Abstract:
Topographic map interpretation methods are used to determine landform origins in the Poplar River-Missouri River drainage divide area in Daniels, Valley, and Roosevelt Counties, Montana. The Poplar River originates in the Wood Mountain region of southern Saskatchewan and flows in a southeast and south direction to join the east oriented Missouri River near Poplar, Montana. Study region drainage routes evolved as the deep east oriented Missouri River valley eroded headward from a major breach in the detached southwest margin of a rapidly melting North American ice sheet and captured massive south-southeast oriented ice sheet marginal melt water floods. South-southeast oriented tributary valleys eroded headward from the actively eroding Missouri River valley and then east and southwest oriented valleys eroded headward from the actively eroding south-southeast oriented valleys. The east and southwest oriented valleys beheaded flood flow routes to actively eroding south-southeast oriented Missouri River tributary valleys. Map evidence supporting this melt water flood origin includes orientations of present day drainage routes and valleys and also through valleys eroded across present day drainage divides.
Preface:
The following interpretation of detailed topographic map evidence is one of a series of essays describing similar evidence for all major drainage divides contained within the Missouri River drainage basin and for all major drainage divides with adjacent drainage basins. The research project is interpreting evidence in the context of a previously unexplored deep glacial erosion paradigm, which is fundamentally different from most commonly accepted North American glacial history interpretations. Project essays available at this site may be found by selecting desired Missouri River tributaries and/or states from this essay’s sidebar category list.
Introduction:
- The purpose of this essay is to use topographic map interpretation methods to explore the Poplar River-Missouri River drainage divide area landform origins in Daniels, Valley, and Roosevelt Counties, 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 and/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 here.
- This essay is also exploring a new geomorphology 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 other essays in the Missouri River drainage basin landform origins research project is a thick North American ice sheet, comparable in thickness to the Antarctic ice sheet, occupied the North American region usually recognized to have been glaciated, and through its weight and erosive actions created a deep North American “hole”. The southwestern rim of that deep “hole” is today preserved in the high Rocky Mountains. The ice sheet 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 Poplar River-Missouri River drainage divide area landform evidence in Daniels, Valley, and Roosevelt Counties, Montana will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm (see menu at top of page for paradigm related essay). This essay is included in the Missouri River drainage basin landform origins research project essay collection.
Poplar River-Missouri River drainage divide area location map
Figure 1: Poplar River-Missouri River drainage divide area location map (select and click on maps to enlarge). National Geographic Society map digitally presented using National Geographic Society TOPO software.
- Figure 1 provides a location map for the Poplar River-Missouri River drainage divide area in northeast Montana. The Canada-United States border is labeled and Montana is the state south of the international border and Saskatchewan is the Canadian province north of the border. Fort Peck Lake in the figure 1 south center region is a large reservoir flooding the Missouri River valley. The Missouri River flows in an east direction from Fort Peck Dam to the North Dakota border along the figure 1 east edge. The Milk River flows from Zurich (along the figure 1 west edge, south of international border) to Malta, Hinsdale and Glasgow before joining the Missouri River a short distance downstream from Fort Peck Dam. The Poplar River originates along the southeast margin of Wood Mountain (just north of the international border, center region) and flows in a southeast and south direction to join the Missouri River at Poplar, Montana. The West Fork Poplar River is the major labeled Poplar River tributary and originates north of Killdeer, Saskatchewan in the Wood Mountain region. East of the Poplar River Big Muddy Creek originates in the Big Muddy Lake area just north of the international border and flows in a southeast and south-southwest direction to join the Missouri River a short upstream from Culbertson, Montana. While not shown in figure 1 a large abandoned northeast-oriented valley extends from near Poplar, Montana to the Medicine Lake area near the North Dakota border (and the figure 1 east edge). Porcupine Creek is a south-oriented Milk River tributary, which joins the Milk River near Nashua, Montana, just before the Milk River joins the Missouri River. The Poplar River-Missouri River drainage divide area investigated in this essay is located south of the international border, north of the Missouri River, east of Porcupine Creek, and south and west of the Poplar River. The Poplar River-Big Muddy Creek drainage divide landform origins essay addresses the region east of the Poplar River and the Wood River-Poplar River drainage divide area landform origins the region north of the international border. These and other Montana Missouri River drainage divide area essays can be found under the MT Missouri River category on the sidebar category list.
