Origin of North America east-west continental divide, Marias River-Flathead River drainage divide area, Montana, USA

Authors

Abstract:

This essay uses topographic map evidence to interpret landform origins along and near the Montana Marias River-Flathead River drainage divide segment of the east-west continental divide. The Marias River is an east-oriented Missouri River tributary with Missouri River water eventually reaching the Gulf of Mexico. Marias River tributaries including northeast-oriented Birch and Badger Creek and the northwest and northeast-oriented South Fork Two Medicine River originate along the east-west continental divide. Immediately to the west are headwaters of south-oriented tributaries to the northwest-oriented Middle Fork Flathead River, which flows to the south-oriented Flathead River, with water eventually reaching the Pacific Ocean. Deep north-south oriented through valleys (or mountain passes) cross the continental divide and also cross drainage divides between Marias River tributary valleys to the east of the continental and Middle Fork Flathead River tributary valleys to the west of the continental divide. These deep through valleys are interpreted to have originated as flood flow channels in what was once an immense south-oriented anastomosing channel complex, which initially was eroded into a high level erosion surface at least as high as the highest elevations in the Marias River-Flathead River drainage divide area today. Headward erosion of much deeper valleys from both the east and west systematically dismembered the south-oriented flood flow channels by beheading flood flow channels and by causing massive flood flow reversals on north ends of beheaded flood flow channels that eroded north-oriented valleys. Flood waters are interpreted to have been derived from a rapidly melting thick North American ice sheet. The ice sheet is interpreted to have been located in a deep “hole” and the Marias River-Flathead River drainage divide area is interpreted to have been located along the deep “hole’s” west or southwest rim. The deep through valleys crossing drainage divides, including the continental divide, the elbows of capture, and the valley orientations all support this previously ignored flood origin interpretation.

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 origin of the North American east-west continental divide in the Montana Marias River-Flathead River drainage divide region,  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 comment with 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 the origin of the North American east-west continental divide along the Montana Marias River-Flathead River drainage divide region will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm (see link to paradigm related essay at top of page). This essay is included in the Missouri River drainage basin landform origins research project essay collection.

