Abstract:

This essay uses topographic map evidence to interpret landform origins along the continental divide between the Red Rock River in Beaverhead County, Montana and Camas Creek in Clark County, Idaho. This continental divide segment is located in the Centennial Mountains east of Monida Pass. The Centennial Mountains are a west-to-east oriented mountain range, which forms the Montana-Idaho border west of Yellowstone National Park. The Red Rock River flows in a west direction in the Centennial Valley north of the Centennial Mountains and west of the study region turns to flow in a north-northwest direction with water eventually reaching the north oriented Missouri River at Three Forks, Montana. Camas Creek originates in the Centennial Mountains and has southeast, south, and southwest oriented headwaters, but south of the Centennial Mountains flows in a south-southwest direction to Mud Lake where it ends as a surface stream, although it is headed toward the southwest oriented Snake River. Three major north-to-south oriented passes or through valleys cross the Centennial Range in the study region and link north oriented Red Rock River tributary valleys with south oriented Camas Creek headwaters valleys. The westernmost pass or through valley is the deepest and is Monida Pass, which is today is used as a major transportation route. East of Monida Pass between Little Table Mountain and Big Table Mountain is Pete Creek Divide, which links the north oriented Peet Creek valley with the south oriented Pete Creek valley. Still further east between Big Table Mountain and Baldy Mountain is a broad north-to-south oriented through valley or series of passes linking the north oriented Jones Creek and Winslow Creek valleys with the south oriented Cottonwood Creek valley. These three major through valleys or mountain passes were eroded as south oriented flood flow channels at a time when immense south oriented melt water floods flowed across the region. Initially the Centennial Mountains did not stand high above surrounding regions as they do today and the west oriented Red Rock River in the Centennial Valley did not exist. As floodwaters flowed across the region the Centennial Mountains began to emerge. At first south oriented flood flow eroded deeper and deeper channels into the emerging mountain mass, but eventually a deep valley eroded headward across the Centennial Valley north of the emerging Centennial Mountains and captured the southeast and east oriented flood flow. Floodwaters on north ends of the beheaded flood flow channels reversed flow direction to form north oriented drainage routes and also captured floodwaters from adjacent yet to be beheaded flood flow channels. Headward erosion of the much deeper Missouri River valley (north and east of the study region) beheaded south oriented flood flow channels supplying floodwaters to a deep south-southeast and east oriented flood flow channel on the present day Red Rock River alignment. The resulting massive reversal of floodwaters created the west and northwest oriented Red Rock River drainage system seen today. The much deeper Missouri River valley eroded headward from space being opened up in a deep “hole” the melting ice sheet had occupied. The massive reversal of flood flow that created the west and north-northwest oriented Red Rock River drainage system was probably greatly aided by crustal warping that had raised the Centennial Mountains and probably the entire study region.

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 are listed on the sidebar category list under their appropriate Missouri River tributary drainage basin, Missouri River segment drainage basin (by state), and/or state in which the Missouri River drainage basin is located.

Introduction

The purpose of this essay is to use topographic map interpretation methods to explore the Red Rock River-Camas Creek drainage divide area landform origins along the continental divide in Beaverhead County, Montana and Clark County, Idaho and 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 in a comment 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 Missouri River drainage basin landform origins research project essays 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 Red Rock River-Camas Creek drainage divide area landform evidence along the continental divide in Beaverhead County, Montana and Clark County, Idaho will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Red Rock River-Camas Creek drainage divide area location map