- Topographic map evidence presented in this essay and in essays interpreting other regional Missouri River drainage basin drainage divide areas suggests the entire figure 1 map area was eroded by immense south and southeast-oriented ice-marginal glacial melt water floods. The ice-marginal floods were flowing along the southwest margin of a rapidly decaying North American ice sheet and at the time the Poplar River-Missouri River drainage divide area was eroded the ice sheet margin was located just east and north of a line connecting Lake of the Rivers (near north edge), Willow Bunch Lake, Big Muddy Lake, and Medicine Lake (in the figure 1 northeast quadrant). Actually at that time the ice sheet’s southwest margin had been detached by a giant southeast-oriented ice-walled and bedrock-floored canyon, the southwest wall of which crossed the figure 1 northeast corner (the northeast-facing Missouri Escarpment is what remains of the ice-walled and bedrock-floored canyon’s southwest wall). The floor of the ice-walled and bedrock-floored canyon was lower in elevation than regions south and west of the detached ice sheet margin and a deep northeast-oriented valley had eroded headward from a breach in that ice barrier to capture the immense southeast-oriented ice-marginal floods and to divert the melt water floods onto the melting ice sheet floor. This large valley today extends from the Poplar region to the Medicine Lake area and is then blocked by glacial debris between the Medicine Lake and the Missouri Escarpment face (east of the figure 1 map area). The Missouri River valley and tributary valleys upstream from the Poplar, Montana area, including the Poplar River valley, were eroded headward from that large northeast-oriented valley. Subsequently continued ice sheet melting opened up north-oriented melt water flood flow routes across the melting ice sheet floor. The massive melt water floods, which had been flowing south to the Gulf of Mexico, were diverted north to the North Atlantic Ocean and Hudson Bay region. These changes in melt water flow direction significantly altered ocean circulation and caused a major climate change, which froze the north-oriented flood waters on the former ice sheet floor and which rejuvenated remnants of the decaying ice sheet. The frozen flood waters then formed what became a thin ice sheet with remnants of the former thick ice sheet embedded in it. This new thin ice sheet blocked the large northeast-oriented Poplar-Medicine Lake valley forcing remaining ice-marginal flood flow to spill eastward along what is now the Missouri River route between Poplar, Montana and the North Dakota border.
Detailed location map for Poplar River-Missouri River drainage divide area
Figure 2: Detailed location map for Poplar River-Missouri River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.
- Figure 2 provides a detailed location for the Poplar River-Missouri River drainage divide area in Daniels, Valley, and Roosevelt Counties, Montana. The west-east oriented international border is located just north of figure 2. The Missouri River forms the Fort Peck Indian Reservation southern boundary in Roosevelt County and flows near the towns of Wolf Point, Poplar, and Brockton. The Poplar River flows in a southeast direction from the figure 2 north center edge to Scobey (in Daniels County) before flowing in a south direction to the Roosevelt County border and then in a southeast and south-southwest direction to join the Missouri River near Poplar. Coal Creek is an east-oriented tributary joining the Poplar River in northern Daniels County. Butte Creek is an east-southeast oriented tributary joining the Poplar River near Scobey. The West Fork Poplar River flows from the figure 2 north edge north of Opheim to Richland on the Valley-Daniels County border to join the Poplar River south of the Daniels-Roosevelt County border. Cottonwood Creek is an east-oriented West Fork Poplar River tributary originating just west of the Roosevelt County northwest corner and joining the West Fork Poplar River on the Daniels-Roosevelt County border. South of east-oriented Cottonwood Creek are several southeast and south-southeast oriented Missouri River tributaries including (from east to west) Boxelder Creek, Chelsea Creek, Tule Creek, and Wolf Creek. These drainage routes provide evidence the region was eroded by massive southeast-oriented flood flow moving in multiple flood flow channels to what was then the newly eroded Missouri River valley, which at that time extended in a northeast direction from the Poplar region. The south-southwest oriented Poplar River valley segment is located on the floor of the large abandoned northeast-oriented valley and represents a reversal of what was once northeast-oriented flow toward a major breach across the detached ice sheet southwest margin. Headward erosion of the east-oriented West Fork Poplar River-Cottonwood Creek valley from the Poplar River valley beheaded southeast and south-southeast oriented flood flow to what were then actively eroding southeast and south-southeast oriented Missouri River tributary valleys. Further north headward erosion of the Butte Creek valley beheaded flood flow routes to actively eroding (unnamed) southeast-oriented Poplar River tributaries and then Coal Creek valley headward erosion beheaded flood flow routes to the actively eroding Butte Creek valley.
