Abstract:

This essay uses topographic map evidence to interpret landform origins in the Illinois River-Colorado River drainage divide in the Colorado Rabbit Ears Range. The Rabbit Ears Range is a west to east oriented mountain range west of the Never Summer Range and east of the Park Range. North Park is a high basin area located between the Park Range and the Never Summer Range (and the Medicine Bow Mountains to the north of the Never Summer Range) and is north of the Rabbit Ears Range and is drained by the north oriented North Platte River and its tributaries with water eventually reaching the Missouri and Mississippi Rivers and the Gulf of Mexico. The Illinois River is a west, northwest, and north oriented North Platte River tributary (via the north oriented Michigan River) originating in the Never Summer Range. The Colorado flows in a south direction east of the Illinois River headwaters and then turns in a southwest, west, and southwest direction with water eventually reaching the Pacific Ocean. North to south oriented through valleys or passes, including a broad through valley separating the Rabbit Ears Range from the Never Summer Range, link north oriented Illinois River headwaters and tributary valleys with south oriented Colorado River tributary valleys. The through valleys or passes are interpreted to have been eroded by south and southeast oriented floodwaters moving from the present day north oriented Illinois River and North Platte River alignments to the southwest oriented Colorado River valley. Floodwaters are interpreted to have been derived from the western margin of a thick North American ice sheet and were flowing from western Canada to and across Colorado at a time when the regional mountain ranges were just beginning to emerge. Mountain ranges emerged as floodwaters flowed across them and eroded surrounding valleys and basins at the same time as ice sheet crustal warping raised the mountain ranges and the entire North Park region. The deep southwest oriented Colorado River valley eroded headward into the region to capture the immense south oriented flood flow. South oriented Colorado River headwaters and tributary valleys then eroded headward from the southwest oriented Colorado River valley. North and northwest oriented Colorado River tributary routes were created by reversals of flood flow on north and northwest ends of beheaded flood flow channels. Uplift of the Rabbit Ears Range, Never Summer Range, other regional mountain ranges, and of the entire North Park region caused a reversal of flood flow in the North Park basin to create the north oriented North Platte River drainage route and its north oriented tributary drainage routes. The reversal of flood flow ended flood flow across the Rabbit Ears Range to the actively eroding Colorado River tributary valleys and created the Illinois River-Colorado River drainage divide, which is today the east-west continental divide.

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 Illinois River-Colorado River drainage divide area landform origins in the Colorado Rabbit Ears 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 Illinois River-Colorado River drainage divide area landform evidence in the Colorado Rabbit Ears Range will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Illinois River-Colorado River drainage divide area location map

Figure 1: Illinois 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 Illinois River-Colorado River drainage divide area in the Colorado Rabbit Ears Range and illustrates a region in north central Colorado and with Wyoming to the north of Colorado. Rocky Mountain National Park is located east of the center of figure 1 and Rabbit Ears Pass is located west of Rocky Mountain Park. The Rabbit Ears Range (not labeled in figure 1) extends in a west to east direction from Rabbit Ears Pass almost to Rocky Mountain National Park. The Never Summer Range (also not shown in figure 1) is located east of the Rabbit Ears Range. The Colorado River flows from near the southwest corner of Rocky Mountain National Park and flows in a southwest direction to the southwest corner of figure 1. South and west of figure 1 the Colorado River eventually reaches the Pacific Ocean. The Medicine Bow Mountains extend in a north-northwest direction from the northwest corner of Rocky Mountain National Park (and the north end of the Never Summer Range) into southern Wyoming. The Park Range is north to south oriented mountain range north of Rabbit Ears Pass. The region between the Park Range and the Medicine Bow Mountains is known as North Park (not labeled in figure 1) and is drained by the north and north-northwest oriented North Platte River, which flows from Cowdrey, Colorado into Wyoming. North of figure 1 the North Platte River flows in a north direction to central Wyoming where it flows around the north end of the Laramie Mountains and then flows in a southeast direction into Nebraska with water eventually reaching the Platte, Missouri, and Mississippi Rivers and the Gulf of Mexico. The unnamed north-northwest oriented tributary flowing through the towns of Gould and Walden to join the North Platte River near Cowdrey is the Michigan River. The unnamed northwest and north-northwest oriented tributary joining the Michigan River at Walden is the Illinois River. The unlabeled northwest, southwest, and south-southeast oriented Colorado River tributary south of the Illinois River headwaters is Willow Creek. The Laramie River originates north of Rocky Mountain National Park and flows in a north direction along the east side of the Medicine Bow Mountains into Wyoming. North of figure 1 the Laramie River flows in a north and northeast direction across the Laramie Mountains in a deep water gap to reach the southeast oriented North Platte River. The Illinois River-Colorado River drainage divide area in the Colorado Rabbit Ears Range investigated in this essay extends from west of Parkview Mountain to near the west boundary of Rocky Mountain National Park.