Marias River-Flathead River drainage divide area location map

Figure 1: Marias River-Flathead 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 Montana Marias River-Flathead River drainage divide, which also serves as the North American east-west continental divide. The Canadian border is located north of Montana along the figure 1 north edge and the Montana-Idaho border crosses the figure 1 southwest corner. Glacier National Park is the green shaded area in the figure 1 northwest quadrant. The east-west continental divide extends in a south-southeast direction through Logan Pass and Marias Pass in Glacier National Park and then along or near the Lewis and Clark Range crest to the figure 1 south center edge (west of Helena). With a minor exception just east of Glacier National and near the figure 1 north edge all drainage east of the continental divide flows to the Missouri River, which flows to the Mississippi River, with water eventually reaching the Gulf of Mexico. The northeast oriented St. Mary River (see St. Mary Lake just east of Glacier National Park) is the sole exception with water eventually reaching Hudson Bay. West of the continental divide all drainage eventually flows to the Columbia River, which flows to the Pacific Ocean. The Missouri River flows in a north-northwest direction from the figure 1 south edge (just east of Helena) to Wolf Creek where it turns to flow in a northeast direction to Great Falls, Fort Benton, Loma and the figure 1 east edge (just north of center). East-oriented tributaries from south to north include the Sun River which joins the Missouri River at Great Falls, the Teton River and the Marias River both of which join the Missouri River near Loma, and the northeast, east, and southeast-oriented Milk River, which flows across southern Alberta just north of the figure 1 map area. The Marias River is formed at the confluence of Cut Bank Creek and the Two Medicine River south of Cut Bank, Montana, with Badger Creek and Birch Creek being important northeast- and east-oriented Two Medicine River tributaries. The Flathead River is formed in the region immediately south and west of Glacier National Park and north of Flathead Lake by its south-southeast oriented North Fork, its north-northwest oriented South Fork, and its northwest-oriented Middle Fork, and then flows in a south direction through Flathead Lake before turning to flow in a west direction to join northwest-oriented Clark Fork near Paradise, Montana, with water eventually reaching the Columbia River and Pacific Ocean. The Marias River-Flathead River drainage divide segment that corresponds with the east-west continental divide is located south of Logan Pass and includes Marias Pass and the Middle Fork Flathead River headwaters. Of importance in this essay are headwaters of northeast-oriented Two Medicine River tributaries in the Marias Pass region and also headwaters of northeast-oriented Badger Creek and Birch Creek.
  • The east-west continental divide is one of the best known North American erosional landforms, yet to my knowledge previous to the Missouri River drainage basin landform origins research project its origin has been ignored, with the scientific community adopting an attitude that it somehow magically evolved over long periods of time. I am not aware of any serious scientific studies to determine the east-west continental divide origin. Further I am not aware of serious scientific studies to determine the origin of deep passes which have been eroded across the east-west continental divide, such as Marias Pass which is located in the Marias River-Flathead River drainage divide area. Some of these deep mountain passes, such as Marias Pass, are seen by hundreds of thousands if not millions of people each year, while other deep mountain passes are hidden in the back country, but can easily be seen on topographic maps. Each of these deep mountain passes is evidence of a water eroded valley, which was eroded at a time when water freely flowed across what is now the east-west continental divide. Reconstructions of these water eroded valleys can be done by using topographic map evidence and provide significant clues to what the region looked like prior to the continental divide formation.
  • Topographic map evidence illustrated and described in the hundreds of essays written to date demonstrates the Missouri River drainage basin systematically evolved as deep valleys eroded headward to capture immense south and southeast-oriented melt water floods flowing from a rapidly melting thick North American ice sheet. The topographic map evidence also makes a strong case for a deep “hole” in which the thick ice sheet was located, where the deep “hole” was probably formed by glacial erosion under the ice sheet and by crustal warping caused by the ice sheet’s great weight. The crustal warping raised high mountain ranges and plateau regions in non glaciated regions of the North American continent, including the mountain ranges seen in figure 1. The figure 1 mountain ranges are located along what was the deep “hole’s” west or southwest rim with the Montana and northern Wyoming Missouri River drainage basin being the deeply eroded remains of the deep “hole’s” southwest wall. Initially the thick ice sheet had stood high above the deep “hole’s” rim and immense south and southeast-oriented ice-marginal melt water floods flowed from Canada across western Montana and into Wyoming (and then across Colorado and into New Mexico) along routes corresponding with the crests of present day high Rocky Mountain ranges and roughly corresponding with the present day east-west continental divide. The east-west continental divide was created, from south to north, as deep valleys eroded headward from both the east and the west to capture the immense south and southeast-oriented floods and to divert the flood waters to either the Gulf of Mexico or the Pacific Ocean. Headward erosion of each deep valley beheaded flood flow routes to the newly eroded valley immediately to the south. This pattern can be seen all along the continental divide and is easily documented along Marias River-Flathead River drainage divide segment of the east-west continental divide, which is illustrated and interpreted in this essay. Headward erosion of the Marias River valley and its tributary valleys beheaded flood flow routes to the newly eroded Teton River valley and its actively eroding tributary valleys. Each east-oriented Marias River tributary valley then beheaded flood flow routes to the newly eroded Marias River tributary valley immediately to the south. Numerous mountain passes, some deep and some not so deep, provide evidence flood waters flowed freely across what is now the east-west continental divide. Reconstructions of the flood flow channels demonstrate headward erosion of Marias River tributary valleys captured flood waters moving to the present day Middle Fork Flathead River valley and also demonstrate the massive flood flow reversal responsible for the northwest-oriented Middle Fork Flathead River drainage basin captured flood flow routes to actively eroding Teton and Sun River tributary valleys and on a more limited basis to Marias River tributary valleys.

Detailed location map for Marias River-Flathead River drainage divide area

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

 

