Abstract:

Introduction:

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

Belle Fourche River-Elk Creek drainage divide area general location map

Figure 1: Belle Fourche River-Elk 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 Belle Fourche River-Elk Creek drainage divide area. South Dakota is the state occupying the eastern two-thirds of figure 1. Montana is located in the figure 1 northwest corner and Wyoming is located south of Montana and west of South Dakota. The Belle Fourche River begins in Wyoming a short distance west of the figure 1 map area and flows northeast just west of the Black Hills uplift area almost to the Montana border before turning southeast to flow into South Dakota. In South Dakota the Belle Fourche River flows southeast along the Black Hills northeast flank and then turns east-northeast to join the northeast-oriented Cheyenne River. Elk Creek begins in the Black Hills a short distance southeast of Deadwood, South Dakota and flows southeast through Piedmont, South Dakota before turning northeast and east to join the northeast-oriented Cheyenne River. Other Black Hills region drainage divide area essays can be found under Black Hills region on the sidebar category list.  The Black Hills uplift region is a domal uplift with an exposed core of Precambrian rocks and stands significantly higher than the surrounding plains region. This essay interprets Belle Fourche River-Elk 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 presented collectively  in the Missouri River drainage basin landform origins research project essays (published on this website) the floods occurred before and/or 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 sedimentary layers.

Belle Fourche River-Elk Creek drainage divide area detailed location map

Figure 2: Belle Fourche River-Elk Creek drainage divide area detailed location map. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 2 provides a detailed location map for the Belle Fourche River-Elk Creek drainage divide area. The green color represents Black Hills National Forest lands, which are primarily located in higher Black Hills uplift areas. Lawrence, Meade, and Pennington Counties are all located in South Dakota. The Belle Fourche River flows southeast from the figure 2 northwest corner to Belle Fourche, Fruitdale, Nisland, Vale, and Volunteer before turning east-northeast just south of Hereford to flow to the northeast-oriented Cheyenne River. Elk Creek originates east of Whitewood Creek, south of Deadwood and north of Custer Peak in central Lawrence County and flows generally southeast past Piedmont, South Dakota before turning northeast and east to flow to the north and northeast-oriented Cheyenne River. Belle Fourche River tributaries discussed here include northeast-oriented Spearfish Creek (which flows through Spearfish in northwestern Lawrence County) northeast-oriented Whitewood Creek (which flows through Deadwood and Whitewood in Lawrence County), northeast-oriented Bear Butte Creek (which flows through Sturgis in western Meade County), and Alkali Creek (which flows east-southeast from its origin just east of Sturgis). Southeast-oriented Antelope Creek, originating east of Piedmont, South Dakota is one of the Elk Creek tributaries discussed below. In figure 2 note the southeast oriented Elk Creek tributaries east of the Black Hills uplift area. Also note southeast oriented Belle Fourche River tributaries and southeast and northwest-oriented Cheyenne River tributaries. This northwest-southeast oriented tributary alignment is evidence major east- and northeast-oriented valleys (such as the Cheyenne River valley, the Elk Creek valley and the Belle Fourche River valley) eroded west and southwest across multiple southeast-oriented flood flow channels, such as might be found in a southeast-oriented anastomosing channel complex. Headward erosion of the deep east- and northeast-oriented valleys  systematically captured southeast-oriented flood water and diverted the captured water to the northeast. Figure 2 evidence suggests the southeast-oriented flood flowed across the entire figure 2 map area north and east of the Black Hills, but the detailed maps below are needed to determine if Black Hills drainage patterns reflect headward erosion of deep valleys to capture southeast-oriented flood waters at higher elevations.

