Abstract:

Introduction:

• The purpose of this essay is to use topographic map interpretation methods to explore western South Dakota Red Canyon-Beaver 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 Red Canyon-Beaver Creek drainage divide area landform evidence will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Red Canyon Creek-Beaver Creek drainage divide area general location map

Figure 1: Red Canyon Creek-Beaver Creek drainage divide area general 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 Red Canyon Creek-Beaver Creek drainage divide area. The map illustrates an area in western South Dakota (Rapid City is located in South Dakota). Immediately west of South Dakota is the state of Wyoming. South of South Dakota is the state of Nebraska (Chadron is in Nebraska). Red Canyon Creek and Beaver Creek both originate in the southern Black Hills and flow to join the Cheyenne River. Red Canyon Creek is the unlabeled stream flowing south from near Custer and joins the Cheyenne River near Edgemont, South Dakota. Red Canyon Creek is the only south-oriented stream in figure 1 flowing from the Black Hills upland region directly to the Cheyenne River south of the Black Hills. Beaver Creek is not shown on figure 1, but also originates near Custer and flows southeast through Wind Cave National Park to Buffalo Gap and then to the northeast-oriented Cheyenne River and is one of the southernmost of several streams flowing southeast from the Black Hills upland region to join the northeast-oriented Cheyenne River. The northernmost of these streams on figure 1 is Boxelder Creek, but north of Boxelder Creek and figure 1 is Elk Creek. Rapid Creek is the unlabeled southeast-oriented stream south of Boxelder Creek and flows through Rapid City. Spring Creek is the unlabeled stream immediately south of Rapid Creek and flows through Hill City. Battle Creek is the unlabeled stream immediately south of Spring Creek and flows through Keystone and Hermosa. French Creek flows through Fairburn. The French Creek-Beaver Creek drainage divide area, the Battle Creek-French Creek drainage divide area, Spring Creek-Battle Creek drainage divide area, Rapid Creek-Spring Creek drainage divide area, Boxelder Creek-Rapid Creek drainage divide area, Elk Creek-Boxelder Creek drainage divide area, and the Belle Fourche River-Elk Creek drainage divide area essays describe other Black Hills drainage divides and can be found under Black Hills on the sidebar category list.

• This essay interprets Red Canyon Creek-Beaver Creek drainage divide area landform origins 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 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, based on evidence from numerous other Missouri River drainage basin landform origins research project essays published on this website the floods occurred while the Black Hills area was being uplifted and can be traced headward to a North American ice sheet location. 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 to divert 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 or even after an immense southeast-oriented flood. Uplift of the Black Hills dome may have been accelerated by crustal unloading as flood waters deeply eroded the Black Hills region and removed overlying rock layers.

Red Canyon Creek-Beaver Creek drainage divide area detailed location map

Figure 2: Red Canyon Creek-Beaver Creek drainage divide area detailed location map. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 2 provides a slightly more detailed map for the Red Canyon Creek-Beaver Creek drainage divide area, where Beaver Creek is shown. Red Canyon Creek, which flows south to join the Cheyenne River at Edgemont, is shown and also labeled. Custer County and Fall River County are located in western South Dakota. Green areas represent Black Hills National Forest lands, which are generally located in the Black Hills upland region. Custer State Park and Wind Cave National Park lands are shown in red. Red Canyon Creek originates west of Sanator in the figure 2 north center and flows south to join the Cheyenne River near Edgemont, South Dakota. Beaver Creek originates a short distance south of Custer and flows south and southeast through Wind Cave National Park to Buffalo Gap and then to the northeast-oriented Cheyenne River. Note how the Cheyenne River flows southeast to the Black Hills south end and then turns northeast. Also note the large number of southeast oriented streams flowing from the Black Hills to the Cheyenne River (figure 1 shows this better than figure 2). Further note in figure 2 northwest-oriented tributaries to the northeast-oriented Cheyenne River. This predominance of southeast and northwest-oriented tributaries to the northeast-oriented Cheyenne River is evidence the northeast-oriented Cheyenne River valley eroded headward across multiple southeast-oriented flood flow routes, such as might be found in a large-scale anastomosing channel complex, and then captured significant southeast-oriented flood flow moving around the Black Hills south end. Headward erosion of a deep northeast-oriented valley across southeast-oriented flood flow channels would have captured the southeast-oriented flood waters and enabled southeast-oriented tributary valleys to erode headward from the newly eroded and deep Cheyenne River valley wall. At the same time capture of the southeast-oriented flood flow would have beheaded southeast-oriented flood flow routes and flood waters on the northwest ends of those beheaded flood flow channels would have reversed flow direction to flow northwest into the newly eroded and deeper northeast-oriented Cheyenne River valley. Because the channels were anastomosing (meaning they were interconnected) reversed flow on beheaded flood flow routes often captured flood waters from yet to be beheaded flood flow routes further to the south or southwest. Capture of water from such yet to be beheaded flood flow routes frequently provided sufficient water to erode significant northwest-oriented tributary valleys. Prior to headward erosion of the deep northeast-oriented Cheyenne River valley flood waters were flowing to what was then the newly eroded northeast-and east-oriented White River valley. The northeast-oriented White River valley is just barely seen in the figure 2 southeast corner (also see figure 1). The Cheyenne River-White River drainage divide essay describes landform origins southeast of the Cheyenne River and can be found under White River on the sidebar category list.