The north oriented North Platte and Laramie River valleys originated as south oriented flood flow channels at a time when the regional mountain ranges were just beginning to emerge. Floodwaters were derived from the western margin of a thick North American ice sheet and were flowing from western Canada to and across the region seen in figure 1. Floodwaters flowed across the region in giant complexes of diverging and converging flood flow channels. Mountain ranges emerged as floodwaters flowed across the region and as floodwaters deeply eroded valleys and basins surrounding the emerging mountain ranges and further as ice sheet related crustal warping raised the mountain ranges and the entire region seen in figure 1. The southwest oriented Colorado River valley eroded headward into the region to capture south oriented melt water flood flow. North and northwest oriented Colorado River tributary drainage routes were created by reversals of flood flow on north and northwest ends of beheaded south and southeast oriented flood flow channels. Flood flow reversals occurred as the much deeper Colorado River valley beheaded the flood flow channels in sequence from west to east. Floodwaters on north and northwest ends of the beheaded flood flow channels reversed flow direction to flow to the much deeper Colorado River valley. South oriented flood flow on the present day north oriented Laramie River and North Platte River alignments then flowed to the newly eroded Colorado River valley and/or to actively eroding south oriented Colorado River tributary valleys. Next headward erosion of deep northeast oriented valleys across the emerging Laramie Range (north of figure 1) beheaded and reversed flood flow channels on the present day north oriented Laramie River alignment to create the present day north and northeast oriented Laramie River drainage route. The reversed flood flow captured at least some of the flood flow still moving in a south direction on the present day north oriented North Platte River alignment. Headward erosion of the deep southeast oriented North Platte River valley around the northwest end of the Laramie Mountains (in central Wyoming-north of figure 1) next beheaded and reversed flood flow channels on the present day north oriented North Platte River alignment to create the present day north and southeast oriented North Platte River drainage route. The flood flow reversals were greatly aided by ice sheet related crustal warping that was the regional mountain ranges and the entire Rabbit Ears Range region.

