Judith River-Armells Creek drainage divide landform origins in Fergus County, Montana, USA

Authors

A geomorphic history based on topographic map evidence

Abstract:

The Judith River-Armells Creek drainage divide area discussed here is located in Fergus County, Montana, USA. Although detailed topographic maps of the Judith River-Armells Creek 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 Judith River-Armells Creek 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 Missouri River valley and Judith River valley captured all 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 Missouri River drainage basin landform origins 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 Judith River-Armells Creek drainage divide area landform origins in Fergus County, Montana, USA. 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 Judith River-Armells Creek drainage divide area landform evidence will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm. This essay is included in  the Missouri River drainage basin landform origins research project essay collection.

Judith River-Armells Creek drainage divide area location map

Figure 1: Judith River-Armells Creek 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 Judith River-Armells Creek drainage divide area location map and illustrates a region in central Montana. The Missouri River flows northeast from the figure 1 west center edge to Great Falls, Fort Benton, and Loma and then turns southeast, east-northeast, and southeast to flow to Fort Peck Lake (located along the figure 1 east edge). The Judith River flows north from the south of the Judith Basin to join the east-oriented Missouri River south of the Bears Paw Mountains. Armells Creek originates in the Judith Mountains (east of the Judith Basin) and flows northeast to join the Missouri River south of the Little Rocky Mountains. The Musselshell River flows from the Little Belt Mountains area (figure 1 southwest quadrant) to Martinsdale and then southeast to Harlowton, Ryegate, and Lavina. From Lavina the Musselshell River flows northeast to Roundup and Melstone, where it turns to flow north to join the Missouri River at Fort Peck Lake. The Judith River-Armells Creek drainage divide area of concern in this essay is the drainage divide between the north-oriented Judith River and the northeast-oriented Armells Creek, which is located north and northwest of the Judith Mountains and south of the Missouri River. Landform evidence in this essay is interpreted in the context of an immense southeast-oriented flood that crossed the entire figure 1 map area. Prior to Missouri River valley headward erosion the deep Musselshell River valley eroded headward into the figure 1 map area to capture southeast-oriented flood waters that had been moving to the newly eroded deep Yellowstone River valley and to divert the captured flood waters further to the north and northeast. Southeast-oriented tributary valleys to the north-oriented Musselshell River valley segment, such as Box Elder Creek valley, originated as southeast-oriented flood flow routes to the newly eroded and deep northeast-oriented Yellowstone River valley (located south of the figure 1 map area). At that time the Judith Mountains did not significantly interfere with flood water movements. However, as immense quantities of flood water moved to the newly eroded and deep northeast-oriented Yellowstone River valley (and subsequently to the newly eroded and deep north-oriented Musselshell River valley) the Judith Mountains emerged as significant obstacles, and the southeast-oriented flood waters were progressively channeled around them. Headward erosion of the east-oriented Missouri River valley, the northeast-oriented Armells Creek valley, and the north-oriented Judith River valley next beheaded and reversed southeast-oriented flood flow routes to the newly eroded north-oriented Musselshell River valley and diverted flood waters north to the newly eroded east-oriented Missouri River valley. The Peoples Creek-Missouri River drainage divide area essay, the Judith River-Musselshell River (Fergus County) drainage divide area essay, the Armells Creek-Box Elder Creek drainage divide are essay, and the Missouri River-Musselshell River drainage divide area essay describe drainage divide areas located near the Judith River-Armells Creek drainage divide areas discussed here. Essays can be found under appropriate river names on the sidebar category list with Armells Creek being a tributary to the MT Missouri River.

