A geomorphic history based on topographic map evidence

The Painted Robe Creek-Yellowstone River drainage divide area discussed here is located in south central Montana, USA. Although detailed topographic maps of the Painted Robe Creek-Yellowstone River 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 Painted Robe Creek-Yellowstone River 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. Flood erosion across the drainage divide ended when headward erosion of the deep Musselshell River valley captured all southeast-oriented flood flow.

Introduction:

• The purpose of this essay is to use topographic map interpretation methods to explore Montana Painted Robe Creek-Yellowstone River 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 essays 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 Painted Robe Creek-Yellowstone River drainage divide area landform evidence will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Painted Robe Creek-Yellowstone River drainage divide area location map

Figure 1: Painted Robe Creek-Yellowstone River 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 Painted Robe Creek-Yellowstone River drainage divide area location map and illustrates a region in south central Montana. The state of Wyoming is located just south of the figure 1 south edge. The Yellowstone River flows northeast from the figure 1 southwest corner area to Livingston and continues to Big Timber, Columbus, Laurel, Billings, Pompeys Pillar, and Custer near the figure 1 east edge. The Musselshell River is located north of the Yellowstone River and flows from Martinsdale, which is located near the figure 1 northwest corner area to Harlowton, Ryegate, Lavina, Roundup, and Melstone, which is located near the figure 1 east edge. At Melstone the Musselshell River turns to flow north-northwest to the figure 1 north edge. Painted Robe Creek is the unnamed northeast-oriented Musselshell River tributary joining the Musselshell River east of Lavina. The parallel unnamed northeast-oriented stream joining the Musselshell River at Lavina is Big Coulee Creek, and this essay addresses some Big Coulee Creek-Painted Robe Creek drainage divide evidence. The Painted Robe Creek-Yellowstone River drainage divide area discussed here is located west of the Bull Mountains and east of a line between Rapelje and Laurel. Based on evidence from the hundreds of Missouri River drainage basin landform origins research project essays published on this website landform evidence illustrated in this essay is interpreted in the context of an immense southeast-oriented flood flowing across the figure 1 map area and which was systematically captured and diverted northeast by headward erosion of deep valleys eroded into a topographic surface at least as high as the figure 1 region highest elevations today. The northeast-oriented Yellowstone River and Musselshell River valleys were two of the deep valleys that eroded southwest to capture southeast-oriented flood water and to divert the flood flow to the northeast. First the deep Yellowstone River valley eroded southwest to capture the southeast-oriented flood waters and to divert flood waters to the northeast. Flood waters on the northwest ends of the beheaded flood flow routes reversed flow direction to flow northwest to the newly eroded Yellowstone River valley. By doing so reversed flood flow eroded northwest-oriented tributary valleys. Subsequently the deep Musselshell River valley eroded south, southwest, and west-northwest to capture the southeast-oriented flood flow and to divert the flood waters further to the northeast (to the Missouri River valley, which is located north of the figure 1 map area). Again flood waters on the northwest ends of beheaded flood flow routes reversed flow direction to flow northwest to the newly eroded Musselshell River valley. Detailed maps below provide evidence supporting this interpretation. The Musselshell River-Yellowstone River drainage divide area in Musselshell and Yellowstone Counties essay and the Musselshell River-Yellowstone River drainage divide in Rosebud and Treasure Counties essay both describe drainage divide areas located east of the drainage divide area discussed here and can be found under either Musselshell River or Yellowstone River on the sidebar category list.