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

Figure 2: Detailed location map Illinois 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 Illinois River-Colorado River drainage divide area in the Colorado Rabbit Ears Range. The red-brown area straddling the east edge of figure 2 is Rocky Mountain National Park. The east-west continental divide is shown with a dashed line extending in an east direction from the west edge of figure 2 (north half) along the crest of the Rabbit Ears Range to the Never Summer Mountains where the continental divide turns in a north direction before turning in a south-southeast and south direction to near the southeast corner of figure 2. The Colorado River originates near Mount Richthofen (near northernmost point on the continental divide in figure 2) and flows in a south direction on the west side of Rocky Mountain National Park to Lake Granby and then turns to flow in a west-southwest and west direction to the town of Kremmling where it turns in southwest direction to flow south of figure 2. South and west of figure 2 the Colorado River eventually flows to the Pacific Ocean. Willow Creek originates south of the Never Summer Range and flows in a northwest, southwest, and southeast direction to join the west-southwest oriented Colorado River as a barbed tributary near the Lake Granby outlet. Further west two branches of Troublesome Creek originate near the continental divide and then join to form south oriented Troublesome Creek, which joins the west oriented Colorado River near the town of Troublesome. North of the continental divide Grizzly Creek flows in a northeast and north-northeast direction across the northwest corner of figure 2. North of figure 2 Grizzly Creek flows in a north direction to join the north oriented North Platte River with water eventually reaching the Platte, Missouri, and Mississippi Rivers and the Gulf of Mexico. Arapahoe Creek is a northwest oriented Grizzly Creek tributary originating near Hyannis Peak. The Illinois River originates near Cascade Mountain (near south end of Never Summer Range) and flows in a northwest direction to near the town of Rand where it turns to flow in a north direction to the north edge of figure 2. North of figure 2 the Illinois River flows in a north direction to join the north-northwest oriented Michigan River, which then flows to the north oriented North Platte River. North and northeast oriented streams originate along the continental divide and then flow to the northwest and north oriented Illinois River. Willow Creek Pass is located east of Parkview Mountain and is where the highway crosses the eastern Rabbit Ears Range.

Willow Creek-Haystack Creek drainage divide area

Figure 3: Willow Creek-Haystack Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 provides a topographic map of Willow Creek-Haystack Creek drainage divide area. The map contour interval for figure 3 is 50 meters. The east-west continental divide serves as the county line and is shown with a labeled dashed line extending from the west edge of figure 3 (north half) to the east edge of figure 3 (north half). Hyannis Peak is a labeled high point in the northwest quadrant of figure 3. The Middle Fork Arapahoe Creek originates south of Hyannis Peak (but north of the continental divide) and flows in a northwest direction to near the northwest corner of figure 3. North and west of figure 3 Arapahoe Creek joins north oriented Grizzly Creek with water eventually reaching the North Platte, Platte, Missouri, and Mississippi Rivers and the Gulf of Mexico. The south, southwest and south oriented stream originating east of the Middle Fork Arapahoe Creek headwaters (and south of the continental divide) is Troublesome Creek. South of figure 3 Troublesome Creek flows to the west and southwest oriented Colorado River with water eventually reaching the Pacific Ocean. The south oriented stream originating near the center of figure 3 is Haystack Creek, which near the south edge of figure 3 turns in a southeast direction to join southwest oriented East Fork (Troublesome Creek) The East Fork originates along the continental divide east of the Haystack Creek headwaters and flows in a southeast direction before turning to flow in a southwest direction to the south center edge of figure 3. South of figure 3 the East Fork Troublesome Creek flows to join south oriented Troublesome Creek. North of the Haystack Creek headwaters and on the north side of the continental are headwaters of north and north-northeast oriented Willow Creek, which north of figure 3 turns to flow in a northwest and west direction before turning in a north direction to join the north oriented Illinois River. A deep pass (Troublesome Pass on more detailed maps) links the north oriented Willow Creek headwaters valley with the south oriented Haystack Creek valley. The Troublesome Pass elevation is between 3050 and 3100 meters. Elevations along the continental divide to the northwest rise to more than 3550 meters. Continental divide elevations east of Troublesome Pass rise to more 3650 meters. These elevations suggest Troublesome Pass is approximately 450 meters deep and is what remains of deep south oriented flood flow channel eroded into the floor of what was once a broad north to south oriented valley crossing the region. At the time the south oriented valley was eroded the Rabbit Ears Range did not stand high above regions to the north as it does today. The north oriented Willow Creek drainage route was created by a reversal of flood flow on the north end of a beheaded south oriented flood flow route with the water on the north end of the beheaded flood flow route flowing in a north direction to what was probably a much deeper beheading valley. Crustal warping that was raising the Rabbit Ears Range as floodwaters flowed across it probably greatly aided in the flood flow reversal.