Judith River-Armells Creek drainage divide area detailed location map

Figure 2: Judith River-Armells Creek 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 Judith River-Armells Creek drainage divide area discussed in this essay. Fergus, Chouteau, Judith Basin, and Petroleum Counties are located in Montana. The Missouri River flows southeast, south, and southeast in the figure 2 northwest quadrant to the Chouteau-Fergus County boundary and then flows east-northeast and southeast along the north edge of Fergus County. The Judith Mountains are located in the figure 2 south center area. Armells Creek originates in the Judith Mountains and flows north-northwest and then northeast to join the east-southeast oriented Missouri River (near where the major north-oriented red highway crosses the Missouri River in the figure northeast quadrant). The Judith River flows north in western Fergus County and joins the Missouri River near the point marked “Ferry” on the secondary red highway between Winifred and Iliad. Note the predominance of northwest-oriented Judith River tributaries. This predominance of northwest-oriented tributaries is interpreted as evidence the Judith River valley eroded headward across multiple southeast oriented flood flow channels, such as might be found in a large-scale southeast oriented anastomosing channel complex. Also note southeast- and northwest-oriented Armells Creek tributaries and headwaters. Flood waters originally were moving to what was probably a newly eroded northeast and north-oriented Musselshell River valley. The Musselshell River valley eroded south and southwest before the Missouri River valley eroded northwest and west. The Armells Creek valley eroded headward from what was then the Missouri River valley head (i.e. there was no Missouri River valley west of that point). Headward erosion of the Missouri River valley then beheaded east- and southeast-oriented flood flow routes to the newly eroded Armells Creek valley. Note the location of north- and northwest-oriented Dog Creek between the Judith River and Armells Creek. This essay looks at evidence along the Dog Creek-Armells Creek (and Missouri River) and along the Judith River-Dog Creek drainage divides. The Dog Creek valley eroded south after the Armells Creek valley eroded southwest. The Judith River valley then eroded south from what was then the Missouri River valley head and beheaded flood flow routes to the newly eroded Dog Creek valley. Headward erosion of the deep northeast-oriented Armells Creek valley and subsequently of the deep north-oriented Judith River valley beheaded southeast-oriented flood flow channels (one by one). Flood waters on the northwest ends of the beheaded flood flow routes reversed flow direction to flow northwest to the newly eroded and deeper north-oriented Judith River valley. Because flood flow routes were anastomosing (or interconnected), reversed flow on newly beheaded flood flow routes usually captured yet to be beheaded flood flow from channels further to the south. Such captures of yet to be beheaded flood flow provided the volumes of water required to erode significant northwest oriented tributary valleys. Headward erosion of the deep southeast-oriented Missouri River valley and its north-oriented tributary Judith River valley ended all southeast-oriented flood flow across the Judith River-Armells Creek drainage divide area.

South end of Dog Creek-Armells Creek drainage divide area

Figure 3: South end of Dog Creek-Armells Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 illustrates the south end of the Dog Creek-Armells Creek drainage divide area. The North Moccasin Mountains are located in the figure 3 southwest corner. Dog Creek flows east from the North Moccasin Mountains and turns north to flow through Moulton and Christina and then to the figure 3 north center edge. Dog Creek eventually flows to the Missouri River. North and northwest-oriented headwaters of Salt Creek are located in the figure 3 northwest quadrant. Northwest of the figure 3 map area Salt Creek flows northwest to join the north-oriented Judith River (see figure 5 below). Armells Creek flows northeast and north to Armells (located in the figure 3 southeast corner) and then northwest, east, north, and northeast to the figure 3 east edge. Deer Creek flows north through Roy Junction and then northeast to join Armells Creek. The Judith Mountains are located southeast of the figure 3 map area and Armells Creek and Deer Creek originate in the Judith Mountains as northwest-oriented streams. Armells Creek flows northeast from the figure 3 map area to join the Missouri River (see figure 10). Note through valleys linking the Dog Creek and Deer Creek and Armells Creek valleys (figure 4 below provides a detailed map of the Roy Junction area). These through valleys provide evidence multiple channels of water once flowed from the Dog Creek valley to the Deer Creek and Armells Creek valleys. The multiple channels suggest the presence of an anastomosing channel complex that was dismembered by headward erosion of the north-oriented Dog Creek valley. Note also northwest-oriented drainage in the figure 3 southeast quadrant. These northwest-oriented drainage routes include the northwest-oriented Armells Creek valley segment and several Armells Creek and Deer Creek tributaries. These northwest-oriented valleys were eroded by reversed flood flow on the northwest ends of beheaded southeast-oriented flood flow routes when the deep northeast-oriented Armells Creek valley eroded headward into the region to capture southeast-oriented flood flow. In addition to the northwest-oriented Armells Creek and Deer Creek tributaries figure 3 also illustrates northwest-oriented Dog Creek and Judith River tributaries and the history of those northwest-oriented is similar, although the Dog Creek valley eroded headward to capture southeast-oriented flood flow moving to what was then the newly eroded Armells Creek and Deer Creek valleys and the Judith River valley subsequently eroded headward to capture southeast-oriented flood flow moving to what was then the newly eroded Dog Creek valley. At the time headward erosion of these deep valleys began the regional topographic surface was higher than it is now and the Moccasin Mountains and Judith Mountains did not stand high above the surrounding landscape as they do today. Deep flood erosion of the figure 3 map area lowered the regional topographic surface to produce the landscape seen today.