Figure 1: Red Rock River-Camas 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 Red Rock River-Camas Creek drainage divide along the continental divide in Beaverhead County, Montana and Clark County, Idaho and illustrates in the north a region in southwestern Montana with Idaho to the south in the west half of figure 1 and the northwest corner of Wyoming appearing in the southeast quadrant of figure 1. The Montana-Idaho state line is located on the east-west continental divide, which follows the crest of the Beaverhead and Centennial Mountains from the west edge of figure 1 to the Wyoming state line. The Red Rock River originates near Upper Red Rock Lake, just north of the Centennial Mountains, and flows in a west direction to near Lima, Montana and then turns to flow in a north-northwest direction to an unnamed lake (Clark Canyon Reservoir). At Clark Canyon Reservoir the Red Rock River is joined by north and east oriented tributaries to form the north-northeast oriented Beaverhead River, which joins the north, southeast, south, and northeast oriented Big Hole River near Twin Bridges to form the northeast and east oriented Jefferson River. The Jefferson River then joins the north oriented Madison and Gallatin Rivers near Three Forks, Montana to form the north oriented Missouri River. North of figure 1 the Missouri River turns to flow in a northeast and east direction to North Dakota where it turns to flow in a southeast and south direction with water eventually reaching the Gulf of Mexico. South of the Centennial Mountains Camas Creek flows in a south and southwest direction to Mud Lake where Camas Creek ceases as a surface stream. East of Camas Creek, near the Wyoming border, is south and southwest oriented Henrys Fork, which flows through the towns of Island Pond, Ashton, and St Anthony to join the Snake River just south of figure 1. The Snake River originates in Yellowstone National Park and flows in a south direction to Jackson Lake and the south edge of figure 1. South of figure 1 the Snake River turns to flow in a northwest direction almost to the figure 1 south edge (south of Sugar City, Idaho), where it joins southwest oriented Henrys Fork and then flows in a southwest and northwest direction across southern Idaho before turning to flow in a north direction with water eventually reaching the Pacific Ocean. The Red Rock River-Camas Creek drainage divide area investigated in this essay is located in the Centennial Mountains east of the highway between Lima, Montana and Spencer, Idaho and west of the south oriented Henrys Fork drainage basin.

A brief look at the big picture erosion history will help in understanding discussions related to detailed maps shown below. Large volumes of south and southeast oriented floodwaters once flowed across the region shown by figure 1. Floodwaters were derived from the western margin of a melting thick North American ice sheet and were flowing in a south and southeast direction from southwest Alberta and southeast British Columbia to and across the figure 1 region. North oriented rivers in figure 1 are generally flowing in valleys that originated as south oriented flood flow channels. The north oriented drainage routes located north of the continental divide in the Missouri River drainage basin area in figure 1 were initially developed as south and southeast oriented flood flow channels. Prior to development of deep flood flow channels adjacent to the emerging mountain ranges the floodwaters flowed across what are today high mountain ranges including the mountain ranges, which today form the east-west continental divide. Monida Pass is located where the highway between Lima, Montana and Spencer, Idaho crosses the state line and is at the west end of this essay’s study region and is a major north-to-south oriented through valley or gap separating the Centennial Mountains to the east from the Beaverhead Mountains to the west. Monida Pass was initially eroded as a deep south oriented flood flow channel. East of Monida Pass are other north-south oriented through valleys eroded across the present day east-west continental divide by south and southeast oriented flood flow before the west-oriented  Red Rock River drainage route to the north evolved and before the Centennial Mountains emerged to become the major topographic barrier they are today.

When floodwaters flowed across the region there was no continental divide and mountain ranges shown in figure 1 were just beginning to emerge. As the mountains emerged floodwaters eroded deep valleys into the emerging mountain masses, with the floodwaters being captured by the most successful of these deep valleys. In time the mountains formed an insurmountable topographic barrier that ended south oriented flood flow into Idaho. Emergence of the mountain ranges was caused to crustal warping related to the thick ice sheet presence north and east of figure 1. The reversal of flood flow that resulted in formation of the north oriented Missouri River drainage basin in western and central Montana occurred when a deep northeast-oriented valley eroded headward into central Montana from space in a deep “hole” the melting ice sheet had once occupied and which beheaded south oriented flood flow channels. Floodwaters on north ends of the beheaded flood flow channels reversed flow direction to form the present day north oriented Missouri River tributary drainage routes. Crustal warping that had raised mountain ranges and the entire region seen in figure 1 greatly aided in this massive flood flow reversal process. The west and north-northwest oriented Red Rock River seen in figure 1 evolved as this massive flood flow reversal took place.

