Little Beaver Creek-Beaver Creek drainage divide area landform origins, Montana and North Dakota, USA

· Little Missouri River, Montana, North Dakota
Authors

A geomorphic history based on topographic map evidence

Abstract:

The Little Beaver Creek-Boxelder Creek drainage divide area is located in Carter and Fallon Counties, Montana and Bowman and Slope Counties, North Dakota, USA. Although detailed topographic maps of the Little Beaver Creek-Boxelder Creek drainage divide area have been available for more than fifty years detailed map evidence has not previously been used to interpret the Little Beaver Creek-Boxelder Creek drainage divide area geomorphic history. The interpretation provided here is based entirely on topographic map evidence. Based on topographic map evidence the Little Beaver Creek-Boxelder Creek drainage divide area is interpreted to have been eroded during immense flood events, the first of which flowed on a topographic surface at least as high as the highest points in the present-day Little Beaver Creek-Boxelder Creek drainage divide area, and which stripped the Little Beaver Creek-Boxelder Creek drainage divide area bedrock layers as deep and broad headcuts, often several or more kilometers in width, eroded headward along major flood flow routes. Flood erosion ended when headward erosion of the deep northeast-oriented Yellowstone River valley headcut 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 eastern Montana Little Beaver Creek-Boxelder 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 eastern Montana Little Beaver Creek-Boxelder Creek drainage divide area landform evidence will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Little Beaver Creek-Boxelder Creek drainage divide area location map

Figure 1: Little Beaver Creek-Boxelder Creek drainage divide area location map (select and click on maps to enlarge). United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Little Beaver Creek begins at Beaver Flats (west center figure 1) and flows in a northeast direction to join the north oriented Little Missouri River at Marmarth, North Dakota (north edge center figure 1). Boxelder Creek begins south of figure 1 and enters the southwest quadrant of the map area to flow in a north-northeast oriented direction near Ridgway, Belltower, and Mill Iron to join the north oriented Little Missouri River at the point in the center of figure 1 where Carter County, Montana; Bowman County, North Dakota; and Harding County, South Dakota meet. Northwest of the Little Beaver Creek drainage basin is the northeast oriented Yellowstone River drainage basin (the Yellowstone River is located northwest of the figure 1 map area). West of the Beaver Flats area is the northeast and northwest-oriented Powder River drainage basin with the Powder River elbow of capture being shown just west of Beaver Flats at the extreme west center of figure 1. The area east of the Little Missouri River in Bowman County, North Dakota is drained by the southeast-oriented North Fork Grand River and is discussed in the Little Missouri River-North Fork Grand River drainage divide essay and the North Fork Grand River drainage basin essay. Another essay discusses the nearby Boxelder Creek-Little Missouri River drainage divide area. These mentioned essays and still additional essays describing nearby drainage divide areas can be found under appropriate river names on the sidebar category list. Visible in figure 1 are many northwest-southeast oriented tributary streams flowing to what are today the major north and northeast-oriented trunk streams. This northwest-southeast aligned drainage will be observed in detail on maps shown below and provides evidence the present-day north and northeast-oriented trunk streams, such as the Little Missouri River, Little Beaver Creek, and Boxelder Creek, captured southeast-oriented floodwaters as large north- and northeast-oriented valley headcuts eroded south and southwest to behead multiple southeast-oriented flood flow routes. The discussion in this essay will begin with evidence in the Little Beaver Creek-Little Missouri River confluence area and then proceed southwest along the Little Beaver Creek-Boxelder Creek drainage divide.

Little Beaver Creek-Little Missouri River confluence area

Figure 2: Little Beaver Creek-Little Missouri River confluence area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 2 illustrates the Little Beaver Creek-Little Missouri River confluence area at Marmarth, North Dakota. Little Beaver Creek flows from the southwest corner of figure 2 to join the north-oriented Little Missouri River at the town of Marmarth. Southeast-oriented tributaries flow to Little Beaver Creek as barbed tributaries and provide stream capture evidence. The fact Little Beaver Creek has captured multiple southeast-oriented tributaries suggests the Little Beaver Creek valley eroded headward across what might have been a southeast-oriented anastomosing channel complex of the type that might form during an immense southeast-oriented flood. Southeast-oriented Little Beaver Creek tributaries are linked by through valleys with northwest-oriented Yellowstone River tributaries as illustrated in figures 3, 4 and 12. Note Little Beaver Creek tributaries from the southeast and Little Missouri River tributaries from the east are oriented in a northwest direction. The Boxelder Creek-Little Missouri River confluence area will not be illustrated and discussed here as it has been illustrated and discussed in the Boxelder Creek-Little Missouri River drainage divide area essay.

