Abstract:

This essay uses topographic map evidence to interpret landform origins in the Michigan River-Colorado River drainage divide area in the Colorado Never Summer Range. The Never Summer Mountains are located west of the south oriented Colorado River headwaters valley in western Rocky Mountain National Park. North of the Never Summer Mountains are the Medicine Bow Mountains. The Michigan River originates as a northeast and north oriented stream near the Colorado River headwaters and then turns to flow in a west, northwest, and north-northwest direction to join the North Platte River west of the Medicine Bow Mountains. North of the north oriented Michigan River headwaters Cameron Pass links a south oriented Michigan River tributary valley with the north-northeast oriented Joe Wright Creek valley with Joe Wright Creek draining to the north and east oriented Cache la Poudre River and linked by a though valley with the north and northeast oriented Laramie River. La Poudre Pass is located just east of the Michigan River headwaters and links a northeast oriented Cache la Poudre River tributary valley with the south oriented Colorado River valley. The Michigan River headwaters valley is linked by higher elevation through valleys or passes with the La Poudre Pass through valley. Further to the south, west and northwest oriented Michigan River tributary valleys are linked by through valleys or passes across the Never Summer Range crest ridge, which is also the east-west continental divide. The through valleys or passes are interpreted to have been formed by diverging and converging flood flow channels at a time when the Never Summer Mountains and other regional mountain ranges were just beginning to emerge. Floodwaters were flowing from the western margin of a thick North American ice sheet and were flowing from western Canada to and across Colorado as the regional mountain ranges emerged. Mountain ranges emerged as ice sheet related crustal warping raised the mountain ranges and the entire Never Summer and Medicine Bow Mountains region and as floodwaters deeply eroded adjacent valleys and basins. The Colorado River valley eroded headward into the region to capture the immense south oriented melt water floods. Uplift of the mountains and of the entire region combined with headward erosion of deeper valleys north of the study area caused flood flow reversals to create the north oriented drainage routes seen today. Floodwaters were reversed on the east side of the Medicine Bow Mountains while floodwaters still moved in a south direction west of the Medicine Bow Mountains. Headward erosion of deeper north oriented valleys east of the Medicine Bow Mountains captured south oriented flood flow from west of the Medicine Bow Mountains and the captured floodwaters made a large U-turn around the south end of the Medicine Bow Mountains as the floodwaters flowed in a southeast and east direction on the present day west and northwest oriented Michigan River alignment and then in a north direction on the Joe Wright Creek alignment to the newly formed north oriented Laramie River and Cache la Poudre River drainage routes.

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 Michigan River-Colorado River drainage divide area landform origins in the Colorado Never Summer Range. Map interpretation methods can be used to unravel many geomorphic events leading up to formation of present-day drainage routes and development of other landform features. While each detailed topographic map feature provides detailed evidence to be explained, the solution must be consistent with explanations for adjacent area map evidence as well as solutions to big picture map evidence puzzles. I invite readers to improve upon my solutions and/or to propose alternate solutions that better explain evidence and are also consistent with adjacent map area and big-picture evidence. Readers may do so either by making comments here or by writing and publishing their own essays and then by leaving a link to those essays 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 Michigan River-Colorado River drainage divide area landform evidence in the Colorado Never Summer Range will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Michigan River-Colorado River drainage divide area location map