Detailed map of Willow Creek-Haystack Creek drainage divide area

Figure 4: Detailed map of Willow Creek-Haystack 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 Willow Creek-Haystack Creek 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 northwest corner of figure 4 to the east edge of figure 4 (slightly north of center). Troublesome Pass is located in the west half of section 11 (near center of figure 4). Haystack Creek flows in a south direction from near Troublesome Pass to the south center edge of figure 4. South of figure 4 Haystack Creek joins southwest and south oriented Troublesome Creek, which then flows to the west and southwest oriented Colorado River with water eventually reaching the Pacific Ocean. North of Troublesome Pass Willow Creek flows in a southeast and northeast direction into section 2 before flowing in a north direction to the north center edge of figure 4. North of figure 4 Willow Creek flows to the north oriented Illinois River, which flows to the north oriented Michigan River, which then flows to the north oriented North Platte River with water eventually reaching the Platte, Missouri, and Mississippi Rivers and the Gulf of Mexico. Troublesome Pass has an elevation of 10,027 feet. Poison Ridge in section 4 to the northwest rises to 11,417 feet and Sheep Mountain, located on the continental divide north and west of figure 4, rises to 11,819 feet. Haystack Mountain in section 12 to the east of section 4 rises to 11,485 feet and Parkview Mountain, located on the continental divide east of figure 4, rises to 12,296 feet. Using elevations seen in figure 4 Troublesome Pass is approximately 1400 feet deep. Using the more distant elevations Troublesome Pass may be as much as 1800 feet deep. The southeast oriented stream originating east of Haystack Mountain and flowing to the southeast corner of figure 4 is the East Fork Troublesome Creek. South of figure 4 the East Fork Troublesome Creek turns to flow in a southwest direction to flow to south oriented Troublesome Creek. The unnamed northwest oriented stream originating north of Haystack Mountain joins Willow Creek in section 2. A  northwest to southeast oriented through valley links the northwest oriented Willow Creek tributary valley with the southeast oriented East Fork Troublesome Creek valley. The through valley floor elevation is between 10,400 and 10,440 feet, which suggests the through valley is approximately 1000 feet deep based on elevations seen in figure 4 and could be almost 1400 feet deep based on more distant elevations. These two through valleys and other passes or notches crossing the continental divide are remnants of what were once diverging and converging south oriented flood flow channels crossing the region seen in figure 4. At that time the region north of the continental divide was at least as high as the floors of the passes seen today. Since that time floodwaters were reversed to create north oriented drainage routes north of the present day continental divide and crustal warping has raised the Rabbit Ears Range.