Belle Fourche River-Elk Creek drainage divide southwest end in the Black Hills

Figure 3: Belle Fourche River-Elk Creek drainage divide southwest end in the Black Hills. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 3 illustrates the Belle Fourche River-Elk Creek drainage divide southwest end area. Elk Creek originates  at the spring east of Dumont in the figure 3 southwest corner and flows northeast and east to Brownsville and Roubaix before turning northeast and then when it reaches the figure 3 east edge it turns southeast. Headwaters of southeast-oriented North Fork Rapid Creek flow through Dumont to the figure 3 south edge. Southwest of Dumont northwest-oriented East Spearfish Creek headwaters flow across the figure 3 extreme southwest corner to eventually reach north-oriented Spearfish Creek, which flows to the southeast-oriented Belle Fourche River. A through valley extends north from Dumont to link southeast-oriented North Fork Rapid Creek headwaters with headwaters of north-oriented Whitewood Creek, which flows to the Belle Fourche River. East of the Woodville Hills (north of Dumont) are headwaters of east and northeast-oriented Bear Butte Creek, which flows east to the highway north of Brownsville and then turns northeast to flow to the figure 3 north edge and then to the southeast-oriented Belle Fourche River. West of Park Hill (figure 3 northeast corner) is north-oriented Park Creek, which flows to northeast-oriented Bear Butte Creek, which in turn flows to the southeast-oriented Belle Fourche River. Through valleys link all major figure 3 drainage routes and are visible even with the limited detail shown in figure 3. As already mentioned a through valley links north-oriented Whitewood Creek headwaters with southeast-oriented North Fork Rapid Creek headwaters. Elk Creek headwaters are linked by a through valley to that Whitewood Creek-North Fork Rapid Creek through valley. Through valleys east of Woodville Hills link the Whitewood Creek valley with the Bear Butte Creek valley and with an east-oriented Elk Creek tributary valley. Through valleys north of Brownsville link the Elk Creek valley with the northeast-oriented Bear Butte Creek valley and provide evidence water from the Elk Creek valley once flowed north and northeast into the northeast-oriented Bear Butte Creek valley (at the same time water was also going east on the present day Elk Creek valley route). Further east, headwaters of north-oriented Park Creek are linked by a through valley with the Elk Creek valley. These through valleys provide evidence of a large-scale anastomosing channel complex crossing what is today the Black Hills uplift area. Detailed maps below illustrate some of the through valleys and provide further information on flow directions.

Spearfish Creek and Whitewood Creek drainage divides with Elk Creek

Figure 4: Spearfish Creek and Whitewood Creek drainage divides with Elk Creek. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 4 provides a more detailed map of through valleys in at the Belle Fourche River-Elk Creek drainage divide southwest end. Dumont is located slightly to the southwest of the figure 4 center. Northwest-oriented East Spearfish Creek flows toward the figure 4 northwest corner (note the parallel Keough Draw through valley northwest of Dumont). North Fork Rapid Creek flows southeast through Dumont to the figure 4 south center edge. Whitewood Creek flows south in the figure 4 northwest quadrant (valley where the “F” in Forest is located) and then makes a U-turn to flow north in one of two parallel north oriented valleys diverging north of Dumont and converging near the figure 4 north edge. Elk Creek originates at the Juso Ranch spring (east of Dumont and northwest of Custer Peak) and flows northeast and then east to Brownsville and is linked by a southwest-northeast through valley with the southeast-oriented North Fork Rapid Creek valley. In the figure 4 north center a through valley links the westernmost of the twin Whitewood Creek valleys with the valley of an east-oriented Elk Creek tributary. Numerous other higher level through valleys can also be identified and provide evidence flood waters eroded anastomosing channel complexes that crossed what are today high level ridges before what are today the deeper and most prominent through valleys were eroded by what were probably final southeast-oriented flood waters to cross the Black Hills uplift area. The deeper and most prominent through valleys provide evidence final flood flow across the figure 4 map area was in a southeast direction. That final flood flow moved southeast in what is now the northwest-oriented East Spearfish Creek valley to what was then the actively eroding southeast-oriented North Fork Rapid Creek valley. Elevation of the drainage divide between the southeast-oriented North Fork Rapid Creek valley and the northeast-oriented Elk Creek valley (southwest of Juso Ranch) is almost identical to the elevation of the drainage divide between East Spearfish Creek and North Fork Rapid Creek (both are slightly lower than the divide to Whitewood Creek north of Dumont). The similarity of divide elevations suggests for a time at least flood waters were going both southeast to erode the North Fork Rapid Creek valley and northeast to erode the Elk Creek valley (and that water also may have been coming south on what is today the north oriented Whitewood Creek valley system). Ultimately the North Fork Rapid Creek valley captured all the flood flow, but until that capture occurred the Elk Creek valley and the North Fork Rapid Creek valley were components of a large-scale southeast-oriented anastomosing channel complex crossing the Black Hills uplift area. Headward erosion of what was probably a deep Belle Fourche River valley to the north (into thick sediment of undetermined thickness that flood waters subsequently removed) and uplift of the Black Hills dome enabled deep north and northeast-oriented valleys to erode headward into what is now the Black Hills uplift area and to capture the southeast-oriented flood flow.

