Sweetwater River-Great Divide Basin drainage divide area landform origins near the Ferris Mountain, Wyoming, USA

Authors

Abstract:

This essay uses topographic map evidence to interpret landform origins in the Sweetwater River-Great Divide Basin drainage divide area located near the Wyoming Ferris Mountains. The Ferris Mountains are a west-northwest to east-southeast oriented mountain ridge located between Green Mountain to the west and the Seminoe Mountains to the southeast. The Sweetwater River flows in an east direction north of Green Mountain and the Ferris Mountains to join the north oriented North Platte River. The Great Divide Basin eastern end is located south of the Ferris Mountains and Green Mountain and west of the Seminoe Mountains with the Great Divide Basin being a large region of internal drainage located along east-west continental divide. The Sweetwater River-Great Divide Basin drainage divide is not located along the high Green Mountain-Ferris Mountain ridge, but is instead located in the low relief region located south of Green Mountain and the Ferris Mountains. Muddy Creek is a southwest, northwest, and north oriented Sweetwater River tributary draining the Ferris Mountains south flank and the Green Mountain east end and flows through a deep gap between Green Mountain and the Ferris Mountains. Sand Creek flows in a southwest direction from the Ferris Mountains east end and the turns to flow in a north and northeast direction through a deep gap between the Ferris Mountains and Bear Mountain. Youngs Pass is a deep through valley eroded across the Ferris Mountains and links north oriented Cherry Creek with the southwest oriented Muddy Creek headwaters valley. Further east in the Seminoe Mountains north-northeast oriented North Platte River tributary valleys are linked by through valleys with south-southeast oriented North Platte River tributary valleys. The deep water gaps, through valleys, and wind gaps are interpreted to have been eroded by south oriented flood flow prior to headward erosion of the deep east oriented Sweetwater River valley and probably at a time when the present day north oriented North Platte River alignment was being used as a south oriented flood flow channel. At that time Wyoming mountain ranges had not emerged and floodwaters were able to flow across what are today major mountain barriers. Floodwaters were derived from the western margin of a thick North American ice sheet and were flowing from western Canada to and across Wyoming to reach actively eroding Colorado River tributary valleys. Mountain ranges emerged as floodwaters deeply eroded surrounding basins and basins and as ice sheet related crustal warping raised the mountain ranges. South oriented flood flow across the emerging Ferris Mountains and Green Mountain ended as headward erosion of the deep east oriented Sweetwater River valley and its northeast oriented tributary valleys beheaded south oriented flood flow routes. Floodwaters on north ends of major south oriented flood flow channels reversed flow direction to flow to the deeper Sweetwater River valley and to create north oriented Sweetwater River tributary drainage routes. Flood flow on the present day north oriented North Platte River alignment was reversed when headward erosion of a much deeper east and southeast North Platte River valley along the Laramie Mountains northeast and north flank beheaded the south oriented flood flow channel west of the Laramie Mountains. Ice sheet related crustal warping that was raising mountain ranges and the entire North Platte River headwaters area contributed to the flood flow reversal.

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 Sweetwater River-Great Divide Basin drainage divide area landform origins near the Wyoming Ferris Mountains. 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 Sweetwater River-Great Divide Basin drainage divide area landform evidence near the Wyoming Ferris Mountains will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Sweetwater River-Great Divide Basin drainage divide area near the Wyoming Ferris Mountains location map