Figure 1: Michigan River-Colorado 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 Michigan River-Colorado River drainage divide area in the Colorado Never Summer Range and illustrates a region in north central Colorado with Wyoming to the north of Colorado. Rocky Mountain National Park is labeled. The Never Summer Range is not shown or labeled in figure 1, but is located in and near the west side of Rocky Mountain National Park. The Medicine Bow Mountains extend in a north-northwest direction from the Never Summer Range (northwest corner of Rocky Mountain National Park) into southern Wyoming. The North Platte River is formed at the confluence of tributaries near Coalmont, Colorado (west of the Rocky Mountain National Park northwest corner) and then flows in a north and north-northwest direction to the north edge of figure 1. North of figure 1 the North Platte River flows in a north direction to central Wyoming and then flows in an east and southeast direction around the northwest end of the Laramie Mountains with water eventually reaching the Platte, Missouri, and Mississippi Rivers and the Gulf of Mexico. The Michigan River (not labeled in figure 1) originates near the northwest corner of Rocky Mountain National Park and flows in a a north-northwest direction to join the North Platte River neat Cowdrey, Colorado. The Illinois River (not labeled in figure 1) originates south of the Michigan River headwaters and flows in a northwest and north direction to join the Michigan River near Walden, Colorado. The Canadian River (not labeled in figure 1) originates in the southern Medicine Bow Mountains and flows in a north-northwest direction to join the North Platte River near Cowdrey. The Laramie River flows in a north direction from near the north edge of Rocky Mountain Park along the east flank of the Medicine Bow Mountains into Wyoming and then turns to flow in a northeast direction to Laramie, Wyoming. North of figure 1 the Laramie River continues in a northeast direction to join the southeast oriented North Platte River. The Cache la Poudre River originates in Rocky Mountain National Park and flows in a north, east, and southeast direction to join the northeast and east oriented South Platte River near Greeley, Colorado. The Colorado River originates in the Rocky Mountain National Park northwest corner and flows in a south direction to Lake Granby near the Rocky Mountain National Park southwest corner. From Lake Granby the Colorado River flows in a west and southwest direction (with a northwest jog between Bond and McCoy) to the south edge of figure 1 (west half). South and west of figure 1 the Colorado River flows in a southwest direction with water eventually reaching the Pacific Ocean. The Michigan River-Colorado River drainage divide area along the continental divide in the Colorado Never Summer Range extends southward from the south end of Medicine Bow Mountains into the northwest quadrant of Rocky National Park.

Rocky Mountain National Park region drainage routes developed during immense melt water floods from the western margin of a thick North American ice sheet. Floodwaters flowed from western Canada to and across the Rocky Mountain National Park region at a time when the regional mountain ranges were just beginning to emerge. Ice sheet related crustal warping was responsible for uplift of the regional mountain ranges and for uplift of the entire region. At first floodwaters flowed across the emerging mountains and later were channeled around the emerging mountain ranges as floodwaters deeply eroded valleys and basins surrounding the mountain ranges. The present day north oriented Laramie and North Platte River drainage routes are located on the alignments of what began as south oriented flood flow channels, with the floodwaters initially flowing in south and southeast directions across the entire region seen in figure 1. Headward erosion of the deep southwest oriented Colorado River valley across the south and southeast oriented flood flow channels captured the floodwaters and diverted the flood flow in a southwest direction to the Pacific Ocean. Floodwaters on north and northwest ends of beheaded flood flow channels reversed flow direction to flow in north and northwest directions to the much deeper Colorado River valley and to create north and northwest oriented Colorado River tributary drainage routes. Crustal warping that was raising mountain ranges south of the actively eroding Colorado River valley contributed to these reversals of flood flow. South oriented flood flow on the present day north oriented Laramie River alignment supplemented by south oriented flood flow from the Michigan River alignment supplied floodwaters that eroded the south oriented Colorado River valley in the Never Summer Range region (western Rocky Mountain National Park).

Headward erosion of what was then the deep northeast oriented Laramie River valley across the emerging Laramie Mountains (north of figure 1) triggered a flood flow reversal that created the north oriented Laramie River drainage route. The reversal of flood flow on the Laramie River alignment occurred while floodwaters were still moving in a south direction on the North Platte River alignment. Reversed flood flow on the Laramie River alignment (and also on the present day north oriented Cache la Poudre River headwaters alignment) then captured flood flow moving from the North Platte River that was moving in a south-southeast and southeast direction on the Michigan River alignment. The captured floodwaters made a large U-turn around the south end of the Medicine Bow Mountains and so as to flow in a north and northeast direction into the Laramie Basin and then to the actively eroding southeast oriented North Platte River valley located east of the Laramie Mountains (north of figure 1). Headward erosion of that southeast oriented North Platte River valley around the northwest end of the Laramie Mountains (north of figure 1) in time captured the south oriented flood flow channels west of the Laramie Mountains, which had been supplying floodwaters to the south oriented flood flow channel on the present day north oriented North Platte River alignment. Floodwaters on the north ends of the beheaded flood flow channels reversed flow direction to flow in a north direction to the much deeper southeast oriented North Platte River valley and to create the present day north and southeast oriented North Platte River drainage route. Reversal of flood flow on the North Platte River alignment also reversed flood flow on the Michigan River alignment to create the northwest and north-northwest oriented Michigan River drainage route. Crustal warping that was raising the Never Summer Range and the entire region seen in figure 1 contributed greatly to the Laramie River and North Platte River flood flow reversals.

