Little Missouri River-Knife River drainage divide landform origins, western North Dakota, USA

Authors

A geomorphic history based on topographic map evidence

Abstract:

The Little Missouri River-Knife River drainage divide area discussed here is located in McKenzie, Dunn and Billings Counties, North Dakota. Although detailed topographic maps of this Little Missouri River-Knife 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. Based on topographic map evidence the Little Missouri River-Knife 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 ended when headward erosion of the deep Little Missouri River valley captured the southeast-oriented flood flow.

Preface:

The following interpretation of detailed topographic map evidence is provided as evidence in the Missouri River drainage basin landform origins research project, which is compiling similar evidence for all major drainage divides contained within the Missouri River drainage basin and for all major drainage divides with and within certain adjacent drainage basins. The research project is interpreting evidence in the context of a previously unexplored geomorphology paradigm, which is briefly described in the introduction below. Project essays are listed on the sidebar category list under their appropriate Missouri River tributary drainage basin, Missouri River segment drainage basin (by state), and/or state in which the Missouri River drainage basin is located.

Introduction:

  • The purpose of this essay is to use topographic map interpretation methods to explore Little Missouri River -Knife River drainage divide area landform origins in Billings, Dunn, and McKenzie Counties, North Dakota. Map interpretation methods can be used to unravel many of the geomorphic events leading up the present-day drainage routes and other landform features observed. While each detailed topographic map provides detailed evidence to be unraveled, the solution must be consistent with the solutions for adjacent map evidence as well as for solutions to big picture evidence. I invite readers to improve upon my solutions or to propose alternate solutions that better explain the detailed evidence and are consistent with adjacent map area evidence 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 floods of glacial melt water. 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 Little Missouri River-Knife River drainage divide area landform evidence will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Little Missouri River-Knife River drainage divide area  location map

Figure 1: Little Missouri River-Knife River drainage divide area  location map. National Geographic Society map digitally presented using National Geographic Society TOPO software.

Figure 1 locates the Knife River basin in western North Dakota. The Knife River flows to the southeast-oriented Missouri River at Stanton, North Dakota, which is downstream from Garrison Dam. A separate essay describes Knife River drainage basin landform evidence and is found under North Dakota Missouri Slope on the sidebar category list. Lake Sakakawea is a modern-day Missouri River reservoir impounded behind Garrison Dam. The northeast-oriented Yellowstone River joins the Missouri River near Trenton, North Dakota. The Little Missouri River (unlabeled on figure 1) flows north through a badlands region and passes through Theodore Roosevelt National Park South Unit and then west of Theodore Roosevelt National Park North Unit turns east and jogs north into the green park area. East of the green park area the Little Missouri River flows east, jogs north, then flows southeast, before jogging north and then east to what is now Lake Sakakawea. A separate essay describes Yellowstone River-Little Missouri River drainage divide area landform evidence and can be found under Little Missouri River on the sidebar category list. South of the Knife River drainage basin is the parallel east-oriented Heart River drainage basin, with the southeast-oriented Green River being a major Heart River tributary. Western Heart River drainage basin landform evidence is described separately in an essay found under North Dakota Missouri Slope. Note southeast-oriented Knife River and Heart River headwaters as well as northwest-oriented Little Missouri River and Yellowstone River tributaries. This northwest-southeast oriented drainage alignment is a relic of immense southeast-oriented floods that crossed the region prior to headward erosion of what are today major river valleys. Detailed maps presented here illustrate how headward erosion of major river valleys beheaded and captured southeast-oriented flood flow routes and created the present day Little Missouri River-Knife River drainage divide area landforms. Evidence presented here is not adequate to determine the flood water source, although by use of other essays published on this website it is possible to trace flood waters to a North American ice sheet location. Glacial meltwater from a rapidly melting North American ice sheet is probably the most logical source. Evidence presented here is not adequate to determine what the regional topographic surface looked like prior to flood events, although this essay provides evidence flood waters once flowed on a topographic surface at least as high as the highest points in the Killdeer Mountains today.