Yellowstone River-Little Beaver Creek drainage divide at Baker, Montana

Figure 3: Yellowstone River-Little Beaver Creek drainage divide at Baker, Montana. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 3 illustrates the headwaters area of the southeast-oriented Little Beaver Creek tributaries shown in figure 2. Northwest-oriented Yellowstone River tributaries including Sandstone Creek are shown in the northwest quadrant of figure 3. Note the shallow northwest-southeast oriented through valley roughly defined by the railroad linking the northwest-oriented Yellowstone River tributaries with the southeast-oriented Little Beaver Creek tributaries. This evidence suggests flood waters responsible for the aligned drainage shown in figure 2 came from northwest of the present-day Yellowstone River drainage divide and headward erosion of the deep Yellowstone River valley captured the flood flow that had been moving southeast across this region and in the process created the Yellowstone River-Little Beaver Creek drainage divide. No well-defined walls to the northwest-southeast oriented through valley are visible in figure 3. While flood erosion removed much of the valley wall evidence the larger area map illustrated in figure 4 will show a northeast valley wall segment.

Relationship of Little Beaver Creek to Beaver Creek escarpment-surrounded upland

Figure 4: Relationship of Little Beaver Creek to Beaver Creek escarpment-surrounded upland. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 4 illustrates the relationship of the Little Beaver Creek-Little Missouri River confluence at Marmarth (southeast corner) to the Beaver Creek escarpment-surrounded upland (north center). The upland’s southwest facing escarpment is a valley wall remnant providing evidence that a large southeast-oriented headcut eroded northwest or headward along a southeast-oriented flood flow route. Remnants of the southeast-oriented headcut’s southwest valley wall are not as easy to identify is illustrated in a separate Little Beaver Creek-Yellowstone River drainage divide landforms essay. The upland’s southeast-facing escarpment was eroded as the northwest or west wall of the north-oriented Little Missouri River valley headcut when it eroded south and southwest to capture southeast-oriented flood waters flowing on the newly eroded southeast-oriented valley floor. Dugout Creek flows northeast to Cannonball Creek (names may be hard to distinguish on figure 4) along the base of the southeast-facing escarpment and Cannonball Creek joins the Little Missouri River in the northeast quadrant of figure 4. This northeast-oriented valley along the southeast-facing escarpment base is evidence flood flow moving on the floor of the flood-eroded southeast-oriented valley was captured and diverted to the newly eroded northeast and north-oriented Little Missouri River valley. The fact the Little Missouri River does not today flow northeast along the Dugout Creek-Cannonball Creek valley provides evidence that while the newly eroded north-oriented Little Missouri River valley did capture southeast-oriented flood flow moving across what is today the Yellowstone River-Little Missouri River drainage divide in the Baker, Montana area, the Little Missouri River valley headcut and its southern tributary headcuts, including the Little Beaver Creek and Boxelder Creek valley headcuts, were able to capture significant flood flow moving along flood flow routes further to the south and west. Also observable in figure 4 is evidence the Little Missouri River valley downstream from the Marmarth area is deeper than it is upstream. Because headward erosion of the Little Missouri valley captured significant southeast-oriented flood flow when it reached the Marmarth (Baker) area, downstream from Marmarth the valley carried more flood water than it did upstream.

