Abstract:

This essay uses topographic map evidence to interpret landform origins in the Medicine Bow River-Pass Creek drainage divide area north of the Wyoming Medicine Bow Mountains. North of the Medicine Bow Mountains the Medicine Bow River flows in a northeast direction before tuning to flow in a northwest, west, and northwest direction to join the north oriented North Platte River, which then flows around the northwest end of the Laramie Mountains and then turns to flow in a southeast direction on the east side of the Laramie Mountains. Pass Creek flows in a northwest and west direction through a deep water gap south of Elk Mountain (west of the adjacent north oriented Medicine Bow River valley) before turning in a north and southwest direction to join the north, northwest, northeast, and north oriented North Platte River as a barbed tributary. Water gaps where modern-day drainage routes cross hogback ridges, wind gaps where former drainage routes cross hogback ridges, barbed tributaries where drainage routes flowing in one direction join drainage routes flowing in the opposite direction, through valleys linking valleys in different drainage basins, and elbows of capture where drainage routes make major changes in their direction of flow, are common in the region between the north, northeast, northwest, west, and northwest oriented Medicine Bow River and northwest, west, north, and southwest oriented Pass Creek are illustrated interpreted here in the context of immense melt water floods flowing from the western margin of a thick North American ice sheet in western Canada to and across Wyoming. When floodwaters first crossed the region mountain ranges, including the Medicine Bow Mountains, had not emerged and floodwaters flowed across what are today major mountain barriers. Mountain ranges emerged as floodwaters deeply eroded valleys and basins surrounding them and as ice sheet related crustal warping raised the mountain ranges and the entire region. The present day north oriented North Platte River route west of the Medicine Bow Mountains (and of the Laramie Mountains north and east of the Medicine Bow Mountains) originated as south oriented flood flow channels. As the Medicine Bow Mountains emerged floodwaters that had been flowing in south directions across and along what are today high Medicine Bow Mountain regions were diverted in southeast, east, and northeast directions into the northern Laramie Basin and then across the emerging Laramie Mountains to the much deeper southeast oriented North Platte River valley, which was eroding headward along the east side of the emerging Laramie Mountains. Headward erosion of the much deeper southeast oriented North Platte River valley around the northwest end of the Laramie Mountains beheaded (in multiple steps) south oriented flood flow channels on the present day north oriented North Platte River alignment. Floodwaters on north ends of  beheaded flood flow channels reversed flow direction to flow to the much deeper southeast oriented North Platte River valley and to create the north and southeast oriented North Platte River drainage route. Reversal of flood flow on the North Platte River alignment also reversed southeast, east, and northeast oriented flood flow channels north of the emerging Medicine Bow Mountains to create west and northwest oriented North Platte River tributary drainage routes and to create elbows of capture where northeast oriented streams turn to flow in northwest directions.

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 Medicine Bow River-Pass Creek drainage divide area landform origins north of the Wyoming Medicine Bow 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 Medicine Bow River-Pass Creek drainage divide area landform evidence north of the Wyoming Medicine Bow Mountains will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Medicine Bow River-Pass Creek drainage divide area location map

Figure 1: Medicine Bow River-Pass Creek drainage divide area location map (select and click on maps to enlarge). National Geographic Society map digitally presented using National Geographic Society TOPO software.