Detailed Little Missouri River-Knife River drainage divide area location map

Figure 2: Detailed Little Missouri River-Knife River drainage divide area location map. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 2 provides a more detailed location map to illustrate the Little Missouri River-Knife River drainage divide area discussed here. Figure 3 below provides a still more detailed map of the Fairfield area in northeast Billings County, North Dakota. Figure 4 features headwaters areas for northwest-oriented Little Missouri River tributaries near Grassy Butte in southeastern McKenzie County and figure 5 features headwaters areas for a north-oriented Little Missouri River tributary east of Grassy Butte and west of the Killdeer Mountains. Figure 6  illustrates the Little Missouri River-Knife River drainage divide at the Killdeer Mountains in northwest Dunn County and figure 7 shows the Little Missouri River-Knife River drainage divide area east of North Killdeer Mountain. Figure 8 illustrates the drainage divide area northeast of the town of Killdeer. Figure 9 illustrates the drainage divide area where the southeast-oriented Little Missouri River valley jogs north before turning east to enter the Missouri River valley. Figure 10 completes the essay’s journey eastward along the Little Missouri River-Knife River drainage divide by illustrating the Hans Creek-Goodman Creek through valley, which crosses the Little Missouri River-Knife River drainage divide.

Little Missouri River-Knife River drainage divide north of Fairfield

Figure 3: Little Missouri River-Knife River drainage divide north of Fairfield. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 illustrates the Knife River headwaters northwest of Fairfield. The Little Missouri River-Knife drainage divide follows the ridge used by the north and northeast-oriented highway going through Fairfield. West of the drainage divide are northwest-oriented headwaters of northwest-oriented Little Missouri River tributaries. East and southeast of the drainage divide are many southeast-oriented tributaries flowing to the east and northeast-oriented Knife River segments. Note how the east-oriented Knife River valley begins in an escarpment-surrounded basin. This escarpment-surrounded basin is an abandoned headcut that was being eroded west to capture southeast-oriented flood flow. At the time active headcut erosion ceased southeast-oriented flood waters were flowing over a topographic surface approximately at the level of the topographic surface defined by the present day Little Missouri River-Knife River drainage divide, although the drainage divide was just beginning to be formed at that time. Southeast-oriented flood flow to the actively eroding Knife River valley was at that time being beheaded and captured by headward erosion of the deep Little Missouri River valley to the north and west. When southeast-oriented flood flow routes were beheaded, flood waters already on the northwest ends of those flood flow routes reversed flow direction to flow northwest into the newly eroded deep Little Missouri River valley. These reversals of flood flow were responsible for creating what is today the Little Missouri River-Knife River drainage divide and also the northwest-oriented Little Missouri River tributaries. The northwest-southeast oriented drainage alignment present here and throughout the region is a relic of the southeast-oriented flood flow that once moved across the region.

Little Missouri River-Knife River drainage divide southeast of Grassy Butte

Figure 4: Little Missouri River-Knife River drainage divide southeast of Grassy Butte. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 illustrates a region northeast of figure 3 and includes northwest-oriented Beicegel Creek headwaters. Beicegel Creek flows northwest to the north-oriented Little Missouri River valley. The north-oriented Crosby Creek drainage basin is east of the highway. Shallow through valleys are carved into that drainage divide. Ranch Creek is the northwest-oriented stream located northwest of Grassy Butte. Charlie Bob Creek is the northwest, and north-oriented stream flowing to the figure 4 northeast corner. Just north of figure 4, Ranch Creek and Charlie Bob Creek join to form north-oriented Crosby Creek, which joins the Little Missouri River at the point where the east-oriented Little Missouri River segment east of the Theodore Roosevelt National Park North Unit turns north to reach the long southeast-oriented Little Missouri River segment (see figure 2). The Little Missouri River-Knife River drainage divide crosses the figure 4 southeast corner and the southeast-oriented stream located there is the Little Knife River, which flows to the Knife River.

  • Prior to headward erosion of the deep Little Missouri River valley flood waters flowed southeast across the present day Beicegel Creek-Crosby Creek drainage divide. The present day shallow through valleys crossing the divide were eroded as southeast-oriented flood flow channels and  flood waters were flowing on a topographic surface at least as high as the highest points today. The southeast-oriented flood water flow routes were captured by headward erosion of the Crosby Creek valley and tributary valleys. Evidence for these captures is found in the present day southeast-oriented tributaries from the west in the north-oriented Crosby Creek drainage basin. Such barbed tributaries can be seen in figure 4. The present day northwest-oriented tributaries from the east also provide evidence for the beheading of southeast-oriented flood flow routes. The northwest-oriented tributaries were eroded by reversals of flow on the northwest ends of beheaded southeast-oriented flood flow routes. Ranch Creek has a semi-circular course today because it successfully eroded as an east and northeast-oriented valley to capture southeast-oriented flow and reversed a southeast-oriented flood flow route that headward erosion of northeast-oriented Charlie Bob Creek valley had previously captured.
  • Headward erosion of the deep Little Missouri River valley west of the present day Crosby Creek mouth progressively captured and beheaded anastomosing southeast-oriented flood flow channels. Flood waters on northwest ends of beheaded flood flow routes reversed flow direction and flowed northwest to erode deep northwest-oriented valleys to the newly eroded and deep Little Missouri River valley south and southeast wall. Southeast-oriented flood waters on yet to be reversed flood flow routes probably were captured by newly reversed northwest-oriented flood flow routes and aided in the erosion of the larger northwest-oriented valleys. Present day southeast-oriented Little Missouri River valley segments were eroded as the deep Little Missouri River valley eroded northwest along one of the southeast-oriented flood channels. North and northeast-oriented Little Missouri River valley segments probably represent routes the deep Little Missouri River valley eroded to capture flood flow in channels further to the southwest. In this manner the deep Little Missouri River valley eroded west until it captured north and northeast-oriented flood waters moving to a shallower northeast-oriented Red Wing Creek-Cherry Creek valley described in the Cherry Creek drainage basin essay (found under Little Missouri River).