Figure 1: Sweetwater River-Great Divide Basin drainage divide area near the Wyoming Ferris Mountains 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 Sweetwater River-Great Divide Basin drainage divide area near the Wyoming Ferris Mountains and illustrates a region in south central Wyoming with Colorado and Utah being located south of Wyoming (Utah is in the southwest corner of figure 1). The Great Divide Basin is a large region of interior drainage located in southern Wyoming along the east-west continental divide. The Wind River Range is north of the Great Divide Basin in the northwest quadrant of figure 1. The Sweetwater River originates near Wind River Peak in the Wind River Range and flows in a south-southeast direction to near South Pass. From South Pass the Sweetwater River flows in an east-northeast and east direction north of the Great Divide Basin to join the north oriented North Platte River at Pathfinder Reservoir. The North Platte River originates in Colorado south of figure 1 and flows in a north-northwest direction between the Sierra Madre and Medicine Bow Mountains to Pathfinder Reservoir. From Pathfinder Reservoir the North Platte River flows in a north-northeast and northeast direction to Casper at the Laramie Mountains northwest end. From Casper the North Platte River flows in an east, south, and east direction to the east edge of figure 1 (north half) and east of figure 1 flows in a southeast direction into Nebraska with water eventually reaching the Gulf of Mexico. West of the Great Divide Basin is the south oriented Green River drainage basin with the Green River joining the southwest oriented Colorado River south and west of figure 1 and water eventually reaching the Pacific Ocean. Little Sandy Creek originates almost next to the Sweetwater River headwaters and flows in a south-southwest direction to join the southwest oriented Big Sandy River, which then joins the south oriented Green River. South of the Great Divide Basin are south oriented drainage routes to the Little Snake River, which flows in a west and southwest direction through Savery, Dixon, and Baggs along the Wyoming-Colorado border and then into Colorado to join the west oriented Yampa River (south of figure 1), which then joins the south oriented Green River. Muddy Creek is a south oriented tributary joining the Little Snake River near Baggs. The Ferris Mountains are located south of the Sweetwater River and west of Pathfinder Reservoir and are east of Green Mountain (Mountains in figure 1). Muddy Gap is located between Green Mountain and the Ferris Mountains. Bairoil and Lamont are towns south of Green Mountain near the Great Divide Basin north rim. The Sweetwater River-Great Divide Basin drainage divide area near the Ferris Mountains investigated in this essay is located along the Great Divide Basin north rim from the Green Mountain eastern end to the Ferris Mountains eastern end and is the drainage divide between north oriented Sweetwater River tributaries and south oriented drainage headed into the Great Divide Basin.

The drainage routes seen in figure 1 developed during immense melt water floods that flowed from the western margin of a thick North American ice sheet in western Canada to and across the region seen in figure 1. At first Montana, Wyoming, Utah, and Colorado mountain ranges had not emerged and floodwaters could freely flow across what are today major mountain barriers. Mountain ranges emerged as floodwaters deeply eroded the surrounding basins and valleys and as ice sheet related crustal warping raised the mountain ranges and the entire region. Ice sheet related crustal warping combined with deep glacial erosion also created a deep “hole” in which the ice sheet was located. The north oriented North Platte River drainage route west of the Laramie Mountains originated as a major south oriented flood flow channel. Floodwaters on that south oriented flood flow channel were beheaded by headward erosion of a much deeper east and southeast oriented flood flow channel on the present day North Platte River alignment downstream from Casper, which had eroded headward around the Laramie Mountains northwest end. Floodwaters on the north end of the beheaded flood flow channel reversed flow direction to flow to the much deeper east and southeast oriented North Platte River valley and to create the north, east, and southeast oriented North Platte River drainage route. The reversal of the North Platte River west of the Laramie Mountains actually occurred in multiple steps and each beheading and flood flow reversal event was probably greatly aided by crustal warping that was raising mountain ranges and the entire region in the present day North Platte River headwaters area.