Painted Robe Creek-Yellowstone River drainage divide area detailed location map

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

Figure 2 illustrates a somewhat more detailed map of the Painted Robe Creek-Yellowstone River drainage divide area discussed here. Sweet Grass, Stillwater, Yellowstone, and Golden Valley Counties are located in Montana. The Yellowstone River flows from Big Timber located on the figure 2 west edge southeast to Columbus and then turns northeast to flow to Laurel, Billings and Pompeys Pillar near the figure 2 east edge. The Musselshell River flows from Harlowton in the figure 2 northwest corner to Ryegate, Lavina and Roundup near the figure 2 north edge (east half). Big Coulee Creek is the northeast-oriented stream joining the Musselshell River at Lavina. Painted Robe Creek is the parallel northeast-oriented stream immediately southeast of Big Coulee Creek and joins the Musselshell River east of Lavina. The Painted Robe Creek-Yellowstone River drainage divide area discussed here is located east of a line which extends northwest from Laurel through the Lake Basin to the Painted Robe Creek headwaters area and west of the north-south highway linking Roundup with Billings. Figure 2 shows numerous southeast-oriented Yellowstone River tributaries. These southeast oriented tributaries are evidence the northeast oriented Yellowstone River valley (and the east and northeast-oriented Musselshell River valley) eroded headward to capture southeast-oriented flood flow. The southeast-oriented tributary valleys were eroded by southeast-oriented flood flow moving into the newly eroded northeast-oriented valleys. Many of the northeast-oriented valleys also have northwest-oriented tributaries. The northwest-oriented tributary valleys were eroded by reversals of flood flow on the northwest ends of beheaded southeast-oriented flood flow routes. Because flood waters move in and erode anastomosing (or interconnected) channels reversed flood flow on a beheaded flood flow route could capture flood flow from yet to be beheaded flood flow routes. Such captures of yet to be beheaded flood flow enabled the reversed flood flow routes to erode much deeper and larger northwest-oriented valleys than would otherwise have been possible. Often evidence for such flow reversals and captures can be found on detailed topographic maps. Detailed maps below start with the Big Coulee Creek-Painted Robe Creek drainage divide area near Lavina and then look at the Comanche Basin area and the Painted Robe Creek and Musselshell River drainage divide with Crooked Creek (east of the Comanche Basin). Moving west the detailed maps look at the Painted Robe Creek-Hailstone Basin and Lake Basin drainage divide areas and conclude with a look at the Lake Basin-Yellowstone River drainage divide area.

Big Coulee Creek-Painted Robe Creek drainage divide area

Figure 3: Big Coulee Creek-Painted Robe Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 illustrates the Big Coulee Creek-Painted Robe Creek drainage divide area immediately south of the Musselshell River. The Musselshell River is located near the figure 3 north edge and flows east-southeast through Slayton Junction and Lavina to the figure 3 northeast corner area and then turns to flow northeast to the figure 3 northeast corner. Painted Robe Creek flows northeast from the figure 3 southwest quadrant to join the east-southeast oriented Musselshell River in the figure 3 northeast quadrant. Note northwest oriented Spring Creek which flows from the figure 3 southeast quadrant to join Painted Robe Creek in the figure 3 center east area. Also note southeast-oriented Painted Robe Creek tributaries in the figure 3 southwest quadrant. Big Coulee Creek flows northeast from the figure 3 west edge and south of Lavina turns north to join the Musselshell River. Note northwest oriented Big Coulee Creek tributary flowing from Haystack Butte area (located near figure 3 west center edge). A close look at figure 3 evidence reveals additional northwest- and southeast-oriented Big Coulee Creek, Painted Robe Creek, and Musselshell River tributaries. The northwest-southeast orientation of these tributaries provides evidence the Musselshell River valley and the Painted Robe Creek and Big Coulee Creek valleys eroded headward across southeast-oriented flood flow to capture the flood waters and to divert the flood waters northeast. Prior to being captured by headward erosion of the northeast-oriented Musselshell River and Painted Robe Creek valleys the southeast-oriented flood waters were probably moving to what was then the newly eroded northeast-oriented Yellowstone River valley to the southeast of the figure 3 map area. The northeast-oriented Musselshell River valley segment (in figure 3 northeast corner) and northeast-oriented Painted Robe Creek valley eroded headward into the figure 3 map area first. The east-southeast-oriented Musselshell River valley eroded west-northwest and the Big Coulee Creek valley eroded southwest to capture southeast-oriented flood flow moving to what was then the newly eroded Painted Robe Creek valley. Flood waters on the northwest ends of beheaded southeast-oriented flood flow routes reversed flow direction to flow northwest and north to the newly eroded northeast-oriented valleys.

