A geomorphic history based on topographic map evidence

The drainage divide between Spearfish Creek and Whitewood Creek and Rapid Creek is located in the South Dakota Black Hills, USA. Although detailed topographic maps of the Spearfish Creek-Whitewood Creek and Rapid Creek drainage divide area have been available for more than fifty years detailed map evidence has not previously been used to interpret the region’s geomorphic history. The interpretation provided here is based entirely on topographic map evidence. The Spearfish Creek-Whitewood Creek and Rapid Creek drainage divide area is interpreted to have been eroded during immense southeast-oriented flood events, the first of which flowed on a topographic surface at least as high as the highest points in the present-day drainage divide area today, although the Black Hills area may have been uplifted during and/or following the flood. Flood flow across the Spearfish Creek-Whitewood Creek and Rapid Creek drainage divide area ended when headward erosion of the deep Spearfish Creek valley captured all southeast-oriented flood flow.

Preface:

Introduction:

• The purpose of this essay is to use topographic map interpretation methods to explore South Dakota Spearfish Creek-Whitewood Creek and Rapid Creek drainage divide area landform origins. 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 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 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 similar essays is a thick North American ice sheet, comparable in thickness to the present day Antarctic ice sheet, occupied approximately the North American region usually recognized to have been glaciated and through its weight and erosive actions created a “deep” North American “hole”, 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 Spearfish Creek-Whitewood Creek and Rapid Creek drainage divide area landform evidence will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Spearfish Creek-Whitewood Creek and Rapid Creek drainage divide area location map

Figure 1: Spearfish Creek-Whitewood Creek and Rapid Creek drainage divide area 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 general location map for the Spearfish Creek-Whitewood Creek and Rapid Creek drainage divide area. South Dakota is the state located in the eastern two-thirds of figure 1. Wyoming is the state to the west and Montana is the state in the extreme northwest corner. Spearfish Creek is the unlabeled stream flowing north through Spearfish, South Dakota to the southeast-oriented Belle Fourche River (near the South Dakota-Wyoming state line in the northern Black Hills). Whitewood Creek is the unlabeled northeast-oriented stream just east of Spearfish Creek and flows through Deadwood and Whitewood, South Dakota. Rapid Creek is the unlabeled southeast-oriented stream flowing through Rochford, Silver City, and Rapid City, South Dakota to the northeast-oriented Cheyenne River. Spearfish Creek flows north to join the northeast-oriented Redwater River prior to flowing to the southeast-oriented Belle Fourche River. Other Black Hills region drainage divide essays can be found under Black Hills region on the sidebar category list.  The Black Hills are a domal uplift with an exposed core of Precambrian rocks and stand significantly higher than the surrounding plains region. This essay interprets the origin of Spearfish Creek-Whitewood Creek and Rapid Creek drainage divide area landforms in the context of an immense southeast oriented flood that flowed across the entire figure 1 map area and that was systematically captured by headward erosion of deep east and northeast-oriented valleys, which diverted flood waters further and further northeast and north. The source of the southeast-oriented flood water cannot be determined from evidence presented here. However, by using evidence from numerous Missouri River drainage basin landform origins research project essays (published on this website) the flood waters can be traced headward to a North American ice sheet location and it can be determined the floods occurred before or while the Black Hills area was being uplifted. Rapid melting of a thick North American ice sheet located in a deep “hole” would explain the flood water source and also why deep valleys eroded west and southwest to capture southeast-oriented flood waters and diverted flood waters further and further northeast and north into space in the deep “hole” the rapidly melting ice sheet had once occupied. In addition, presence of a thick North American ice sheet in a deep “hole” north and east of the Black Hills might explain crustal warping that uplifted the Black Hills dome during an immense southeast-oriented flood. Uplift of the Black Hills dome may have been accelerated by crustal unloading as flood waters deeply eroded the region and removed overlying sedimentary layers.