Aligned drainage and through valleys in the Big Gumbo Creek area

Figure 5: Aligned drainage and through valleys in the Big Gumbo Creek area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 5 illustrates the Little Beaver Creek-Little Missouri River drainage divide a short distance southwest of the Little Beaver Creek-Little Missouri River confluence area shown in figure 2. Big Gumbo Creek is a southeast-oriented tributary flowing to the north-oriented Little Missouri River located along the eastern edge of figure 5. Little Beaver Creek flows northeast across the northwest corner of figure 5. Note the southeast-oriented barbed tributaries flowing from the Little Beaver Creek-Little Missouri River drainage divide to the north-oriented Little Missouri River. These barbed tributaries provide evidence the Little Missouri River valley eroded headward to capture multiple southeast-oriented flow routes that once flowed further east (note northwest-oriented Little Missouri River tributaries). Northwest-southeast oriented through valleys at the heads of the southeast-oriented Little Missouri River tributaries provide links to northwest-oriented drainage to northeast-oriented Little Beaver Creek and provide evidence the Little Beaver Creek valley eroded headward to behead and capture multiple southeast-oriented flow routes that once flowed to the Little Missouri River. The northwest-southeast aligned drainage provides evidence a southeast-oriented flood once flowed across the region and was captured first by Little Missouri River valley headward erosion and later by Little Beaver Creek valley headward erosion. You may also note a northwest-southeast oriented oil field present in the figure 5 region. Presence of this oil field is evidence of a northwest-southeast oriented structure. Some observers have suggested the aligned drainage is related to northwest-southeast oriented bedrock structures. However, the aligned drainage patterns are not limited to regions where bedrock structures exist, nor do drainage alignments always reflect bedrock structure orientations. Further, aligned drainage explanations depending solely on underlying bedrock structures do not explain the through valleys (sometimes subtle) that are almost always found where aligned drainage routes cross drainage divides.

Aligned drainage and through valleys in the Coal Bank Creek area

Figure 6: Aligned drainage and through valleys in the Coal Bank Creek area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 6 illustrates the Little Beaver Creek-Boxelder Creek drainage divide at a location southwest of the figure 5 map area. North and South Fork Forks of Coalbank Creek join just southeast of the figure 6 southeast corner to form Coalbank Creek which flows southeast as a barbed tributary to northeast-oriented Boxelder Creek. Soda Creek (west center figure 6) and Fiasted Creek (south center figure 6) are additional southeast-oriented barbed tributaries flowing to northeast-oriented Boxelder Creek. Most prominent on the figure 6 are the multiple northwest-oriented tributaries to the northeast-oriented Little Beaver Creek. Close study of the Little Beaver Creek-Boxelder Creek drainage divide reveals the northwest-oriented Little Beaver Creek tributaries are linked by shallow through valleys with the southeast-oriented Boxelder Creek tributaries. The aligned drainage pattern observed here along with the through valleys crossing the Little Beaver Creek-Boxelder Creek drainage divide provide evidence the Little Beaver Creek valley was eroded headward to behead and capture multiple southeast-oriented flow routes of the type that might represent a southeast-oriented complex of anastomosing channels formed during an immense flood that flow across the entire region.

Terrell Creek and HS Creek drainage divide with Coal Creek

Figure 7: Terrell Creek and HS Creek drainage divide with Coal Creek. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 7 is located a short distance southwest along the Little Beaver Creek-Boxelder Creek drainage divide from figure 6. Note Fiasted Creek in the northeast corner of figure 7 and the south center of figure 6. Boxelder Creek flows northeast across the figure 6 southeast corner. Little Beaver Creek flows in a northeast direction just northwest of the figure 7 map area. Again note the northwest-southeast orientation of the Little Beaver Creek and Boxelder Creek tributaries flowing away from the drainage divide. The most prominent southeast-oriented Boxelder Creek tributary, Coal Creek, is linked by through valleys with the northwest-oriented HS and Terrell Creeks, flowing to northeast-oriented Little Beaver Creek. The figure 8 discussion will offer evidence flood waters once flowed southeast across the drainage divide, with the southeast-oriented flow routes systematically beheaded by headward erosion of the Little Beaver Creek valley headcut. Floodwaters already on the beheaded flood flow routes reversed flow direction to flow northwest into the newly eroded and deeper Little Beaver Creek valley. In many cases reversed flow routes were able to capture southeast-oriented flood flow from yet to be beheaded flow routes further to the southwest. Especially evident on figure 7 are the east, north, and northeast-oriented headwaters of HS Creek that begin in the Ekalaka Hills. After flowing northeast from the Ekalaka Hills HS Creek turns and flows northwest to reach northeast-oriented Little Beaver Creek. That east, north and northeast-oriented HS Creek segment and HS Creek elbow of capture represent where reversed flow on what was a newly beheaded southeast-oriented HS Creek-Coal Creek flood flow route captured yet to be beheaded flood flow still flowing southeast on the Ekalaka Hills topographic surface. Harmon Creek (south center figure 7) flows southeast to Boxelder Creek and its headwaters flow from a southeast-oriented escarpment-surrounded basin formed when southeast-oriented flood waters flowing on the Ekalaka Hills topographic surface eroded a large southeast-oriented headcut into the Ekalaka Hills topographic surface. Flood flow over the Ekalaka Hills ceased when the Little Beaver Creek headcut eroded southwest to behead and capture the flood flow, diverting the flood flow to the northeast. This abandoned headcut provides evidence of how flood waters eroded the regional landscape and also provides a minimum measure of the amount of flood erosion that occurred, although much more occurred as will be seen in figures 11 and 12.