Detailed location map for Red Rock River-Camas Creek drainage divide area

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

Figure 2 provides a more detailed location map for the Red Rock River-Camas Creek drainage divide area along the continental divide in Beaverhead County, Montana and Clark County, Idaho and shows drainage routes not seen in figure 1. The continental divide serves as the Montana-Idaho state line and is shown with a well-marked dashed line extending from the west center edge of figure 2 to the east edge of figure 2 (near Raynolds Pass, north half). Green shaded areas are National Forest lands, which generally are located in mountainous regions. The Red Rock River flows in a west direction in the north half of figure 2 from Upper Red Rock Lake to near Lima, Montana and then in a north-northwest direction to the northwest corner of figure 2. East and south from Lima the highway and railroad cross the continental divide and state line at Monida Pass, which is the west end of the continental divide segment investigated in this essay. The south oriented stream flowing from near Monida Pass along the highway and railroad is Beaver Creek. South of figure 2 Beaver Creek joins Camas Creek, which then flows to Mud Lake and ends as a surface stream. East of Monida Pass the continental divide follows the crest of the Centennial Mountains. Note multiple unnamed north and north-northwest oriented Red Rock River tributaries originating in the Centennial Mountains. More detailed maps provide names and show additional Red Rock River tributaries, although those shown in figure 2 illustrate the drainage pattern north of the Centennial Mountains. South of the Centennial Mountains are headwaters of south-southwest oriented Camas Creek, which flows to the south center edge of figure 2. South of figure 2 Camas Creek ends as a surface stream at Mud Lake, but is headed toward the southwest oriented Snake River. Named Camas Creek tributaries from west to east are southeast oriented West Camas Creek, east-southeast oriented East Camas Creek, south-southeast and south-southwest oriented Ching Creek, and south-southwest oriented Spring Creek. More detailed maps show many tributaries to these tributaries and additional streams, but again figure 2 illustrates the drainage pattern south of the Centennial Mountains. As seen in detailed maps below some of the north oriented Red Rock River tributary valleys are linked by through valleys (or mountain passes) across the Centennial Mountains to valleys of the south oriented Camas Creek tributaries, although the through valleys or passes in the Centennial Mountains are not as deep as Monida Pass.

Red Rock River-West Camas Creek drainage divide area 

Figure 3: Red Rock River-West Camas Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 provides a topographic map of the Red Rock River-West Camas Creek drainage divide area and is located at the west end of the continental divide segment investigated in this essay. The east-west continental divide serves as the state and county line and is the labeled dashed line extending from the west edge of figure 3 (south half) to the east edge of figure 3. The Red Rock River flows in a west direction along and across the north edge of figure 3 and Lima Reservoir is flooding the west oriented Red Rock River valley. Note the north and northwest oriented Red Rock River tributaries originating near the continental divide. Monida Pass is near the west margin of figure 3 and is where the highway and railroad cross the continental divide. Beaver Creek is an east-northeast oriented stream that flows from the west edge of figure 3 (south of the continental divide) to the highway and railroad and then in a south-southeast direction along the highway and railroad to the south edge of figure 3. Monida Pass is a major gap between two mountain ranges and has an elevation where the railroad crosses the drainage divide of between 2050 and 2100 meters (the map contour interval for figure 3 is 50 meters). Elevations on Little Table Mountain to the east rise to more than 2550 meters and even higher elevations are found along the continental divide in the Beaverhead Mountains west of figure 3 suggesting Monida Pass is a gap or through valley at least 450 meters deep. Little Table Mountain is the westernmost mountain in the Centennial Mountains and West Camas Creek flows in a southeast direction just to the south of Little Table Mountain. East of Little Table Mountain is an unlabeled mountain pass, or through valley, linking the north and northwest oriented Peet Creek valley with the south oriented Pete Creek valley, which drains to West Camas Creek south of figure 3. The through valley, or pass, elevation at the drainage divide is between 2300 and 2350 meters. Little Table Mountain to the west rises to more than 2550 meters and Big Table Mountain, which can be seen along the east edge of figure 3, rises to more than 2750 meters suggesting the through valley, or pass, is at least 200 meters deep. The through valley, or pass, is a remnant of a south oriented flood flow channel that once crossed what were at that time the emerging Centennial Mountains. At that time the deep west oriented Red Rock River valley to the north did not exist and floodwaters flowed in a south and southeast direction to and across the emerging Centennial Mountains and into Idaho. Headward erosion of the deep west oriented Red Rock River valley ended all south oriented flood flow across the emerging Centennial Mountains.