Spearfish Creek-Whitewood Creek and Rapid Creek drainage divide area detailed location map

Figure 2 provides a more detailed location map for the Spearfish Creek-Whitewood Creek and Rapid Creek drainage divide area. Green areas denote Black Hills National Forest lands. The Spearfish Creek-Whitewood Creek and Rapid Creek drainage divide area is located in Lawrence County, South Dakota. Spearfish Creek flows northeast to Cheyenne Crossing, where it turns northwest before turning northeast again to flow to Spearfish. From Spearfish it flows north-northwest to join the Redwater River and then flow east and north to join the Belle Fourche River. Whitewood Creek originates near Cheyenne Crossing and flows northeast through Deadwood and Whitewood, South Dakota before joining the Belle Fourche River. Rapid Creek also begins near Cheyenne Crossing and flows southeast to Rochford and Silver City and then south and east of the figure 2 map area to Rapid City and the northeast-oriented Cheyenne River. Rapid City, South Dakota is the unlabeled urban area located in the figure 2 southeast corner. This essay begins with detailed maps of the Spearfish Creek-Whitewood Creek drainage divide area north of the Black Hills and then proceeds south into the Black Hills uplift area west of Deadwood and Lead, South Dakota. South of the Whitewood Creek headwaters near Deer Mountain the detailed maps illustrate Spearfish Creek-Rapid Creek drainage divide evidence and also Spearfish Creek-East Spearfish Creek drainage divide area evidence.

Spearfish Creek-Whitewood Creek drainage divide area north end

Figure 3: Spearfish Creek-Whitewood Creek drainage divide area north end. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 3 illustrates the north end of the Spearfish Creek-Whitewood Creek drainage divide area where north oriented Spearfish Creek and northeast-oriented Whitewood Creek flow to the east oriented Belle Fourche River. Spearfish Creek flows north from the figure 3 southwest corner to join the east and north oriented Redwater River, which flows to the Belle Fourche River near Belle Fourche, South Dakota (figure 3 northwest corner). The southeast-oriented Belle Fourche River is located along the figure 3 north edge (northeast half). Whitewood Creek flows northeast across the figure 3 southeast corner and east of figure 3 joins the Belle Fourche River. False Bottom Creek flows northeast in the figure 3 south center before turning northwest to follow the highway to join the north oriented Redwater River in the figure 3 northwest quadrant. Crooked Creek flows north and northeast to join the Belle Fourche River west of Fruitdale (figure 3 north center edge). Maloney Creek flows north to join the Belle Fourche River southeast of Fruitdale. East of Maloney Creek, Stinkingwater Creek flows northeast and northwest to the Belle Fourche River. Landform origins in this figure 3 map area are interpreted in the context of an immense southeast-oriented flood. In addition to being a northwest-oriented Redwater River tributary, False Bottom Creek (and also Crooked Creek, Maloney Creek, and Stinkingwater Creek) has northwest-oriented tributaries. Northwest-oriented tributary valleys are best explained by reversals of flood flow on the northwest ends of beheaded southeast-oriented flood flow routes. The multiple valleys in which these northwest-oriented tributaries exist suggests deep north- and northeast-oriented valleys beheaded multiple southeast-oriented flood flow routes or channels, such as might be found in a southeast-oriented anastomosing channel complex. Reversed flow on what are today larger valleys probably captured significant yet to be beheaded flood flow on southeast-oriented flood flow routes further to the south. For example, the large northwest-oriented False Bottom Creek valley required large amounts of water to be eroded. A northwest-southeast oriented through valley located just northeast of Spearfish may have been used by yet to be beheaded (by headward erosion of what was then the deep Redwater River-Spearfish Creek valley) southeast-oriented flood water that was captured by reversed flow on the northwest-oriented False Bottom Creek alignment. Capture of such yet to be beheaded flood flow could account for the large volumes of northwest-oriented water required to erode the present day northwest-oriented False Bottom Creek valley.