The east oriented Sweetwater River valley initially eroded headward from the south oriented flood flow channel on the present day north oriented North Platte River alignment to capture south oriented flood flow west of the present day North Platte River valley (see how the Sweetwater turns to flow in a south direction to join the north oriented North Platte River at Pathfinder Reservoir). Floodwaters captured by headward erosion of the deep east oriented Sweetwater River valley had been flowing across the Rattlesnake Hills and Ferris Mountains and then across the eastern Great Divide Basin where the floodwaters diverged with some flood flow turning in an east and southeast direction to converge with south oriented flood flow on the North Platte River alignment and the remaining flood flow turning in a southwest direction to flow to what was then the evolving south oriented Muddy Creek and the Little Snake River valley system. Headward erosion of the deep east oriented Sweetwater River valley beheaded these flood flow routes across the eastern Great Divide Basin and floodwaters on north ends of beheaded flood flow routes reversed flow direction to create north oriented Sweetwater River tributary drainage routes. Reversal of flood flow on the North Platte River alignment probably took place as the deep east oriented Sweetwater River valley was eroding headward across flood flow still moving in a south direction further to the west. Subsequently flood flow reversals caused by headward erosion of the deep northeast oriented Yellowstone River valley across Montana (north of figure 1) ended flood flow to actively eroding Sweetwater River valley. The deep northeast oriented Yellowstone River was eroding headward from space at the south end of the deep “hole” the melting ice sheet was opening up and which at first was being drained in a south direction across eastern Nebraska.

Detailed location map for Sweetwater River-Great Divide Basin drainage divide area near the Ferris Mountains

Figure 2: Detailed location map Sweetwater River-Great Divide Basin drainage divide area near the Ferris Mountains. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 2 provides a more detailed location map for the Sweetwater River-Great Divide Basin drainage divide area near the Wyoming Ferris Mountains. The North Platte River flows in a north direction from Seminoe Reservoir straddling the southeast corner of figure 2 to Pathfinder Reservoir straddling the northeast corner of figure 2. North and east of figure 2 the North Platte River flows in a north-northeast, east, and southeast direction around the northwest end of the Laramie Mountains. The Sweetwater River flows in an east, southeast, east, southeast, east, northeast, east, and south direction from the northwest corner of figure 2 to join the North Platte River at Pathfinder Reservoir (near northeast corner of figure 2). The Ferris Mountains are located slightly south and east of the center of figure 2. West of the Ferris Mountains is Green Mountain and east of the Ferris Mountains are the Seminoe Mountains. Seminoe Dam is located where the North Platte River flows through a deep water gap eroded across the Seminoe Mountains. Muddy Creek drains the Ferris Mountains south side and flows in a southwest, west-northwest, north, north-northeast direction to and through the town of Muddy Gap to join the east oriented Sweetwater River. Muddy Gap is also the name of the water gap where Muddy Creek flows between Green Mountain and the Ferris Mountains. Camp Creek is an east-southeast and northeast oriented tributary joining Muddy Creek south of the water gap. East of north-northeast oriented Muddy Creek and north of the Ferris Mountains are north oriented Sweetwater River tributaries including Cherry Creek, Pete Creek, and Rush Creek. Further east is north-northeast oriented Arkansas Creek, which flows to the flooded Sweetwater River valley at Pathfinder Reservoir, and east-southeast and northeast oriented Sand Creek, which flows to the flooded north oriented North Platte River valley at Pathfinder Reservoir. West of north-northeast oriented Muddy Creek is north, northeast, and north-northeast oriented Willow Creek, which originates at the Green Mountain east end and which flows to the east oriented Sweetwater River. The dashed line extending from the west edge of figure 2 (south of Green Mountain) in an eastward direction south of the Muddy Creek drainage basin and then turning in south direction to Bradley Peak and the south edge of figure 2 (east half) is the Great Divide Basin north and east rim. Streams south and west of that Great Divide Basin rim end within the Great Divide Basin and there is no overflow to external drainage routes. Lost Soldier Creek is an east and east-southeast oriented south of the Green Mountain eastern end. South of the Ferris Mountains Stone Creek flows in a west and southwest direction north and west of Table Mountain. The north oriented North Platte River valley is very close to the Great Divide Basin eastern rim, which is a clue that drainage routes in the region differ from what they once were.