- West of the Cottonwood Creek headwaters are headwaters of south-oriented Little Porcupine Creek, which joins the Missouri River near Frazer. And west of Little Porcupine is Porcupine Creek, which forms the Fort Peck Indian Reservation western boundary and which joins the southeast-oriented Milk River near Nashua. The Milk River flows from Glasgow to Nashua and joins the Missouri River just south of the figure 2 south edge. A significant Porcupine Creek tributary of interest in this essay is Snow Coulee, which originates near Opheim in the figure 2 northwest quadrant and which flows in a south-southeast direction to the Fort Peck Indian Reservation northern border and then turns to flow in a southwest direction to join south-oriented Porcupine Creek. Note how south-southeast-oriented flood flow routes to the south-southeast oriented Snow Coulee headwaters and tributaries was beheaded by headward erosion of east-oriented Roanwood Creek (and northeast-oriented tributaries), which joins the southeast-oriented West Fork Poplar River north of Glentana. Also note how headward erosion of the southwest-oriented Snow Coulee valley segment captured south-southeast oriented flood flow routes which had been flowing to south-southeast oriented East Fork and West Fork Little Porcupine Creeks and to East Fork Porcupine Creek. Orientations of these drainage routes alone (without seeing any topographic map evidence) makes a strong case for systematic headward erosion of valleys along and across massive south-southeast oriented floods, which almost certainly were derived from a rapidly melting North American ice sheet and which were flowing along the ice sheet’s southwest margin. Topographic maps provide additional evidence supporting this massive flood origin hypothesis and the following eight figures illustrate only a few examples of the abundant evidence available.
Coal Creek-Butte drainage divide area
Figure 3: Coal Creek-Butte Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.
- Figure 3 illustrates the Coal Creek-Butte Creek drainage divide area in northwest Daniels County. The Middle Fork Poplar River flows in a southeast direction across the figure 3 northeast corner and joins the East Fork Poplar River east of the figure 3 southeast corner (near Scobey, unseen in figure 3) to form the Poplar River. Coal Creek flows in an east-southeast, east, and east-northeast direction from the figure 3 west edge (south of northwest corner) to join the Middle Fork Poplar River near the figure 3 north edge. Fisherty Coulee is a northeast-oriented Coal Creek tributary near the figure 3 west edge. Butte Creek flows in an east and southeast direction from west of the town of Butte Creek (south and west of figure 3 center) to the figure 3 southeast corner and then joins the Poplar River south and east of the figure 3 map area. The southeast-oriented stream flowing to the figure 3 south edge (south of the town of Butte Creek) is Police Creek, which joins the West Fork Poplar River south of figure 3. Note how Coal Creek tributaries from the north are generally oriented in southeast directions. These southeast-oriented tributaries provide evidence headward erosion of the Coal Creek valley captured multiple southeast-oriented flood flow routes. Also note the shallow through valley linking the east-oriented Coal Creek valley with valleys of southeast-oriented Butte Creek tributaries (the through valley is located on a line between the towns of Carbert and Butte Creek). The map contour interval is 20 meters and the through valley is defined by a single contour line on each side. The large northwest-southeast oriented through valley crossing the present day Coal Creek-Butte Creek drainage divide provides evidence of a large former southeast-oriented flood flow channel which supplied flood waters to the actively eroding Butte Creek valley prior to Coal Creek valley headward erosion. A similar shallow through valley links the east-northeast oriented Lewarton Coulee valley (which drains to Butte Creek near the town of Butte Creek) with the southeast-oriented Police Creek headwaters valley. While these through valleys are subtle features they exist and combined with the drainage route orientations can be used to reconstruct the regional drainage history. In the case of figure 3 headward erosion of the Butte Creek valley first beheaded multiple southeast-oriented flood flow routes to what were then actively eroding southeast-oriented Poplar River and West Fork Poplar River tributary valleys (including the Police Creek valley). Next headward erosion of the Coal Creek valley captured the southeast-oriented flood flow routes and beheaded flood flow routes to what were then actively eroding southeast-oriented Butte Creek tributary valleys.
