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.

• The purpose of this essay is to use topographic map interpretation methods to explore the Smith River-Belt Creek drainage divide area landform origins north of Little Belt Mountains, 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 making 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 Smith River-Belt Creek drainage divide area landform evidence north of the Little Belt Mountains, Montana will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm (see essay listed at header). This essay is included in the Missouri River drainage basin landform origins research project essay collection.

Figure 1: Smith River-Belt 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 location map for the Smith River-Belt Creek drainage divide area north of the Little Belt Mountains and illustrates a region in central Montana. The green shaded area straddling the figure 1 northwest corner is Glacier National Park. The east-west continental divide extends in a south-southeast direction from Glacier National Park along or near the Lewis and Clark Range crest to the figure 1 south edge (west of Helena). The Big Belt Mountains are oriented in a north-northwest to south-southeast direction just north of the figure 1 south center edge. The Little Belt Mountains are also labeled and are located in the figure 1 southeast quadrant east of the Big Belt Mountains. The Missouri River flows in a north-northwest direction along the west side of the Big Belt Mountains from the figure 1 south center edge to near Wolf Creek and then turns to flow in a northeast direction to Great Falls, Fort Benton, Loma, and a short distance beyond. South of the town of Big Sandy the Missouri River turns abruptly to flow in a south-southeast and east direction to the figure 1 east edge (north of center). The Smith River flows in a north-northwest direction along the Big Belt Mountain east side (and west of the Little Belt Mountains) to join the northeast-oriented Missouri River a short distance upstream from Great Falls. Note other unlabeled north and north-northwest tributaries flowing to the northeast-oriented Missouri River segment. The unlabeled north- and northwest-oriented stream originating in the Little Belt Mountains and flowing through the town of Belt (east of Great Falls), before reaching the Missouri River, is Belt Creek. The Smith River-Belt Creek drainage divide area north of the Little Belt Mountains investigated in this essay is located east of the Smith River, west of Belt Creek, south of Missouri River, and north of the Little Belt Mountains. The Smith River-Belt Creek drainage divide area landform origins, Little Belt Mountains essay illustrates and describes topographic map evidence in the region directly to the south. Links to other Smith River drainage divide area essays can be found by selecting Smith River from this essay’s sidebar category list.

• The Smith River-Belt Creek drainage divide area north of the Little Belt Mountains is today a region drained by north-oriented streams and generally has a north-oriented slope, which begins in the high Little Belt Mountains. That north-oriented slope and the high Little Belt Mountains did not exist at the time valleys for figure 1 rivers and streams were being eroded, but was evolving as those valleys were being eroded. At that time immense south and southeast-oriented floods were flowing across the figure 1 map area and deeply eroding the entire figure 1 map area. The flood waters were derived from a rapidly melting thick North American ice sheet located in a deep “hole.” The Montana and northern Wyoming Missouri River drainage basin is the deep “hole’s” deeply eroded southwest wall. Flood waters reaching the Smith River-Belt Creek drainage divide area north of the Little Belt Mountain were flowing from the deep “hole’s” western rim located along the crest of the present day Canadian Rockies in western Alberta and eastern British Columbia. The deep “hole” did not exist when the ice sheet first formed, but was created by deep glacial erosion (under the ice sheet) and by crustal warping caused by the ice sheet’s tremendous weight. Crustal warping raised mountain ranges and high plateau area throughout non glaciated areas of the North American continent, but most important to this essay raised mountain ranges along the deep “hole’s” western and southwest rim as immense south and southeast-oriented ice-marginal floods flowed across them. Based on today’s topography the idea that the Smith River-Belt Creek drainage divide area north of the Little Belt Mountains was eroded by massive south and southeast-oriented floods may appear intuitively wrong because massive flood flow reversals were responsible for erosion of the north and north-northwest oriented Missouri River tributary valleys, including the Smith River and Belt Creek valleys.