Bear Butte Creek and Park Creek drainage divides with Elk Creek

Figure 5: Bear Butte Creek and Park Creek drainage divides with Elk Creek. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 5 illustrates drainage divides between Bear Butte Creek and Park Creek with Elk Creek seen in less detail in figure 3. Northeast-oriented Elk Creek is located in the figure 5 south center and southeast quadrant. Northeast-oriented Bear Butte Creek flows from the figure 5 west edge (center south) into the figure 5 northwest quadrant and to the figure 5 north edge (center west). North-oriented Park Creek flows from the figure 5 center to the figure 5 north edge and then joins Bear Butte Creek north of the figure 5 map area. Note the northwest-southeast oriented through valley linking Park Creek headwaters with a southeast-oriented Elk Creek tributary. That through valley extends west and northwest to the Bear Butte Creek valley, although the drainage divide elevation is higher than the divide southeast of Park Creek. The valley was eroded by southeast-oriented flood flow, although the northwest end was eroded by reversed flood waters after the deep northeast-oriented Bear Butte Creek valley beheaded the southeast-oriented flood flow. Also note the two north-south oriented through valleys south of the north-oriented Park Creek valley, which link the Park Creek valley with the east-oriented Elk Creek valley. Those valleys were eroded by north-oriented flood flow moving from what was probably a much higher level Elk Creek valley north to flow north on the Park Creek valley route. For a time some of that north-flowing flood water continued north on the Park Creek valley route and some of that flow turned southeast to flow back to the east-oriented Elk Creek route. These are just a few of the many through valleys located in this figure 5 map area. Working with present day drainage divide elevations it is possible to reconstruct at least some of the drainage history. However, a summary of what was happening is a southeast-oriented anastomosing channel complex was being captured by headward erosion of deep northeast-oriented valleys. Those deep northeast-oriented valleys were eroding headward from what was then a deep Belle Fourche River valley (eroded into sedimentary cover of undetermined thickness that has subsequently removed by flood erosion) and their headward erosion into what is now a high elevation area was being aided by on-going uplift of what is today the Black Hills uplift area.

Elk Creek valley and drainage basin near Piedmont, South Dakota

Figure 6 illustrates the Elk Creek drainage basin area near Piedmont, South Dakota. Elk Creek flows southeast from the figure 6 west edge to near Piedmont and then flows east to the figure 6 southeast corner. Little Elk Creek originates southwest of Flagstaff Mountain (southwest quadrant near west edge) and flows southeast and east to join Elk Creek north of Piedmont. Southeast and northeast-oriented Meadow Creek is located along the figure 6 west edge just west of Flagstaff Mountain. A through valley visible in figure 6 (but better seen on more detailed figure 6a below) links the southeast-oriented Meadow Creek valley segment with the southeast-oriented Little Elk Creek valley. Headward erosion of the deep Elk Creek valley enabled the northeast-oriented Meadow Creek valley to erode southwest and to behead the southeast-oriented flood flow route that had been eroding the Little Elk Creek valley and diverted the flood water to the actively eroding Elk Creek valley. Subsequently headward erosion of the north oriented Elk Creek tributary valley seen along the figure 6a west edge beheaded flood flow that had been eroding the Meadow Creek valley and diverted the flood water north to the actively eroding Elk Creek valley. Bulldog Gulch (figure 6 northwest quadrant) drains to Pleasant Valley Creek, which flows to Elk Creek. Immediately northwest of Bulldog Gulch are north and northeast-oriented headwaters of Alkali Creek, which drains to the Belle Fourche River.  East of the forested Black Hills area the northwest-southeast oriented highway is located in a through valley now drained by multiple east-oriented streams including Elk Creek, Morris Creek and Pleasant Valley Creek. The valley’s east margin is an east-northeast dipping hogback ridge, however the valley was at one time eroded by southeast-oriented flood water, which was progressively captured by headward erosion of the east-oriented valleys. When headward erosion of the east-oriented streams began elevations were not what they are today. Flood waters removed significant sedimentary cover from the figure 6 map area and Black Hills uplift was probably taking place as flood erosion progressed. Also, flood waters were probably flowing in an ever-changing complex of anastomosing channels, which means the Elk Creek, Morris Creek, and Pleasant Valley Creek water gaps across the east-northeast dipping hogback ridge were probably eroded simultaneously. In the figure 6 northeast quadrant note southeast-oriented tributaries to Pleasant Valley Creek. The southeast-orientation of these tributaries combined with the southeast-orientation of other figure 6 valleys, while in some cases reflecting the underlying geologic structure) is also evidence of southeast-oriented flood flow which crossed the figure 6 map area. Flood flow across all areas of the figure 6 map area occurred as the Black Hills area was being uplifted and as the figure 6 region was being deeply eroded.