Detailed location map for Michigan River-Colorado River drainage divide area

Figure 2: Detailed location map Michigan River-Colorado River 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 Michigan River-Colorado River drainage divide area in the Colorado Never Summer Range. Rocky Mountain National Park is the region shown with the red-brown color. Green colored areas are National Forest lands. The east-west continental divide is shown with a dashed line extending in an east direction from near the southwest corner of figure 2 to Cascade Mountain (north of the south center edge of figure 1). At Cascade Mountain the continental divide turns in a north-northeast direction to the north end of the Kawuneeeche Valley near Mount Richthofen at the northwest corner of Rocky Mountain National Park and then turns in a south-southeast direction to the south edge of figure 2 (east half). The Colorado River originates near Mount Richthofen and flows in a south direction through the Kawuneeche Valley to the south edge of figure 2 (east of center). South of figure 2 the Colorado River turns to flow in a southwest direction to eventually reach the Pacific Ocean. The Never Summer Mountains are located west of the Kawuneeche Valley. The Michigan River originates near Mount Richthofen and flows in a northeast, west, and northwest direction to be joined by the Illinois River near Walden (near northwest corner of figure 2). The Illinois River originates near Cascade Mountain and flows in a northwest, north-northwest, and north direction to join the Michigan River near Walden. North of figure 2 the Michigan River flows to the north oriented North Platte River, which in central Wyoming turns to flow in a southeast direction into Nebraska with water eventually reaching the Platte, Missouri, and Mississippi Rivers and the Gulf of Mexico. The South Fork Michigan River originates in the Never Summer Mountains south of the Michigan River headwaters and flows in a north, northwest, and north direction. The North Fork Michigan River is located north of the Michigan River headwaters and flows in a west-northwest, west-southwest, and northwest direction to join the Michigan River. The Canadian River originates north of the North Fork Michigan River and flows in a north-northwest direction to the north edge of figure 2 (west half) and north of figure 2 joins the north oriented North Platte River. Cameron Pass is located north of Mount Richthofen and an unlabeled north-northeast oriented stream (Joe Wright Creek on more detailed maps) flows from Cameron Pass to Chambers Lake and then to the north, northeast, and east oriented Cache la Poudre River, which east of figure 2 flows to the South Platte River. The north oriented stream flowing from Chambers Lake is the Laramie River, which north of figure 2 flows in a north and northeast direction to eventually join the southeast oriented North Platte River. Note how a northeast oriented Cache la Poudre River tributary (La Poudre Pass Creek on more detailed maps) originates near the south oriented Colorado River headwaters near Mount Richthofen.

South Fork Michigan River-Baker Gulch drainage divide area

Figure 3: South Fork Michigan River-Baker Gulch drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 provides a topographic map of South Fork Michigan River-Baker Gulch drainage divide area. The map contour interval for figure 3 is 50 meters. The east-west continental divide extends in a south direction from the north edge of figure 3 (at Mount Richthofen) along the Never Summer Mountains crest to Mount Nimbus and then makes a jog to the west and southwest across Baker Pass to Farview Mountain. From Farview Mountain the continental continues in a south direction across Bowen Pass to Ruby Mountain and then turns in a west direction to the west edge of figure 3 (south half). North and west of the continental divide along the Never Summer Mountains crest streams drain to the North Platte River with water eventually reaching the Platte, Missouri, and Mississippi Rivers and the Gulf of Mexico. Little Yellowstone is located near the north edge of figure 3 east of Mount Richthofen. The Colorado River originates near Little Yellowstone and flows in a south direction to the south edge of figure 3. South of figure 3 the Colorado River turns to flow in a southwest direction with water eventually reaching the Pacific Ocean. East of Little Yellowstone the continental divide can be seen extending in a south direction from the north edge of figure 3 to Specimen Mountain and then in a south-southeast direction to Mount Ida and the east edge of figure 3 (south half). In other words the continental divide makes a loop around the Colorado River headwaters and areas east of the eastern continental divide line drain to the South Platte River with water eventually reaching the Platte River. The South Fork Michigan River originates on the north side of Baker Pass (near center of figure 3) and flows in a north, west-northwest, and north-northwest direction to the north edge of figure 3 (west half). North of figure 3 the South Fork joins the north-northwest oriented Michigan River, which flows to the north oriented North Platte River. South of Baker Pass are south oriented headwaters of southeast oriented Baker Gulch, which drains to the south oriented Colorado River. Baker Pass is a north to south oriented through valley linking the north oriented South Fork Michigan River headwaters valley with the south oriented Baker Gulch headwaters valley. The Baker Pass elevation is between 3400 and 3450 meters. Mount Nimbus to the east rises to 3873 meters. Parika Peak and Farview Mountain to the southwest each rise to more than 3700 meters. These elevations suggest Baker Pass could be as much as 250 meters deep. Baker Pass was eroded by southeast and south oriented flood flow moving from the present day north and northwest oriented South Fork Michigan River alignment to the south and southeast oriented Baker Gulch valley and the south oriented Colorado River valley. Other similar passes or through valleys seen in figure 3 link northwest oriented Michigan River tributary valleys with south and southeast oriented Colorado River tributary valleys. For example, Bowen Pass links the west, northwest, and west oriented Illinois River valley with the east-southeast oriented Bowen Gulch valley. Bowen Pass was eroded by southeast oriented flood flow from the Illinois River alignment flowing to the south oriented Colorado River valley. Uplift of the Never Summer Mountains as floodwaters were flowing across them contributed to the reversals of flood flow that created the northwest and north oriented South Fork Michigan and Illinois River drainage routes and the Michigan River-Colorado River drainage divide. West of figure 3 the Illinois River flows in a north-northwest and north direction to join the north oriented Michigan River. Long Meadows near the southeast corner of figure 3 is located in a through valley linking a northwest oriented Colorado River tributary valley with a southwest oriented Colorado River tributary valley. The Long Meadow through valley was eroded by a diverging and converging south oriented flood flow channel that was beheaded and reversed by headward erosion of the much deeper south oriented Colorado River valley.