  • Figure 2 provides a detailed location map for the Marias River-Flathead River drainage divide segment of the east-west continental divide. Flathead Lake is located in the figure 2 southwest corner. The dark brown shaded area in the figure 2 northwest region is Glacier National Park and the lighter brown shaded area east of Glacier National Park is the Blackfeet Indian Reservation. Green shaded areas are National Forest lands and are generally located in mountain regions. County boundaries are shown and county names are labeled. Glacier County, Pondera County, and Teton County are east of the east-west continental divide and Flathead County, which is directly to the west is west of the continental divide. An exception is a small region near the figure 2 south center edge where a north arm of Lewis and Clark County (not labeled in figure 2) is between the Teton County west boundary and the Flathead County east boundary, with the Flathead County east boundary being the east-west continental divide. The east-west continental divide in summary extends in a south-southeast direction from the figure 2 north edge (west half) along the Glacier County, Pondera County, and Teton County west boundaries to near Mt. Wright and then makes a jog to the southwest to near Kevan Mt. before continuing in a south direction to the figure 2 south center edge. Named passes located and identified on figure 2 along the Marias River-Flathead River drainage divide segment investigated in this essay are Marias Pass, Muskrat Pass, and Badger Pass.
  • Cut Bank, Montana is a town located near the figure 2 northeast corner and east-northeast and southeast oriented Cut Bank Creek flows through Cut Bank. Near the Glacier County southeast corner (south and east of Cut Bank) Cut Bank Creek joins the Two Medicine River to form the east-southeast oriented Marias River, which flows to the figure 2 east edge (north half). The Two Medicine River originates in the southeast corner of Glacier National Park and in the Glacier County and Pondera County regions south and east of Glacier National Park. Major Two Medicine River tributaries include the northwest and northeast-oriented South Fork Two Medicine River, northeast-oriented Badger Creek, and northeast-oriented Birch Creek. West of the continental divide are headwaters of the northwest-oriented Middle Fork Flathead River, which West of West Glacier (a town south of Lake McDonald in figure 2 northwest quadrant) turns to flow in a southwest direction to join other Flathead River forks and to form the south-oriented Flathead River. Bear Creek is the unnamed southwest-oriented tributary flowing from Marias Pass along the Glacier National Park south boundary to join the northwest-oriented Middle Fork Flathead River near Nimrod at the Glacier National Park southern tip.
  • Note how the northwest-oriented Middle Fork Flathead River has a number of south oriented tributaries, which originate along the east-west continental divide. These south-oriented Middle Fork Flathead River tributaries provide evidence of multiple south-oriented flood flow routes from north and east of the east-west continental divide, which flowed across the continental divide initially to what was at that time a major southeast-oriented flood flow channel to the actively eroding south-southeast oriented North Fork Sun River valley (south of the figure 2 map area and also east of the continental divide). The deep Middle Fork Flathead River valley eroded headward after headward erosion of the deep south-oriented Flathead River valley (west of the figure 2 map area) beheaded that major southeast-oriented flood flow channel to the south-southeast oriented North Fork Sun River valley. Flood waters on the northwest end of the beheaded flood flow channel reversed flow direction to erode a deeper northwest-oriented Middle Fork Flathead River valley, which captured what had been converging south-oriented flood flow channels, which had been flowing to the original southeast-oriented flood flow channel. Next headward erosion of the deep Two Medicine River valley and its deep tributary valleys beheaded and reversed at least some of the south- and southeast-oriented flood flow routes to the newly reversed Middle Fork Flathead River while headward erosion of the southwest-oriented Bear Creek valley beheaded and reversed additional south-oriented flood flow channels to create the drainage seen today.

Summit Creek-South Fork Two Medicine River drainage divide area

Figure 3: Summit Creek-South Fork Two Medicine River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