Detailed map of Coal Creek-Butte Creek drainage divide area
Figure 4: Detailed map of Coal Creek-Butte Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.
- Figure 4 illustrates a detailed topographic map of the Coal Creek-Butte Creek drainage divide area seen in less detail in figure 3 above. Coal Creek is the unlabeled east-oriented stream flowing along and across the figure 4 north edge. Flaherty Coulee drains in a northeast direction to Coal Creek in the figure 4 northwest quadrant and has an unnamed north-northeast oriented tributary originating near the figure 4 southwest corner. Note southeast-oriented tributaries from the northwest and short northwest-oriented tributaries from the southeast to northeast-oriented Flaherty Coulee (see sections 29, 30, and 32). Also note north oriented Coal Creek tributary valleys east of Flaherty Coulee. Butte Creek flows in an east direction near the figure 4 south edge (east half) to the southeast corner. Study of the Flaherty Coulee-Butte Creek and Coal Creek-Butte Creek drainage divides reveals through valleys linking northwest-oriented Flaherty Coulee and north oriented Coal Creek tributary valleys with east-southeast and southeast oriented Butte Creek tributary valleys. For example near the corner of sections 2, 3, 32, and 32 in the figure 4 west half a well-defined through valley links a north-northwest oriented Flaherty Coulee tributary valley with an east-southeast-oriented Butte Creek tributary valley. The contour interval for this map is ten feet and the through valley floor elevation is between 2900 and 2910 feet. A spot elevation of 2925 feet is located just east of the through valley and elevations greater than 2930 feet can be found nearby. Elevations greater than 3000 feet can be found to the southwest of the through valley. By following the drainage divide across sections 32, 33, and 34 several additional and similar through valleys can be seen. Generally the through valleys are defined by two or three contour lines on each side suggesting they are 20-40 feet deep, at least in a local sense. The multiple through valleys crossing the drainage divide suggest headward erosion of the Butte Creek valley captured multiple southeast-oriented flood flow channels such as might be found in a southeast-oriented anastomosing channel complex. Headward erosion of the Coal Creek-Flaherty Coulee valley next captured the southeast-oriented flood flow channels in sequence from east to west. Flood waters on north ends of beheaded flood flow channels reversed flow direction to erode north- and northwest-oriented Coal Creek and Flaherty Coulee tributary valleys. Because flood flow channels were beheaded one at a time from east to west newly reversed flood flow channels could capture significant flood flow from west of the actively eroding Coal Creek-Flaherty Coulee valley head. Such captures of yet to be beheaded flood flow provided water volumes required to erode significant north- and northwest-oriented tributary valleys and also eroded what are today shallow through valleys crossing drainage divides between Coal Creek and Flaherty Coulee tributary valleys.
Cottonwood Creek-Wolf Creek drainage divide area
Figure 5: Cottonwood Creek-Wolf Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.
- Figure 5 illustrates the Cottonwood Creek-Wolf Creek drainage divide area located south of the figure 3 map area. Cottonwood Creek is the east-northeast oriented stream located in the deep valley in the figure 5 north region and joins the West Poplar River east and north of the figure 5 map area. Note how headward erosion of the deep Cottonwood Creek valley beheaded south-southeast oriented flood flow to what were once several south-southeast oriented Missouri River tributary valleys. The labeled south-southeast oriented streams in those valleys originating in Valley County are the Middle Fork Wolf Creek and the East Fork Wolf Creek. The West Fork Wolf Creek can be seen flowing across the figure 5 southwest corner. South-southeast oriented Tule Creek and North Fork Tule Creek headwaters flow to the figure 5 south edge in Roosevelt County. Well defined through valleys link the south-southeast oriented Middle and East Fork Wolf Creek valleys with the east-northeast oriented Cottonwood Creek valley. A somewhat more subtle through valley east of the Wall Air Field can be seen linking the south-southeast oriented Tule Creek valley with east-northeast oriented Cottonwood Creek valley. The through valleys provide evidence of multiple south-southeast oriented flood flow routes flowing across the figure 5 map area such as might be found in a large south-oriented anastomosing channel complex. The south-southeast oriented flood flow channels were eroding headward from what was at that time the newly eroded Missouri River valley, which had eroded headward from a breach through the ice barrier which was the detached southwest margin of a decaying North American ice sheet. The deep south-southeast oriented Poplar River valley east of the figure 5 map area was eroded headward along such a south-southeast oriented flood flow channel. The deep east-northeast oriented Cottonwood Creek valley then eroded headward from the newly eroded West Poplar River valley to capture south-southeast oriented flood flow west of the actively eroding Poplar River valley. Figure 5 is illustrating where headward erosion of the east-northeast oriented Cottonwood Creek valley beheaded south-southeast oriented flood flow routes to what at that time were actively eroding Tule Creek and Wolf Creek valleys.