• For much its early history the thick North American ice sheet stood high above its western and southwestern rims and immense south and southeast oriented ice marginal floods flowed across Montana and Wyoming into Colorado and even New Mexico. However, as time passed ice sheet related crustal warping raised the Rocky Mountains and other areas while deep east and west-oriented valleys eroded headward to capture (in sequence from south to north) the massive south and southeast oriented flood flow. Eventually a combination of Rocky Mountain uplift and of ice sheet melting created a situation where a different melt water flood flow pattern began to evolve. Ice sheet melting lowered the ice sheet surface (especially near the ice sheet’s southern margin) while at the same time Rocky Mountain uplift was blocking the south and southeast-oriented flood flow routes. Most important to upper Missouri River drainage basin development in Montana and northern Wyoming was a large southeast- and south-oriented ice-walled canyon being carved by an immense southeast- and south-oriented supra-glacial meltwater river into the decaying ice sheet’s surface in present day Saskatchewan, North Dakota, and South Dakota. Over time that giant ice-walled canyon became an ice-walled and bedrock-floored canyon and detached the ice sheet’s southwest margin. Today the northeast and east-facing Missouri Escarpment in Saskatchewan, North Dakota, and South Dakota is what remains of that giant canyon’s southwest and west wall.

• Huge northeast and east-oriented valleys eroded headward from that giant southeast and south oriented ice-walled canyon into Montana and northern Wyoming to capture the immense south and southeast-oriented ice-marginal melt water floods flowing across what were rising mountain regions. The deep valleys eroded headward in sequence from the southeast to the northwest, with the deep Missouri River valley being one of those large valleys. The northeast-oriented Missouri River valley segment that eroded headward across the figure 1 map area was much deeper than the anastomosing south and southeast-oriented flood flow channels which were moving the south and southeast-oriented ice-marginal floods across the region (probably on a high level erosion surface now preserved, if it is preserved at all, in the highest figure 1 mountain regions). Flood waters on north ends of the beheaded flood flow channels reversed flow direction to erode what are today north and northwest-oriented Missouri River tributary valleys including the north and north-northwest oriented Belt Creek and Smith River valleys. Headward erosion of the deep Missouri River valley beheaded and reversed the south and southeast-oriented flood flow channels in sequence from east to west, which meant a newly beheaded and reversed flood flow channel could capture south- and southeast-oriented flood flow from flood flow channels west of the actively eroding Missouri River valley head. Such captures of flood flow eroded east-oriented valleys and supplied the water volumes required to erode deep north-oriented valleys. As the deep Missouri River valley eroded headward across the figure 1 region the Little Belt Mountains were also being uplifted, which further aided in the flood flow reversal process, although very deep flood water erosion was also lowering regions surrounding the present day Little Belt Mountains.

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

 

. 

Focusing now on the Smith River-Belt Creek drainage divide area north of the Little Belt Mountains figure 2 provides a more detailed location map. Green shaded areas are National Forest lands and are generally located in mountainous areas. The green shaded area along the figure 2 south edge is the Little Belt Mountains region while the smaller green shaded area in the figure 2 northeast quadrant is the Highwood Mountains area. The Missouri River flows in a northeast direction from the figure 2 west edge (south half) to the figure 2 north center edge. The Smith River flows in a north and north-northwest direction from the figure 2 south edge (along west of edge of the green shaded area) to join the Missouri River upstream from Great Falls. Belt Creek flows in a north-northwest and north direction from the figure 2 south edge (east half, near red highway) to the towns of Monarch, Armington, and Belt before turning to flow in a northwest direction to join the Missouri River near the figure 2 north center edge. Between the Smith River and Belt Creek are several other named streams. Ming Coulee is a north-northwest and west oriented Smith River tributary joining the Smith River at the west end of Ming Coulee Ridge. East of Ming Coulee is north- and west-oriented Sand Coulee Creek, which flows to the towns of Centerville and Tracy before turning to flow in a west direction to join the Missouri River. Between Sand Coulee Creek and Belt Creek is north-, northwest, and north oriented Box Elder Creek, which joins the Missouri River downstream from Great Falls. Most other streams in the study region are unnamed, but are generally oriented in north, northwest, and west directions. Almost every stream in the study region south and east of the Missouri River and north and west of the Little Belt Mountains is flowing in a valley eroded by reversed flood flow in what had originally been south oriented flood flow channels, with the massive flood flow reversed by headward erosion of a very deep northeast-oriented Missouri River valley and by uplift of the Little Belt Mountains (which was occurring as flood waters flowed across the region). North and east of the northeast-oriented Missouri River a different drainage pattern can be seen. The east-oriented river joining the Missouri River at Great Falls is the Sun River. The deep east-oriented Sun River valley eroded headward from the newly eroded and deep Missouri River valley to capture south- and southeast-oriented flood flow, which was moving to the newly eroded Missouri River valley to the south. Essays illustrating and describing Sun River drainage basin drainage divide areas can be found by selecting Sun River from this essay’s sidebar category list.