Willow Creek-Lost Soldier Creek drainage divide area

Figure 3: Willow Creek-Lost Soldier 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-Lost Soldier Creek drainage divide area. The map contour interval for figure 3 is 20 meters. Green Mountain is the forested upland in the northwest quadrant of figure 3. Whiskey Peak is the eastern end of the Green Mountain upland and is located slightly north and west of the center of figure 3. Willow Creek flows in a northeast direction from Green Mountain to the north center edge of figure 3. North of figure 3 Willow Creek flows in a north-northeast direction to join the east oriented Sweetwater River. Muddy Creek flows in a northwest, north, and north-northeast direction from the east edge of figure 3 (south half) to the north edge of figure 3 (near northeast corner). Muddy Gap near the northeast corner of figure 3 is where Muddy Creek has eroded a water gap across the Red Hills. North of figure 3 Muddy Creek flows in a north-northeast direction to join the Sweetwater River. Murphree Creek and Camp Creek are east-southeast and northeast oriented Muddy Creek tributaries in the southeast quadrant of figure 3. Lost Soldier Creek flows in an east direction near the south center edge of figure 3 and east of Bairoil turns in a southeast direction and south of figure 3 ceases to exist as a surface stream. Southeast oriented Lost Soldier Creek tributaries originate on the southeast-facing Stratton Rim and Whiskey Ridge escarpment and include Laundry Draw, Reed Creek, and Abel Creek. These tributaries join Lost Soldier Creek near Bairoil. North and west of the southeast-facing Stratton Rim and Whiskey Ridge escarpment are the northeast oriented Willow Creek headwaters, which are linked by a through valley with south-southwest oriented Crooks Creek (not labeled in figure 3) headwaters. The Willow Creek-Crooks Creek through valley orientation is probably determined by the orientation of dipping resistant strata, although the through valley is also a water-eroded valley. The through valley is almost 200 meters deep and appears to be on the dip slope side of a large hogback ridge with the southeast-facing escarpment being on the scarp side. The southeast-facing escarpment appears to be an abandoned southeast-facing headcut, which had been eroded by southeast oriented flood flow. If correctly interpreted the large headcut was eroded at a time when the region to the north and west was at least as high as the headcut rim and large volumes of southeast oriented flood flow were moving to a much deeper southeast oriented valley eroding headward along the present day Lost Soldier Creek alignment. Headward erosion of deep northeast oriented Willow Creek valley from what was at that time the actively eroding and deep east oriented Sweetwater River valley head captured the southeast oriented flood flow and diverted floodwaters in a northeast and east direction. Probably the south-southwest oriented Crooks Creek headwaters valley eroded headward from the deep southeast oriented valley on the Lost Soldier Creek alignment, although it was subsequently captured by a flood flow reversal to flow in a northwest and north direction around the Green Mountain west end.

Detailed map of Willow Creek-Lost Soldier Creek drainage divide area

Figure 4: Detailed map of Willow Creek-Lost Soldier 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-Lost Soldier Creek drainage divide area seen in less detail in figure 3. The map contour interval for figure 4 is 20 feet. Willow Creek flows in a southeast direction near the northwest corner of figure 4 and then turns to flow in a northeast direction to the north edge of figure 4(west of center). North of figure 4 Willow Creek flows in a north-northeast direction to join the east oriented Sweetwater River. The southwest oriented stream in the northwest quadrant of section 23 flowing to the west edge of figure 4 (south of center) is a tributary to south-southwest, northwest, north, and northeast oriented Crooks Creek, which flows around the Green Mountain west end. Stratton Rim in section 24 and Whiskey Ridge in sections 18, 17, and 16 form the crest of what may have originated as a large southeast oriented headcut. At the time the headcut was eroded southeast oriented floodwaters from north and west of figure 4 were flowing to a much deeper southeast oriented valley eroding headward into the region. At that time elevations north of Green Mountain were at least as high as the top of Green Mountain today and there was no deep east oriented Sweetwater River valley to the north of figure 4. Note how in sections 18 and 17 the escarpment crest elevation is lower than on either side providing evidence of what may have been a southeast oriented valley eroded into the high level erosion surface on which the floodwaters were flowing. Reed Creek originates in section 19 and Abel Creek originates in section 20 south of the former southeast oriented valley and flow in south-southeast and southeast direction to southeast oriented Lost Soldier Creek (south of figure 4). Elevations along the Whiskey Ridge crest drop to less than 8400 feet at points near the border between sections 18 and 19, while Stratton Rim to the west rises to 8725 feet and Whiskey Peak to the east rises 9225 feet. The Willow Creek-Crooks Creek through valley west of the southeast-facing escarpment was eroded as floodwaters were captured by headward erosion of the deep northeast oriented Willow Creek valley from what at that time was the actively eroding east oriented Sweetwater River valley head and by headward erosion of the south oriented Crooks Creek headwaters valley, probably from the deep southeast oriented Lost Soldier Creek flood flow channel. Headward erosion of that deep through valley ended all southeast oriented flood flow across the southeast oriented headcut face. Subsequently headward erosion of the deep east oriented Sweetwater River valley and its tributary valleys eroded the north flank of Green Mountain to produce the landscape seen today.