Snyder Creek-Pass Creek drainage divide area

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

Figure 5 illustrates the Snyder Creek-Pass Creek drainage divide area east and slightly 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 labeled dashed line extending from the west edge of figure 5 (south half) along the Rabbit Ears Range crest to the Never Summer Range and then to the east edge of figure 5 (north half). The mountains along the east edge of figure 5 are in the Never Summer Range. Bowen Pass is located near the east center edge of figure 5. The Illinois River originates north of Bowen Pass and flows in a west, north, northwest, west, and northwest direction to the north edge of figure 5 (slightly west of center). North of figure 5 the Illinois River flows in a north direction to join the Michigan River, which then flows to the north oriented North Platte River with water eventually reaching the Platte, Missouri, and Mississippi Rivers and the Gulf of Mexico. Troublesome Pass (unlabeled in figure 5) is located on the continental divide near the west edge of figure 5. Willow Creek flows in a north, north-northeast, and north direction from Troublesome Pass to the north edge of figure 5 (west half) and joins the Illinois River north of figure 5. The south to north oriented highway from the south center edge of figure 5 to the north edge of figure 5 (west half) crosses the continental divide at Willow Creek Pass (not labeled in figure 5 and the name is related to a Willow Creek south of the continental divide). Snyder Creek flows in a north-northeast direction from Willow Creek Pass to join the west and northwest oriented Illinois River. Pass Creek flows in a southeast, south, and south-southeast direction from Willow Creek Pass to join south-southwest oriented Willow Creek. Willow Creek originates near the southeast corner of figure 5 and flows in a northwest, southwest, and south-southwest direction to the south center edge of figure 5. South of figure 5 Willow Creek turns to flow in a south-southeast and southeast direction to join the west-southwest oriented Colorado River as a barbed tributary. Willow Creek Pass has an elevation of between 2900 and 2950 meters. Continental divide elevations west of Willow Creek Pass rise to more than 3700 meters as do elevations to the east of Willow Creek Pass. These elevations suggest Willow Creek Pass may be as much as 750 meters deep. A much broader north to south oriented through valley or pass is located between the east end of the Rabbit Ears Range and the Never Summer Range and links the west oriented Illinois River headwaters valley with south oriented Willow Creek tributary valleys (and is seen again in figures 7 and 8). The northwest-southwest Willow Creek elbow of capture is located south of this large north to south oriented through valley. Through valleys or passes crossing the continental divide in figure 5 were eroded by diverging and converging flood flow channels moving floodwaters in a south and southeast direction from the present day northwest and north oriented Illinois River alignment to actively eroding south oriented Colorado River tributary valleys. Uplift of the Rabbit Ears and Never Summer Ranges and of the entire region in figure 5 contributed to the reversal of flood flow on the Illinois River alignment and on the present day north oriented Michigan River and North Platte River alignments further to the north. The flood flow reversals were probably triggered by headward erosion of the much deeper southeast oriented North Platte River valley around the northwest end of the Laramie Mountains (in central Wyoming), which beheaded the south oriented flood flow channels supplying floodwaters that were flowing across the region seen in figure 5.

Detailed map of Snyder Creek-Pass Creek drainage divide area

Figure 6: Detailed map of Snyder Creek-Pass 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 Snyder Creek-Pass 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 extending from the west edge of figure 6 (south half) to the east edge of figure 6 (north half). North and west of the continental divide streams drain to the Illinois River with water eventually reaching the Mississippi River and Gulf of Mexico. South and east of the continental divide streams drain to the Colorado River with water eventually reaching the Pacific Ocean. Willow Creek Pass is located near the center of figure 6 and has an elevation of 9621 feet. Elevations on Parkview Mountain to the west rise to 12,296 feet and Radial Mountain to the east rises to 11,241 feet. East of figure 6 in the Never Summer Range elevations along the continental divide reach 12,442 feet. Based on the Radial Mountain elevation Willow Creek Pass is at least 1600 feet deep. Using the Never Summer Range elevations the Willow Creek Pass depth may document erosion of as much as 2800 feet. Snyder Creek is the north oriented stream north of Willow Creek Pass and north of figure 6 flows to the west and northwest oriented Illinois River. Pass Creek is the southwest, southeast, and south oriented stream flowing to the south edge of figure 6 (east of center). South of figure 6 Pass Creek flows to south-southwest, south-southeast, and southeast oriented Willow Creek, which flows to the west-southwest oriented Colorado River as a barbed tributary. Willow Creek Pass is a deep channel eroded into the floor of a much broader north to south oriented through valley bounded on the west by Parkview Mountain and on the east by the Never Summer Range. The broad through valley was eroded by south and southeast oriented flood flow moving from the present day northwest and north oriented Illinois River and north oriented Michigan and North Platte River alignments across the region between the Rabbit Ears Range and the Never Summer Range. Prior to headward erosion of the deep southwest oriented Colorado River valley the floodwaters flowed in a southeast and south direction along the present day north and northwest oriented Fraser River alignment and then across the present day Front Range to valleys draining today to the north and northeast oriented South Platte River. If correctly interpreted floodwaters initially flowed on an erosion surface equivalent in elevation to the present tops of the Parkview Mountain and the high peaks in the Never Summer Range (east of figure 6 and seen in figures 7 and 8), although the entire region has probably been significantly uplifted since that time. Floodwaters eroded deep and broad valleys into that former erosion surface. Headward erosion of the deep southwest oriented Colorado River valley captured the southeast and south oriented flood flow and south oriented Colorado River tributary valleys then eroded headward from that newly eroded Colorado River valley. Subsequently crustal warping raised the Rabbit Ears Range, the Never Summer Range, and the entire region and caused a major reversal of flood flow (with many associated flood flow captures( north of figure 6 that ended flood flow to the actively eroding Colorado River tributary valley and that created the Illinois River-Colorado River drainage divide.