Red Canyon Creek-Beaver Creek drainage divide area northwest of Pringle

Figure 3: Red Canyon Creek-Beaver Creek drainage divide area northwest of Pringle. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 3 illustrates the north end of the Red Canyon Creek-Beaver Creek drainage divide area northwest of Pringle, South Dakota (located in figure 3 southeast corner). The dark green area in the figure 3 northwest corner is Jewel Cave National Park. The south-oriented drainage network flowing from Fourmile (located in the figure 3 north center on Fourmile Creek) to Pleasant Valley in the figure 3 south center drains to Red Canyon and the Cheyenne River south of the Black Hills. Beaver Creek originates near the landing strip along the figure 3 north edge (northeast corner by highway) and flows south along the highway to Pringle and then turns east to follow the east-oriented highway from Pringle. A large through valley extends south from Pringle and links the south-oriented Beaver Creek valley with southeast oriented Shirttail Canyon (south of figure 3, but seen in figures 5 and 6), which drains to Cold Brook and Fall River, which flows from Hot Springs, South Dakota to the Cheyenne River between Beaver Creek and Red Canyon Creek (see figure 2). The through valley linking the Beaver Creek valley and Shirttail Canyon is evidence flood water once flowed south in the south-oriented Beaver Creek valley to Pringle and then split with some water going east to erode the present day Beaver Creek valley and some water going south to erode the Shirttail Canyon valley. West of Pringle is south-oriented Carroll Creek, which flows to southeast-oriented Cold Brook and the Fall River. Note how a through valley used by the railroad and a road links the Carroll Creek valley with the Beaver Creek and Shirttail Canyon valleys at Pringle. This through valley, which is illustrated in more detail in figure 5 below is further evidence of a large anastomosing channel complex crossing the figure 3 map region. Note how many tributaries to the south-oriented Pleasant Valley drainage network area are southeast-oriented. Also note through valleys linking south-southwest oriented Fourmile Creek (flowing to Pleasant Valley) with the south-oriented Beaver Creek valley. For example the west-oriented Ninemile Draw valley and the Hay Creek valley draining to Fourmile Creek are linked to the south-oriented Beaver Creek. The southeast-oriented Fourmile Creek tributaries and through valleys linking the south-southwest oriented Fourmile Creek valley with the south-oriented Beaver Creek valley provide evidence the Fourmile Creek valley eroded north from the Red Canyon valley to capture multiple southeast- and east-oriented flood flow routes providing water to what was then the actively eroding Beaver Creek (and Shirttail Canyon valley). Maps below illustrate some details.