Little Missouri River (Crosby Creek)-Knife River drainage divide

Figure 5: Little Missouri River (Crosby Creek)-Knife River drainage divide. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the Little Missouri River (Crosby Creek)-Knife River drainage divide east of the figure 4 map area and some of the drainage basin that today empties into north-oriented Crosby Creek, formed where Ranch Creek and Charlie Bib Creek join at the center top of figure 5. The Little Missouri River (Crosby Creek)-Knife River drainage divide follows the upland ridge extending from the figure 5 southwest corner to the Killdeer Mountains in the figure 5 northeast corner. Southeast of that drainage divide are southeast-oriented tributaries to the southeast, east, and southeast-oriented Little Knife River, flowing along the figure 5 south edge. Note the anastomosing channel pattern of shallow southeast-oriented valleys in the Little Knife River drainage area. This anastomosing channel pattern is evidence southeast-oriented flood waters flowed into the Little Knife River drainage basin prior to Little Missouri River (Crosby Creek)-Knife River drainage divide creation. Why did the deep north-oriented Crosby Creek drainage basin develop where it did? The answer lies in the location of the Killdeer Mountains. The Killdeer Mountains today represent high flat-topped hills standing above the surrounding plains. Bedrock composing the Killdeer Mountain mass extends in a southwest to northeast direction and was more resistant to erosion than the surrounding bedrock material. Flood waters originally flowed on a topographic surface at least as high as the Killdeer Mountain tops and the present day height of the Killdeer Mountains above the surrounding upland surface provides a minimum measure of how deeply flood waters eroded the region. Southeast-oriented flood waters eroded deep valleys headward until the Killdeer Mountain resistant rock mass became a barrier that influenced flood flow directions. Flood flow routes north and south of the Killdeer Mountain resistant rock mass eroded deeper valleys than those routes flowing across the Killdeer Mountain resistant rock mass. The Little Knife River drainage basin was eroded headward by flood waters moving southeast through what is today the Crosby Creek drainage basin around the Killdeer Mountain resistant rock mass south end. However, flood waters moving around the Killdeer Mountain north end were able to erode the deeper southeast-oriented valley now used by the Little Missouri River. This deeper valley around the Killdeer Mountain north end enabled headward erosion of the north-oriented Crosby Creek valley to behead and capture southeast-oriented flood flow to the Little Knife River drainage basin. Flood waters on the northwest ends of the beheaded flood flow routes reversed their flow directions and eroded the deep northwest-oriented Crosby Creek tributary valleys.  Subsequently the deep Little Missouri River valley eroded west and then south from the Crosby Creek mouth to behead and capture southeast-oriented flood flow moving to the developing north-oriented Crosby Creek drainage basin, and rapid erosion of the Crosby Creek drainage basin ceased and the Crosby Creek drainage basin has changed little since.

Little Missouri River-Knife River drainage divide at the Killdeer Mountains

Figure 6: Little Missouri River-Knife River drainage divide at the Killdeer Mountains. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