Illinois River-Willow Creek drainage divide area

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

Figure 7 illustrates the Illinois River-Willow Creek drainage divide area east of figure 5 and includes an overlap area with figure 5. The map contour interval for figure 7 is 50 meters. Willow Creek Pass is located near the west center edge of figure 7. The east-west continental divide serves as the county line and extends in an east direction from the west center edge of figure 7 along the crest of the Rabbit Ears Range to the Never Summer Range and then in a north-northeast direction along the crest of the Never Summer Range to the north edge of figure 7 (east half). The Colorado River flows in a south direction from the north edge of figure 7 and near the east edge of figure 7 to the south edge of figure 7. South of figure 7 the Colorado River turns to flow in a west-southwest, west, and southwest direction with water eventually reaching the Pacific Ocean. Baker Gulch and Bowen Gulch are southeast oriented Colorado River tributaries located in the east center area of figure 7. Timber Creek is a northwest oriented barbed tributary flowing to the south oriented Colorado River (along east edge of figure 7-north half). Willow Creek originates near the south center edge of figure 7 and flows in a northeast, northwest, southwest, and south-southwest direction to the south edge of figure 7 (near southwest corner). South of figure 3 Willow Creek turns to flow in a south-southeast and southeast direction to join the west-southwest oriented Colorado River as a barbed tributary. The Illinois River originates near Bowen Pass (in the Never Summer Range west of Bowen Mountain) and flows in a west, north, northwest, west, and northwest direction to the northwest corner of figure 7. North of figure 7 the Illinois River flows in a north direction to join the north oriented Michigan River, which then joins the north oriented North Platte River with water eventually reaching the Platte, Missouri, and Mississippi Rivers and the Gulf of Mexico. A north to south oriented through valley near the center of figure 7 marks the east end of the Rabbit Ears Range and links the Illinois River valley with south oriented Willow Creek tributary valleys and also with the Willow Creek elbow of capture (where Willow Creek turns from flowing in a northwest direction to flowing in a southwest direction). The through valley floor elevation is between 3050 and 3100 meters. As previously described in the discussion for figure 5 elevations in the Rabbit Ears Range to the west (of figure 7) rise to more than 3700 meters and elevations in the Never Summer Range (east of the through valley) also rise to more than 3700 meters. These elevations suggest the through valley is at least 600 meters deep. This broad 600-meter deep through valley was eroded by south oriented flood flow moving from the present day north oriented Illinois, Michigan, and North Platte River alignments to the actively eroding Colorado River valley and the valley of its tributary Willow Creek. A reversal of flood flow greatly aided by crustal warping that was raising the region seen in figure 7 created the present day north oriented Illinois River, Michigan River, and North Platte River drainage routes.