Painted Robe Creek-Comanche Flat drainage divide area

Figure 4: Painted Robe Creek-Comanche Flat drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 illustrates the Painted Robe Creek-Comanche Flat (Basin) drainage divide area south of the figure 3 map area and includes a thin overlap strip with figure 3. Northeast-oriented Painted Robe Creek is located in the figure 4 northwest corner. Note northwest-oriented Gooseneck Creek flowing from the figure 4 north center area to join Painted Robe Creek just north of the figure 4 north edge. Also note Lost Creek headwaters located south of Gooseneck Creek, originating near the Painted Robe Creek valley edge and then flowing southeast and south to the figure 4 south enter edge area. Further note in the figure 4 center area the through valley linking southeast-oriented Lost Creek headwaters at the elbow of capture (where Lost Creek turns south) with southeast-oriented Comanche Creek headwaters. A similar, but more subtle through valley links headwaters of east-oriented South Comanche Creek with the south-oriented Lost Creek valley. Note also how northwest-oriented Gooseneck Creek headwaters are linked by through valleys with Comanche Creek and the Comanche Flat (Basin) area. The drainage orientations and through valleys provide evidence the northeast-oriented Painted Robe Creek valley eroded headward across an ever-changing southeast-oriented anastomosing channel complex moving large quantities of southeast-oriented flood water to the Comanche Flats area. In an ever-changing anastomosing channel complex flood waters erode interconnected channels across a large region, and as one channel erodes deeper it captures flood flow from adjacent channels, which is what was happening when headward erosion of the south-oriented Lost Creek valley channel beheaded southeast-oriented flood flow to the Comanche Creek channels. Headward erosion of the northeast-oriented Painted Robe Creek valley then captured the southeast-oriented flood flow and diverted the flood waters northeast. Flood waters on the northwest ends of the beheaded southeast-oriented flood flow routes reversed flow direction to flow northwest and north to the newly eroded and deeper Painted Robe Creek valley. Because the Painted Robe Creek valley eroded headward southeast-oriented flood flow channels were captured one at a time from the northeast to the southwest. Further because the southeast-oriented flood flow channels were interconnected, when flood waters on a newly beheaded flood flow channel reversed flow direction to flow northwest to the newly eroded and deeper Painted Robe Creek valley, they often could capture flood flow from yet to be beheaded flood water channels further to the southwest. Such a capture occurred when newly reversed flood flow in the Gooseneck Creek valley captured yet to be beheaded flood flow from the southeast-oriented Lost Creek headwaters valley. Evidence of this capture can be seen in the form of north-northeast oriented Gooseneck Creek tributaries, which are linked by shallow through valleys with the southeast-oriented Lost Creek headwaters valley.

Painted Robe Creek and Musselshell River-Hay Basin drainage divide area

Figure 5: Painted Robe Creek and Musselshell River-Hay Basin drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the Painted Robe Creek and Musselshell River drainage divide area with the Comanche Flats and Hay Basin areas and is located southeast of figure 3 and east of figure 4 and includes overlap areas with figures 3 and 4. Northwest-oriented Spring Creek is located in the figure 5 northwest quadrant. Northwest-oriented Dean Creek is located in the western section of the figure 5 northeast quadrant and northwest oriented headwaters of Goulding Creek can be seen in the figure 5 northeast corner. Dean Creek and Goulding Creek flow to the northeast-oriented Musselshell River. The escarpment surrounding the Hoskin Basin (seen in figure 6 below) is located in the figure 5 southeast corner. The Hoskin Basin is drained by southeast-oriented Crooked Creek to the northeast-oriented Yellowstone River. Hay Basin is a large abandoned headcut eroded by southeast-oriented flood waters, which were apparently limited in their ability to erode deeply by erosion resistant strata that today are exposed in cliffs along the Hoskin Basin rim. The Comanche Flat probably has a similar origin. Immense volumes of southeast-oriented flood waters moved across the figure 5 map area to what was then the newly eroded and deep northeast-oriented Yellowstone River valley. At one time the southeast-facing escarpment was a giant waterfalls. Headward erosion of the deep Musselshell River valley to the north systematically captured the southeast-oriented flood flow as it eroded headward from the northeast to the southwest and west. Flood waters on the northwest ends of the beheaded flood flow routes reversed flow direction to flow northwest and north to the newly eroded and deep Musselshell River valley. Reversed flow flood water channels captured yet to be beheaded flood flow from flood flow channels further to the southwest and were able to erode significant northwest and north-oriented Musselshell River tributary valleys.