Muddy Creek-Lost Soldier Creek drainage divide area

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

Figure 5 illustrates the Muddy Creek-Lost Soldier Creek drainage divide area east of figure 3 and there is an overlap area with figure 3. The map contour interval for figure 5 is 20 meters. The west end of the Ferris Mountains can be seen in the east half of figure 5. Muddy Creek flows in a southwest, northwest, and north direction from the east edge of figure 5 (along the Ferris Mountains southwest flank) to Muddy Gap near the north center edge of figure 5. North of figure 5 Muddy Creek flows in a northeast direction to join the east oriented Sweetwater River. Crest Creek is the northwest oriented tributary joining Muddy Creek near the southeast corner of figure 5. Whiskey Creek originates along the Ferris Mountains northeast flank and flows in a northwest direction to Whiskey Gap and then in a north direction to the north edge of figure 5 (east of center). North of figure 5 Whiskey Creek flows in a northeast direction toward the Sweetwater River. Muddy Gap and Whiskey Gap are water gaps eroded across hogback ridges. In the same region other water gaps and wind gaps can be seen. These water and wind gaps provide evidence the regional drainage routes originated on an erosion surface higher in elevation than the tops of the hogback ridges. Probably, south oriented flood flow channels initiated the Muddy Gap and Whiskey Gap water gap valleys. The south oriented flood flow channels were beheaded and reversed by headward erosion of deeper northeast oriented valleys from what at that time was the actively eroding east oriented Sweetwater River valley. Lost Soldier Creek flows in an east and southeast direction near the southwest corner of figure 5 and south of figure 5 flows into the Great Divide Basin and then ends. Whiskey Peak is located near the west edge of the northwest quadrant of figure 5 and represent the Green Mountain eastern end. A broad and deep northwest to southeast oriented through valley linking the north oriented Sweetwater River tributary valleys with south oriented Lost Soldier Creek valley is located between Green Mountain to the west and the Ferris Mountains to the east. The through valley floor elevation north of Lamont is between 2060 and 2080 meters. Whiskey Peak reaches an elevation of 2812 meters and elevations greater than 2900 meters can be found in the western Ferris Mountains. These elevations suggest the north to south oriented through valley is approximately 700 meters deep. While the through valley is probably related to regional geologic structures the through valley is also an erosional feature. Probably at the time floodwaters first flowed across the region the entire region had an elevation equivalent to or higher than the tops of the Ferris Mountains and of Green Mountain (although crustal warping may have raised the mountains and/or region since that time). In other words the Ferris Mountains and Green Mountain did not exist (at least as topographic features) at that time. The Ferris Mountains and Green Mountain emerged as floodwaters deeply eroded the surrounding areas, although crustal warping that raised the mountains may also have played a role.