Detailed map of Illinois River-Willow Creek drainage divide area

Figure 8: Detailed map of Illinois River-Willow 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 Illinois River-Willow Creek drainage divide seen in less detail in figure 7. The map contour interval for figure 8 is 40 feet. The east-west continental divide serves as the county line and is shown with a labeled dashed line extending from the west edge of figure 8 (north of center) to near the northeast corner of figure 8. Mountains in the east half of figure 8 are in the Never Summer Range. West of figure 8 the continental divide follows the crest of the Rabbit Ears Range. Bowen Mountain is located near the east center edge of figure 8 and Bowen Pass is located just west of Bowen Mountain. The Illinois River originates north of Bowen Pass and flows in west and north direction to the north edge of figure 8 (west of center). North of figure 8 the Illinois River flows in a northwest, west, northwest, and north direction to join the north oriented Michigan River, which then flows to the north oriented North Platte River with water eventually reaching the Gulf of Mexico. South of Bowen Pass are south oriented headwaters of southeast oriented Bowen Gulch, which east of figure 8 drains to the south and west-southwest oriented Colorado River with water eventually reaching the Pacific Ocean. The Bowen Pass elevation is 11,478 feet. Bowen Mountain to the east rises to 12,524 feet and Ruby Mountain to the southwest rises to 12,008 feet. These elevations suggest Bowen Pass is approximately 500 feet deep. Bowen Pass was eroded as a south oriented flood flow channel prior to headward erosion of the deeper west oriented Illinois River headwaters valley. South oriented streams in the west half of figure 8 flow to northwest, southwest, and southeast oriented Willow Creek (south of figure 8), which flows to the southwest oriented Colorado River as a barbed tributary. Slightly west of the center of figure 8 a north to south oriented through valley links the north oriented Illinois River valley with a south oriented Willow Creek tributary valley. The through valley floor elevation is between 10,120 and 10,160 feet. As seen in earlier figures elevations along the Rabbit Ears Range crest west of figure 8 rise to 12,296 feet suggesting the through valley could be as much as 2200 feet deep. However deep the through valley is it is a deeper channel eroded into the floor of a much broader north to south oriented through valley eroded between Rabbit Ears Range to the west and the Never Summer Range to the east. This broad through valley was eroded by south oriented flood flow moving from the present day north oriented Illinois, Michigan, and North Platte River drainage routes to the actively eroding Colorado River valley and its actively eroding Willow Creek tributary valley and tributary valleys. Uplift of the region as floodwaters flowed across it eventually led to the reversal of flood flow on the Illinois, Michigan, and North Platte River alignments and creation of the Illinois River-Willow Creek drainage divide, which is today the east-west continental divide. After flood flow across the region had ended and the Never Summer Range had emerged as a high mountain range alpine glaciers formed in the Never Summer Range. The alpine glaciers filled many of the Never Summer Range valleys and deepened those valleys and otherwise altered the valley shapes. However, the glaciers probably did not erode new valleys or change valley orientations. Regions in the west half of figure 8, which are west of the Never Summer Range, do not appear to have been significantly altered by glaciation.