The Killdeer Mountains played a major role in determining the Little Missouri River valley location. Today the flat-topped Killdeer Mountains stand more than 300 meters above the surrounding upland surface and represent a southwest to northeast oriented mass of resistant lacustrine sediments approximately 11 kilometers in length. These lacustrine sediments had been embedded in layers of much easier to erode bedrock and were left after erosion of the surrounding bedrock materials as erosional residuals. Southeast-oriented flood waters flowed across the Killdeer Mountain rock mass and eroded northwest to southeast oriented valleys visible today. Evidence shown in figure 6 documents southeast-oriented flood waters originally flowed across the present-day Killdeer Mountains. Northwest-oriented Chase Creek flows from a wind gap between the main Killdeer Mountain upland and North Killdeer Mountain to the north-oriented Crosby Creek. This Killdeer Mountain wind gap is a through valley and headwaters of southeast-oriented streams can be seen on the southeast side. The wind gap was eroded by southeast-oriented flood waters prior to headward erosion of the deep north-oriented Crosby Creek valley. Southeast-oriented flood water flow ended when the deep north-oriented Crosby Creek valley eroded south to capture flood flow moving southeast on the Chase Creek route. Flood waters on the beheaded Chase Creek flood flow route then reversed their flow direction and flowed northwest to the newly eroded and deep north-oriented Crosby Creek valley, eroded the northwest-oriented Chase Creek valley and created a drainage divide at the Killdeer Mountain gap. A somewhat similar history can be described for a high level gap at the southeast end of northwest-oriented Norrad Creek. The elevation of that wind gap is evidence flood waters flowed on a topographic surface at least as high as the present day Killdeer Mountains tops.  A similar wind gap at the southeast end of northwest-oriented Oak Gulch provides evidence headward erosion of the deep north-oriented Crosby Creek valley beheaded the southeast-oriented flood route that had been eroding the southeast-oriented Little Knife River drainage basin.

Little Missouri River valley north and east of North Killdeer Mountain

Figure 7: Little Missouri River valley north and east of North Killdeer Mountain. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the Little Missouri River valley north and east of North Killdeer Mountain. The north-oriented Little Missouri River tributary in the figure 7 southeast quadrant is Jim Creek and the southeast-oriented Jim Creek tributary is Corral Creek. Frank Creek flows east from the wind gap between the main Killdeer Mountains and North Killdeer Mountain. The unnamed stream beginning in the same wind gap and flowing southeast is Jim Creek, which south of figure 7 turns north to flow to the Little Missouri River valley. This suggests the presence of an anastomosing southeast-oriented channel pattern that was captured by headward erosion of a north-oriented valley from what was probably the deep and newly eroded Little Missouri River valley. The Little Missouri River valley in this region is generally oriented in a northwest-southeast direction (see figures 1 and 2) although some jogs are present as shown in figure 7. This Little Missouri River valley segment’s northwest-southwest alignment continues southeast along the Hans Creek-Goodman Creek through valley (see figures 9 and 10) and also northwest along a southeast-oriented Cherry Creek segment, illustrated and described in the Cherry Creek drainage basin essay.  Because the Killdeer Mountain bedrock material was more resistant to erosion than materials surrounding it, flood waters moving north and south of the Killdeer Mountain resistant rock mass were able to erode more rapidly and flood waters became concentrated on those routes. The present day southeast-oriented Cherry Creek-Little Missouri River valley, northwest-oriented Hans Creek valley and southeast-oriented Goodman Creek valley route became the primary southeast-oriented flood route north of the Killdeer Mountain resistant rock mass. Flow in this channel was subsequently captured by headward erosion of what is today the (flooded) east-oriented Missouri River valley upstream from Garrison Dam. Evidence for the capture will be illustrated in figure 9. Reasons why that deep east-oriented Missouri River valley eroded west and captured southeast-oriented flood flow moving along the Cherry Creek-Little Missouri River-Hans Creek-Goodman Creek alignment cannot be determined from evidence illustrated here, although for some reason base level was lowered significantly and that lower base level enabled the Missouri-Little Missouri River to erode a much deeper valley headward.

Little Missouri-Knife River drainage divide southeast of Killdeer Mountains

Figure 8: Little Missouri River-Knife River drainage divide southeast of Killdeer Mountains. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 illustrates the area immediately south of the figure 7 map area with some overlap along the figure 8 north edge. The figure 8 northwest quadrant shows the Jim Creek elbow of capture described in the figure 7 discussion. Just east of Killdeer in the figure 8 southwest corner southeast-oriented Gumbo Creek joins east-oriented Spring Creek. Spring Creek headwaters are southeast-oriented and flow from the Killdeer Mountain mass (see unnamed southeast streams southwest of Gumbo Creek in figure 6). West of the Spring Creek headwaters is the south and southeast-oriented anastomosing channel complex discussed in figure 5, which developed as the south route flood waters around the Killdeer Mountain mass used to reach what was then the actively eroding Knife River valley prior to being beheaded by headward erosion of the deeper northern route, which is now the Little Missouri River valley. Note the pattern of valleys in the area between Jim Creek in the northwest and east-oriented Spring Creek in the south, especially in the Killdeer and Dunn Center regions. This region demonstrates evidence of having been formed as a flood formed anastomosing channel complex, with the evidence continuing south and west of Lake Ilo and the figure 8 map area. Note also the southeast-oriented unnamed Spring Creek tributary north of Werner in the figure 8 southeast quadrant.