Detailed map of South Fork Michigan River-Baker Gulch drainage divide area

Figure 4: Detailed map of South Fork Michigan River-Baker Gulch 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 South Fork Michigan River-Baker Gulch drainage divide area seen in less detail in figure 3. The map contour interval for figure 4 is 40 feet. The east-west continental divide is shown with a labeled line extending from the south edge of figure 4 (west half) to Farview Mountain, Parika Peak, Baker Pass, Mount Nimbus, Mount Cumulus, and the north center edge of figure 4. The Colorado River flows in a south direction from near the northeast corner of figure 4 to the south edge of figure 4 (near southeast corner). South of figure 4 the Colorado River turns to flow in a southwest direction with water eventually reaching the Pacific Ocean. Baker Gulch originates in section 16 on the south side of Baker Pass and drains in a south and southeast direction to the south edge of figure 4. South of figure 4 Baker Gulch drains to the south oriented Colorado River. The South Fork Michigan River originates in section 9 on the north side of Baker Pass and flows in a north direction to the north edge of figure 4. North of figure 4 the South Fork Michigan River turns to flow in a west-northwest and north direction to join the north-northwest oriented Michigan River, which flows to the north oriented North Platte River with water eventually reaching the Platte, Missouri, and Mississippi Rivers and the Gulf of Mexico. Jacks Creek originates in section 17 (west of the Baker Gulch headwaters) and flows in a northwest and west direction to the west edge of figure 4 (north of center). West of figure 4 Jacks Creek eventually joins the north-northwest and north oriented Illinois River, which flows to the Michigan River. Baker Pass has an elevation of 11,253 feet. Mount Nimbus to the east rises to 12,706 feet. Parika Peak to the southwest rises to 12,394 feet. These elevations suggest Baker Pass could be as much as 1450 feet deep. Baker Pass was eroded by south oriented flood flow moving from the present day north oriented South Fork Michigan River alignment to the south oriented Baker Gulch headwaters valley alignment. Study of the continental divide between Parika Peak and Mount Nimbus suggests Baker Pass is a deep valley eroded into the floor of a much broader through valley linking the Jacks Creek headwaters valley and the South Fork Michigan River headwaters valley with the south oriented Baker Gulch headwaters valley. This broader through valley suggests diverging and converging flood flow channels were once eroded into an erosion surface now represented, if it is represented at all, by the tops of the high Never Summer Mountains peaks today. Uplift of the Never Summer Mountains since that time contributed to flood flow reversals on the present day Jacks Creek and South Fork Michigan River alignments and to the creation of the Michigan River-Colorado River drainage divide.