Detailed map of Muddy Creek-Whiskey Creek drainage divide area

Figure 6: Detailed map of Muddy Creek-Whiskey 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 Muddy Creek-Whiskey Creek drainage divide area seen in less detail in figure 5. The map contour interval for figure 6 is 20 feet. Whiskey Creek flows in a northwest direction from near the southeast corner of figure 6 to Whiskey Gap in section 12 and then turns to flow in a north-northeast direction to the north edge of figure 6 (east half). North of figure 6 Whiskey Creek flows in a northeast direction toward the east oriented Sweetwater River. Whiskey Gap is a water gap eroded across the northwest end of the Ferris Mountains structure. Whiskey Creek crosses the 6540-foot contour line as it flows through Whiskey Gap. Elevations in section 1 to the northwest rise to 7335 feet. Much higher elevations are found in the Ferris Mountains to the southeast. These elevations suggest Whiskey Gap is at least 800 feet deep. A wind gap in the southwest quadrant of section 12 links the north-northeast oriented Whiskey Creek valley with the north oriented Muddy Creek valley south of figure 6. The wind gap or through valley floor elevation is shown as being 6635 feet. Elevations to the northwest rise to more than 7140 feet suggesting the wind gap is at least 500 feet deep. An interesting water gap is located in section 11 and drains in a south direction across a northwest to southeast oriented ridge. The south oriented stream crosses the 6460-foot contour in the water gap. Elevations to the northwest rise to more than 6720 feet and to the southeast to more than 6660 feet. These elevations suggest the water gap is at least 200 feet deep. Muddy Creek flows in a north direction from the south edge of figure 6 (west half) to Muddy Gap (in northwest corner of section 3) and then flows in a northeast direction to the north edge of figure 6 (slightly west of center). Muddy Gap is a water gap eroded across the Red Hills structure. Muddy Creek crosses the 6300-foot contour line shortly before flowing through Muddy Gap. Elevations to the northwest rise to 6961 feet and elevations exceed 7000 feet to the southeast. These elevations suggest the Muddy Gap water gap is more than 660 feet deep. Note how northwest to southeast oriented through valleys link northwest oriented Muddy Creek tributaries with a southeast oriented Whiskey Creek tributary and with the south oriented water gap in the southwest quadrant of section 11. These through valleys follow the geologic structure orientation, but are also water-eroded valleys. Drainage routes in figure 6 were initiated on an erosion surface at least as high as the tops of the ridges now crossed by the water and wind gaps. In other words floodwaters stripped 800 feet or more of bedrock material from the region surrounding the higher ridges. Floodwaters first moved in south direction across the region and then were beheaded and reversed by headward erosion of the deep east-oriented Sweetwater River valley north of figure 6.

Cherry Creek-Muddy Creek drainage divide area

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

Figure 7 illustrates the Cherry Creek-Muddy Creek drainage divide area east of figure 5 and includes an overlap area with figure 5. The map contour interval for figure 7 is 20 meters. Figure 7 shows the entire Ferris Mountains upland area. Youngs Pass is a labeled pass near the center of the Ferris Mountains. Muddy Creek originates south of Youngs Pass and flows in a southwest direction to the base of the southwest flank of the Ferris Mountains upland and then turns to flow in a west-northwest, north, and west direction to the west center edge of figure 7. West of figure 7 Muddy Creek turns to flow in a north direction to Muddy Gap and then in a northeast direction to the east oriented Sweetwater River. Cherry Creek originates north of Youngs Pass and flows in a north direction to the north center edge of figure 7 and then to the east oriented Sweetwater River. Youngs Pass is a through valley eroded across the Ferris Mountains and links the north oriented Cherry Creek valley with the southwest oriented Muddy Creek headwaters valley. It is difficult to determine the Youngs Pass elevation on figure 7, but it appears to be between 2640 and 2660 meters. Elevations in the Ferris Mountains on either side of Youngs Pass exceed 2900 meters suggesting Youngs Pass is approximately 250 meters deep. Unlike Muddy Gap and Whiskey Gap to the northwest Youngs Pass is a through valley eroded across the highest regions in the Ferris Mountains and provides evidence of a south oriented flood flow channel that originally flowed on a surface equivalent in elevation if not higher to the Ferris Mountains highest elevations. When floodwaters flowed across the Ferris Mountains the deep east oriented Sweetwater River valley north of the figure 7 did not exist and the region north of the Ferris Mountains was at least as high as the tops of Ferris Mountains. It is possible crustal warping since that time has raised the region and/or the Ferris Mountains. The south oriented flood flow was moving to deep south-oriented valleys eroding headward across the present day Great Divide Basin. South oriented flood flow crossing the Ferris Mountains deeply eroded the region south of the Ferris Mountains while headward erosion of the deep east oriented Sweetwater River valley and its tributary valleys deeply eroded the region to the north. The north oriented Cherry Creek drainage route developed when headward erosion of the deep Sweetwater River valley beheaded the south oriented flood flow channel moving floodwaters across Young Pass. Floodwaters on the north end of the beheaded flood flow channel reversed flow direction to flow to the much deeper east oriented Sweetwater River valley.