Hoskin Basin abandoned headcut area

Figure 6: Hoskin Basin abandoned headcut area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 illustrates the large Hoskin Basin abandoned headcut located southeast of figure 5 and includes overlap areas with figure 5. The northeast-oriented Yellowstone River can be seen in the figure 6 southeast corner. Crooked Creek is drainage system draining Hoskin Basin today and flows southeast to join the Yellowstone River in the figure 6 southeast corner. Hoskin Basin is a large escarpment-surrounded basin that was eroded by an immense southeast-oriented flood. Flood waters were flowing into what was then the newly eroded northeast-oriented Yellowstone River valley. As previously mentioned, at one time the escarpment surrounding Hoskin Basin was the location of a gigantic waterfalls. Flood flow from the northwest into the Hoskin Basin ceased when flood waters were captured by headward erosion of the deep Musselshell River valley to the north and headward erosion of the Hoskin Basin headcut stopped. Hoskin Basin is one of several similar large abandoned headcuts located in the northern plains and Rocky Mountain regions. Plotting positions of these large abandoned headcuts on a map can be used to reconstruct flood flow routes as a test of the more detailed drainage divide analysis being done in this essay series. The source of the southeast-oriented flood waters cannot be determined from evidence presented in this here. However, essays in this Missouri River drainage basin landform origins research project essay series when taken as a group can be used to trace flood waters both up flood to source areas and down flood to see where flood waters were going. A logical flood water source would be rapid melting of a thick North American ice sheet located in a deep “hole” occupying approximately the North American location usually recognized to have been glaciated. The deep “hole” would have been created by deep glacial erosion and by crustal warping caused by the ice sheet weight. Such a flood water source would not only explain the immense southeast-oriented floods this essay series describes, but would also explain why deep valleys were eroding headward to capture the southeast-oriented flood waters and diverting the flood waters further and further to the northeast and north into space in the deep “hole” the rapidly melting thick ice sheet had once occupied. In addition, such a flood water source may explain uplift of the mountains regions during an immense southeast-oriented flood. A thick North American ice sheet in deep “hole” created in part due to the ice sheet’s weight would probably create crustal warping elsewhere on the continent, especially along ice sheet margins. Further, rapid erosion of overlying material might trigger localized uplifts of what are today high mountain regions, such as mountain ranges south and west of the Painted Robe Creek-Yellowstone River drainage divide area.

Comanche Flat-Yellowstone River drainage divide area

Figure 7: Comanche Flat-Yellowstone River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the Comanche Flat-Yellowstone River drainage divide located south and west of the figure 6 map and includes overlap areas with figure 6. The northeast-oriented Yellowstone River is located in the figure 7 southeast corner and the city located there is Billings. The southeast-oriented Yellowstone River tributaries provide evidence flood water flowing from the Comanche Flat area to the Yellowstone River valley was southeast-oriented. Note how tributaries have not eroded deeply into the Comanche Flats area, suggesting the presence of erosion resistant bedrock underlying the region, or at least the escarpment rim area. Today Comanche Flat is a shallow closed depression with no external drainage. As seen in figures 4 and 5 above southeast-oriented flood waters flowed into and across Comanche Flat to reach what was then the newly eroded and deep northeast-oriented Yellowstone River valley. The Comanche Flat depression was deeply scoured by flood waters flowing across the area and the erosion resistant rock along the rim of the southeast-facing Yellowstone River valley wall escarpment protected the escarpment rim area. Southeast-oriented flood flow across the Comanche Flat area ended when headward erosion of the northeast-oriented Musselshell River-Painted Robe Creek valley captured the southeast-oriented flood water and diverted the flood water northeast. The figure 7 evidence and other evidence illustrated in this essay can be explained in the context of an immense southeast-oriented flood first captured in this region by headward erosion of the deep northeast-oriented Yellowstone River valley and that was subsequently captured by headward of the Missouri River-Musselshell River-Painted Robe Creek valley. As previously mentioned the immense flood can be explained by rapid melt of a thick North American ice sheet. The southeast-oriented flood flow direction can be explained if the present day northeast-oriented northern Missouri River drainage basin is the deeply eroded wall of the deep North American “hole” the ice sheet once occupied and the flood waters were moving southeast along the ice sheet margin. Headward erosion of the deep northeast-oriented valleys to capture the southeast-oriented flood waters can be explained by rapid melting of the thick ice sheet, which opened up space in the deep “hole” allowing flood waters to move northeast into space the thick ice sheet had once occupied.