  • Figure 3 illustrates the Summit Creek-South Fork Two Medicine River drainage divide area east of Marias Pass (or Theodore Roosevelt Pass as labeled on the map). The east-west continental divide is labeled and also serves as the Flathead County eastern boundary. The South Fork Two Medicine River flows in a northwest direction from just north of the figure 3 southeast corner to the figure 3 center and then turns to flow in a northeast direction to the figure 3 north edge (just west of the northeast corner). Summit Creek originates on the southeast slope of Little Dog Mountain and flows in a southeast direction toward the location labeled as Summit, but then turns to flow in a northeast direction to join the South Fork Two Medicine River just south of the railroad location labeled False Summit (east of the figure 3 north center edge region). The location labeled Summit is the summit of Marias Pass and the southwest-oriented stream flowing from the Summit region to the figure 3 southwest corner is Bear Creek, which flows to the northwest oriented Middle Fork Flathead River. While figure 3 contains many interesting landforms this essay will focus on the origin of  just two, Marias Pass itself and the northwest- and northeast-oriented South Fork Two Medicine River valley. Both landforms are erosional features and were eroded by running water, although it is possible glacial activity further modified the valleys. The figure 3 map contour interval is 50 meters and the Marias Pass floor elevation at the continental divide appears to be between 1550 and 1600 meters. Elevations along the continental divide near the figure 3 south edge rise to 2250 meters. The continental divide elevation on Little Dog Mountain on the other side of Marias Pass rises to more than 2500 meters. In other words Marias Pass is at least 650 meters deep, which means it was eroded by a major river which once flowed across the present day continental divide. The northwest-oriented South Fork Two Medicine River segment flows in a large northwest-southeast oriented valley, which is more than 300 meters deep (compared to the adjacent mountain ridges). This large northwest-southeast oriented valley was also eroded by a major river.
  • Based on a study of adjacent map areas (some of which are shown below) the figure 3 map area was eroded by immense south and southeast-oriented flood flow, which initially flowed on a high level erosion surface probably as high as the highest figure 3 elevations today and which gradually eroded a network of deep diverging and converging deep south oriented flood flow channels into that high level erosion surface. This process of erosion of deep south-oriented flood flow channels and the subsequent dismembering of these south-oriented flood flow channels as much deeper valleys eroded headward into the region from both east and west was probably aided by significant uplift of the figure 3 region, which occurred as the massive south- and southeast-oriented floods flowed across the rising mountain region. The northwest-oriented South Fork Two Medicine River was initiated as southeast-oriented flood flow channel along the present day northwest-oriented South Fork Two Medicine River alignment. Probably at the same time headward erosion of a southwest-oriented flow channel on the present day Bear Creek valley alignment (from what was initially a southeast-oriented flood flow channel on the present day northwest-oriented Middle Fork Flathead River alignment) occurred along a diverging flood flow channel, which diverged from a south-oriented flood flow channel along the present day highway and railroad alignment in the False Summit region. Other diverging flood flow channel locations can also be seen. Headward erosion of the much deeper south-oriented Flathead River valley (west of figure 3) beheaded the southeast-oriented flood flow channel on the Middle Fork Flathead River alignment and flood waters on the northwest end of the beheaded flood flow channel reversed flow direction to erode a much deeper northwest-oriented Middle Fork Flathead River valley. The knick point from this much deeper Middle Fork Flathead River valley eroded headward along the Bear Creek alignment into the figure 3 southwest quadrant. At about the same time headward erosion of the deep Marias River valley (from the deep Missouri River valley) and its Two Medicine River tributary valley (and northeast-oriented South Fork Medicine River valley segment) beheaded the flood flow channel on the present day northwest-oriented South Fork Two Medicine River alignment. Flood waters on the northwest end of the beheaded flood flow channel reversed flow direction to erode a deeper northwest-oriented South Fork Two Medicine River valley. At the same time the deeper South Fork Two Medicine River valley also beheaded the diverging southwest-oriented flood flow channel to the actively eroding Bear Creek valley. Flood waters on the northeast end of the beheaded flood flow channel reversed flow direction to erode the northeast-oriented Summit Creek valley.

Skyland Creek-Dodge Creek drainage divide area

Figure 4: Skyland Creek-Dodge Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

  • Figure 4 illustrates the Skyland Creek-Dodge Creek drainage divide area west and south of the figure 3 map area and includes overlap areas with figure 3. The east-west continental divide is marked and labeled and extends in a southeast and south direction from the figure 4 north center edge to the figure 4 southeast corner region. Southwest-oriented Bear Creek flows from the figure 4 north center edge to the figure 4 west center edge and its valley is used by both the railroad and the highway in Stevens Canyon en route to Theodore Roosevelt Pass, which is located just north of the figure 4 map area. The northwest-oriented South Fork Two Medicine River can be seen flowing across the figure 4 northeast corner. South-oriented drainage routes flowing the figure 4 south edge flow to the northwest-oriented Middle Fork Flathead River, which is located south of the figure 4 map area. The south oriented stream flowing to the figure 4 south center edge is Granite Creek, which is formed near the figure 4 center by south-oriented Dodge Creek and west and southwest-oriented Challenge Creek. Note how south-oriented Dodge Creek is linked by a through valley with north and northwest oriented Skyland Creek, which flows to southwest-oriented Bear Creek. The Skyland Creek-Dodge Creek through valley is evidence of a southeast and south-oriented flood flow channel that existed prior to headward erosion of the deep Bear Creek valley. Southeast and south-oriented flood waters were probably flowing to what were then southeast and south- oriented flood flow channels in the present day Middle Fork Flathead River headwaters area, which had been captured by headward erosion of the deep Sun River valley. Headward erosion of the south-oriented Flathead River valley west of the figure 4 map area then beheaded the southeast-oriented flood flow on the Middle Fork Flathead River alignment. Flood waters on the northwest end of the beheaded flood flow channel reversed flow direction to erode a deeper northwest-oriented Middle Fork Flathead River valley, which also captured the south-oriented flood flow channels seen in figure 4, which had been supplying flood water to what was then the actively eroding North Fork Sun River valley. The deep northwest-oriented Middle Fork Flathead River valley knick point also eroded headward along the southwest-oriented Bear Creek alignment to erode a much deeper southwest-oriented Bear Creek valley, which beheaded what had been diverging south-oriented flood flow channels. Flood waters on north ends of these diverging south-oriented flood flow channels reversed flow direction to erode north and northwest-oriented Bear Creek tributary valleys and to create the Bear Creek-Middle Fork Flathead River drainage divide.