Little Missouri-Knife River drainage divide at Little Missouri River mouth

Figure 9: Little Missouri River-Knife River drainage divide at Little Missouri River mouth. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the Little Missouri River-Knife River drainage divide east of figure 7 and northeast of figure 8. The Little Missouri River valley here is today flooded by Lake Sakakawea, which is impounded behind Garrison Dam on the Missouri River. The Little Missouri River valley joins the Missouri River valley just east of the figure 9 northeast corner. The Little Missouri River-Knife River drainage divide is located in the figure 9 southeast corner where southeast-oriented drainage is to east and southeast-oriented Spring Creek and then to the Knife River. The northwest-oriented stream in the figure 9 southeast quadrant flowing to meet the southeast-oriented Little Missouri River valley segment where it turns abruptly north is Hans Creek, which is linked by a through valley with southeast-oriented Goodman Creek (figure 10 below will further illustrate and discuss Goodman Creek). Events recorded here begin with southeast-oriented flood flow moving across the entire figure 9 map area (there were no Little Missouri River or Missouri River valleys at that time). For reasons  not determinable from evidence illustrated here further east in the Knife River drainage basin a deeper channel began to capture flood water and erode headward along the southeast-oriented Cherry Creek-Little Missouri River-Hans Creek-Goodman Creek channel, a segment of which is shown in figure 9. However, again for reasons not determinable from evidence presented here, a still deeper east-oriented valley eroded west along the present day east-oriented “Missouri River” valley route (between the Garrison Dam area and the Little Missouri River mouth) and captured the Cherry Creek-Little Missouri River valley southeast-oriented flood flow at a point where the present day Little Missouri River valley turns north to enter the Missouri River valley. This capture of the southeast-oriented flood flow caused a reversal of flood waters on the northwest end of the beheaded flood flow route. Reversed flood waters eroded the present day Hans Creek valley and that created the Hans Creek-Goodman Creek drainage divide. This deeper east-oriented “Missouri River” valley then rapidly eroded northwest. There was no Little Missouri River valley or drainage basin prior to headward erosion of this deep valley and its tributary valleys. Headward erosion of the deep Little Missouri River valley and tributary valleys probably took place rapidly as immense quantities of southeast-oriented flood waters were captured and diverted to the east-oriented “Missouri River” valley. Flood flow from the northwest to the deep Little Missouri River valley did not continue, but was first captured by Little Missouri River valley tributaries and subsequently by the parallel and deeper Yellowstone River valley, which eroded southwest and diverted the southeast-oriented flood waters to the northeast.

Hans Creek-Goodman Creek through valley

Figure 10: Hans Creek-Goodman Creek through valley. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 illustrates the Little Missouri River-Knife River drainage divide area east end. Northwest-oriented Hans Creek flows to the southeast, north, and east oriented Little Missouri River valley shown in figure 9. Southeast-oriented Goodman Creek joins southeast-oriented Spring Creek south and east of figure 10 and Spring Creek then flows to the east and northeast-oriented Knife River. In the figure 10 southwest quadrant south-oriented North Creek joins east and southeast oriented Spring Creek near Werner, just south of the figure 10 southwest corner. The present day southeast-oriented Cherry Creek-Little Missouri River valley, northwest-oriented Hans Creek valley and southeast-oriented Goodman Creek valley route originated as the northern route eroded around the Killdeer Mountain resistant bedrock material used by southeast-oriented flood waters moving to what was then the newly eroded Knife River valley. However as described in the figure 9 discussion a still deeper east-oriented valley eroded west along the present day east-oriented “Missouri River” valley route and captured the Cherry Creek-Little Missouri River valley southeast-oriented flood flow at a point where the present day Little Missouri River valley turns north and then east to enter the Missouri River valley. This capture of the southeast-oriented flood flow caused a reversal of flood waters on the northwest end of the beheaded flood flow route. Reversed those flood waters eroded the present day Hans Creek valley and that created the Hans Creek-Goodman Creek drainage divide. Note northeast-oriented Hans Creek tributaries. Those tributary valleys originated when southeast-oriented flood flow on the Hans Creek-Goodman Creek route was beheaded and flood flow on that route reversed. The reversed flow captured southeast-oriented flood flow on yet to be beheaded southeast-oriented flood flow routes further to the southwest and that captured flood water further eroded the northwest-oriented Hans Creek valley.

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 TOPO software and digital map data. TOPO software and map data can be obtained from the National Geographic Society and/or dealers offering National Geographic Society digital map data.

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