Figure 3: Missouri River-Red Coulee drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

Figure 3 illustrates the Missouri River-Red Coulee drainage divide area south and east of Great Falls, Montana. The Missouri River flows in a north direction from the figure 3 southwest corner to near the figure 3 west center edge and then turns to flow in an east-northeast direction to the figure 3 north edge (west half). Sand Coulee Creek is the north and west-oriented Missouri River tributary flowing from the figure 3 south edge (near town of Tracy, just west of center). Antelope Coulee is a west-northwest and west oriented Sand Coulee Creek tributary. Also note how east of Malmstrom Air Force Base there is a meandering north-south oriented through valley linking the Missouri River valley and the north-oriented Sand Coulee Creek valley. Box Elder Creek is the north, west, northwest, north, northwest, and north oriented tributary joining the Missouri River just south of the figure 3 north center edge. Note how northwest oriented segments of Box Elder Creek have north-oriented tributaries. Belt Creek is the northwest-oriented tributary flowing across the figure 3 northeast corner and joining the Missouri River as a barbed tributary just north of the figure 3 map area. Note how Belt Creek also has north-oriented tributaries. Red Coulee is the north-oriented Belt Creek tributary near the figure 3 east edge. While north-oriented drainage routes predominate south of the Missouri River the north-oriented tributary valleys were eroded by reversals of flood flow on north ends of beheaded south-oriented flood flow channels, although today there is a gradual north-oriented slope toward the Missouri River valley and based simply on figure 3 map evidence the north-oriented valleys could reasonably be said to have been eroded by streams simply flowing down that slope. The north-oriented Missouri River valley segment along the figure 3 west edge was eroded by a reversal of flow on the north end of a south-oriented flood flow channel beheaded by headward erosion of the much deeper east-northeast oriented Missouri River valley, although that flood flow reversal may have occurred after events responsible for reversals of flood flow on north-oriented Missouri River tributary valleys, which extend further to the south. There appears to be evidence for an earlier Missouri River valley in the form of the meandering north-south oriented through valley east of Malmstrom Air Force Base, which links the present day Missouri River valley with the west-oriented Sand Coulee Creek valley. Apparently at one time at least some of the Missouri River water flowed in an east direction from the figure 3 southwest corner along the present day west-oriented Sand Coulee Creek valley to Johnson Flats and then in a north direction in the abandoned valley east of Malmstrom Air Force Base. Headward erosion of the more direct and deeper east-northeast oriented Missouri River valley through Great Falls beheaded and reversed a south-oriented flood flow channel moving flood water to that earlier Missouri River valley. The reversed flood flow captured the Missouri River, which caused a reversal of flood flow in the Sand Coulee Creek valley to erode the present day west-oriented Sand Coulee Creek valley.

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

 