Detailed map of Dog Creek-Deer Creek drainage divide area

Figure 4: Detailed map of Dog Creek-Deer Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 provides a detailed map of through valleys linking the Dog Creek valley with the Deer Creek valley near Roy Junction (the figure 4 map area is seen in less detail in figure 3 above). Deer Creek is the north and north-northeast oriented stream flowing through Roy Junction in the figure 4 east half. Note multiple northwest-oriented Deer Creek tributaries from the east. Northeast and northwest-oriented Dog Creek is located in the figure 4 west half. Note also northwest-oriented Dog Creek tributaries. Multiple through valleys cross the drainage divide between the Dog Creek drainage basin and the Deer Creek drainage basin. The deepest of the through valleys is a west to east oriented valley north of Roy Junction in which the abandoned railroad line is located. Another deep through valley is located near the figure 4 north edge. However, a close look at the drainage divide reveals several other much shallower through valleys. The through valleys provide evidence the north-oriented Deer Creek valley eroded headward to capture what must have been multiple channels of southeast or east-oriented flood flow, such as would be present in a southeast or east-oriented anastomosing channel complex. As in any anastomosing channel complex the channels were probably constantly changing. As one channel eroded deeper it would capture flow from adjacent channels. The two deep through valleys seen in figure 4 probably represent two of the more successful channels in terms of being able to erode deeper and in terms of capturing flood flow. The through valleys were eroded by headward erosion of tributary valleys into the west wall of what was then the newly eroded and deep Deer Creek valley. Subsequently the deep Dog Creek valley eroded south to capture the same southeast-oriented flood flow channels. Flood waters on the northwest or west ends of the beheaded flood flow channels reversed flow direction to flow northwest or west to newly eroded Dog Creek valley. These reversal of flood flow eroded the northwest and west-oriented Dog Creek tributary valleys and also created the present day Dog Creek-Deer Creek drainage divide.

South end of Judith River-Dog Creek drainage divide area

Figure 5: South end of Judith River-Dog Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the Judith River-Dog Creek drainage divide area west of the figure 3 map area and includes overlap areas with figure 3. The Judith River is flowing in a northeast direction across the figure 5 northwest corner. Note northwest-oriented Judith River tributaries, which were eroded by reversals of flood waters on the northwest ends of southeast-oriented flood flow routes beheaded by headward erosion of the deep northeast-oriented Judith River valley. The Judith River valley eroded southwest across multiple southeast-oriented flood flow channels, such as might be found in an anastomosing channel complex. Channels were beheaded in sequence from the northeast to the southwest. Because channels were anastomosing (or interconnected) reversed flood flow in a newly beheaded flood flow channel could usually capture yet to be beheaded flood flow from channels further to the southwest. Capture of yet to be beheaded flood flow enable the reversed flow channels to erode significant northwest-oriented valleys. The North Moccasin Mountains are located in the figure 5 south center area. Dog Creek originates in the North Moccasin Mountains and flows east and northwest to Moulton and then northeast to the figure 5 east edge. Dog Creek then flows north and northwest in the area east of figure 5 and eventually flows to join the Missouri River near the location where the Judith River joins the Missouri River (see figure 8 below). Little Dog Creek is the east-oriented Dog Creek tributary joining Dog Creek at Moulton. Note how Little Dog Creek headwaters are located near headwaters of northwest-oriented Box Elder Creek, which flows to the Judith River north of the figure 5 northwest corner. The Dog Creek valley eroded headward into the figure 5 map area before the Judith River valley eroded headward into the figure 5 map area. Southeast-oriented flood in a channel using the Box Elder Creek alignment was captured by the newly eroded Dog Creek valley and made a U-turn north of the North Moccasin Mountains to flow north and northwest in the newly eroded Dog Creek valley to the Missouri River valley. Headward erosion of the deep Judith River valley then beheaded the southeast-oriented flood flow channel and flood waters on the northwest end reversed flow direction to erode the northwest-oriented Box Elder Creek valley. Erosion of the northwest-oriented Box Elder Creek valley was probably aided by capture of yet to beheaded flood flow using channels on the present day Plum Creek, Willow Creek, and Ming Coulee alignments.