Painted Robe Creek-Hailstone Basin drainage divide area

Figure 8: Painted Robe Creek-Hailstone Basin drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 illustrates the Painted Robe Creek headwaters area and is located west and south of the figure 4 map area and includes overlap areas with figure 4. Big Coulee Creek flows northeast in the figure 8 northwest quadrant. Note southeast and northwest-oriented Big Coulee Creek tributaries, which provide evidence the Big Coulee Creek valley eroded headward across southeast-oriented flood flow routes. The northwest-oriented escarpment surrounded basin eroded into the southeast wall of the Big Coulee valley is probably an abandoned headcut eroded by reversed flood flow, which captured significant amounts of flood water from yet to be beheaded flood flow routes further to the southeast. Painted Robe Creek flows northeast to the figure 8 northeast corner. Northwest-oriented Gooseneck Creek flows across the county line in the figure 8 northeast corner area. South of Gooseneck Creek Lost reek flows southeast and south to the figure 8 southeast corner area. Hailstone Basin is located in the figure 8 south center. Note the northwest-southeast oriented through valley now used by a Lost Creek tributary linking Hailstone Basin with the south-oriented Lost Creek valley. Hailstone Basin is a northern extension of Lake Basin located to the south and seen in figure 9 below. Hailstone Basin drainage today flows to Lake Basin, which like Comanche Flat does not have a drainage outlet. Note southeast-oriented streams flowing in Hailstone Basin providing evidence the basin was eroded by southeast-oriented flood water. The relatively flat upland surface along the present day drainage divides probably reflects underlying bedrock structure, but was developed as southeast-oriented flood waters (and northwest-oriented reversed flow of the southeast-oriented flood waters) scoured the region.

Lake Basin drainage basin area

Figure 9 illustrates the Lake Basin area immediately south of Hailstone Basin and figure 8 map area and includes overlap areas with figure 8. Hailstone Basin is located at the east end of the figure 9 northwest quadrant. East of Hailstone Basin in the figure 9 northeast quadrant is south-oriented Lost Creek, which on entering Lake Basin turns to flow west. Lake Basin today is a large northwest-southeast flat-floored basin draining southeast to the Big Lake at the southeast end. The Big Lake is located in a shallow closed depression and has no present day outlet. Generally drainage on the basin floor is southeast-oriented, although northeast-oriented streams flow in from the southwest and Lost Creek flows west after entering the basin. Lake Basin is a water eroded landscape feature and was eroded by immense volumes of southeast-oriented flood water moving across the figure 9 map area to what was then the newly eroded and deep northeast-oriented Yellowstone River valley. Figure 10 below illustrates the rim area, which was protected by erosion resistant rock, which prevented a deep valley from eroding headward along the southeast-oriented flood flow route. Flood waters probably scoured the basin floor deeper than the rim rock elevation, creating the present day closed depression. Flood flow across the Lake Basin floor ended when headward erosion of the northeast-oriented Musselshell River-Big Coulee Creek valley captured the southeast-oriented flood waters and diverted the flood flow northeast. The size of Lake Basin, Hailstone Basin, Comanche Flat, Hay Basin, and Hoskins Basin provide clues as to the immensity of the southeast-oriented flood involved. These are water eroded landscape features and they were eroded rapidly as flood waters moved across the region. In addition to eroding large northeast-oriented valleys the southeast-oriented flood waters deeply eroded what are today drainage divide regions separating those deep northeast-oriented valleys.

Canyon Creek abandoned headcut

Figure 10: Canyon Creek abandoned headcut. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 illustrates the Canyon Creek valley at the Lake Basin southeast end and is located south and east of figure 9 and includes a small overlap area with figure 9. The northeast-oriented Yellowstone River is located in the figure 10 southeast corner. Billings is the city located along the figure 10 east edge. The tip of the lake located in the southeast end of Lake Basin is located just west of Mott in the figure 10 northwest corner. Mott is located in a through valley linking Lake Basin with the Yellowstone River valley. The railroad follows the through valley to the Canyon Creek valley, which is the Yellowstone River tributary valley draining the drainage divide southeast side. Southeast-oriented flood waters that scoured the Lake Basin floor flowed southeast into the what was then the newly eroded and deep northeast-oriented Yellowstone River valley. Erosion resistant bedrock prevented a deep southeast-oriented valley from being eroded headward into the Lake Basin area, although a large southeast-oriented headcut did erode headward as can be seen in figure 10 above. At one time the southeast-oriented escarpment was a giant waterfalls. Flood flow across the Lake Basin area was systematically beheaded by headward erosion of the northeast-oriented Big Coulee Creek valley, which meant the volume of southeast-oriented flood flow reaching the figure 10 map area decreased gradually. Final flood flow across the Lake Basin area eroded the present day through valley at Mott and the Canyon Creek valley seen today. Before headward erosion of the Big Coulee Creek valley started to decrease flood volumes reaching the figure 10 map area, flood waters probably flowed across the entire 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.