Figure 4 provides a reduction of a more detailed topographic map of the Missouri River-Sand Coulee Creek drainage divide area which was seen in less detail in figure 3 above. The Missouri River flows in an east-northeast direction in the figure 4 northwest corner. Box Elder Creek is north, west, and north-oriented stream near the figure 4 east edge. Sand Coulee Creek flows in a north direction to the figure 4 south center edge (south of Johnson Flats) and then turns to flow in a west direction in a large valley along the figure 4 south edge to the southwest corner. Gibson Flats is located in what was at one time a large incised meander, which had been eroded by a much larger river than the present day Sand Coulee Creek. Johnson Flats, just north of the present day Sand Coulee Creek elbow of capture (where Sand Coulee Creek turns from flowing in a north direction to flowing in a west direction) is located in a large valley, which also provides evidence of erosion by a large river. North of Johnson Flats is a meandering north-oriented valley, which extends to the figure 4 north edge and the Missouri River valley north of the figure 4 map area. The meandering north-oriented valley could logically be considered to be a northward extension of the north-oriented Sand Coulee Creek valley, although there is no evidence of similar Sand Coulee Creek meanders south of the figure 4 map area. The meandering valley is eroded into what is today a north-northwest oriented slope leading to the east-northeast oriented Missouri River valley. While several different interpretations are possible it appears as though for a time at least some of the Missouri River flowed in an east direction along the present day west-oriented Sand Coulee Creek valley alignment and eroded the Gibson Flats incised meander as it flowed eastward to join the north-oriented Sand Coulee Creek in the Johnson Flats area. At least for a time flood waters were flowing along this route and along the present day Missouri River alignment, which as previously mentioned had developed as a result of a reversal of south-oriented flood flow west of the figure 4 map area. Headward erosion of the deep north-oriented Missouri River valley segment west of figure 4 beheaded and reversed flow to create the present day west-oriented Sand Coulee Creek valley and to capture the north-oriented Sand Coulee Creek segment upstream from figure 4. This reversal of flood flow and the resulting capture ended north-oriented flow in the meandering valley north of Johnson Flats.

Figure 5: Sand Coulee Creek-Belt Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

Figure 5 illustrates the Sand Coulee Creek-Belt Creek drainage divide area south and slightly east of the figure 3 map area and includes overlap areas with figure 3. Belt Creek flows in a north direction near the figure 5 east edge. West and northwest-oriented Belt Creek tributaries can be seen between Belt Creek and the figure 5 east edge. Sand Coulee Creek flows in a north-northwest direction from the figure 5 south edge (west half) to Tracy and then in a north direction to the south edge of Johnson Flats where it turns to flow in a west direction to the figure 5 west edge (north half). Antelope Coulee is a west-northwest oriented tributary to the west-oriented Sand Coulee Creek segment and has at least two north-oriented tributaries. Several north and north-northeast oriented Sand Coulee Creek tributaries can be seen near the figure 5 west edge. Between north-oriented Sand Coulee Creek and north-oriented Belt Creek is Box Elder Creek, which flows in a north-northeast, west, north-northwest, west, and north direction from the figure 5 south edge (just east of center) to the figure 5 north edge (west of center). Spring Creek is a north-oriented Box Elder Creek tributary flowing from the figure 5 south center edge and Shellrock Creek is a north-northeast oriented Box Elder Creek tributary just west of Spring Creek. The figure 5 map contour interval is 50 meters and a north-oriented slope is visible. Based on the figure 5 map evidence figure 5 shows north-oriented streams flowing down a north-oriented slope, although with a more detailed contour interval the picture becomes somewhat different. What are today north-oriented valleys originated as south-oriented flood flow channels and were beheaded and reversed by headward erosion of the much deeper northeast-oriented Missouri River valley, probably at a time when crustal warping was raising the Little Belt Mountains to the south. Headward erosion of the deep Missouri River valley beheaded and reversed the south-oriented flood flow channels one channel at a time (from east to west). In other words south-oriented flood flow on the Belt Creek alignment was beheaded and reversed before flood flow on the Box Elder Creek was beheaded and reversed, which occurred before flood flow on the Sand Coulee Creek alignment was beheaded and reversed. Reversed flood flow on the newly beheaded Belt Creek alignment captured yet to be beheaded flood flow on the Box Elder Creek alignment. When flood flow on the Box Elder Creek alignment was beheaded and reversed it captured yet to be beheaded and reversed flood flow on the Sand Coulee Creek alignment. Evidence for such captures can be seen on more detailed topographic maps and also further south along the drainage divides.