Michigan River-Neola Creek drainage divide area

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

Figure 5 illustrates the Michigan River-Neola Creek drainage divide area north of figure 3 and there is an overlap area with figure 3. The map contour interval for figure 5 is 50 meters. The east-west continental divide is shown with a dashed line extending in a north direction along the crest of the Never Summer Mountains from the south center edge of figure 5 to Mount Richthofen (in north center area of figure 5) and then in an east direction to La Poudre Pass before turning in a south direction to Specimen Mountain, Milner Pass, and the south edge of figure 5 (east half-near southeast corner). The Colorado River originates south of La Poudre Pass and flows in a south-southwest and south direction to the south edge of figure 5. South of figure 5 the Colorado River turns to flow in a southwest direction with water eventually reaching the Pacific Ocean. Areas east of the continental divide  (and Colorado River) in figure 5 drain to the South Platte River while areas west of the continental divide (and Colorado River) in figure 5 drain to the North Platte River. The North and South Platte Rivers join in Nebraska to form the Platte River with water eventually reaching the Missouri and Mississippi Rivers and the Gulf of Mexico. The Michigan River originates at Snow Lake (north of Mount Richthofen) and flows in a northeast, north, west, and northwest direction to the northwest corner of figure 5. North and west of figure 5 the Michigan River flows in a north-northwest direction to join the north oriented North Platte River. Lulu Mountain is located east of Mount Richthofen. Lulu Creek is a southeast oriented Colorado River tributary south of Lulu Mountain. A north to south oriented through valley or pass links the Michigan River headwaters valleys with the southeast oriented Lulu Creek valley. The through valley elevation is between 3450 and 3500 meters. Mount Richthofen rises to more than 3900 meters and Lulu Mountain rises to 3727 meters suggesting the through valley is at least 227 meters deep. North of the through valley is Cameron Pass, which links the Michigan River headwaters valley with the north-northeast oriented Joe Wright Creek valley (seen in figures 7 and 8). The Michigan River-Lulu Creek through valley was eroded by south oriented flood flow moving across the Michigan River headwaters drainage basin area to the south oriented Colorado River valley. North of Lulu Mountain is another through valley or pass between Lulu Mountain and Iron Mountain linking the west oriented Michigan River valley with the southeast oriented Neola Creek valley. Neola Creek flows in a southeast direction to join northeast oriented La Poudre Pass Creek, which originates at La Poudre Pass. La Poudre Pass was eroded by southwest oriented flood flow moving to the south oriented Colorado River valley. The Neola Creek valley and the Michigan River-Neola Creek through valley was eroded by southeast flood flow moving from the Michigan River drainage basin to the south oriented Colorado River valley. Uplift of the Never Summer Mountains and the entire region contributed to the flood flow reversals that ended south oriented flood flow to the south oriented Colorado River valley and that created the northeast oriented La Poudre Pass Creek, north-northeast oriented Joe Wright Creek, and north, west, northwest, and north-northwest oriented Michigan River drainage routes.