Spearfish Creek-Whitewood Creek drainage divide area between Spearfish and Whitewood, South Dakota

Figure 4: Spearfish Creek-Whitewood Creek drainage divide area between Spearfish and Whitewood, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 4 illustrates the Spearfish Creek-Whitewood Creek drainage divide area south of the figure 3 map area and includes overlap areas with figure 3. Spearfish Creek flows north-northeast from the figure 4 southwest corner to Spearfish and then north-northwest to the figure 4 north edge. Whitewood Creek flows northeast from the figure 4 south edge through Whitewood and then to the figure 4 northeast corner. False Bottom Creek flows northwest from the figure 4 south edge (center west) and then turns north to flow west of the airport before turning northeast and then turning northwest o flow to the figure 4 north edge (by the highway). Polo Creek flows northeast in Polo Gulch (figure 4 south center) and then north to join False Bottom Creek and has a northwest-oriented tributary at the Centennial Prairie southeast end. Miller Creek flows north just west of Polo Peak (figure 4 south center) and then northeast across Centennial Prairie to reach Polo Creek. The northwest-southeast oriented Centennial Prairie valley is today a through valley drained by multiple north-oriented drainage routes eroded by southeast-oriented flow to what is today the northeast-oriented Whitewood Creek valley, although during late erosion stages flood waters on the northwest ends of beheaded flood flow routes in some cases were reversed to flow northwest to newly eroded north-oriented valleys. Figure 4 evidence can be explained by southeast-oriented flood flow moving across the entire figure 4 map area in an ever-changing southeast-oriented anastomosing channel complex on a topographic surface significantly higher than the present day Centennial Valley floor (and the Black Hills uplift was just beginning meaning flood waters were moving across what are today uplifted Black Hills areas to the south of figure 4). Headward erosion of a deep southeast-oriented Belle Fourche River valley to the north of figure 4 enabled a deep northeast-oriented Whitewood Creek valley to erode southwest into rising Black Hills uplift area. Headward erosion of the deep Whitewood Creek valley captured southeast-oriented flood flow and diverted the water northeast to the newly eroded and deep Belle Fourche River valley. The northwest-southeast-oriented Centennial Prairie valley was eroded headward at this time. Headward erosion of the deep Belle Fourche River valley next enabled other north- and northeast-oriented tributary valleys, such as the Redwater River valley to erode south. Headward erosion of the deep Redwater River valley beheaded southeast-oriented flood flow on the present day northwest-oriented False Bottom Creek route, causing flood waters on the northwest end of that beheaded flood flow route to reverse flow direction. The reversed flow captured southeast-oriented flood flow from the Centennial Prairie valley route and diverted that water north. Meanwhile deep erosion of the Centennial Prairie valley and areas north of it combined with on-going Black Hills uplift was enabling north-oriented valleys to erode headward into the Black Hills uplift area and to divert southeast-oriented flood flow into the  much deeper valleys to the north and east. Headward erosion of these deep north-oriented valleys captured significant amounts of southeast-oriented flood flow and diverted the water north, which also eroded north-oriented valleys across what is today the northwest-southeast oriented Centennial Prairie through valley.

Spearfish Creek-Whitewood Creek drainage divide area west of Deadwood and Lead, South Dakota