Figure 1 provides a location map for the Medicine Bow River-Pass Creek drainage divide area north of the Wyoming Medicine Bow Mountains and illustrates a region in southern Wyoming. The Wyoming-Colorado state line is located along the south edge of figure 1. The Laramie Mountains extend in a southeast and south direction from the north edge of figure 1 (east half) to near the southeast corner of figure 1. The Medicine Bow Mountains extend in a south-southeast direction from near highway 80 to the south edge of figure 1 (east of center) and continue south of figure 1 into Colorado. The Laramie Basin (not labeled in figure 1) is located between the Medicine Bow Mountains and the Laramie Mountains. The North Platte River flows in a north-northwest direction along the west side of the Medicine Bow Mountains and north of highway 80 turns to flow in a northeast, north, and north-northeast direction to the north center edge of figure 1. North of figure 1 the North Platte River flows around the northwest end of the Laramie Mountains and then turns to flow in a southeast direction across the northeast corner of figure 1. The Medicine Bow River originates in the northern Medicine Bow Mountains and flows in a north direction to the town of Elk Mountain and then turns to flow in a northeast and northwest direction to the town of Medicine Bow. From Medicine Bow the Medicine Bow River flows in a northwest, west, and northwest direction to join the North Platte River at Seminoe Reservoir. Rock Creek is an unlabeled Medicine Bow River tributary originating east of Medicine Bow Peak and flowing in a north and northeast direction to McFadden and Rock River before turning in a northwest direction to join the Medicine Bow River near the town of Medicine Bow. Pass Creek originates in the northern Medicine Bow Mountains (west of the Medicine Bow River headwaters) and then flows in a northwest, west, north, and southwest direction to join the north oriented North Platte River as a barbed tributary. The unnamed northwest, southwest, and northwest oriented stream joining the North Platte River near the town of Fort Steele is Saint Marys Creek. The Laramie River flows in a north and northeast direction from south edge of figure 1 (on east side of Medicine Bow Mountains) to the city of Laramie and then flows in a north direction to near Wheatland Reservoir before turning in an east and northeast direction across the Laramie Mountains (in a deep valley) and to the east edge of figure 1 (north of center). East of figure 1 the Laramie River joins the southeast oriented North Platte River. The Medicine Bow River-Pass Creek drainage divide area investigated in this essay is north of the Medicine Bow Mountains, south and west of the Medicine Bow River, north and east of Pass Creek, and east of the North Platte River.

The Medicine Bow River, Pass Creek, and other drainage routes north of the Medicine Bow Mountains developed during immense melt water floods from the western margin of a thick North American ice sheet with floodwaters flowing from western Canada to and across Wyoming. At the time floodwaters flowed across the region the Medicine Bow Mountains, Laramie Mountains, and other regional mountain ranges were just beginning to emerge and at first floodwaters could freely flow across what are today major mountain barriers. The present day north oriented North Platte River alignment originated as south oriented flood flow channels west of the emerging Laramie and Medicine Bow Mountains. Likewise the present day north oriented Laramie River drainage route originated as south oriented flood flow channels between the emerging Medicine Bow and Laramie Mountains. Floodwaters flowed in diverging and converging flood flow channels and east and southeast oriented flood flow channels diverged from the south oriented flood flow channels on the North Platte River alignment to flow to south oriented flood flow channels on the Laramie River alignment and some of these diverging and converging flood flow channels became concentrated in the region north of the emerging Medicine Bow Mountains (and south of the Shirley Mountains). Headward erosion of northeast oriented valleys eroding headward from a much deeper southeast oriented North Platte River valley (which was eroding headward east of the Laramie Mountains) captured floodwaters entering the Laramie Basin and diverted the floodwaters in an east and northeast direction to the much deeper southeast oriented North Platte River valley. This diversion of floodwaters across the Laramie Mountains also beheaded and reversed the south oriented flood flow channels in the Laramie Basin. Floodwaters on north ends of beheaded flood flow channels reversed flow direction to flow to the deeper east and northeast oriented flood flow routes and to create the present day north and northeast oriented Laramie River drainage system. Headward erosion of the deep southeast oriented North Platte River valley around the northwest end of the Laramie Mountains (north of figure 1) next beheaded in multiple steps the south oriented flood flow channels on the present day North Platte River alignment west of the Laramie and Medicine Bow Mountains. Floodwaters on north ends of the beheaded flood flow channels reversed flow direction to flow 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. The northwest and west oriented Medicine Bow River drainage route and the west oriented Saint Marys Creek drainage route were created by reversals of southeast, east, and northeast oriented flood flow flowing from the south oriented flood flow channels on the North Platte River alignment across the northern Laramie Basin and the emerging Laramie Mountains to the much deeper southeast oriented North Platte River valley east of the Laramie Mountains at the time flood flow on the North Platte River alignment was reversed. Flood flow reversals and headward erosion of deep valleys in the region north of Medicine Bow Mountains was aided by ice sheet related crustal warping raising the mountain ranges and the entire region.