Detailed map of Cherry Creek-Muddy Creek drainage divide area

Figure 8: Detailed map of Cherry Creek-Muddy 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 Cherry Creek-Muddy Creek drainage divide area seen in less detail in figure 7. The map contour interval for figure 8 is 20 feet. Youngs Pass is located near the center of figure 8 and is located in the northeast quadrant of section 36. Cherry Creek originates in section 26 immediately to the north of Youngs Pass and flows in a north direction to the north edge of figure 8 (slightly west of center). North of figure 8 Cherry Creek flows to the east oriented Sweetwater River. A Muddy Creek tributary originates immediately to the south of Youngs Pass and flows in a south and southwest direction to join Muddy Creek in section 1. From section 1 Muddy Creek flows in a southwest direction to the south edge of figure 8 (west half). South of figure 8 Muddy Creek turns to flow in a northwest, north, and northeast direction around the west end of the Ferris Mountains to eventually reach the east oriented Sweetwater River. The Youngs Pass elevation is between 8740 and 8760 feet. Elevations in section 27 near the west edge of figure 8 reach 9670 feet and elevations in section 4 near the southeast corner of figure 8 reach 10,037 feet. These elevations suggest Youngs Pass is at least 900 feet deep. Youngs Pass like the water gaps and wind gaps seen in figures 5 and 6 is a water-eroded through valley and was eroded by south oriented flood flow at a time when the Ferris Mountains did not stand high above the region to the north. At that time there was no deep east oriented Sweetwater River valley north of figure 8 and floodwaters were flowing on an erosion surface at least as high as the highest Ferris Mountains elevations today. The Ferris Mountains were emerging as floodwaters flowed across the region and the floodwaters stripped several hundred meters of bedrock material from surrounding regions. Floodwaters flowed across the emerging Ferris Mountains to and across the present day Great Divide Basin to reach actively eroding Colorado River tributary valleys. Flood flow across Youngs Pass was beheaded by headward erosion of the deep east oriented Sweetwater River valley north of figure 8. Floodwaters on the north end of the beheaded flood flow route reversed flow direction to create the north oriented Cherry Creek drainage route. Ice sheet related crustal warping may have raised the Ferris Mountains as floodwaters were flowing across Youngs Pass and may have contributed to the flood flow reversal and creation of the Cherry Creek-Muddy Creek drainage divide.