Detailed map of Peet Creek-Pete Creek drainage divide area 

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

Figure 4 provides a detailed topographic map of the Peet Creek-Pete Creek drainage divide area seen is less detail in figure 3. The continental divide serves as the county and state line and is shown with a labeled dashed line extending from the west edge of figure 4 (south half) to the east edge of figure 4 (north half). Peet Creek is the north oriented stream north of the continental divide flowing through sections 10 and 3 to the north center edge of figure 4 and north of figure 4 flows to the west oriented Red Rock River. Pete Creek is a south oriented stream south of the continental divide flowing through section 23 to the south center edge of figure 4 and south of figure 4 flows to southeast oriented West Camas Creek. Pete Creek Divide is the pass or through valley linking the north oriented Peet Creek valley with the south oriented Pete Creek valley. The map contour interval for figure 4 is 40 feet and the Pete Creek Divide elevation at the continental divide is shown as 7640 feet. Little Table Mountain to the west rises to more than 8600 feet. To the east in section 12 the continental divide rises to 8995 feet. These elevations suggest the Pete Creek Divide through valley is more than 960 feet deep. The Pete Creek Divide through valley is a water-eroded feature and was eroded as a south oriented flood flow channel when the deep Red Rock River valley to the north did not exist. At that time the Centennial Mountains did not stand high above surrounding regions and initially floodwaters flowed on a surface equivalent in elevation, if not higher, to the top of Little Table Mountain. Crustal warping related to a thick North American ice sheet north and east of the study region and deep erosion of surrounding valleys and basins as immense melt water floods flowed across the region were responsible for the Centennial Mountains emergence as the high mountain range they are today. Headward erosion of the deep west oriented Red Rock River valley north of figure 4 beheaded the south oriented flood flow channels one at a time and floodwaters on north ends of the beheaded flood flow channels reversed flow direction to erode north oriented Red Rock River tributary valleys. Reversed flood flow in newly beheaded flood flow channels captured yet to be beheaded flood flow from adjacent yet to be beheaded flood flow channels and this captured flood water eroded north oriented Red Rock River tributary valleys and the present day continental divide north side.

Winslow Creek-Cottonwood Creek drainage divide area

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

Figure 5 illustrates the Winslow Creek-Cottonwood Creek drainage divide area east of figure 3 and includes an overlap area with figure 3. The east-west continental divide serves as the county and state line and extends along the crest of the Centennial Mountains from the west edge of figure 5 (south half) to the east edge of figure 5 (south half). North of the forested Centennial Mountains is the Centennial Valley, which is drained by the west oriented Red Rock River, which is located a short distance north of figure 5. Lower Red Rock Lake is the lake near the northeast corner of figure 5 and drains to the Red Rock River. Named north oriented Red Rock River tributaries from west to east include Peet Creek, Bean Creek, Bear Creek, Jones Creek, Winslow Creek and its northwest oriented Tipton Creek tributary, Curry Creek, Matsingale Creek, Humphry Creek, and Shambow Creek.  The Pete Creek Divide pass, or through valley, seen in figure 4, crosses the continental near the west edge of figure 5. East of Pete Creek Divide is Big Table Mountain, which rises to more than 2750 meters (the map contour interval for figure 5 is 50 meters). East Camas Creek is the southeast oriented stream originating on Big Table Mountain and flowing to the south center edge of figure 5. East of Big Table Mountain another deep gap or through valley crossing the Centennial Mountains crest ridge links the north-northwest oriented Jones and Winslow Creek valleys with the south-southeast oriented Cottonwood Creek valley. The gap or through valley floor elevation at the Winslow Creek-Cottonwood Creek drainage divide is shown as being 2417 meters. East of that deep gap is Baldy Mountain, which rises to more than 3000 meters suggesting the gap or Winslow Creek-Cottonwood Creek through valley is at least 330 meters deep. The Winslow Creek-Cottonwood Creek through valley or gap is evidence of what was once a series of south oriented flood flow channels crossing what was then the emerging Centennial Mountains. The flood flow channels were eroded into a surface equivalent in elevation, if not higher, to the elevations seen along the Centennial Mountains crest ridge today. It is probable crustal warping since that time has raised the Centennial Mountains, although deep erosion of surrounding region by flood water erosion also contributed the Centennial Mountains emergence as the high mountain range seen today.

