detached southwest margin.

Missouri Coteau southeast of Wishek, North Dakota

Figure 8: Missouri Coteau southeast of Wishek, North Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 illustrates a typical Missouri Coteau region southeast of Wishek, North Dakota and includes overlap areas with figure 7. Wishek is located in the figure 8 northwest corner area. The town located on the west-to-east oriented red highway crossing the figure 8 south half is Ashley, North Dakota. Unlike areas closer to the Missouri River valley this Missouri Coteau region has no integrated drainage pattern. Instead the region has many small interior drainage basins with lakes partially filling some of the basins. The landscape includes many small hills and is typical of glacial moraine regions. This region is interpreted here to be where the detached west and southwest margin of a rapidly melting thick North American ice sheet slowly melted and deposited whatever debris it contained. The ice sheet’s southwest margin was detached when immense south-oriented supra glacial melt water rivers sliced giant ice-walled and bedrock-floored valleys into the thick ice sheet surface. The Missouri Escarpment seen in figures 9 and 10 below is interpreted to be what remains of the west wall of the ice-walled and bedrock-floored valley that detached the ice sheet’s southwest margin. Landscapes east of the Missouri Escarpment are lower in elevation than the Missouri Coteau and also lack evidence of the thick glacially deposited debris found in the Missouri Coteau region. The Missouri Coteau is found between the southeast and south-oriented Missouri River and the northeast and east-facing Missouri Escarpment continuously from northwest North Dakota southeast and south into southern South Dakota. The northeast-facing Missouri Escarpment can be traced in a northwest direction across Saskatchewan and into east central Alberta and for that entire distance there is a band of Missouri Coteau type landscape at its crest. At various points there is evidence ice marginal floods broke through the detached ice sheet margin (named here the Southwest Ice Sheet) to flow northeast and east to the deeper southeast and south-oriented ice-walled and bedrock-floored valley northeast and east of the Missouri Escarpment (named here the Midcontinent Trench). Where ice marginal floods broke through the Southwest Ice Sheet ice barrier they sliced narrow ice-walled and bedrock-floored valleys, which were later blocked by a subsequent glacial event.

Missouri Coteau and Missouri Escarpment in Dickey County, North Dakota

Figure 9: Missouri Coteau and Missouri Escarpment in Dickey County, North Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the Missouri Coteau eastern edge and the Missouri Escarpment in Dickey County, North Dakota and is located east and north of the figure 8 map area. Edgeley, North Dakota is the town at the highway intersection near the figure 9 north center edge. The southeast and south-oriented Maple River flows through Edgeley to Monango in the figure 9 southeast corner and then east to the figure 9 east edge. The Maple River and all other figure 9 drainage routes are tributaries of the south-oriented James River, which is located east of the figure 9 map area. The Missouri Coteau is located in the western third of figure 9. East of the Missouri Coteau is the well-drained east-facing Missouri Escarpment slope. Note the numerous east-oriented streams originating near the Missouri Escarpment crest and flowing to the Maple River and/or to Maple River tributaries. Elevations along the figure 9 east edge are generally about 200 meters lower than elevations in the Missouri Coteau near the figure 9 west edge. As already described the Missouri Escarpment is interpreted to have formed as the lower part of the west wall of a giant southeast and south-oriented ice-walled and bedrock-floored valley sliced into a rapidly melting thick ice sheet. At one time the walls of this ice-walled and bedrock-floored valley may have been hundreds of meters high (if not higher) and the valley and canyon size and depth may have rivaled any existing canyons on Earth today. This immense southeast and south-oriented Midcontinent Trench was not unique. Other giant ice-walled and bedrock-floored valleys were sliced into the decaying ice sheet at other locations. Headward erosion of these ice-walled and bedrock-floored valleys chopped the decaying ice sheet up into a number of detached and isolated smaller ice sheet masses. This process of chopping up the decaying ice sheet probably greatly increased the ice sheet’s melting rate. Immense melt water floods moved south from the ice sheet and eventually reached the Gulf of Mexico. The ice sheet’s rapid melt down ended when headward erosion of north-oriented ice-walled and bedrock-floored valley intersected with the south-oriented ice-walled and bedrock-floored valleys. The north-oriented valleys had shorter routes to sea level and hence steeper gradients and were able to capture the south-oriented melt water floods. Diversion of the immense melt water floods from the Gulf of Mexico to Hudson Bay and the Arctic Ocean caused a major climate change, which resulted in flood waters freezing on the former ice sheet floor and probably the formation of a thin ice sheet with thick ice sheet remnants located in it. Melting of that thin ice sheet did not produce the immense melt water floods that had occurred previously.