Detailed map of Cottonwood Creek-Wolf Creek drainage divide area
Figure 6: Detailed map of Cottonwood Creek-East Fork Wolf Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.
- Figure 6 provides a detailed topographic map of the Cottonwood Creek-East Fork Wolf Creek drainage divide area seen in less detail in figure 5 above. The deep east-northeast oriented Cottonwood Creek valley is seen in the figure 6 north half, with Cottonwood Creek itself being located north of the figure 6 map area. Remember Cottonwood Creek flows to the West Poplar River. The somewhat shallower East Fork Wolf Creek valley extends from the Cottonwood Creek valley south edge in a south-southeast direction to the figure 6 south center edge. The East Fork Wolf Creek flows to Wolf Creek, which then flows to the Missouri River. The map contour interval is 10 feet with some dotted contour lines at 5 foot intervals. The Cottonwood Creek-East Fork Wolf Creek drainage divide elevation in the west half of section 12 (where the south-southeast oriented East Fork Wolf Creek valley begins) is between 2830 and 2840 feet. The Cottonwood Creek valley (directly north of the figure 6 map area) has an elevation of less than 2500 feet, although the lowest elevations cannot be seen in figure 6. Elevations in sections 11 and 12 on either side of the East Fork Wolf Creek valley north end rise to more than 2900 feet. Note also how East Fork Wolf Creek tributaries from the west are oriented in southeast and east directions while the tributary from the east begins as a south-oriented stream also linked to the Cottonwood Creek valley by a shallow through valley. The figure 6 map evidence suggests the deep south-southeast oriented East Fork Wolf Creek valley first eroded headward from the deep and probably newly eroded Missouri River valley along and across south-southeast and southeast oriented flood flow moving on a topographic at least as high as the highest figure 6 elevations today. The deeper east-northeast Cottonwood Creek valley next eroded headward from the newly eroded West Poplar River valley across south-southeast oriented flood flow to behead actively eroding south-southeast oriented Missouri River tributary valleys, such as the south-southeast oriented East Fork Wolf Creek valley. Note how some of the Cottonwood Creek tributaries are oriented in north-northwest directions. These tributary valleys were eroded by reversals of flood flow on north-northwest ends of beheaded south-southeast oriented flood flow routes.
Little Porcupine Creek-Cottonwood Creek drainage divide area
Figure 7: Little Porcupine Creek-Cottonwood Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.
- Figure 7 illustrates the Little Porcupine Creek-Cottonwood Creek drainage divide area west of the figure 5 map area and includes overlap areas with figure 5. Cottonwood Creek originates near the west edge of the figure 7 northeast quadrant and flows in a south direction before turning to flow in an east direction to the figure 7 east center edge. The south-oriented Cottonwood Creek headwaters valley is joined by the valley of a short north oriented tributary, which is linked by a west-oriented through valley to the southeast and southwest-oriented East Fork Little Porcupine Creek valley and also to a north-south oriented through valley to the south-southeast oriented West Fork Wolf Creek valley. The south-southeast oriented stream in the figure 7 southeast quadrant east of the Landing Field is the Middle Fork Wolf Creek while the stream west of the Landing Field is the West Fork Wolf Creek. Note how the south-oriented East Fork Little Porcupine Creek valley segment near the figure 7 north edge (near northwest corner) is linked by a through valley with the south-southeast oriented West Fork Little Porcupine Creek valley and how a second south-southwest oriented through valley just to the east also links the East and West Fork valleys of Little Porcupine Creek. This maze of through valleys illustrates what was once an anastomosing complex of flood flow channels. Initially the figure 7 region was crossed by south-southeast oriented flood flow moving on a topographic surface at least as high as the highest figure 7 elevations today and south-southeast oriented tributary valleys began to erode headward into the figure 7 map area from the newly eroded Missouri River valley (located south of figure 7). Headward erosion of the east and east-northeast oriented Cottonwood Creek valley from the newly eroded West Poplar River valley (east of the figure 7 map area) then entered the figure 7 at probably about the same time as headward erosion of the deep Little Porcupine Creek valley and its southwest-oriented East Fork Little Porcupine Creek valley also entered the region. Apparently enough flood flow was moving to the actively eroding Wolf Creek valley (especially the West Fork) that both the Cottonwood Creek valley and the southwest-oriented East Fork Little Porcupine Creek valley were each able to capture some of the flow. The southeast-oriented East Fork Little Porcupine Creek valley was probably eroded headward from the deep Cottonwood Creek valley and southwest-oriented East Fork Little Porcupine Creek valley intersection to capture south-oriented flood flow moving to the Little Porcupine Creek valley. In the process Cottonwood Creek captured the south-oriented West Fork Wolf Creek headwaters and the deep East Fork Little Porcupine Creek valley beheaded and reversed a segment of the West Fork Wolf Creek flood flow channel to erode a north- and west-oriented East Fork Little Porcupine Creek tributary valley.