Detailed map of Winslow Creek-Cottonwood Creek drainage divide area

Figure 6: Detailed map of Winslow Creek-Cottonwood 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 Winslow Creek-Cottonwood Creek drainage divide area seen in less detail in figure 5. The east-west continental divide serves as the state and county line and extends from the west edge of figure 6 (south half) to the east edge of figure 6 (north half). North of the continental divide Bear Creek is the labeled north oriented stream flowing near the west edge of figure 6. East of Bear Creek the north-northeast and north oriented stream without a name is Jones Creek. Further east Winslow Creek is the labeled west and north-northwest oriented stream flowing to the north center edge of figure 6. South of the continental divide labeled Cottonwood Creek flows in a south direction to the south center edge of figure 6. Labeled Cottonwood Creek tributaries include southeast oriented Coon Creek, south-southwest oriented Lake Creek, and south-southwest oriented Salamander Creek. The map contour interval for figure 6 is 40 feet and the low point on the continental is shown as being 7907 feet (south and east of the words “MONTANA” and “IDAHO”) and links a north-northwest oriented Jones Creek tributary valley with the south-southeast oriented Cottonwood Creek valley. A short distance to the northeast on the continental divide is another low point with an elevation of 7929 feet, which links the north-northwest oriented Winslow Creek valley with south-southeast oriented Cottonwood Creek valley. Between the two low points the continental divide rises to more than 8040 feet. But near the east edge of figure 6 the continental divide rises to more than 9840 feet while near the west edge of figure 6 the continental divide rises to more than 9200 meters. These elevations suggest the through valleys or passes on the floor of the much broader through valley are 1200-1300 feet lower than the surrounding continental divide elevations. The two deep passes or through valleys provide evidence of what were once two converging south oriented flood flow channels supplying floodwaters to what was then the actively eroding south oriented Cottonwood Creek valley. The much broader and larger gap provides evidence of immense volumes of south oriented flood flow that moved across the emerging Centennial Mountains prior to headward erosion of the deeper west oriented Red Rock River valley to the north. It is possible and even probable that the Red Rock River valley was first eroded as an east oriented valley and later reversed to become the west oriented valley it is today, although evidence to support that hypothesis is not included in this essay’s study region.