Detailed map of Box Elder Creek-Dog Creek drainage divide area

Figure 6: Detailed map of Box Elder Creek-Dog Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 provides a detailed map of the Box Elder Creek-Dog Creek drainage divide area seen in less detail in figure 5 above. Box Elder Creek flows northwest to the figure 6 northwest corner and then to the northeast oriented Judith River. Little Dog Creek flows east from the figure 6 center area to the figure 6 east edge. East of figure 6 Little Dog Creek joins Dog Creek and Dog Creek flows north and northwest to join the Missouri River. Northeast and north-oriented headwaters of Middle Fork of Salt Creek are located in the figure 6 north center area and East Fork Salt Creek headwaters are located in the figure 6 northeast quadrant. North of figure 6 Salt Creek flows north and northwest to join the northeast and north-oriented Judith River (see figure 7 below). Note the through valley linking the present day northwest-oriented Box Elder Creek valley with the east-oriented Little Dog Creek valley. Also note less obvious linkages between the northwest-oriented Middle Fork Salt Creek valley and the Box Elder Creek valley. Figure 6 evidence demonstrates southeast-oriented flood flow on the Box Elder Creek alignment moved into the northeast and north oriented Middle Fork Salt Creek valley and also moved into the east-oriented Dog Creek valley. This evidence demonstrates the north-oriented Dog Creek valley eroded headward into the region east of figure 6 before southeast-oriented flood flow on the Box Elder Creek alignment was beheaded and reversed. Also figure 6 evidence demonstrates the north-oriented Middle Fork Salt Creek valley eroded headward into the figure 6 map area before headward erosion of the Judith River valley beheaded and reversed southeast-oriented flood flow on the Box Elder Creek alignment. Figure 6 evidence tells the story of how the Judith River valley eroded headward into the region.

Judith River-Dog Creek drainage divide area near Winifred

Figure 7: Judith River-Dog Creek drainage divide area near Winifred. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the Judith River-Dog Creek drainage divide area near Winifred and does not include overlap areas with previous detailed maps. The Judith River flows north, northwest, and north in the figure 7 west edge area. Dog Creek flows north and northwest from the figure 7 south edge to Winifred and to join Flax Coulee in the figure 7 north center area and then turns northeast to flow to Cutbank Creek. After joining northwest-oriented Cutbank Creek Dog Creek flows west-northwest to the figure 7 northwest corner area. North of figure 7 Dog Creek joins the Missouri River just east of where the Judith River joins the Missouri River (see figure 8 below). Salt Creek is the northwest-oriented Judith River tributary located near the figure 7 south edge. Note other northwest-oriented Judith River tributaries. These northwest-oriented tributaries were formed by reversals of southeast-oriented flood flow as headward erosion of the deep north-oriented Judith River valley beheaded multiple southeast-oriented flood flow routes. Southeast-oriented flood flow routes beheaded by Judith River valley headward erosion were moving flood waters to what was then the newly eroded north-oriented Dog Creek valley, which had eroded south shortly before the Judith River valley eroded south. Note through valleys linking headwaters of the northwest-oriented Judith River tributary valleys with the Dog Creek valley. Headward erosion of the Dog Creek valley also beheaded southeast-oriented flood flow routes that had been moving flood waters to what was then the newly eroded northeast-oriented Armells Creek valley. Northwest-oriented Rose Creek and Cutbank Creek were formed by reversals of flood flow on two of those beheaded southeast-oriented flood flow routes. Northwest-oriented Dog Creek valley segments were also eroded by reversals of flood flow on the northwest ends of beheaded southeast-oriented flood flow routes. Northeast-oriented Dog Creek tributary valleys eroded southwest in sequence to capture yet to be beheaded (by headward erosion of the deep north-oriented Judith River valley) southeast-oriented flood flow routes. When headward erosion beheaded the southeast-oriented flood flow routes to those northeast-oriented Dog Creek tributary valleys headward erosion of those northeast-oriented Dog Creek tributary valleys ceased.

North end of Judith River-Dog Creek drainage divide area

Figure 8: North end of Judith River-Dog Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 illustrates the north end of the Judith River-Dog Creek drainage divide area located north of the figure 7 map area and includes significant overlap areas with figure 7. The Missouri River flows east, east-southeast, and northeast across the figure 8 north half. The Judith River flows north along the figure 8 west edge to join the east-oriented Missouri River. Dog Creek flows northwest in the figure 8 south center area to join northeast-oriented Flax Coulee and then flow northeast to join northwest-oriented Cutbank Creek. After joining Cutbank Creek, Dog Creek flow west-northwest to join the Missouri River near the figure 8 west edge. Note how Dog Creek flows almost in the opposite direction of the Missouri River. This opposing flow direction developed when headward erosion of the deep Missouri River valley beheaded east-southeast oriented flood flow in a parallel flood flow channel and provides evidence the Missouri River valley eroded headward along one of several anastomosing flood flow routes. Flood waters on west-northwest end of the beheaded flood flow channel reversed flow direction to flow west-northwest to the newly eroded and much deeper east-oriented Missouri River valley. Northwest-oriented Cutbank Creek (flowing from the figure 8 southeast corner) and west-southwest oriented Taffy Creek formed as reversals of flood waters that had originally been moving southeast and east-northeast to the Missouri River valley east of figure 8. Figure 9 below illustrates where the southeast and east-northeast oriented flood flow was going. Note how the northeast-oriented Missouri River valley in the figure 8 northeast quadrant has several west-northwest oriented tributary valleys. These west-northwest oriented tributary valleys were also eroded by reversals of flood flow on the west-northwest ends of east-southeast oriented flood flow routes beheaded by headward erosion of the deep Missouri River valley. These barbed tributaries are difficult or impossible to explain by any other mechanism and provide evidence the Missouri River valley eroded headward across an immense east-southeast oriented flood.