Figure 6: Detailed map of Sand Coulee Creek-Box Elder 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 Sand Coulee Creek-Box Elder Creek drainage divide area seen in less detail in figure 5 above. Tracy is the small town near the figure 6 southwest corner. Sand Coulee Creek flows in a north direction from Tracy to the figure 6 northwest corner region and then turns at the south end of Johnson Flats to flow in a west direction to the figure 6 west edge. Antelope Coulee is the north and northwest tributary flowing from near the figure 6 south center edge to join Sand Coulee Creek near the figure 6 northwest corner. Box Elder Creek flows in a north direction (with a short jog to the west near the southeast corner) from the figure 6 southeast corner almost to the figure 6 north edge and then turns to flow in a west direction to the figure 6 north center edge before turning to flow in a north direction again. Note in section 33 (in figure 6 northwest quadrant) two through valleys linking north-northeast oriented Box Elder Creek tributary valleys with the northwest-oriented Antelope Coulee valley. The figure 6 map contour interval is 20 feet and the eastern through valleys is defined by three contour lines on the west and more on the east, suggesting it is at least 40 feet and probably deeper. The through valleys provide evidence of north-northeast oriented flood flow routes to the north-oriented Box Elder Creek valley prior to headward erosion of the deep northwest-oriented Antelope Coulee valley. Some of this north-northeast oriented flood flow could have been captured south-oriented flood flow from a south-oriented flood flow channel on the present day north-oriented Missouri River segment west of the figure 6 map area. The captured flood flow moved in an east direction to Johnson Flats with some of the flood water then moving in a southeast direction along the Antelope Coulee alignment and then in a north-northeast direction to the newly beheaded and reversed Box Elder Creek flood flow channel. Evidence of additional captures of such east and southeast-oriented flood flow can be seen in shallow through valleys near the corner of sections 2, 3, 10 and 11 along the Antelope Coulee-Box Elder Creek drainage divide further to the southeast. A west-oriented Antelope Coulee tributary valley is linked by shallow through valleys with a north-northeast oriented Box Elder Creek tributary valley and also with a shorter northeast-oriented Box Elder Creek tributary valley and with the north-northeast oriented Shellrock Creek valley. These through valleys are shallow and are defined by only a single contour line, but they do provide evidence of former flood flow routes, probably eroded by south-oriented flood water from west of the actively eroding Missouri River valley head flowing to the newly beheaded and reversed Box Elder Creek flood flow channel, which had been beheaded and reversed by headward erosion of the deep Missouri River valley.

Figure 7: Smith River-Sand Coulee Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

Figure 7 illustrates the Smith River-Sand Coulee Creek drainage divide area west and somewhat south of the figure 5 map area and includes overlap areas with figure 5. The Missouri River meanders along the north edge of the figure 7 northwest quadrant before turning to flow in a north direction to the figure 5 north edge (just west of center). The Smith River is the north-oriented Missouri River tributary flowing along the figure 7 west edge. Goodman Coulee is a west-oriented Smith River tributary located south of Truly Bench. Ming Coulee is the west-northwest and west oriented tributary flowing from the figure 7 south center edge to join the Smith River near the figure 7 southwest corner. Swede Bench and Ming Coulee Ridge form the drainage divide between west-oriented Goodman Coulee and west-oriented Ming Coulee. Sand Coulee Creek flows in a north direction from Three Forks (near figure 7 southeast corner) and then turns to flow in a north-northwest direction to Tracy near the figure 7 north edge (east half). Note how Sand Coulee Creek has north and north-northeast oriented tributaries including Number Five Coulee and its tributary Cottonwood Creek near Stockett in the figure 7 east center region. Spring Coulee, which originates in the figure 7 center area, drains in a north-northeast direction to join Sand Coulee Creek north of the figure 7 map area. Eden is a small town just north of the figure 7 south center edge. Note in the region directly north and east of Eden northeast-oriented through valleys linking the west-oriented Ming Coulee valley with the north and north-northeast oriented Number Five Coulee valley, which drains to the north-oriented Sand Coulee Creek valley. The figure 7 map contour interval is 50 meters and the through valleys are generally defined by a single contour line on each side. The through valleys provide evidence of south-oriented flood flow routes from what was once the yet to be beheaded and reversed (by headward erosion of the deep Missouri River valley) south-oriented flood flow on the Smith River alignment that was captured by reversed flood flow on what was then the newly beheaded and reversed Sand Coulee Creek-Number Five Coulee alignment. The present day north-oriented Smith River valley was initiated as a south-oriented flood flow channel supplying flood waters to what is now the south-oriented Shields River (south of figure 1 map area), which flows to the east and northeast-oriented Yellowstone River valley (which eroded headward into Montana in advance of the deep Missouri River valley). Headward erosion of the deep Missouri River valley, probably aided by uplift of regions south of figure 7, beheaded and reversed the south-oriented flood flow to erode the north-oriented Smith River valley.