Detailed map of Skyland Creek-Dodge Creek drainage divide area

Figure 5: Detailed map of Skyland Creek-Dodge Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

  • Figure 5 provides a detailed topographic map of the Skyland Creek-Dodge Creek drainage divide area seen in less detail in figure 4 above. Dodge Creek originates in section 19 (near figure 5 center) and flows in a south-southeast direction to the figure 5 south edge. South of the figure 5 map area Dodge Creek joins west and southwest-oriented Challenge Creek (which flows across the figure 5 southeast corner) to form south-oriented Granite Creek, which flows to the northwest-oriented Middle Fork Flathead River. A north-oriented tributary to the West Fork Skyland Creek originates near the east center edge of section 24 and flows to the northwest- and north-oriented West Fork Skyland Creek, which joins west-northwest and northwest oriented Skyland Creek (which can be seen flowing across the figure 5 northeast quadrant). Note how the north-oriented West Fork Skyland Creek tributary valley is linked by a deep through valley with the Dodge Creek headwaters valley. The figure 5 map contour interval is 40 feet and the through valley floor elevation at the drainage divide is between 5560 and 5600 feet (a spot elevation of 5583 feet is shown). Elevations in the section 16 southwest corner to the east rise to 6680 feet while an elevation of 6914 feet is found near the south edge of section 24 to the west. In other words the through valley is at least 1080 feet deep and could be even deeper (much higher elevations can be found by looking both east and west of the figure 5 map area). A second higher level through valley can be seen in the section 19 northeast quadrant and links the northwest-oriented West Fork Skyland Creek headwaters valley with the south-southeast oriented Dodge Creek valley. This second through valley has a floor elevation of between 5840 and 5880 feet at the drainage divide. This second through valley provides evidence of diverging and converging flood flow channels and also adds to evidence that flood waters eroded the much deeper first through valley. Study of the figure 5 map area reveals many higher level through valleys crossing other drainage divides. For example near the north center edge of section 20 in the figure 5 northeast quadrant a through valley crosses the drainage divide between the west-northwest oriented Skyland Creek valley and the valley of a west- and south-oriented Challenge Creek tributary. The floor elevation of this through valley at the drainage divide is between 6240 and 6280 feet. A hill to the east rises to 6680 feet while the hill immediately to the east rises to 6480 feet, although much higher elevations are found in the figure 5 west half. The numerous north-south oriented through valleys found in figure 5 provide evidence of multiple diverging and converging south-oriented flood flow channels, such as might be found in a large-scale south-oriented anastomosing channel complex. Initially the flood waters flowed on a high level erosion surface at least as high as the highest figure 5 elevations today. Headward erosion of deep valleys into the region from both east and west probably combined with mountain uplift systematically dismembered the south-oriented flood flow channels by beheading diverging flood flow channels and causing reversals of flood flow on north ends of the beheaded channels.

South Fork Two Medicine River-Badger Creek drainage divide area

Figure 6: South Fork Two Medicine River-Badger Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