Detailed location map for Medicine Bow River-Pass Creek drainage divide area

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

Figure 2 provides a detailed location map for the Medicine Bow River-Pass Creek drainage divide area north of the Wyoming Medicine Bow Mountains. The Medicine Bow Mountains are south of the southeast quadrant of figure 2. The North Platte River meanders in a north direction from the south edge of figure 2 (west half) to Fort Steele and then turns in a northwest and northeast direction to enter Seminoe Reservoir where the North Platte River valley again is oriented in a north direction to the north edge of figure 2. Pass Creek flows in a northwest, west, north, and southwest direction from the south center edge of figure 2 to join the north oriented North Platte River as a barbed tributary (north of Sand Basin in the southwest quadrant of figure 2). Rattlesnake Creek originates on Elk Mountain (north of south center edge of figure 2) and flows in a southwest, north, northwest, southwest, and west direction to join north oriented Pass Creek. Saint Marys Creek originates in the region west of the Saddleback Hills and flows in a northwest, southwest, and west-northwest direction to join the North Platte River near Fort Steele. Big Ditch flows in a west and northwest direction from near Hanna to join the North Platte River at Seminoe Reservoir. The Medicine Bow River flows in a north direction from the south edge of figure 2 (east of center) to the town of Elk Mountain and then turns to flow in a northeast direction almost to the east edge of figure 2 before turning to flow in a northwest direction to the town of Medicine Bow. From Medicine Bow the Medicine Bow River flows in a northwest, west, and northwest direction to join the North Platte River at Seminoe Reservoir just north of figure 2. First Sand Creek is a north-northeast oriented stream east of the Saddleback Hills flowing towards the northwest oriented Medicine Bow River. Rock Creek is the northeast oriented stream flowing across the southeast corner of figure 2 to the town of McFadden. East of figure 2 Rock Creek flows in a northeast direction almost to the north oriented Laramie River before turning in a northwest direction to join the Medicine Bow River near the east edge of figure 2 (near where Medicine Bow River turns to flow in a northwest direction just east of the town of Medicine Bow). Most drainage routes seen in figure 2 originated as flood flow channels flowing in a direction exactly opposite to the direction the drainage routes flow today. Uplift of the Medicine Bow Mountains and of the entire region contributed to the flood flow reversals, which were triggered by headward erosion of deeper valleys, especially by headward erosion of the deep southeast oriented North Platte River valley around the northwest end of the Laramie Mountains (north of figure 2).

Rattlesnake Creek-Pass Creek drainage divide area

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

Figure 3 provides a topographic map of Rattlesnake Creek-Pass Creek drainage divide area. The map contour interval for figure 3 is 20 meters. Elk Mountain is the high mountain in the east half of figure 3 and is located at the northwest end of the Medicine Bow Mountains. The top of Elk Mountain has an elevation of 3400 meters. Pass Creek flows in a northwest, west, and north direction from the south edge of figure 3 (east of center) to the north edge of figure 3 (near northwest corner) and north and west of figure 3 Pass Creek turns to flow in a southwest direction to join the north oriented North Platte River. Pass Creek has eroded a deep water gap at the south end of Elk Mountain with Coad Mountain being located south of Elk Mountain and of the water gap. The top of Coad Mountain has an elevation of 2882 meters, although Medicine Bow Mountains peaks to the south reach higher elevations (e.g. Kennaday Peak to the south of Coad Mountain reaches 3295 meters). The elevation in the water gap between Elk Mountain and Coad Mountain is between 2200 and 2300 meters suggesting the Pass Creek water gap is at least 600 meters deep and may be as much as 1000 meters deep. This deep water gap is evidence of deep erosion of the region north of the Medicine Bow Mountains since the time the west oriented Pass Creek drainage route was established. Elk Mountain is probably an erosional residual left after floodwaters removed up to 1000 meters of bedrock material from the surrounding region. Rattlesnake Creek originates on the west side of Elk Mountain and flows in a northwest, southwest, north, northwest, southwest, and west direction to join north oriented Pass Creek near the northwest corner of figure 3. Brush Creek also originates on the west side of Elk Mountain (south of the Rattlesnake Creek headwaters) and flows in a northwest, southwest, and south direction to join west oriented Pass Creek at the west end of the Pass Creek water gap. Parallel north to south oriented through valleys link the north oriented Pass Creek valley with the south oriented Brush Creek valley. The deeper through valley floor elevation is between 2460 and 2480 meters. Sheephead Mountain to the west rises to 2680 meters suggesting the through valleys are approximately 200 meters deep if not deeper. The through valley orientations are probably determined by regional geologic structures, but the through valleys are water-eroded valleys and were eroded by south oriented flood flow moving to the west oriented Pass Creek valley at a time when the deep west oriented Rattlesnake Creek valley to the north did not exist. Headward erosion of the west oriented Rattlesnake Creek valley captured the south oriented flood flow and diverted the floodwaters in a west direction to what at that time was probably a south oriented flood flow channel on the present day north oriented Pass Creek alignment. Flood flow on north ends of the beheaded south oriented flood flow channels reversed flow direction to flow to the deeper west oriented Rattlesnake Creek valley and to create the southwest, north, and west oriented Rattlesnake Creek drainage route.