Detailed map of East Fork Little Porcupine Creek-Cottonwood Creek drainage divide area
Figure 8: Detailed map of East Fork Little Porcupine Creek-Cottonwood Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.
- Figure 8 provides a detailed map of the East Fork Little Porcupine Creek-Cottonwood Creek drainage divide area seen in less detail in figure 7 above. The East Fork Little Porcupine Creek flows in a southeast direction from the figure 8 northwest corner to the south center of section 34 and then turns to flow in a west direction to the figure 8 west edge (south half). Cottonwood Creek flows in a south direction from the figure 8 north center edge to the section 26 southeast quadrant and then flows in a southeast direction to the south half of section 31 before turning to flow in a northeast direction to the figure 8 east center edge. The south-oriented stream originating near the figure 8 southeast corner is the Middle Fork Wolf Creek and the south-oriented valley originating in section 11 (near figure 8 south center edge) is the West Fork Wolf Creek valley. The highest elevation shown in figure 8 is in section 10 near the south edge and exceeds 2940 feet (the map contour interval is ten feet with some dotted lines at 5 foot intervals). The floor of the drainage divide in through valley linking the East Fork Little Porcupine Creek valley with the Cottonwood Creek valley has an elevation of between 2660 and 2665 feet and both the East Fork Little Porcupine Creek and Cottonwood Creek appear to be flowing in valleys with similar floor elevations. In other words a large flood today in either stream could spill across the drainage divide and reach the other stream. The floor of the drainage divide in the through valley in section 11 linking a north and west-oriented East Fork Little Porcupine Creek tributary and the south-oriented West Fork Wolf Creek headwaters has an elevation of between 2880 and 2890 feet. The drainage divide in the through valley (near the figure 8 southeast corner) linking a north-northwest oriented Cottonwood Creek tributary valley with the south-oriented Middle Fork Wolf Creek valley has an elevation of between 2840 and 2850 feet. Figure 8 evidence suggests headward erosion of the east-oriented Cottonwood Creek valley captured south-oriented flood flow channels moving water to what were then actively eroding Middle Fork and West Fork Wolf Creek valleys and also captured a southeast-oriented flood flow channel moving flood water to the actively eroding West Fork Wolf Creek valley. The west-oriented East Fork Little Porcupine Creek valley segment was probably initiated as an east-oriented Cottonwood Creek valley extension, but was beheaded and reversed west of the figure 8 map area by headward erosion of the southwest-oriented East Fork Little Porcupine Creek valley segment seen in figure 7.
Snow Coulee-East Fork Porcupine Creek drainage divide area
Figure 9: Snow Coulee-East Fork Porcupine Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.