Figure 5: Spearfish Creek-Whitewood Creek drainage divide area west of Deadwood and Lead, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 5 illustrates the Spearfish Creek-Whitewood Creek drainage divide area south of he figure 4 map area and includes overlap areas with figure 4. Spearfish Creek flows northeast from the figure 5 south edge to Cheyenne Crossing and flows northwest to Savoy, where it turns to flow northeast to the figure 5 north edge. East Spearfish Creek flows northwest to join Spearfish Creek at Cheyenne Crossing. Little Spearfish Creek flows northeast to join Spearfish Creek at Savoy. Whitewood Creek flows northeast from the figure 5 south edge (center) through Englewood and Deadwood to the figure 5 northeast corner. False Bottom Creek flows northwest and north to the figure 5 north edge (center). Note the northwest-oriented tributaries to the northeast-oriented Little Spearfish Creek-Spearfish Creek valley. From north to south these include Rubicorn Gulch, Squaw Creek, Long Valley, Calamity Gulch, and Spearfish Creek. Also note southeast-oriented Whitewood Creek tributaries (as well as northwest-oriented Whitewood Creek tributaries). While some of this northwest-southeast oriented drainage alignment may reflect underlying Black Hills structures, the drainage alignment also provides evidence of multiple southeast-oriented flood flow channels, such as might be found in a southeast-oriented anastomosing channel complex. Through valleys link many of the southeast-oriented Whitewood Creek tributaries with northwest-oriented Spearfish Creek tributaries, although today the through valleys are often passes across high ridges. Figure 6 below illustrates the through valley linking Icebox Gulch (a Spearfish Creek tributary) with Whitewood Creek (figure 5 south center). Such through valleys and the northwest-southeast oriented drainage alignment provide evidence flood waters flowed on a surface at least as high as the highest figure 5 elevations today. However, it is quite possible, in fact probable, the Black Hills elevation above the surrounding plains was achieved during (and perhaps following) flood events that eroded the figure 5 map area. Other Black Hills region essays demonstrate flood waters removed at least 300 meters of sediment cover from areas immediately south of the Black Hills and lesser, but still significant amounts of sediment cover from areas north of the Black Hills. Further evidence presented in this essay and other Black Hills region essays suggests the Black Hills uplift area was rising as flood waters eroded the region.

Spearfish Creek-Whitewood Creek drainage divide area west of Englewood, South Dakota

Figure 6: Spearfish Creek-Whitewood Creek drainage divide area west of Englewood, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 6 illustrates a detailed map of the through valley linking Spearfish Creek with Whitewood Creek at Icebox Gulch (see figure 5 south center for location). Icebox Gulch is a southwest, northwest, southwest, and northwest-oriented valley draining to northwest-oriented Spearfish Creek at Cheyenne Crossing. Northwest-oriented East Spearfish Creek joins Spearfish Creek at Cheyenne Crossing and East Spearfish Creek and is located in the figure 6 southwest corner. Northeast-oriented Whitewood Creek flows from the figure 6 southeast quadrant through Englewood to the figure 6 west edge. Note the through valley used by the highway linking west and northwest-oriented Icebox Gulch with an unnamed Whitewood Creek tributary, which joins Whitewood Creek at Englewood. That through valley is approximately 450 feet lower than the Deer Mountain top to the south and 80-100 feet lower than the hill to the north. The valley is evidence of a former stream-eroded valley. On the ridge extending north of Deer Mountain there is evidence of at least three more such former valleys, although they are at higher elevations. On the ridge south of Icebox Gulch there is a southeast-oriented through valley to the south and southeast-oriented Whitewood Creek headwaters, which flow to the figure 6 south center (and then make a U-turn seen in figure 7 below to flow northeast to Englewood). Further west (south of the word Gulch) is another through valley to a south-oriented East Spearfish Creek tributary. East of Deer Mountain many additional through valleys link Whitewood Creek tributaries with each other and with the Whitewood Creek valley. This maze of through valleys is best explained in the context of an ever-changing southeast-oriented anastomosing complex of flood water channels, which initially flowed on a topographic surface at least as high as the highest figure 6 elevations today, and which was captured by headward erosion of the deep northeast-oriented Whitewood Creek valley and subsequently captured by headward erosion of the deep Spearfish-East Spearfish Creek valley. Again remember, flood erosion of this figure 6 region occurred as the Black Hills region was gaining its present elevation, which probably means the Black Hills region was being raised as flood waters eroded the figure 6 map area.