Detailed map of Michigan River-Neola Creek drainage divide area

Figure 6: Detailed map of Michigan River-Neola 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 Michigan River-Neola Creek drainage divide area seen in less detail in figure 5. The map contour interval for figure 6 is 40 feet. The east-west continental divide is shown with a labeled line and extends from the west edge of figure 6 (south half) to Thunder Pass, Lulu Mountain, Thunder Mountain, Mount Neola, La Poudre Pass and then in a south direction to the south edge of figure 6 (east half). The Colorado River originates at La Poudre Pass Lake (just south of La Poudre Pass) and flows in a south-southwest direction to the south edge of figure 6 (slightly west of center). South of figure 6 the Colorado River flows in a south and then southwest direction with water eventually reaching the Pacific Ocean. La Poudre Pass Creek originates on the north side of La Poudre Pass and flows in a northeast direction to Long Draw Reservoir. East and north of figure 6 La Poudre Pass Creek joins the north and east oriented Cache la Poudre River, which flows to the South Platte River with water eventually reaching the Platte River and Gulf of Mexico. Neola Creek is a southeast oriented stream joining La Poudre Pass Creek just north of La Poudre Pass. Lulu Creek originates south of Thunder Pass and flows in a southeast direction to the south edge of figure 6 and south of figure 6 joins the south oriented Colorado River. Snow Lake is located near the west edge of figure 6 and just north of the continental divide. The Michigan River originates at Snow Lake and flows in a northeast, north, and west direction to the west edge of figure 6. West and north of figure 6 the Michigan River flows in a west, northwest, and north-northwest direction to eventually join the North Platte River with water eventually reaching the Platte River and Gulf of Mexico. The south oriented Michigan River tributary valley in the northwest corner of figure 6 is linked at Cameron Pass (north of figure 6 and seen in figures 7 and 8) with the north-northeast oriented Joe Wright Creek valley. Thunder Pass links the north oriented Michigan River headwaters valley with the southeast oriented Lulu Creek valley and was eroded by south oriented flood flow moving to the actively eroding south oriented Colorado River valley. La Poudre Pass was eroded by southwest oriented flood flow moving from the present north oriented Cache la Poudre River alignment (north and east of figure 6) to the actively eroding Colorado River valley. The Michigan River-Neola Creek through valley between Iron Mountain and Thunder Mountain was eroded by east and southeast oriented flood flow moving from the present day Michigan River drainage basin to the south oriented Colorado River valley. The through valley or pass elevation is between 11,240 and 11,280 feet. Iron Mountain to the north rises to 12,265 feet and Thunder Mountain to the south rises to more than 12,040 feet suggesting the Michigan River-Neola Creek through valley is at least 760 feet deep. After flood flow across the region had ended and after the Never Summer Mountains had been uplifted to become the high mountains they are today valley glaciers filled the flood-eroded valleys and deepened and otherwise altered the valley shapes. However, the glaciers filled pre-existing valleys and did not erode new valleys or change valley orientations or significantly change the location of through valleys or passes.

Michigan River-Joe Wright Creek drainage divide area

Figure 7: Michigan River-Joe Wright Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the Michigan River-Joe Wright Creek drainage divide area north of figure 5 and includes an overlap area with figure 5. The map contour interval for figure 7 is 50 meters. The entire region seen in figure 7 is north of the continental divide and drains to the Platte River with water eventually reaching the Gulf of Mexico. The Jackson-Larimer County line extends in a north direction from the south center edge of figure 7 to Iron Mountain and then in a west direction to Diamond Peaks before continuing in a north and north-northwest direction along the crest of the Medicine Bow Mountains to the north edge of figure 7 (west half). The Michigan River flows in a north and west direction from the south center edge of figure 7 to the west edge of figure 7 (near southwest corner). West of figure 7 the Michigan River turns to flow in a northwest and north-northwest direction to join the north oriented North Platte River. The Cache la Poudre River flows in a north, northwest, and north direction from near the southeast corner of figure 7 to the north edge of figure 7 (east half). North of figure 7 the Cache la Poudre River turns to flow in an east direction and eventually joins the South Platte River. Cameron Pass is located north of the Michigan River and east of Diamond Peaks. Joe Wright Creek originates near Cameron Pass and flows in a north-northeast direction to Chambers Lake. From Chambers Lake Joe Wright Creek flows in a north-northeast direction to join the Cache la Poudre River near the north edge of figure 7. The north oriented stream draining from Chambers Lake is the Laramie River. North of figure 7 the Laramie River flows in a north and northeast direction and eventually joins the North Platte River. Cameron Pass has an elevation of between 3100 and 3150 meters. Diamond Peaks to the west rise to 3612 meters and Iron Mountain to the east rises to 3738 meters. These elevations suggest Cameron Pass could be as much as 450 meters deep. Cameron Pass was eroded initially by south oriented flood flow moving on the present day north oriented Laramie River alignment east of what were at that time the emerging Medicine Bow Mountains. A south and south-southwest oriented flood flow channel on the present day north oriented Cache la Poudre River and north-northeast oriented Joe Wright Creek alignment converged with the south oriented flood flow on the Laramie River alignment in the Chambers Lake location. The south-southwest oriented flood flow channel on the Joe Wright Creek alignment diverged from a south oriented flood flow channel on the present day north oriented Cache la Poudre River alignment. The south oriented flood flow converged with south, southeast, and east oriented flood flow on the Michigan River alignment to flow to the actively eroding south oriented Colorado River valley. When viewed in the context of south oriented flood flow channels the present day valleys seen in figure 7 describe anastomosing flood flow channels, which were eroded into the regional landscape as crustal warping raised the region. In time regional uplift combined with headward erosion of deeper valleys (north of figure 7) triggered flood flow reversals that created the present day north oriented drainage routes. The reversals of flood flow occurred first on the east side of the Medicine Bow Mountains, which enabled reversed flood flow on the Joe Wright Creek alignment to capture the south, southeast, and east flood flow still moving on the Michigan River alignment and to divert that flood flow in a north direction through Cameron Pass to the newly formed north oriented Laramie River and Cache la Poudre River drainage routes.