  • Figure 6 illustrates the South Fork Two Medicine River-Badger Creek drainage divide area east of the figure 4 map area and includes overlap areas with figure 4. The east-west continental divide is marked and labeled and extends in a southeast and south direction from the figure 6 west edge (north half) to the figure 6 south edge (west half). The South Fork Two Medicine River originates north of the figure 6 center and flows in a south direction to enter its large northwest-oriented valley near the figure 6 center and then flows in a northwest direction to the figure 6 west edge (just south of northwest corner). The north-northeast oriented stream originating near the figure 6 south edge, just east of the continental divide, is North Badger Creek. Note how North Badger Creek appears to be flowing toward the northwest-oriented South Fork Two Medicine River, but upon entering the large northwest-oriented South Fork Two Medicine River valley North Badger Creek turns to flow in a southeast direction to join north-oriented South Badger Creek and north-northwest oriented Lonesome Creek to form north-northeast oriented Badger Creek, which then flows to the figure 6 north edge (just west of northeast corner). The South Fork Two Medicine River-North Badger Creek through valley near the figure 6 center provides an excellent example of how a major southeast-oriented flood flow channel was dismembered. As previously noted the northwest-oriented South Fork Two Medicine River valley was initiated as a southeast-oriented flood flow channel, which split in the figure 6 southeast quadrant with two of the diverging channels being a south-oriented flood flow channel on the present day north-oriented South Badger Creek alignment and a south-southeast oriented flood flow channel on the present day north-northwest oriented Lonesome Creek alignment (probably there were other diverging flood flow channels, but these two are listed for illustrative purposes). Headward erosion of the much deeper north-northeast oriented Badger Creek valley captured the southeast-oriented flood flow and beheaded flood flow channels on the South Badger Creek and Lonesome Creek alignments. Flood waters on north ends of the beheaded flood flow channels reversed flow direction to erode deeper and north-oriented South Badger Creek and north-northwest oriented Lonesome Creek valleys. Next headward erosion of the deeper Two Medicine River valley north of the figure 6 map area beheaded the southeast-oriented flood flow moving to the newly eroded north-northeast oriented Badger Creek valley. Flood waters on the northwest end of the beheaded flood flow channel reversed flow direction to erode a deeper northwest-oriented South Fork Two Medicine River valley.

Detailed map of South Fork Two Medicine River-North Badger Creek drainage divide area

Figure 7: Detailed map of South Fork Two Medicine River-North Badger Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

  • Figure 7 provides a detailed topographic map of the South Fork Two Medicine River-North Badger Creek drainage divide area seen in less detail in figure 6 above. Whiterock Creek flows in a south-southwest direction from the figure 7 north edge (just east of center) to section 16 where it enters a large northwest-southeast oriented through valley extending across the figure 7 map area. In section 16 Whiterock Creek turns to flow in a northwest direction as the South Fork Two Medicine River which flows to the figure 7 north edge (near the figure 7 northwest corner). Note in section 21 (directly south of section 16) a north-northeast, east, southeast, and east-southeast stream which flows near the Badger Guard Station in section 22. That stream which joins north-northeast and southeast oriented North Badger Creek in the section 23 southeast quadrant. Returning to section 16 note how the North Badger Creek tributary valley is linked by a large northwest-southeast oriented through valley with the northwest-oriented South Fork Two Medicine River valley. The figure 7 contour interval is 40 feet and there are no contour lines indicating a rise in elevation between the northwest-oriented South Fork Two Medicine River channel and the southeast-oriented North Badger Creek tributary channel, although further to the southeast the North Badger tributary enters what is a much deeper southeast-oriented North Badger Creek valley. How did this large northwest-southeast oriented through valley form? As previously stated the large northwest-southeast oriented through valley extending across the figure 7 map area was initiated as southeast-oriented flood flow channel, which had multiple diverging and converging flood flow channels, although the major flood flow was in a southeast direction from the figure 7 north edge (west half) to the figure 7 east edge (south half). Figures 8 and 9 below show where the water was initially going. Headward erosion of what was then a much deeper north-northeast oriented Badger Creek valley (east of the figure 7 map area) captured the southeast-oriented flood flow and the deep Badger Creek valley knick point began to erode headward along the large southeast-oriented flood flow channel. Headward erosion of the still deeper Two Medicine River valley north of the figure 7 map area beheaded the large southeast-oriented flood flow channel and flood waters on the northwest end of the beheaded flood flow channel reversed flow direction to erode a deeper northwest-oriented South Fork Two Medicine River valley and to create the South Fork Two Medicine River-North Fork Badger Creek drainage divide. Apparently at that time there were still large volumes of flood water flowing at high elevations (relative to valley floors in figure 7) west and south of the figure 7 (and the east-west continental divide) and some of that flood water was captured by the north-northeast oriented North Badger Creek valley, which was then deeply eroded by the captured north-northeast oriented flood flow which moved in a north direction to the deep southeast-oriented North Badger Creek valley, which led to the north-northeast oriented Badger Creek valley.