Spearfish Creek-Whitewood Creek and Rapid Creek drainage divide area southeast of Cheyenne Crossing, South Dakota

Figure 7: Spearfish Creek-Whitewood Creek and Rapid Creek drainage divide area southeast of Cheyenne Crossing, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 7 illustrates the south end of the Spearfish Creek-Whitewood Creek drainage divide area located south of the figure 5 map area and includes overlap areas with figure 5. Figure 7 also illustrates the Spearfish Creek-Rapid Creek drainage divide area. Whitewood Creek originates in the figure 7 north center south of Deer Mountain (as seen in figure 6 above) and flows south and southeast before making a U-turn to flow northeast through Englewood and then to the figure 7 north edge. Spearfish Creek flows northeast from the figure 7 west edge to Cheyenne Crossing and then flows northwest to the figure 7 north edge. The southeast-oriented North Fork of Rapid Creek originates near Dumont (figure 7 center) and flows southeast to Nahant and the figure 7 south edge. East and southeast-oriented Tilson Creek flows in the figure 7 south center to join the North Fork Rapid Creek at Nahant. Note how southwest of Englewood and the Whitewood Creek U-turn there is a southwest-northeast oriented through valley linking the East Spearfish Creek valley with the Whitewood Creek valley and also a north-south through valley linking northeast-oriented Whitewood Creek with southeast-oriented North Fork Rapid Creek. Also note the northwest-southeast oriented through valley linking northwest-oriented East Spearfish Creek with southeast-oriented North Fork Rapid Creek headwaters at Dumont. These through valleys are illustrated in more detailed in figure 8 below, but they provide additional evidence the figure 7 map area was eroded by a southeast-oriented anastomosing complex of flood  water channels that were systematically captured by headward erosion of deep north- and northeast-oriented valleys. Detailed maps below also illustrate the through valley at Clayton Draw (see figure 7 southwest quadrant) linking the east and southeast-oriented Tilson Creek valley and the South Fork Rapid Creek valley (not seen in figure 7) with the northeast-oriented Spearfish Creek valley and the through valley at Long Draw (figure 7 west center) linking Spearfish Creek with East Spearfish Creek.

Spearfish Creek-Whitewood Creek and Rapid Creek drainage divide area near Dumont, South Dakota

Figure 8: Spearfish Creek-Whitewood Creek and Rapid Creek drainage divide area near Dumont, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 8 illustrates the deep through valleys linking the Spearfish Creek, Whitewood Creek and Rapid Creek drainage basins located near Dumont, South Dakota and is located immediately south of the figure 6 map area (and includes some overlap areas with figure 6). Whitewood Creek flows south and southeast in the figure 8 north center before turning northeast to flow to the figure 8 north edge. A north-south through valley used by a road and railroad (in figure 8) links the Whitewood Creek valley with southeast-oriented North Fork Rapid Creek at Dumont (located in the figure 8 southeast quadrant). East Spearfish Creek flows northwest from the figure 8 south center west of Dumont to the figure 8 northwest corner and is linked by a through valley with the southeast-oriented North Fork Rapid Creek valley. The East Spearfish Creek headwaters area is interesting because to the south is Keough Draw, which is linked by a through valley to the same through valley that links East Spearfish Creek headwaters with North Fork Rapid Creek headwaters. While the deep through valleys seen here probably were eroded by the final flood waters to cross the Black Hills uplift area the twin valleys provide further evidence to support the southeast-oriented anastomosing channel complex interpretation (southeast-oriented flood flow also moved southeast-along the Icebox Gulch and south and southeast-oriented Whitewood Creek headwaters alignment to erode the north-south through valley linking Whitewood Creek and the North Fork Rapid Creek. In other words, figure 8 evidence documents multiple channels of southeast-oriented flood flow coming from what is now the Spearfish Creek drainage basin and flowing to what is now the Rapid Creek drainage basin. Study of figure 8 reveals many higher level through valleys. Numerous through valleys are located throughout the figure 8 map area. For example east and northeast of Hanna (located on East Spearfish Creek) is a northwest-southeast oriented through valley now drained by a northwest-oriented stream. That through valley provides evidence of an earlier stage of erosion.