Figure 8: Detailed map of Ming Coulee-Number Five Coulee drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

Figure 8 provides a detailed topographic map of the Ming Coulee-Number Five Coulee drainage divide area seen in less detail in figure 7 above. Ming Coulee drains in a west-northwest direction across the figure 8 southwest corner and west of the figure 8 map area drains to the north-oriented Smith River. Number Five Coulee drains in a north direction in the figure 8 east half and is joined by north-northeast oriented Giffen Coulee near the abandoned town of Giffen (near figure 8 north edge). An unnamed north-northeast tributary drains to the figure 8 north center edge and joins Number Five Coulee north of the figure 8 map area. North of figure 8 Number Five Coulee drains in a north-northeast direction to north-oriented Sand Coulee Creek. Note how in sections 33 and 34 (east and south of Stony Point) the Ming Coulee valley is linked by a well-defined north-northeast oriented through valley with the north-northeast oriented Giffen Coulee valley. The figure 8 map contour interval is 20 feet and the through valley floor elevation at the drainage divide is between 4300 and 4320 feet. Stony Point to the northwest rises to more than 4500 feet and elevations greater than 4460 feet can be found near the figure 8 southeast corner (much higher elevations can be found further to the south and east). This north-northeast oriented through valley is approximately 200 feet deep and is a water eroded through valley. Shallower north-northeast oriented through valleys are located near the corner of sections 20, 21, 28, and 29 and link the Ming Coulee valley with the unnamed north-northeast Sand Coulee Creek tributary valley. These through valleys and the west-oriented Ming Coulee valley provide evidence of a major floor flow channel used by flood waters captured by the newly beheaded and reversed Sand Coulee Creek flood flow channel. Headward erosion of the very deep northeast-oriented Missouri River valley beheaded and reversed what had been south-oriented flood flow on the Sand Coulee Creek-Number Five Coulee alignment. The newly reversed flood flow captured yet to be beheaded south-oriented flood flow from the Smith River flood flow channel, which was still west of the actively eroding and deep Missouri River valley head. The captured flood waters flowed in an east direction along the present day Ming Coulee alignment and then in a north-northeast direction to the north-oriented Number Five Coulee-Sand Coulee Creek flood flow channel. Headward erosion of the very deep Missouri River valley subsequently beheaded and reversed the Smith River flood flow channel and a deep north-oriented knick point eroded headward along that flood flow channel. The deep knick point then beheaded and reversed the east-oriented flood flow in the Ming Coulee flood flow channel and a deep west-oriented knick point eroded headward along the Ming Coulee flood flow channel and beheaded the north-northeast oriented flood flow channel to the Number Five Coulee flood flow channel.

Figure 9: Smith River-Ming Coulee drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