Detail map of the Terrell Creek-Coal Creek drainage divide area

Figure 8: Detail map of the Terrell Creek-Coal Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 8 illustrates a detail map of the through valley linking northwest-oriented Terrell Creek with southeast-oriented Coal Creek. The through valley was carved when southeast-oriented flood water was still flowing across what is now the Little Beaver Creek-Boxelder Creek drainage divide. The drainage divide was created when Little Beaver Creek beheaded southeast-oriented flood flow on the Terrell Creek-Coal Creek flow route and water on the northwest end of the beheaded flood flow reversed direction to flow northwest to the newly eroded Little Beaver Creek valley. When the Terrell Creek flow route was first beheaded southeast-oriented flood flow was yet to be beheaded on the HS Creek flow route. The unnamed northwest-oriented stream in the southwest corner of figure 8 flows to northwest-oriented HS Creek, which is located just west of the figure 8 map area. A through valley links that unnamed HS Creek tributary with the northwest-oriented Terrell Creek headwaters and was probably eroded by yet to be beheaded southeast flood flow using the HS Creek route that was captured and reversed to flow northwest on the newly beheaded Terrell Creek flow route. Captures of yet to be beheaded flood flow apparently were quite common and enabled reversed flow on beheaded flood flow routes to erode their northwest-oriented valleys and drainage basins. Study of figure 8 will reveal many other subtle flow routes, suggesting a much more complicated pattern of flow routes and captures than two through valley pattern I have described.

Ekalaka Hills area

Figure 9: Ekalaka Hills area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

The Ekalaka Hills area represents the major upland region on the Little Beaver Creek-Boxelder Creek drainage divide. Note flat-topped areas defining an Ekalaka Hills topographic surface. Map evidence suggests southeast-oriented floodwaters flowed on a topographic surface at least as high as the Ekalaka Hills topographic surface. The figure 7 discussion described the east, north, northeast-oriented HS Creek headwaters segment observed in the figure 9 center north and shown in detail in figure 10. This east, north, and northeast-oriented HS Creek segment and its major tributary are linked by through valleys with northwest-oriented Heggen Creek headwaters and are routes used by what was yet to be beheaded southeast-oriented flood waters captured by reversed flow on the HS Creek flow route. Those HS Creek captured flood waters first flowed southeast on the high level Ekalaka Hills topographic surface (the Heggen Creek valley and Little Beaver Creek valley to the northwest did not yet exist) along a route used by the present day northwest-oriented Heggen Creek valley. When the captured flood water reached where the present-day Heggen Creek headwaters begin the captured flood water turned east to flow along the routes now used by the east, north, and northeast-oriented HS headwaters. Then at what is today the HS Creek elbow of capture, the captured flood waters turned northwest to flow to what was then the newly eroded Little Beaver Creek valley. Apparently there was enough reversed flow and captured flood water to erode the HS Creek drainage basin we see today. Once headward erosion of the Little Beaver Creek valley beheaded southeast-oriented flood flow on the Terrell Creek route the process was repeated and flood flow to the HS Creek drainage ended, which also ended erosion of the HS Creek drainage basin. Russell Creek flows northwest from an unusually large and well-defined northwest-facing escarpment-surrounded basin or abandoned headcut. The Russell Creek escarpment-surrounded basin is facing in the wrong direction to have been cut by southeast-oriented flood flow and can only be explained in the context of unusually large amounts of reversed flood flow. Reasons why the southwest end of the Little Beaver Creek-Boxelder Creek drainage divide may have experienced unusually large amounts of reversed flow are included in the figure 11 and 12 discussions below.