Spearfish Creek-Rapid Creek drainage divide area at Clayton Draw

Figure 9: Spearfish Creek-Rapid Creek drainage divide area at Clayton Draw. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 9 illustrates through valleys linking the north-oriented Spearfish Creek valley with east and southeast-oriented Tilson Creek (a North Fork Rapid Creek tributary seen in figure 7) and with southeast-oriented South Fork Rapid Creek (not seen in figure 7). Spearfish Creek flows north in the figure 9 northwest quadrant to the figure 9 north edge. Tilson Creek originates northwest of Besant Park and flows east in the figure 9 northeast quadrant to the figure 9 east edge. The South Fork Rapid Creek originates in the figure 9 south center and flows southeast to the figure 9 south edge. Clayton Draw is a northwest-oriented tributary valley that joins the Spearfish Creek valley near the figure 9 north edge. Note how there is a north-south valley linking the east-oriented Tilson Creek valley at Besant Park with the southeast-oriented South Fork Rapid Creek valley. Also note the northwest-southeast through valley (used by a road) linking the northwest-oriented Clayton Draw valley and north-oriented Spearfish Creek valley with the north-south valley linking the Tilson Creek valley and the South Fork Rapid Creek valley. Numerous other higher level through valleys can also be seen crossing divides between the deeper valleys. The northwest-southeast oriented through valley (now used by the road) represents the final route used by southeast-oriented flood waters in the figure 9 map area to flow from what is now the Spearfish Creek drainage basin to what was then the actively eroding South Fork Rapid Creek valley and also the actively eroding Tilson Creek valley. Flood water moved southeast along the Clayton Draw alignment and also south along the Spearfish Creek valley to the southeast-oriented through valley and then flowed over the present day drainage divide to reach the actively eroding Rapid Creek drainage basin. Flood flow across the divide ended when headward erosion of the deep Spearfish Creek valley further to north beheaded these southeast-oriented flood flow channels and caused a reversal of flood flow on the north and northwest ends of the beheaded flood flow routes. Yet to be beheaded southeast-oriented flood waters further to the south were captured by the reversed flood flow in the figure 9 newly formed north-oriented Spearfish Creek drainage basin and helped erode what are now deeper Spearfish Creek and tributary valleys.

Spearfish Creek-East Spearfish Creek drainage divide area at Long Draw

Figure 10: Spearfish Creek-East Spearfish Creek drainage divide area at Long Draw. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 10 illustrates in detail the Spearfish Creek-East Spearfish Creek through valley at Long Draw (seen in less detail in figure 7). Figure 10 has overlap areas with figure 8 above. Spearfish Creek flows north in the figure 10 west half. Northeast-oriented Ward Draw flows to northwest-oriented East Spearfish Creek (see figure 8). Long Draw is today an east-oriented valley draining to northeast-oriented Ward Draw and is linked by a northwest-southeast oriented through valley to north-oriented Spearfish Creek. That northwest-southeast oriented through valley is evidence water flowed south on what is now the north-oriented Spearfish Creek valley alignment, then southeast in the through valley, east along the Long Draw valley route, northeast in the Ward Draw valley and then southeast in the East Spearfish Creek valley to the through valley linking the East Spearfish Creek valley with the South Fork Rapid Creek valley (seen in figure 8). The Long Draw through valley carried flood water at the same time southeast-oriented flood water was flowing in what is now the northwest-oriented East Spearfish Creek valley to the northwest (see figure 8) and is further evidence of deeply eroded anastomosing flood flow channels. Figure 10 also contains evidence of much higher level through valleys. For example, northwest of the word “Draw” in Long Draw is a well-defined higher level northwest-southeast oriented through valley linking Spearfish Creek (just north of figure 10) with Long Draw and provides evidence southeast-oriented flood flow once moved across that higher level divide. Such higher level through valleys document flood waters originally flowed across a topographic surface at least as high as the highest figure 10 map area elevations today. However, the Black Hills uplift area was probably gaining elevation relative to the surrounding plains region as flood waters eroded the figure 10 map area.

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.