Detailed map of Michigan River-Joe Wright Creek drainage divide area

Figure 8: Detailed map of Michigan River-Joe Wright 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 Michigan River-Joe Wright Creek drainage divide seen in less detail in figure 7. The map contour interval for figure 8 is 40 feet. The Michigan River flows in north direction from the south edge of figure 8 (east half) and then turns to flow in a west direction to the west edge of figure 8 (south half). The Michigan River-Neola Creek through valley or pass seen in figure 6 is located near the southeast corner of figure 8 and is east of the Michigan River elbow of capture (where the north oriented Michigan River turns to flow in a west direction). Cameron Pass is located near the center of figure 8 and has an elevation of 10,276 feet. Joe Wright Creek flows in a north-northeast direction from near Cameron Pass to the north edge of figure 8 (east of center). North of figure 8 Joe Wright Creek flows in a north-northeast direction to Chambers Lake and then to join the north and east oriented Cache la Poudre River with water eventually flowing to the South Platte River. Chambers Lake is also drained in a north direction by the north and northeast oriented Laramie River with water eventually reaching the North Platte River. An unnamed southeast and south-southeast oriented stream flows from Cameron Pass to the north and west oriented Michigan River. Diamond Peaks are located west of Cameron Pass and rise to 11,852 feet. East of Cameron Pass mountains exceed 12.000 feet in elevation. These elevations suggest Cameron Pass could be as much as 1500 feet deep. Cameron Pass was initially eroded by south oriented flood flow moving from the present day north oriented Laramie and Cache la Poudre River alignments to the present day north oriented Michigan River alignment and then to the south oriented Colorado River valley. The south oriented flood flow from east of the emerging Medicine Bow Mountains converged with south, southeast, and east oriented flood flow from west of the emerging Medicine Bow Mountains, which was moving on the present day Michigan River alignment. Regional uplift, which occurred as floodwaters flowed across the region, caused floodwaters to erode deeper and deeper valleys (or flood flow channels) into the emerging mountain masses. Eventually flood flow east of the emerging Medicine Bow Mountains was reversed to create the north oriented Laramie River, Cache la Poudre River, and Joe Wright Creek drainage routes. At that time floodwaters were still flowing in a south direction west of the emerging Medicine Bow Mountains and at least some of that south oriented flood flow was captured by the newly formed Joe Wright Creek drainage route and then flowed to the newly formed north oriented Laramie River and Cache la Poudre River drainage routes. The captured flood flow moved in a south, southeast, and east direction on the Michigan River alignment and then in a north direction through Cameron Pass to the Joe Wright Creek alignment. These captured floodwaters made a large U-turn around the south end of the emerging Medicine Bow Mountains and lowered the Cameron Pass valley so today the Cameron Pass elevation is almost 1000 feet lower than the Michigan River-Neola Creek through valley or the Thunder Pass elevation (which reflect the elevation of the south oriented flood flow channels leading to the south oriented Colorado River valley). Continued regional uplift eventually reversed flood flow west of the Medicine Bow Mountains to create the present day north oriented Michigan River drainage route and ended flood flow across Cameron Pass. Since that time valley glaciers have probably deepened and streamlined valleys to create the landscape seen today.