- Figure 9 illustrates the Snow Coulee-Porcupine Creek drainage divide area located west of the figure 7 map area and includes overlap areas with figure 7. Porcupine Creek is formed near the figure 9 west edge (north half) at the confluence of south and southwest-oriented Middle Fork (labeled) and south-southeast East Fork (not labeled) and then flows in a south and south-southeast direction to the figure 9 south edge and is labeled near the south edge. Snow Coulee is a west-southwest oriented Middle Fork tributary seen near the figure 9 north center edge and originates near Opheim (see figure 2) as a south-southeast oriented drainage route before turning to drain in a west-southwest direction to Middle Fork which flows to south-oriented Porcupine Creek. The East Fork Little Porcupine Creek can be seen in the figure 9 northeast corner and further south the south-southeast oriented West Fork Little Porcupine Creek flows to the figure 9 east edge (from north of center to south of center). South of the West Fork Little Porcupine Creek is northeast and southeast-oriented Spring Valley, which drains to Little Porcupine Creek. The East Fork Porcupine Creek begins in the figure 9 northeast quadrant as a south-oriented stream and then turns to flow in a southwest, west, and south-southwest direction to the figure 9 south edge (just west of center). South of the figure 9 map area the East Fork Porcupine Creek joins south-oriented Porcupine Creek, which then flows to the Missouri River. Note how a large north-south oriented through valley, named The Pass, links the southwest-oriented Snow Coulee valley with the south-southwest oriented East Fork Porcupine Creek valley. Except at its north end The Pass through valley is drained in a south direction by an East Fork Porcupine Creek tributary. Figure 9 has a ten meter contour interval and elevations along the drainage divide in The Pass are between 830 and 840 meters with elevations exceeding 900 meters on either side. Note the south-oriented East Fork Porcupine Creek tributary originating just south of the word INDIAN (east of The Pass) and how that tributary originates in a large south-oriented amphitheater shaped basin. That south-oriented amphitheater-shaped basin is an abandoned flood formed head cut, which was eroded by south-oriented flood flow moving to the actively eroding East Fork Porcupine Creek valley prior to headward erosion of the deep The Pass through valley. Headward erosion of The Pass valley and also of the Middle Fork-Snow Coulee valley beheaded south-oriented flood flow routes to the what had been the actively eroding head cut face. Once flood flow to the head cut ceased headward erosion of the south-oriented head cut face also ceased.
Detailed map of Snow Coulee-East Fork Porcupine Creek drainage divide area
Figure 10: Detailed map of Snow Coulee-East Fork Porcupine Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.
- Figure 10 provides a detailed topographic map of The Pass, which is located along the Snow Coulee-East Fork Porcupine Creek drainage divide and which was seen in less detail in figure 9 above. The Pass is a south-southwest and south-southeast oriented through valley linking the southwest-oriented Snow Coulee valley with the south-southwest oriented East Fork Porcupine Creek valley (see figure 9). Snow Coulee drains in a west-southwest direction along the figure 10 northwest corner and eventually drains to south-oriented Porcupine Creek, which is located west of the figure 10 map area. The East Fork Porcupine Creek is located south of the figure 10 map area and also flows to south-oriented Porcupine Creek. The figure 10 map contour interval is 20 feet and the southwest-oriented Snow Coulee floor directly north of The Pass crosses the 2700 foot contour line. The north-south drainage divide in The Pass has an elevation of between 2740 and 2760 feet. Elevations greater than 2960 feet are found on both sides of The Pass, indicating The Pass is at least 200 feet deep. The Pass was one of at least two major south-oriented flood flow channels such as might be found in a south-oriented anastomosing channel complex (the south-oriented Porcupine Creek valley to the west of figure 10 and to which Snow Coulee water eventually drains is the other major flood flow channel). Initially south and south-southeast oriented flood flow moved across the entire figure 10 map area on a topographic surface at least as high as the highest figure 10 elevations today. A large south-oriented head cut began to develop east of The Pass and the rim of that head cut is the drainage divide that can be seen east of The Pass. Note how there are very shallow through valleys (defined by one contour line on a side) eroded across that head cut rim. The Pass developed when a deep valley eroded headward west of the developing south-oriented head cut and then eroded headward across the south-oriented flood flow moving to the actively eroding head cut face. Refer back to figure 2 to see how Snow Coulee has south-southeast oriented headwaters and headwaters today, indicating the west-southwest oriented Snow Coulee valley captured multiple south-southeast oriented flood flow channels. Refer back to figure 9 and note how the south- and southwest-oriented Middle Fork Porcupine Creek valley is located just east of the figure 10 northwest corner. The present day Snow Coulee valley drains to the Middle Fork valley, which then joins West Fork Porcupine to form south-oriented Porcupine Creek, suggesting that for a time the Snow Coulee flood flow channel diverged at the north end of The Pass with one channel continuing to the Middle Fork Porcupine Creek valley while the other channel went south through The Pass to the East Fork Porcupine 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.
Missouri River drainage basin landform origins research project 
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