Figure 6a: Meadow Creek-Little Elk Creek through valley discussed in the figure 6 discussion above. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Alkali Creek-Elk Creek drainage divide northeast of Tilford, South Dakota

Figure 7: Alkali Creek-Elk Creek drainage divide northeast of Tilford, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 7 illustrates the  Alkali Creek-Elk Creek drainage divide area north of the figure 6 map area and includes overlap area with figure 6. Alkali Creek headwaters flow north and northeast from the area just southwest of Bulldog Gulch along the figure 7 west center edge. Once on the plains Alkali Creek turns east and southeast to eventually flow to the Belle Fourche River. South of the east and southeast-oriented Alkali Creek valley are southeast-oriented Elk Creek tributaries. Several northwest-southeast oriented through valleys linking the Alkali Creek valley with the southeast-oriented Elk Creek tributary valleys can be identified using the limited detail shown in figure 7, however they are much more visible in more detailed maps. Figure 7a below illustrates the Alkali Creek-Pleasant Valley Creek drainage divide east of where Pleasant Valley Creek turns from flowing east to flowing southeast. A prominent through valley is located near the figure 7a west center edge. Another prominent northwest-southeast oriented through valley extends northwest from the figure 7a southeast corner. Both through valleys were initially eroded by southeast-oriented flood flow to what was then a deep and newly eroded Elk Creek valley. Headward erosion of the deep east-oriented Alkali Creek valley captured the southeast-oriented flood and diverted the flood waters east to the Belle Fourche River. Flood waters on the north end of the through valley near the figure 7a west center edge reversed flow direction and eroded a north-oriented tributary valley. Figure 7 and 7a evidence makes a strong case for capture of multiple southeast-oriented flood flow routes or channels by headward erosion of the deep Alkali Creek valley.

Figure 7a: detailed map of Alkali Creek-Pleasant Valley Creek drainage divide discussed with figure 7 above.  United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Alkali Creek-Antelope Creek drainage divide area east of Black Hills

Figure 8: Alkali Creek-Antelope Creek drainage divide area east of Black Hills. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 8 illustrates the Alkali Creek-Antelope Creek drainage divide area east of the figure 7 map area and includes overlap areas. Antelope Creek is a southeast-oriented Elk Creek tributary. Alkali Creek is a southeast-oriented Belle Fourche River tributary. Southeast-oriented Antelope Creek tributaries flow from the Alkali Creek-Antelope Creek drainage divide to southeast-oriented Antelope Creek. These tributaries are evidence of multiple southeast-oriented flood flow routes that eroded the north wall of what was a newly eroded and deep Antelope Creek valley. In other words, a deep Antelope Creek valley eroded headward into a topographic surface higher than any figure 8 elevations today to capture southeast-oriented flood water and the southeast-oriented flood water eroded the newly eroded Antelope Creek valley wall to produce a southeast-oriented slope. Headward erosion of the parallel and deep Alkali Creek valley next eroded northwest just to the north of the newly eroded Antelope Creek valley (with its newly eroded southeast-sloping north wall) and carved a broad southeast-oriented valley with steep slopes on either side. The newly eroded Alkali Creek valley north wall was eroded by southeast-oriented flood flow in much the same way the Antelope Creek valley north wall had been eroded. However, the steep north wall was carved by captured southeast-oriented flood flow to the Antelope Creek valley as the deep Alkali Creek valley head eroded northwest. That captured flood water moved in a northeast-oriented direction to reach the actively eroding Alkali Creek valley head and the northeast-oriented movement of that captured flood water initiated what are today northeast-oriented Alkali Creek tributary valleys flowing down the steep Alkali Creek valley south wall. Figure 9 below illustrates the Alkali Creek-Antelope Creek drainage divide ridge characteristics in more detail.