Fourmile Creek-Beaver Creek drainage divide area west of Sanator

Figure 4: Fourmile Creek-Beaver Creek drainage divide area west of Sanator. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 4 provides a more detailed map of the Fourmile Creek-Beaver Creek drainage divide area west of Sanator. Fourmile Creek flows southwest across the figure 4 northwest corner and eventually flows to Pleasant Valley and then to Red Canyon and to the Cheyenne River south of the Black Hills. Beaver Creek drainage originates in the figure 4 northeast corner and follows the railroad south along the figure 4 east edge and then turns east and southeast to flow to the northeast-oriented Cheyenne River southeast of the Black Hills. A number of through valleys can be identified linking the Fourmile Creek valley with the Beaver Creek valley. One such through valley is located in section 10 in the figure 4 northeast corner and links southeast-oriented Beaver Creek headwaters with west, southwest, northwest, south, west and southwest-oriented Hay Creek, which flows to Fourmile Creek west of the figure 4 map area. Note how the northwest oriented Hay Creek valley segment (located in section 9 in the figure 4 north center) is linked by a through valley with a northwest and west-oriented Fourmile Creek tributary valley. Further south, in the figure 4 southeast corner, southeast-oriented Echo Valley headwaters are linked a through valley in section 15 with the northwest-oriented Hay Creek valley segment. In the figure 4 south center, in section 21, a through valley links Echo Valley headwaters with headwaters of a northwest-oriented Hay Creek tributary. Note also in section 20 in the figure 4 southwest quadrant how a through valley links west-oriented Ninemile Draw with the valley of the northwest-oriented Hay Creek tributary. A close look at figure 4 reveals many more such through valleys. These through valleys provide evidence a southeast-oriented flood once crossed the entire figure 4 map area and was flowing on surface at least as high as the highest figure 4 elevations today. Headward erosion of what was then a deep Beaver Creek valley and various tributary valleys captured the southeast-oriented flood flow and diverted the water south, east, and southeast probably to an actively eroding deep White River valley (the northeast-oriented Cheyenne River valley probably was just eroding southwest and the Black Hills uplift probably was just beginning). Headward erosion of the deep Red Canyon valley and its headwaters Fourmile Creek valley and tributary valleys next captured the southeast-oriented flood and diverted the water south. Flood flow reversals on the northwest ends of beheaded flood routes created what are today the northwest-oriented tributary valleys to southwest-oriented Fourmile Creek and southwest-oriented Fourmile Creek tributaries.

Beaver Creek-Shirttail Canyon drainage divide at Pringle

Figure 5: Beaver Creek-Shirttail Canyon drainage divide at Pringle. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 5 illustrates the Beaver Creek-Shirttail Canyon through valley south of Pringle and the Carroll Creek-Beaver Creek through valley west of Pringle. Beaver Creek flows south in Beaver Valley and then turns east (and east of figure 5 southeast) to flow to the northeast-oriented Cheyenne River. Shirttail Canyon drains southeast to Cold Brook, which flows southeast and south to the southeast-oriented Fall River at Hot Springs. Fall River then flows southeast to the northeast-oriented Cheyenne River (see figure 2 above). Carroll Creek, which is located just west of the figure 5 map area, flows south to Cold Brook (see figure 6 below). The figure 5 through valleys provide evidence at one time all major valleys were channels in a large-scale anastomosing channel complex probably crossing what is today the entire Black Hills upland region. Water flowing south in the Beaver Creek valley split when it arrived at Pringle, with some water flowing east to erode the east and southeast-oriented Beaver Creek valley and some water flowing south to erode the Shirttail Canyon valley. The through valley west of Pringle probably at one time carried water east from what is today the Carroll Creek drainage basin to the Pringle area, where the water probably split with some water going east and some water going south. However, after headward erosion of the south-oriented Carroll Creek valley there probably was a reversal of flow in the present day through valley with water moving west to the deeper Carroll Creek valley. The westward flow was not as strong or as long-lasting as the eastward flow because headward erosion of the Carroll Creek valley and headward erosion of the Pleasant Valley-Fourmile Creek valley further to west captured the southeast-oriented flood flow that had been moving to what had been the actively eroding the Beaver Creek valley. Figure 5 illustrates many other through valleys providing evidence flood flow originally moved on a topographic surface at least as high as the highest figure 5 elevations today. For example, in sections 23 and 24 southwest of Pringle there is a southeast-oriented valley linking the Carroll Creek-Beaver Creek through valley west of Pringle with the Shirttail Canyon valley south of Pringle. That southeast-oriented valley provides evidence headward erosion of the Carroll Cree-Beaver Creek through valley beheaded southeast-oriented flood flow from the present day Carroll Creek drainage basin to Shirttail Canyon.

Shirttail Canyon-Cold Springs Creek drainage divide area west of Wind Cave National Park