Muskrat Creek-Cox Creek drainage divide area

Figure 8: Muskrat Creek-Cox Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

  • Figure 8 illustrates the Muskrat Creek-Cox Creek drainage divide area south of the figure 6 map area and includes a small overlap region with figure 6. The east-west continental divide is marked and labeled (and also serves as the Flathead County eastern and northern boundary) and extends in a south, east-southeast, and south-southeast direction from the figure 8 north edge (near northwest corner) to the figure 8 southeast corner. Beaver Lake is a small lake located just south of the continental divide in the region east of the figure 8 center. The southwest, south, and southwest oriented stream flowing from Beaver Lake is Cox Creek which joins the west and northwest oriented Middle Fork Flathead River just west of the figure 8 south center edge area. North of Beaver Lake is a deep north-south oriented through valley across the continental divide (Muskrat Pass, not labeled in figure 8) and the northwest-oriented stream north of Muskrat Pass is Muskrat Creek. Muskrat Creek flows to northeast-oriented Elbow Creek, which joins north-oriented South Badger near the figure 8 north center edge. East of Muskrat Pass the northwest-oriented South Badger Creek headwaters are linked by another deep north-south oriented through valley across the continental Divide (Badger Pass, also not labeled in figure 8) with headwaters of south-oriented Strawberry Creek, which flows to figure 8 south edge. South of figure 8 Strawberry Creek makes a U-turn to join the north-oriented Middle Fork Flathead River, which then flows into the figure 8 southwest quadrant where it flows in a west and northwest direction. As seen in figure 6 northwest- and north-oriented South Badger Creek joins southeast-oriented North Badger Creek to form north-northeast oriented Badger Creek, which flows to the Two Medicine River with water eventually reaching the Gulf of Mexico. Also as described in the figure 6 discussion the southeast-oriented North Badger Creek valley segment was initiated as a southeast-oriented flood flow channel which split into several diverging south-oriented flood flow channels, including the a south-oriented flood flow channel on the South Badger Creek alignment. That south-oriented diverging flood flow channel then split just south of the figure 8 north center edge with one flood flow channel continuing in a southeast direction to a south-oriented flood flow channel on the Strawberry Creek alignment while the other flood flow channel used the Elbow Creek-Muskrat Creek alignment to reach the south- and west-oriented Cox Creek flood flow channel alignment. In other words figure 8 is showing where south-oriented flood flow from north of the continental divide was flowing across the present day continental divide to enter south-oriented Middle Fork Flathead River tributary valleys. Prior to capture of the south-oriented flood flow by headward erosion of the deep northwest-oriented Middle Fork Flathead River valley the south-oriented flood flow moved back across the continental divide (south of the figure 8 map area at Sun River Pass and other passes) to enter what were then actively eroding Sun River and Teton River tributary valleys. Note in the figure 8 southeast corner the words ” Big River Meadows”, which will be seen again near Gateway Pass in figure 10.

Detailed map of Muskrat Creek-Cox Creek drainage divide area

Figure 9: Detailed map of Muskrat Creek-Cox Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

  • Figure 9 provides a detailed topographic map of the Muskrat Creek-Cox Creek drainage divide area at Muskrat Pass and also of the South Badger Creek-Strawberry Creek drainage divide area at Badger Pass, both of which were seen in less detail in figure 8 above. The east-west continental divide appears in figure 9 to be a north-south drainage divide, but is well-marked and labeled as it extends from the figure 9 west center edge to the figure 9 east edge (south half). The figure 9 map area north of the continental divide drains today to the Marias River and eventually the Gulf of Mexico. The figure 9 map area south of the continental divide today drains to the northwest-oriented Middle Fork Flathead River and eventually to the Pacific Ocean. Muskrat Pass is located north and west of Beaver Lake and is labeled on figure 9. Muskrat Creek flows in a northwest direction from Muskrat Pass and as seen in figure 8 joins northeast-oriented Elbow Creek, which then joins north-oriented South Badger Creek. Cox Creek flows in a southwest direction from Beaver Lake. The figure 9 contour interval is 40 feet and the Muskrat Pass elevation at the continental divide is shown as being 5974 feet. Just to the northeast of Muskrat Pass the continental divide reaches an elevation of 7172 feet while to the west the continental divide reaches an elevation of 7375 feet. In other words is a deep north-south oriented through valley is at least 1200 feet deep and provides evidence of a major water eroded valley. To the southeast, but also on the continental divide, is Badger Pass which has a somewhat higher valley floor elevation at the continental divide of between 6240 and 6280 feet. North of Badger Pass are northeast-oriented South Badger Creek headwaters while south of Badger Pass are south-oriented Strawberry Creek headwaters. While not as deep as Muskrat Pass the Badger Pass through valley is also a significant north-south through valley. In section 32 near the figure 9 center is another unlabeled west to east oriented through valley also crossing the continental divide. The floor of this west to east oriented through valley also has an elevation of between 6240 and 6280 feet at the continental divide. These three deep through valleys crossing the continental divide in figure 9 provide evidence of what were once diverging and converging south-oriented flood flow channels in what was at that time a much larger south-oriented anastomosing channel complex. Headward erosion of a deeper valley along the Cox Creek valley from what was probably the actively eroding (and reversed) northwest-oriented Middle Fork Flathead River valley eroded a deeper valley at Muskrat Pass, which beheaded the diverging east-oriented flood flow channel to the Badger Pass through valley. Next the south-oriented flood flow channels in figure 9 were dismembered when headward erosion of the deep northeast-oriented Badger Creek valley north of the figure 9 map area beheaded the south-oriented flood flow channels and flood waters on the north ends of the beheaded flood flow channels reversed flow direction to erode the north-oriented Muskrat Creek and South-Badger Creek valleys.