Sand Creek-Riddle Creek drainage divide area

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

Figure 9 illustrates the Sand Creek-Riddle Creek drainage divide area east and south of figure 7 and there is an overlap area with figure 7. The map contour interval for figure 9 is 20 meters. The Ferris Mountains straddle the north edge of figure 9 with Bear Mountain being the isolated upland near the east edge of figure 9 (north half). Sand Creek is the southeast, northeast, north, and northeast oriented stream originating near southeast end of the Ferris Mountains and flowing in a north direction through Sand Creek Canyon between the Ferris Mountains and Bear Mountain to the northeast corner of figure 9. North and east of figure 9 Sand Creek flows in a northeast direction to join the north oriented North Platte River at Pathfinder Reservoir. Sand Creek Canyon is located in a major north to south oriented valley eroded between the Ferris Mountains to the west and Bear Mountain to the east. Sand Creek crosses the 2000-meter contour line before entering the deep water gap. Elevations on Bear Mountain exceed 2280 meters and much higher elevations are found in the Ferris Mountains to the west. These elevations suggest the Sand Creek Canyon water gap when viewed in larger sense is almost 300 meters deep. This 300-meter deep water gap was not eroded by Sand Creek, but was initially eroded by south oriented flood flow moving to and across what is now the eastern Great Divide Basin. Sand dunes shown in figure 9 probably include flood-transported sediments that were deposited where floodwaters spread out in the region south of the emerging Ferris Mountains. Riddle Creek can be seen flowing in a west direction slightly east of the south center edge of figure 9. South of figure 9 Riddle Creek flows to southwest oriented Stone Creek, which flows to the Boggy Meadows area where it ends. The Boggy Meadows area also receives water from north and northeast oriented Separation Creek, which is linked by through valleys with south oriented Muddy Creek and the west and southwest Little Snake River drainage basin (which drains to the Green and Colorado Rivers). The Boggy Meadows area is also linked by a north-northwest to south-southeast oriented through valley with the north oriented North Platte River valley south of Haystack Mountain (the North Platte River has eroded a deep water gap across the Haystack Mountains structure. These through valleys (not seen in this essay) provide evidence of diverging and converging south oriented flood flow channels that existed prior to the reversal of flood flow on the present day North Platte River alignment.

Deweese Creek-Hurt Creek drainage divide area

Figure 10: Deweese Creek-Hurt Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 provides a topographic map of the Deweese Creek-Hurt Creek drainage divide area seen in less detail in figure 9. The map contour interval for figure 10 is 20 meters. The North Platte River flows in a north direction from Seminoe Reservoir near the southeast corner of figure 10 to the south end of Pathfinder Reservoir near the northeast corner of figure 10 (Pathfinder Reservoir extends for a considerable distance to the north of figure 10). Sand Creek flows in a southeast and north direction across the northwest corner of figure 10 and north of figure 10 flows in a northeast direction to join the North Platte River at Pathfinder Reservoir. East of north oriented Sand Creek is Bear Mountain and east of Bear Mountain is north-northwest and north-northeast oriented Deweese Creek. Deweese Creek originates east of Bradley Peak in the Seminoe Mountains and flows to the north center edge of figure 10 and north of figure 10 joins the north oriented North Platte River at Pathfinder Reservoir. South of the Deweese Creek headwaters are headwaters of south-southeast oriented Hurt Creek, which flows to the south edge of figure 10 (slightly east of center). South of figure 10 Hurt Creek flows in a southeast direction to join the north oriented North Platte River as a barbed tributary. A through valley across the Seminoe Mountains west end links the north oriented Deweese Creek valley with the south oriented Hurt Creek valley. The through valley floor elevation is between 2400 and 2420 meters. Bradley Peak to the west rises to more than 2700 meters and elevations east of the through valley rise to 2544 meters. These elevations suggest the through valley is at least 120 meters deep. Similar through valleys further to the east in the Seminoe Mountains link northeast oriented Long Creek and Hamilton Creek headwaters valleys with the southeast and east-southeast oriented Morgan Creek valley. And east of those through valleys is the deep North Platte River water gap eroded across the Seminoe Mountains. The through valleys crossing the Seminoe Mountains provide evidence of diverging and converging south oriented flood flow channels that existed at a time before erosion of the deep North Platte River water gap and before the reversal of flood flow on the North Platte River alignment. At that time diverging and converging flood flow channels crossed the region and elevations north of the Seminoe Mountains were at least as high as the highest Seminoe Mountain ridges today (although crustal warping since that time may have raised the Seminoe Mountains and/or the entire region). Also, elevations west of the Seminoe Mountains were also probably as high as the Seminoe Mountains. South oriented floodwaters probably initiated erosion of the deep North Platte River water gap prior to the reversal of flood flow that created the north oriented North Platte River drainage route and that created the northeast oriented North Platte River tributary drainage routes.

Additional information and sources of maps studied

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

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