Detailed map of Alkali Creek-Antelope Creek drainage divide area east of Black Hills

Figure 9: Detailed map of Alkali Creek-Antelope Creek drainage divide area east of Black Hills. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 9 illustrates asymmetric Alkali Creek-Antelope Creek drainage divide characteristics in more detail than figure 8 above. Antelope Creek flows southeast in the figure 9 south center and is linked by a through valley with a northeast-oriented Alkali Creek tributary located in the figure 9 northwest corner. Southeast-oriented Pleasant Valley Creek drains the figure 9 region southwest of the northwest-southeast oriented asymmetric ridge extending from the figure 9 northwest corner to the figure 9 south center. Headward erosion of the southeast-oriented Alkali Creek valley proceeded by headward erosion of northeast-oriented valleys to capture southeast-oriented flood flow moving to the newly eroded Elk Creek valley south of figure 9. That southeast-oriented flood flow eroded the southeast-oriented slope seen in the figure 9 south half and southeast-oriented tributary valleys, such as the Antelope Creek valley were eroded into that southeast-oriented slope. At that time there was no Alkali Creek valley or Belle Fourche River valley to the north and flood waters were flowing southeast over a topographic surface at least as high as the highest figure 9 elevations today. Headward erosion of the deep Alkali Creek valley then captured the southeast-oriented flood flow. Headward erosion proceeded by eroding northeast-oriented tributary valleys to the southwest to capture southeast-oriented flood flow moving to the newly eroded Elk Creek valley. The northeast-oriented Alkali Creek tributary valley in the figure 9 northwest corner would be an example of such a northwest-oriented tributary valley. That figure 9 northwest corner tributary captured southeast-oriented flood flow that had been moving to what had been the actively eroding Antelope Creek valley. The captured flood flow then moved northeast to the actively eroding Allkali Creek valley head and helped erode the large Alkali Creek valley further to the east and northeast. This process was repeated over and over again and produced what is today a rather remarkable and distinctive Alkali Creek-Antelope Creek drainage divide ridge.

Belle Fourche River-Elk Creek drainage divide area west of Cheyenne River

Figure 10: Belle Fourche River-Elk Creek drainage divide area west of Cheyenne River. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 10 illustrates the Belle Fourche River-Elk Creek drainage divide area where Elk Creek and the Belle Fourche River join the north and northeast-oriented Cheyenne River. Elk Creek flows northeast from the figure 10 southwest corner and turns east in the figure 10 south center before flowing to the north and northeast-oriented Cheyenne River. The Belle Fourche River flows east-northeast from the figure 10 west edge center to the northeast-oriented Cheyenne River in the figure 10 northeast corner. Note how both the Belle Fourche River valley north wall and the Elk Creek north valley wall have been eroded by multiple southeast-oriented streams. This essay previously described how the deep Elk Creek valley eroded west into a high level topographic surface (now removed) and southeast-oriented flood water flowed across the newly eroded north wall to produce a southeast-sloping erosion surface. The same process took place in this figure 10 map area, not only with the Elk Creek valley, but also with the Belle Fourche River valley. Interestingly, here the Elk Creek valley appears to have eroded west slightly in advance of the Belle Fourche River valley. This sequence is in reverse to what would be expected because the deep Cheyenne River valley eroded headward from north to south. This reverse order suggests headward erosion of the Elk Creek valley may have been initiated by deep erosion occurring east of the Cheyenne River and was later captured by headward erosion of the deep north-oriented Cheyenne River valley. To the east of the Cheyenne River valley are Bad River headwaters and the deep White River. Cheyenne River-Bad River drainage divide area evidence and Cheyenne River-White River drainage divide area evidence is described in essays for those drainage divides (essays can be found under Bad River and White River respectively on the sidebar category list). Those essays also establish a strong case for large volumes of southeast-oriented flood water flowing from this figure 10 map area in an east and southeast direction. The nature of the figure 10 drainage divides also makes a strong case for immense quantities of flood flow.

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.