Detail map of HS Creek headwaters area in the Ekalaka Hills

Figure 10: Detail map of HS Creek headwaters area in the Ekalaka Hills. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 10 provides a detail map of the HS Creek-Heggen Creek drainage divide discussed in figure 9. HS Creek flows east from the road in the south center to just east of the National Forest boundary, then turns north to reach an east-oriented tributary and then turns northeast to flow toward the figure 10 northeast corner. Heggen Creek and a Heggen Creek tributary begin just west of the HS Creek and HS Creek tributary headwaters (but on the west side of the road and of the high ridge that defines the drainage divide) and flow northwest to the northwest corner of figure 10. Shallow through valleys can be observed crossing the high ridge connecting Heggen Creek with HS Creek at both points. This subtle evidence is evidence southeast-oriented flood water once flowed from what is today the Heggen Creek drainage basin to the HS Creek drainage basin and probably played a key role in eroding the HS Creek drainage basin we see today.  What is important to remember is HS Creek was able to capture the high-level southeast-oriented flood flow because the Little Beaver Creek valley headcut had yet to be eroded far enough southwest to behead flow on the Heggen Creek route (and cause the Heggen Creek reversal of flow that eroded the Heggen Creek valley we see today). The landscape we see today was systematically produced by these flood events and did not fully evolve until the flood events were completed.

Little Beaver Creek-Boxelder Creek-Powder River drainage divide area

Figure 11: Little Beaver Creek-Boxelder Creek-Powder River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 11 illustrates the truncated Little Beaver Creek-Boxelder Creek drainage divide west end and the deep Powder River valley. The Powder River elbow of capture is located just west of this truncated Little Beaver Creek-Boxelder Creek drainage divide. East of the deep Powder River valley is the Beaver Flats (Flats on figure 11) escarpment-surrounded upland where the northeast-oriented Little Beaver Creek drainage basin begins. Also east of the deep Powder River valley (and of Chalk Buttes along the Powder River valley rim) is a slightly lower erosion surface drained by southeast-oriented Boxelder Creek tributaries. The northeast-oriented Boxelder Creek upstream segment parallels the deep north-northeast-oriented Powder River valley rim south of figure 11. The Powder River elbow of capture occurred because the deep northwest-oriented Yellowstone River beheaded a major southeast-oriented flood flow route that was probably flowing southeast along what is today the Powder River north-northwest valley segment. Reversed flow on that beheaded flood flow route rapidly began to erode the deep north-northwest-oriented Powder River valley segment southwest toward the present-day Beaver Flats region. Reversed flow on the north-northwest-oriented Powder River downstream segment probably captured what was then northeast-oriented floodwaters flowing to the northeast-oriented Little Beaver headcut face. This capture caused headward erosion of the deep Powder River valley to change from eroding south-southeast to eroding south-southwest and created the Powder River elbow of capture. To fully understand what was happening we need to see the Beaver Flats escarpment-surrounded upland.

Beaver Flats escarpment surrounded upland

Figure 12: Little Beaver Creek headwaters area at Beaver Flats escarpment surrounded upland. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 12 better illustrates the Beaver Flats escarpment-surrounded upland. Beaver Flats is drained by northeast-oriented Little Beaver Creek. The Little Beaver Creek-Yellowstone River drainage divide can be seen along the top of the west half of figure 12. Northwest-oriented streams flow down the face of what is a west-northwest-facing escarpment to north and northwest-oriented O’Fallon Creek, which eventually reaches the deep northeast-oriented Yellowstone River valley (figure 1 shows north-oriented and unnamed O’Fallon Creek, but the Yellowstone River is north of the figure 1 map area). The southwest-facing escarpment is drained by northwest-oriented tributaries to the north-northwest-oriented downstream Powder River. The present-day Beaver Flats erosion surface was defined by the floor of the deep Little Beaver Creek valley headcut, which eroded headward from the newly formed Little Missouri River valley as described in this essay. The slightly lower Boxelder Creek erosion surface seen in figure 11 was defined by the floor of the Boxelder Creek headcut, which also eroded headward from the Little Missouri River valley. The difference in elevation between the two erosion surfaces is explained by headward erosion of the deep Yellowstone River valley, which was proceeding faster than headward erosion of the Little Beaver Creek headcut and southeast-oriented flow to the Little Beaver Creek headcut was beheaded and reversed to rapidly erode the deep north-northwest-oriented Powder River downstream valley segment. At the same time the Boxelder Creek headcut was eroding further southwest by capturing yet to be beheaded (by the Yellowstone River valley headcut) southeast-oriented flood water. As a result the Boxelder Creek drainage basin was able to erode a lower erosion surface (or deeper) drainage basin than the adjacent Beaver Flats.

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, but could not be included due to Google space limitations. Readers are encouraged to look at mosaics of the detailed 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 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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