Willow Creek-Trail Creek drainage divide area

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

Figure 9 illustrates the Willow Creek-Trail Creek drainage divide area south and slightly east of figure 7 and there is an overlap area with figure 7. The map contour interval for figure 9 is 50 meters. The east-west continental divide is located north of figure 9 and the entire region in figure 9 drains to the Colorado River with water eventually reaching the Pacific Ocean. The Colorado River flows in a south direction near the east edge of figure 9 from the north edge of figure 9 to near the southeast corner of figure 9. South of figure 9 the Colorado River turns to flow in a west-southwest, west, and southwest direction. Lost Lake is located in the north center area of figure 9. Willow Creek originates on the north slope of Gravel Mountain and flows in a northeast to near Lost Lake where it turns and flows in a northwest direction almost to the north edge of figure 9 and then turns to flow in a southwest direction almost to the west edge of figure 9 before turning to flow in a south-southeast direction to the south edge of figure 9 (west half). South of figure 9 Willow Creek turns to flow in a southeast direction to join the west-southwest oriented Colorado River as a barbed tributary. The southeast oriented stream located south of Lost Lake is Stillwater Creek, which south of figure 9 joins Willow Creek. A north to south oriented through valley between Gravel Mountain and Porphyry Peaks links the northwest oriented Willow Creek valley near Lost Lake with the southeast oriented Stillwater Creek valley. The through valley floor elevation is between 3150 and 3200 meters. Gravel Mountain reaches 3567 meters and Porphyry Peaks reach 3462 meters suggesting the through valley is at least 250 meters deep. The through valley was eroded by southeast oriented flood flow moving to the actively eroding Stillwater Creek valley. The flood flow channel east of Gravel Mountain diverged from the southwest and south-southeast oriented flood flow channel west of Gravel Mountain and then the two diverging flood flow channels converged again in the Colorado River valley south of figure 9. Floodwaters had flowed in a south direction on the present day north oriented Illinois, Michigan, and North Platte River alignments and had eroded the deep through valley between the Rabbit Ears Range and Never Summer Range seen in figure 7 and 8. Headward erosion of a deeper valley on the flood flow channel west of Gravel Mountain beheaded the south oriented flood flow channel east of Gravel Mountain. Floodwaters on the northwest end of the beheaded flood flow channel reversed flow direction to flow to the much deeper southwest and south-southeast oriented valley and to create the northwest, southwest, and south-southeast oriented Willow Creek drainage route.

Detailed map of Willow Creek-Stillwater Creek drainage divide area

Figure 10: Detailed map of Willow Creek-Stillwater 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 Willow Creek-Stillwater Creek drainage divide area seen in less detail in figure 9. The map contour interval for figure 10 is 40 feet. Lost Lake is located in the north center area of figure 10. Willow Creek originates on the north slope of Gravel Mountain (in west half of figure 10) and flows in a northeast direction to near Lost Lake and then turns to flow in a northwest direction to the north edge of figure 10 (west of center). Pony Park is located in the south center area of figure 10. Stillwater Creek flows in a southeast, south, and southeast direction into and across Pony Park to the south edge of figure 10 (east half-east of Apiatan Mountain). South of figure 10 Stillwater Creek flows to the south and west-southwest oriented Colorado River.  Trail Creek originates south of Gravel Mountain and flows in a southeast direction to the south edge of figure 10. South of figure 10 Trail Creek turns in a south direction to join southeast oriented Willow Creek, which then joins the west-southwest oriented Colorado River.  A through valley links the northeast oriented stream on the northwest side of Apiatan Mountain with the south oriented Trail Creek valley south of figure 10. A north to south oriented through valley south of Lost Lake links the northwest oriented Willow Creek valley with the southeast oriented Stillwater Creek valley. The through valley floor elevation is between 10,360 and 10,400 feet. Gravel Mountain to the west rises to 11,769 feet. Porphyry Peaks to the east have a high point of 11,305 feet. These elevations suggest the through valley is approximately 900 feet deep. The through valley was eroded by southeast oriented flood flow moving from the present day northwest oriented Willow Creek alignment to the southeast oriented Stillwater Creek valley. The southeast oriented flood flow channel split at Apiatan Mountain with one flood flow channel continuing in a southeast direction on the present day Stillwater Creek alignment while a diverging flood flow channel moved floodwaters in a southwest direction to the present day south oriented Trail Creek alignment (west of Apiatan Mountain). Headward erosion of a deeper southeast oriented valley on the Stillwater Creek alignment beheaded the diverging southwest oriented flood flow channel. Floodwaters on the northeast end of the beheaded flood flow channel reversed flow direction to create the northeast oriented Stillwater Creek tributary drainage route. Subsequently headward erosion of the deeper southwest oriented Willow Creek valley (north and west of figure 10) beheaded the southeast oriented flood flow channel between Gravel Mountain and Porphyry Peaks to the southeast oriented Stillwater Creek valley. Flood flow on the northwest end of the beheaded flood flow channel reversed flow direction to create the northwest oriented Willow Creek drainage route.

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.