Figure 6: Shirttail Canyon-Cold Springs Creek drainage divide area west of Wind Cave National Park. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 6 illustrates a flood eroded anastomosing channel complex located immediately southeast of the figure 5 map area and which has eroded the Wind Cave National Park surface landscape. Southeast and south-oriented Shirttail Canyon is located in the figure 6 northwest corner and drains to Cold Brook Canyon, which extends from the figure 6 west center edge to the figure 6 southeast corner. East-oriented Beaver Creek is located in the figure 6 northeast corner. Cold Springs Creek flows southeast in the figure 6 northwest quadrant to the National Park Water Supply Area and then northeast and east to join Beaver Creek in the figure 6 northeast corner. Note the through valley just west of the National Park Water Supply Area linking the northeast and east-oriented Cold Springs Creek valley with the southeast and south-oriented Shirttail Creek valley. Then note the southeast-oriented through valley linking the Cold Springs Creek valley in the National Park Water Supply Area with southeast-oriented Cottonwood Creek, which east of figure 6 flows to southeast-oriented Beaver Creek. Note also how multiple through valleys link that Cold Springs Creek-Cottonwood Creek through valley with southeast-oriented Antelope Canyon, which flows to southeast-oriented Cold Brook, which in turn flows southeast and south to the southeast-oriented Fall River. This maze of valleys linking what are today separate drainage basins is a classic anastomosing channel complex and provides evidence of flood erosion by a large-scale southeast-oriented flood. Flood waters were coming from the northwest, which is today the Black Hills upland area. Today there is no flood source in the Black Hills upland area capable of generating a flood of the magnitude required to erode this anastomosing channel complex. Flood waters must have come from northwest of the Black Hills area, and that would have been impossible if the Black Hills had stood high above the surrounding region (as is the case today). In other words, when flood waters eroded this figure 6 map region the Blacks Hills did not stand high above the surrounding region, which means either the surrounding region has since been eroded and/or the Black Hills have since been uplifted. Most likely flood water deeply eroded the surrounding region while the Black Hills upland area was being uplifted.

Drainage divides in the Bradley Flats area

Figure 7: Drainage divides in the Bradley Flats area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 7 illustrates the Red Canyon-Hot Brook-Cheyenne River drainage divide area in the Minnekahta or Bradley Flats area and is located south of the previous detail map areas. Red Canyon is located along the figure 7 west edge and drains south to the Cheyenne River near Edgemont (see figure 9 below). Hot Brook originates in the figure 7 center and flows east to Hot Springs (located on the figure 7 east edge) and then to southeast-oriented Fall River. Cottonwood Springs Creek is a major southeast-oriented Hot Brook tributary. South of Bradley Flats is south-oriented Chilson Canyon, which drains to the Cheyenne River (see figure 9 below). Northwest of Bradley Flats is a northwest-oriented Red Canyon tributary. In the figure 7 southeast quadrant is Albaugh Canyon, which is a north-south through valley linking the Hot Brook valley with the Cheyenne River valley south of figure 7 (figure 9 better illustrates Albaugh Canyon). South-oriented drainage between Chilson Canyon and Albaugh Canyon drains to the Cheyenne River (see figure 9). Figure 7 illustrates more of the through valley system that provides evidence of the large-scale flood eroded anastomosing channel complex that once crossed what is today the Red Canyon-Beaver Creek drainage divide area. The east-oriented Hot Brook valley and the south-oriented Albaugh Canyon valley provide evidence water flowing east from the Bradley Flats area and southeast along the Cottonwood Springs Creek valley split with some water going south through Albaugh Canyon and some water going east to the Fall River. The south-oriented Chilson Canyon valley provides evidence that at the same time water also going south through Chilson Canyon. Headward erosion of the deep Red Canyon valley beheaded flood flow to these diverging flood flow routes, causing a reversal of flood flow on the northwest end of one flood flow route to create what is today the northwest-oriented Red Canyon tributary valley flowing northwest from Bradley Flats. Figure 8 illustrates a detailed map of the Matias Peak area in the figure 7 southwest quadrant (between Red and Chilson Canyons).

Drainage divides west of Matias Peak

Figure 8: Drainage divides west of Matias Peak. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 8 illustrates a detailed map of the Matias Peak area seen in less detail in the figure 7 southwest quadrant. South-oriented Chilson Canyon is located in the figure 8 southeast corner and drains south to the Cheyenne River (see figure 9). Red Canyon Creek flows south in the figure 8 west half from the figure 8 north edge to the figure 8 south edge. Southeast-oriented Craven Canyon is located in the figure 8 southwest corner. Bradley Flats is located in the figure 8 northeast corner. Figure 8 illustrates another flood eroded anastomosing channel complex. A southwest-oriented through valley links the south-oriented Red Canyon Creek valley with the southwest-oriented Craven Creek valley in the figure 8 west center. To east on the other side of Red Canyon a north-south and southwest-oriented through valley isolates a large erosional residual. South of that through valley are additional through valleys that isolate additional erosional residuals. In fact the entire upland mass in the figure 8 could be considered an erosional residual isolated by valleys eroded around it (see figures 7 and 9 for bigger picture views). These valleys provide evidence of an immense flood that in the figure 8 map area was primarily south-oriented, with headward erosion of the deep Red Canyon Creek valley eventually capturing the flood waters (at least flood waters moving across figure 8 map areas east of Red Canyon).