East Fork Camas Creek-Cottonwood Creek drainage divide area

Figure 7: East Fork Camas Creek-Cottonwood Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the East Fork Camas Creek-Cottonwood Creek drainage divide area south of figure 5 and includes a significant overlap area with figure 5. The contour interval for an easy to identify area in the southeast quadrant of figure 7 is 20 meters and elsewhere in figure 7 is 50 meters. The east-west continental divide serves as the county and state line and extends from the west edge of figure 7 (north half) to the north edge (east half) and then north of figure 7 turns to extend in a southeast direction across the northeast corner of figure 7. South of the continental divide West Camas Creek flows in a southeast direction from near the west center edge of figure 7 to near the south center edge of figure 7. East Camas Creek originates on Big Table Mountain (northwest quadrant of figure 7) and flows in a southeast and south direction to the south edge of figure 7 (east half). East of East Camas Creek is south-southeast and south oriented Cottonwood Creek, which flows from near the continental divide (east of center in figure 7) to the south edge of figure 7 (east of center). Pasture Creek and its tributary Bear Trap Creek are interesting Cottonwood Creek tributaries located north of the word “TARGHEE” in figure 7. Both streams appear to be flowing toward the southeast and south oriented East Camas Creek valley, but after Bear Trap Creek joins Pasture Creek, Pasture Creek makes a U-turn to flow in a northeast direction around a high erosional residual to join southeast oriented Cottonwood Creek. West of the erosional residual is the south-southeast oriented East Camas Creek valley, to the east is the southeast oriented Cottonwood Creek valley, and to the north is the Pasture Creek valley. Several similar erosional residuals are found in the same region of figure 7. These erosional residuals provide evidence of former diverging and converging flood flow channels that once crossed the region. At the time floodwaters were flowing across the region the Centennial Mountains were emerging and the diverging and converging flood flow channels eroded deeper and deeper valleys into the emerging mountain mass. Over time deeper southeast and south-southeast flood flow channels captured flood flow from flood flow channels linking those major south oriented flood flow routes. These captures of flood flow left the former west-to-east oriented flood flow channels as abandoned valleys linking the deeper valleys on either side. Floodwaters appear to have deposited considerable alluvial debris in the non-forested region seen in the southeast quadrant of figure 7.

Detailed map of Pasture Creek-East Fork Camas Creek drainage divide area

Figure 8: Pasture Creek-East Fork Camas Creek 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 Pasture Creek-East Fork Camas Creek drainage divide area seen in less detail in figure 7. The contour interval for figure 8 is 40 feet in the north half and 20 feet in the south half. East Camas Creek flows in a southeast and south-southeast direction from the west edge of figure 8 (north half) to the south edge of figure 8 (west of center). Spruce Creek is the south-southeast oriented East Camas Creek tributary in section 26 in the northwest quadrant of figure 8. Cottonwood Creek flows in a southeast direction from the north edge of figure 8 (west of center) to the south edge of figure 8 (east half). Note how Cottonwood Creek has formed an alluvial fan in its valley in the southeast quadrant of figure 8 with multiple flow channels diverging from the main the main Cottonwood Creek channel. These diverging channels illustrate on a small-scale the diverging and converging flood flow channels that once crossed the emerging Centennial Mountains. Pasture Creek originates in the northwest quadrant of figure 8 and flows in a southeast and south direction to Hirschi Flat, where as Pasture Creek approaches East Camas Creek it turns to flow in a northeast and then east-southeast direction to join Cottonwood Creek. Note how Hirschi Flat forms a through valley between the southeast and south-southeast oriented East Camas Creek valley and the east oriented Pasture Creek drainage route to southeast oriented Cottonwood Creek. The through valley floor elevation at the lowest point on the drainage divide is 6920 feet. The high point in section 31 (on the erosional residual) is 7496 feet. Elevations on the Centennial Mountain crest ridge to the north are much higher as are elevation along the south half of the west edge of figure 8 suggesting the Hirschi Flat through valley is at least 1275 feet deep. The through valley was probably eroded by southeast oriented converging flood flow channels that split into two major diverging southeast oriented flood flow channels so as to flow around the emerging erosional residual seen in section 31. Deep valleys were then eroded on either side of the erosional residual and then as the Centennial Mountains to the north emerged the floodwaters began to deposit alluvial debris in those valleys forming an alluvial fan that extended headward into the Hirschi Flat region, which was higher in elevation in the west than in the east. Subsequently flood flow in the Cottonwood Creek flood flow channel was beheaded prior to the beheading of flood flow in the East Camas Creek valley, which enabled the East Camas Creek flood flow channel to erode a deeper valley headward into the alluvial fan.