Dog Creek-Armells Creek drainage divide area

Figure 9: Dog Creek-Armells Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the Dog Creek-Armells Creek drainage divide area east and south of the figure 8 map area and includes overlap areas with figure 8. Armells Creek flows northeast, east, and northeast in the figure 9 southeast corner area and joins the southeast oriented Missouri River east of the figure 9 map area (see figure 10 below). East-oriented Two Calf Creek in the figure 9 northeast quadrant also flows to the southeast oriented Missouri River east of the figure 9 map area. Northwest and west-southwest-oriented Taffy Creek is located in the figure 9 northwest quadrant. Cutbank Creek flows northwest from the figure 9 central area to the figure 9 west edge and then to join Taffy Creek and Dog Creek and finally to flow west-northwest to the east-oriented Missouri River. Rose Creek originates in the figure 9 southwest quadrant and flows north and northwest to the figure 9 west edge. Note shallow through valleys linking the east-oriented Armells Creek and Missouri River tributaries with the west- and northwest-oriented Dog Creek tributaries. The drainage orientations and the through valleys provide evidence that prior to headward erosion of the Missouri River, southeast- and east-oriented flood flow moved across the entire figure 9 map area to what was then the newly eroded southeast-oriented Missouri River valley east of the figure 9 map area. The deep Missouri River valley then eroded headward, first northwest, then southwest, then west-northwest, and finally west to behead the southeast- and east-oriented flood flow routes moving flood waters across the figure 9 map area. Flood waters on the northwest and west ends of those beheaded flood flow routes reversed flow direction to flow northwest and west-northwest to the newly eroded and deeper Missouri River valley. The reversed flow flood waters eroded the northwest and west-northwest oriented Dog Creek and Dog Creek tributary valleys and also created the present day Dog Creek-Armells Creek and Dog Creek-Missouri River drainage divide.

Two Calf Creek-Armells Creek drainage divide area

Figure 10: Two Calf Creek-Armells Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 10 illustrates the Two Calf Creek-Armells Creek drainage divide area east of the figure 9 map area and includes overlap areas with figure 9. The Missouri River flows southeast from the figure 10 north edge to the figure 10 east edge. Armells Creek flows northeast from the figure 10 south center edge area to join the Missouri River near the figure 10 east edge (where the highway crosses the Missouri River). The South Fork Two Calf Creek flows east from the figure 10 west center edge to join southeast oriented Two Calf Creek north of Knox Ridge and then to flow east to join the southeast oriented Missouri River. Two Calf Creek flows southeast from the figure 10 west edge (north half) to join the South Fork north of Knox Ridge. As previously described the deep Missouri River valley eroded headward across the figure 10 map area to capture southeast and east-oriented flood flow. When the Missouri River valley reached the figure 10 east edge two separate valleys began to erode headward. One valley, the present day Armells Creek valley,  eroded southwest to capture southeast and east-oriented flood flow moving across the present day Dog Creek-Armells Creek drainage divide area. The second valley eroded northwest to capture southeast and east-oriented flood flow moving across the present day Dog Creek-Missouri River drainage divide area seen in figure 9 above. Apparently the northern valley was able to capture more flood water and to erode deeper because it eroded headward to behead the east-southeast oriented flood flow routes supplying flood waters to the figure 10 map area. The southern valley (or Armells Creek) encountered resistant rock masses in the Judith Mountains and North Moccasin Mountains areas, which probably slowed its ability to erode headward. As a result the Missouri River valley was not only able to behead and reverse the east-southeast oriented flood flow route that is now the west-northwest oriented Dog Creek valley, but the north-oriented Dog Creek valley was able to erode headward (or south) to capture southeast and east oriented flood water moving to the newly eroded Armells Creek valley. And shortly after, the deep north-oriented Judith River valley was able to erode south (west of the erosion resistant Moccasin Mountains) to capture all southeast and east oriented flood flow moving to what was then the newly eroded north-oriented Dog 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 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.

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