Missouri Coteau and Escarpment along the North Dakota-South Dakota border

Figure 10: Missouri Coteau and Escarpment along the North Dakota-South Dakota border. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 illustrates the Missouri Coteau and Missouri Escarpment along the North Dakota-South Dakota border and is located south of the figure 9 map area and east and slightly south of the figure 8 map area. The west-to-east oriented North Dakota-South Dakota border is marked on figure 10. The Missouri Escarpment in this figure 10 map area has an east-southeast slope orientation and is again well-drained by east- and southeast-oriented streams. At the Missouri Escarpment crest is the Missouri Coteau. Note how the streams draining the Missouri Escarpment slope have not eroded valleys headward into the Missouri Coteau region. The Missouri Escarpment south-southwest orientation parallels the orientation of the James River course east of the figure 10 map area and also of the west-northwest-facing escarpment along the west edge of the Prairie Coteau upland, which mirrors the Missouri Escarpment-Missouri Coteau on the east side of the James River lowland region (see figure 10a below and the James River-Wild Rice River drainage divide area essay-found under James River on sidebar category list). In South Dakota the James River flows south in a broad lowland bounded on both sides by escarpments with coteau regions at their crest. To the west is the Missouri Escarpment with the Missouri Coteau at its crest. To the east is the west-facing escarpment at the west edge of the Prairie Coteau upland. The Prairie Coteau upland is here interpreted to have an origin similar to the Missouri Coteau origin. In other words, the Prairie Coteau upland represents an area where the rapidly melting thick ice sheet was isolated by headward erosion of ice-walled and bedrock-floored valleys being sliced into the thick ice sheet surface by what began as immense south-oriented supra glacial melt water rivers. In the case of the Prairie Coteau upland the Midcontinent Trench ice-walled and bedrock-floored valley eroded headward to the west and an ice-walled and bedrock-floored valley eroded headward along the present day Minnesota River valley alignment to the east. The two ice-walled and bedrock-floored valleys intersected in southeast North Dakota (just north of the North Dakota-South Dakota border east of the figure 10 map area-see figure 10a below). Further north the eastern valley eroded headward along what is now the north-oriented Red River valley alignment while the Midcontinent Trench eroded north and northwest following the present day Missouri Escarpment alignment.

Figure 10a: Prairie Coteau upland located on east side of James River lowland and east of the figure 10 map area (west-to-east oriented North Dakota-South Dakota border crosses Prairie Coteau upland north tip). United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Additional information and sources of maps studied

This essay has provided only a sample of the detailed topographic map evidence supporting the flood erosion interpretation. Many additional illustrations could be provided. Readers are encouraged to look at mosaics of detailed topographic maps to see the abundance of available data. Maps used in this study were created and published by the United States Geologic Survey and can be obtained directly from the United States Geological Survey and/or from dealers offering United States Geological Survey maps. Hard copy maps can also be observed at United States Geological Survey map depositories which are located throughout the United States and elsewhere. Illustrations used here were created using National Geographic Society TOPO software and digital map data. TOPO software and map data can be obtained from the National Geographic Society and/or dealers offering National Geographic Society digital map data.

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