Canadian River-North Fork Michigan River drainage divide area

Figure 9: Canadian River-North Fork Michigan River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the Canadian River-North Fork Michigan River drainage divide area west and slightly north of figure 7 and there is an overlap area with figure 7. The map contour interval for figure 9 is 50 meters. The Larimer-Jackson County line follows the Medicine Bow Mountains crest and extends in a north-northwest direction from the south edge of figure 9 (east of center) to the north center edge of figure 9. Joe Wright Creek flows in a north-northeast direction from the south edge of figure 9 (just east of the county line) to Chambers Lake and then to join the north and northeast oriented Cache la Poudre River near the east edge of figure 9. East and north of figure 9 the Cache la Poudre River flows to the South Platte River. The north oriented stream flowing from Chambers Lake is the Laramie River, which north of figure 9 flows in a north and northeast direction with water eventually reaching the North Platte River. The Michigan River flows in a north-northwest direction from the south edge of figure 9 (west half) to the west edge of figure 9 (north of center). West and north of figure 9 the Michigan River joins the north oriented North Platte River, which flows into central Wyoming where the North Platte River flows around the northwest end of the Laramie Mountains and then in a southeast direction to the join the South Platte River in Nebraska. The North Fork Michigan River flows in a northwest and west-southwest direction from the south center edge of figure 9 to join the Michigan River near the south edge of figure 9. The North and South Forks of the Canadian River originate as south-southeast oriented streams in the high Medicine Bow Mountains (near the center of figure 9) and then make U-turns as they flow to the west side of the Medicine Bow Mountains where they join to form the north-northwest oriented Canadian River, which then flows to the north edge of figure 9 (west half). North of figure 9 the Canadian River flows to the north oriented North Platte River. Kelly Creek is a north and west oriented Canadian River tributary originating north of the North Fork Canadian River headwaters and is linked by a through valley with the North Fork Canadian River headwaters. The through valley in the high Medicine Bow Mountains is evidence of a former south oriented flood flow channel. A similar through valley is located east of the Medicine Bow Mountains links the northeast oriented West Branch Laramie River valley with the southeast and east oriented Fall Creek valley. A north-northwest to south-southeast oriented through valley west of the Medicine Bow Mountains links the north-northwest oriented Canadian River valley with the northwest oriented North Fork Michigan River headwaters valley. Each of these through valleys is at different elevations today, but each through valley was eroded by southeast oriented flood flow as the Medicine Bow Mountains emerged. Headward erosion of deeper valleys beheaded and reversed the south and southeast oriented flood flow channels to create the north oriented drainage routes seen today with crustal warping contributing to the flood flow reversals.

Detailed map of Canadian River-North Fork Michigan River drainage divide area

Figure 10: Detailed map of Canadian River-North Fork Michigan River 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 Canadian River-North Fork Michigan River drainage divide area seen in less detail in figure 9. The map contour interval for figure 10 is 40 feet. The North Fork Michigan River flows in a north direction from the south edge of figure 10 (east half) and then turns to flow in a west-southwest direction to near the south edge of figure 10 where it enters the broad northwest oriented Michigan River valley (the Michigan River is located west of figure 10) and the North Fork Michigan River then turns to flow in a north-northwest and northwest direction to the west center edge of figure 10. West of figure 10 the North Fork Michigan River joins the north-northwest oriented Michigan River, which then flows to the north oriented North Platte River. The South Fork Canadian River flows in a southwest, west, northwest and north-northwest direction from the east edge of figure 10 (near northeast corner) to the north edge of figure 10 (west of center) and north of figure 10 joins the North Fork Canadian River to form the north-northwest oriented Canadian River, which then flows to the north oriented North Platte River. The North Fork Canadian River flows in a south, west, and northwest direction from the north edge of figure 10 (near northeast corner) to the north edge of figure 10 (east of center) and north of figure 10 joins the South Fork to form the north-northwest oriented Canadian River. A north-northwest oriented South Fork Canadian River tributary flows across the center of figure 10 and is linked by a through valley with a southeast and southwest oriented North Fork Michigan River tributary. The through valley floor elevation is between 9120 and 9160 feet. Bull Mountain to the west rises to 9708 feet suggesting the through valley is approximately 550 feet deep. The through valley was eroded by southeast oriented flood flow moving from the present day north-northwest oriented Canadian River alignment to the North Fork Michigan River valley. South of the figure 10 the North Fork Michigan River valley is linked by through valleys with the west oriented Michigan River valley to the south. These through valleys are today several hundred feet higher in elevation than the South Fork Canadian River-North Fork Michigan River through valley seen in figure 10, which suggests one of three possibilities occurred. The first possibility is crustal warping raised the ridge that now forms the North Fork Michigan River-Michigan River drainage divide south of figure 10. The second possibility is headward erosion of the west-southwest oriented North Fork Michigan River from a south-southeast oriented flood flow channel on the present day north-northwest oriented Michigan River alignment captured south-southeast oriented flood flow on the Canadian River alignment and beheaded and reversed the southeast oriented flood flow on the present day northwest oriented North Fork Michigan River alignment. The third possibility is some combination of the first two possibilities took place. Whichever possibility is correct a major flood flow reversal subsequently occurred to create the north-northwest and north oriented Michigan River and North Platte River drainage systems seen today.

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.