Chilson Canyon-Alabaugh Canyon drainage divide area

Figure 9: Chilson Canyon-Alabaugh Canyon drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 9 illustrates the Chilson Canyon-Albaugh Canyon drainage divide area south of the figure 7 map area and includes overlap areas with figure 7. South-oriented Red Canyon is located along the figure 9 west edge (north half) and flows southwest of figure 9 to join the Cheyenne River just west of figure 9 (the Cheyenne River is located in the figure 9 southwest corner and in the figure 9 south center and southeast corner. Chilson Canyon is a through valley extending south from Bradley Flats (along the figure 9 north edge (west half) to Chilson Station, where it turns southeast to drain to the Cheyenne River. Note the Chilson Canyon south oriented drainage basin originates just south of Bradley Flats, which is evidence Chilson Canyon was eroded by water coming from outside the present day Chilson Canyon drainage basin. Albaugh Canyon is a north-south through valley in the figure 9 east half linking the east-oriented Hot Brook valley in the figure 9 northeast quadrant with the east-oriented Cheyenne River valley in the figure 9 southeast quadrant. Today the north end of Albaugh Canyon is drained by a north-oriented Hot Brook tributary while most of Albaugh Canyon is drained by a south oriented Cheyenne River tributary. Water that eroded Albaugh Canyon came from north of Albaugh Canyon, which means at one time water flowed both east in the Hot Brook valley to Fall River and south in the Albaugh Canyon valley to the east-oriented Cheyenne River valley. East of Albaugh Canyon a through valley links south oriented Albaugh Canyon with the southeast-oriented Whaley Canyon, which drains to Shep Canyon and to the northeast-oriented Cheyenne River valley (also a southwest-northeast oriented through valley extends from Whaley Canyon headwaters to Hot Springs in the figure 9 northeast corner). Between Chilson Canyon and Albaugh Canyon is an anastomosing maze of south and southeast-oriented valleys. A close look at headwaters of these valleys reveals high-level through valleys providing evidence the water that eroded the south and southeast-oriented canyons came from what is today the east-oriented Hot Brook drainage basin (or north of it). This anastomosing maze of deeply eroded valleys again provides evidence of an immense south and southeast-oriented flood that flowed across the figure 9 map region.

Cold Brook-Martin Valley drainage divide area

Figure 10: Cold Brook-Martin Valley drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 10 illustrates the Cold Brook-Marin Valley drainage divide area and is located east of the figure 7 map area and northeast of the figure 9 map area and includes overlap areas with figures 7 and 9. The Cheyenne River here has flowed around the Black Hills south end and is flowing northeast from the figure 10 south center to the figure 10 east edge. Fall River flows southeast from Hot Springs to the Cheyenne River. Beaver Creek flows southeast from the figure 10 north center through Buffalo Gap to the northeast-oriented Cheyenne River. Cold Brook flows south from the figure 10 northwest corner area to Hot Springs, where it joins east-oriented Hot Brook to form the southeast oriented Fall River. Note the southwest-northeast oriented through valley linking the Cold Brook valley with the southeast and northeast-oriented Martin valley. Also note the south and southeast oriented valleys draining the area between the Cold Brook-Martin Valley through valley and the northeast-oriented Cheyenne River valley. These valleys include the southeast oriented Elm Creek valley and Spring Creek valley and the south-oriented Dudley Creek valley. Note how the Spring Creek valley eroded headward to capture south-oriented flood flow that had been eroding the south-oriented Dudley Creek valley. Also note the maze of high-level through valleys linking headwaters of these valleys with each other and with the Cold Brook-Martin Valley through valley. A similar maze of valleys can be seen in the figure 10 southwest corner where the southwest-northeast oriented through valley linking southeast-oriented Whaley Canyon headwaters (see figure 9) with the southeast-oriented Fall River valley is located just west of the Seven Sisters Range. Note how multiple southeast-oriented canyons originate in the Seven Sisters Range and have formed through valleys linking the southwest-northeast oriented through valley with the northeast-oriented Cheyenne River valley. These canyons and through valleys were not eroded by present day drainage networks, but provide evidence of an immense southeast- and south-oriented flood responsible for eroding the deep northeast-oriented Cheyenne River valley headward around the Black Hills south end.

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.