Detailed map of Gateway Creek-South Fork Birch Creek drainage divide area

Figure 10: Detailed map of Gateway Creek-South Fork Birch 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 area just south and east of the words “Big River Meadows” in the figure 8 southeast corner. The east-west continental divide is both marked and labeled and extends from the figure 10 north center edge to the figure 10 southeast corner. Note the word “Meadows” near the figure 10 north edge (west half), which is identifying the Big River Meadows area seen in figure 8. Big River Meadows is located along the north side of northwest and southwest-oriented Gateway Creek, which flows from Gateway Pass (across the continental divide) to the figure 10 north edge and then to the figure 10 west edge (north half). West of figure 10 Gateway Creek flows to south-oriented Strawberry Creek, which today makes a U-turn to join the northwest-oriented Middle Fork Flathead River with water eventually reaching the Pacific Ocean. South of the Strawberry Creek U-turn is a large north-south oriented through valley leading to Sun River Pass (across the continental divide) and then to the south-oriented North Fork Sun River where water eventually reaches the Gulf of Mexico. The southeast-oriented stream originating on the south side of Gateway Pass flows to northeast-oriented South Fork Birch Creek with water eventually reaching Birch Creek, the Marias River, and the Gulf of Mexico. My Creek is a north-northeast oriented South Fork Birch Creek tributary originating just north of the continental divide in section 5. Note how south of the My Creek headwaters there is a well-defined through valley linking the north-oriented My Creek valley with a south-oriented stream valley. That south-oriented stream flows to west-southwest oriented Trail Creek, which today flows to Strawberry Creek. Note also in the section 5 northwest quadrant a through valley linking the southeast-oriented stream valley (from Gateway Pass) with the north-northeast My Creek valley, but more importantly with the north-south oriented through valley across the continental divide in section 5. What has happened is the deep northeast-oriented South Fork Birch Creek valley has eroded headward to capture the southeast-oriented flood flow channel that initiated the northwest-southeast oriented Gateway Pass through valley (at that time the flood flow channel floor had an elevation comparable to the through valley floor elevation in the section 5 northwest quadrant). That southeast-oriented flood flow channel on the Gateway Pass through valley alignment had converged in section 5 with a south-southwest oriented flood flow channel on the My Creek alignment. Southeast-oriented flood flow from north and west of the figure 10 map area then eroded the deep northeast-oriented South Fork Birch Creek valley and the knick point eroded headward across Gateway Pass to what is now the Gateway Creek valley, but was unable to behead a deeper southwest-oriented flood flow channel on the present day southwest-oriented Gateway Creek alignment. Interpreting the flood flow movements is complex and I have only provided a few examples to illustrate how interpretation needs to be done, but I hope the examples demonstrate how massive floods once flowed along and across the east-west continental divide in this Marias River-Flathead River drainage divide area.

Additional information and sources of maps studied

This essay has provided only a sample of the detailed topographic map evidence supporting the flood erosion interpretation. Many additional illustrations could be provided. Readers are encouraged to look at mosaics of detailed topographic maps to see the abundance of available data. Maps used in this study were created and published by the United States Geologic Survey and can be obtained directly from the United States Geological Survey and/or from dealers offering United States Geological Survey maps. Hard copy maps can also be observed at United States Geological Survey map depositories, which are located throughout the United States and elsewhere. Illustrations used here were created using National Geographic Society TOPO software and digital map data. TOPO software and map data can be obtained from the National Geographic Society and/or dealers offering National Geographic Society digital map data.

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