Odell Creek-Cottonwood Creek drainage divide area

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

Figure 9 illustrates the Odell Creek-Cottonwood Creek drainage divide area east of figure 7 and includes a significant overlap area with figure 7. The continental divide serves as the county and state line and extends from the west edge of figure 9 (north half) to the east edge of figure 9 (north half). West Camas Creek flows across the southwest corner of figure 9. Sheridan Reservoir near the southeast corner of figure 9 and north of Sheridan Ridge drains to Sheridan Creek, which flows to south-oriented Henrys Fork, which is east of figure 9. Antelope Valley to the west is drained by south, east, and south oriented Scalp Creek, which flows to southwest oriented Dry Creek, which in turn flows to Camas Creek. Note how Dry Creek originates as West Dry Creek near continental divide and flows in a south-southeast direction before turning to flow in a southwest direction to the south edge of figure 9 (east half). Just east of West Dry Creek and flowing in the same valley for a distance is south, southeast, and east-northeast oriented East Dry Creek, which originates near the continental divide and which flows to Sheridan Reservoir. Note how West Dry Creek and East Dry Creek flow in the same valley adjacent to each other before diverging and flowing in completely different directions. Cottonwood Creek flows to the south edge of figure 9 just west of Antelope Ridge. Ching Creek is a south-southeast and south-southwest oriented tributary joining Cottonwood Creek at the west end of the Antelope Valley. Note how Ching Creek and Scalp Creek also flow adjacent to each other in the same valley and then diverge to flow in opposite directions around Antelope Ridge (and then to converge again south of figure 9). Note north of the continental divide and east of Ching Creek in the north center region of figure 9 how Odell Creek flows in a southeast direction parallel to the continental divide and then turns to flow in a north direction to the north edge of figure 9 (east half). The diverging and converging valleys seen in figure 9 originated at a time when immense south and southeast oriented floods eroded diverging and converging flood flow channels into what was then an emerging Centennial Mountains mountain mass. Before being beheaded and reversed to form the west oriented Red River valley north of figure 9 the immense south and southeast oriented floods deposited considerable alluvium, which formed alluvial fans that back filled the southern ends of the deep flood eroded valleys. Those alluvial fan surfaces today are today ideal for illustrating small-scale examples of the much larger-scale diverging and converging flood flow channel patterns that eroded deep valleys into the emerging Centennial Mountains.

Detailed map of Cottonwood Creek-Scalp Creek drainage divide area

Figure 10:Detailed map of Cottonwood Creek-Scalp 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 Cottonwood Creek-Scalp Creek drainage divide area seen in less detail in figure 9. Cottonwood Creek flows in a south-southeast direction from the northwest corner of figure 10 to section 9, where it is joined by south-southwest and south-southeast oriented Little Creek and south-southwest oriented Ching Creek and then flows in a south-southwest direction to the south edge of figure 10 (west half). Note how the Cottonwood Creek channel splits into several diverging south and southeast oriented channels on the alluvial fan surface filling the former Cottonwood Creek valley in the west half of figure 10. Ching Creek flows in a south-southwest direction from near the north center edge of figure 10 to join Cottonwood Creek in section 9. East of Ching Creek is south and southeast oriented Scalp Creek, which flows from the north edge of figure 10 to Antelope Valley and then to the south edge of figure 10 (east half). Note how Ching Creek and Scalp Creek are flowing on opposite sides of the alluvial fan that has backfilled a large south oriented valley and then diverge to flow in opposite directions around Antelope Ridge, the northwest end of which is seen in sections 15 and 16 along the south margin of figure 10. Moose Creek is a southwest and south oriented stream east of Scalp Creek and joins Scalp Creek near the northwest end of Antelope Valley. Note how the Moose Creek and Scalp Creek channels also split to form diverging channels on the alluvial fan surface. The alluvial fans filling the deep valleys seen in figure 10 were deposited in deep valleys formed by south and southeast oriented floodwaters prior to formation of the deep west oriented Red Rock River valley north of the Centennial Mountains. The diverging channels seen in figure 10 suggest active deposition on the alluvial fan surface may still be taking place, which suggests the possibility that at least some of the alluvial fan deposits post date the immense south and southeast oriented melt water flood events that eroded the deep valleys in which the alluvial fans have been deposited. However, it is also possible the alluvial fans were primarily deposited during late stages of the immense melt water floods, prior to formation of the deep west oriented Red River valley in the Centennial Valley north of the Centennial Mountains.

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.