Figure 9 illustrates the Smith River-Ming Coulee drainage divide area south and slightly east of the figure 7 map area and located along the Little Belt Mountains northern margin. The Smith River meanders in a north and northwest direction from the figure 9 south edge (west half) to the figure 9 west edge (north of center). Ming Coulee drains in a north-northwest direction from the figure 9 south edge (east half) to the figure 9 north edge (slightly west of center). Sand Coulee Creek flows in a north and north-northwest direction from the figure 9 south edge (just east of Ming Coulee) to near the figure 9 north edge where it makes a northeast jog to the north edge (east half). Black Butte is a high point located between the north-oriented Smith River and Ming Coulee valleys in the figure 9 south half. Note how north of Black Butte there are southwest-oriented tributaries flowing to the northwest-oriented Smith River. These southwest-oriented Smith River tributaries are linked by a southwest-northeast oriented through valley with a northeast-oriented Ming Coulee tributary. The figure 9 map contour interval is 50 meters and the through valley floor elevation at the drainage divide is between 1450 and 1500 meters. Elevations on what is probably a hogback ridge to the north rise to 1688 meters and the Black Butte elevation is given as 1946 meters. These adjacent elevations suggest the northeast-southwest oriented through valley linking the Ming Coulee and Smith River valleys is approximately 250 meters deep. While the through valley is probably related to underlying geologic structures it is also a water eroded feature and was eroded by flood waters between the two north-oriented valleys. Additional through valleys can be seen in the figure 9 map area and provide further clues. Note the shallower through valleys eroded across the southwest-northeast oriented (hogback?) ridge just north of the southwest-northeast oriented Smith River-Ming Coulee through valley. Northwest and west-oriented Smith River tributaries originate on the north ends of these through valley while south and southwest-oriented tributaries to the southwest-oriented Smith River tributary originate at the south ends of these through valleys. Also through valleys link the north-oriented Ming Coulee valley with the north-oriented Sand Coulee Creek valley. This maze of through valleys makes a strong case for an anastomosing channel complex, which once would have moved flood waters across the region. Based on present day topography a strong case can be made for north-oriented flood flow, although probably preceding the north-oriented flood flow the water movement was to the south. The south-oriented flood flow across this figure 9 map region was reversed when headward erosion of the much deeper Missouri River valley to the north beheaded the south-oriented flood flow channels (in sequence from east to west). Probably at the same time the Little Belt Mountains were being uplifted, which strongly aided the flood flow reversal process which eroded the present day north-oriented valleys.

Figure 10: Detailed map of Smith River-Ming Coulee 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 Smith River-Ming Coulee drainage divide area seen in less detail in figure 9 above. The meandering Smith River flows in a north direction across the figure 10 southwest corner. Ming Coulee flows in a north-northwest direction across the figure 10 northeast corner. Note the southwest, west, and southwest-oriented tributary flowing from the section 2 west edge (in figure 10 northeast quadrant) to join the Smith River near the north end of the meander seen in the figure 10 southwest corner. That Smith River tributary is linked by a through valley in the north half of section 2 with a northeast-oriented Ming Coulee tributary. The figure 10 map contour interval is 40 feet and the through valley floor elevation at the drainage divide is between 4800 and 4840 feet. The high point in section 35 (south of figure 10 north edge) is shown as 5284 feet (even higher elevations can be found north of the figure 10 map area) while elevations south of the through valley rise even higher. In other words based on elevations seen in figure 10 the through valley is at least 440 feet deep. The through valley was probably initially eroded by diverging south-oriented flood flow channel moving flood waters from what was then a south-oriented flood flow channel on the Ming Coulee alignment (and on a south-oriented flood flow channel on the Sand Coulee Creek alignment-to the east of figure 10) to converge with a south-oriented flood flow channel on the Smith River alignment. As previously noted the flood flow direction was subsequently reversed by headward erosion of the deep northeast-oriented Missouri River valley north of figure 10 and also by Little Belt Mountains uplift (which also included the figure 10 map area). Uplift of the Little Belt Mountains was probably occurring as flood waters flowed across the region.

• This essay has shown just a few examples of the topographic evidence in the Smith River-Belt Creek drainage divide area documenting erosion by massive south and then north-oriented floods. The descriptions of the flood movements in this essay are probably greatly over simplified and can probably be significantly improved. Less important than the specific flood flow movements described here is the concept the region was eroded by massive floods. At first the floods moved in a south direction on a high level erosion surface (at least high level based on present day topography) until uplift of the Little Belt Mountains region and headward erosion of a very deep northeast-oriented Missouri River valley combined to cause massive flood flow reversals. The present day topography is not the topography that existed when flood waters first flowed across the region. Instead the present day topography was created by a combination of Little Belt Mountains uplift and of deep flood water erosion. Evidence the Little Belt Mountains were being uplifted as flood waters flowed across them suggests the Little Belt Mountains uplift was related to crustal warping caused by the thick North American ice sheet to the north and east and perhaps was also related to crustal unloading caused by deep flood water erosion of bedrock material from the rising Little Belt Mountains area.

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.