Medicine Bow River-Pass Creek drainage divide area

Figure 4: Medicine Bow River-Pass Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 provides a topographic map of the Medicine Bow River-Pass Creek drainage divide area east of figure 3 and includes an overlap area with figure 3. The map contour interval for figure 4 is 20 meters. Elk Mountain (elevation 3400 meters) is located in the west half of figure 4 and Coad Mountain is located near the southwest corner of figure 4. South of Coad Mountain is Oberg Pass (a wind gap with an elevation of about 2500 meters) and south of Oberg Pass is Pennock Mountain, which reaches an elevation of more than 3000 meters. South of Pennock Mountain is Cedar Pass with an elevation of 2592 meters and south of Cedar Pass is Kennaday Peak with an elevation of 3285 meters. Pass Creek flows in a north, northwest, and west direction from the south edge of figure 4 (west half) to flow between Elk Mountain and Coad Mountain and then to flow to west edge of figure 4. West of figure 4 Pass Creek flows in a north and southwest direction to join the north oriented North Platte River. The Medicine Bow River flows in a north direction from the south edge of figure 4 (east of center) to the north edge of figure 4 (east of center-near town of Elk Mountain). North of figure 4 the Medicine Bow River turns to flow in a northeast direction before tuning to flow in a northwest, west, and northwest direction to join the north oriented North Platte River. O’Mara Creek is the northeast oriented Medicine Bow River tributary east of Elk Mountain and is linked by a northeast to southeast oriented through valley with south and southwest oriented Thode Creek, which flows to west oriented Pass Creek. The O’Mara Creek-Thode Creek through valley floor elevation is between 2380 and 2400 meters. Pass Creek and the Medicine Bow River both originate at much higher elevations in the Medicine Bow Mountains to the south of figure 4. Based on elevations seen in figure 4 the O-Mara Creek-Thode Creek through valley is at least 100 meters deep, although based on elevations along the Pass Creek-Medicine Bow River drainage divide to the south of figure 4 a case could be made that the through valley is more than 400 meters deep. Probably the through valley alignment was initiated by southwest oriented flood flow diverging from a south oriented flood flow channel on the present day north oriented Medicine Bow River alignment and flowing to a west oriented valley eroding headward between Elk Mountain and Coad Mountain (probably from a south oriented flood flow channel west of figure 4). At the time the through valley was initiated the Medicine Bow Mountains to the south were still emerging and floodwaters had been able to flow in a south direction across what are today high mountain areas, but were gradually being diverted around the rising mountain mass. Uplift of the mountains to the south and headward erosion of the deep west oriented Pass Creek valley beheaded and reversed the south oriented flood flow channel on the present day north oriented Pass Creek alignment south of figure 4 to create the north, northwest, and west oriented Pass Creek drainage route seen in figure 4, which captured south oriented flood flow still moving on the present day north oriented Medicine Bow River alignment. Flood flow on the Medicine Bow River alignment was next beheaded and reversed by headward erosion of a northeast oriented valley (probably from east and northeast oriented flood flow channels leading to the Laramie Basin and to the much deeper southeast oriented North Platte River valley east of the emerging Laramie Mountains). Uplift of the Medicine Bow Mountains and of the entire region was occurring as these flood flow captures and reversals were taking place.

Rattlesnake Creek-Medicine Bow River drainage divide area

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

Figure 5 illustrates the Rattlesnake Creek-Medicine Bow River drainage divide area north and east of figure 4 and there is an overlap area with figure 4. The map contour interval for figure 5 is 20 meters. The Medicine Bow River flows in a north and east direction across the southeast corner of figure 5. East of figure 5 the Medicine Bow River flows in a northeast direction before turning to flow in a northwest, west, and northwest direction to join the north oriented North Platte River (which is located west of figure 5). First Sand Creek flows in a north-northeast and northeast direction (east of Simpson Ridge) to near the northeast corner of figure 5. North and east of figure 5 First Sand Creek flows toward the northwest oriented Medicine Bow River. The north end of Elk Mountain straddles the south edge of figure 5 (slightly west of center). Rattlesnake Creek flows in a north, northwest, southwest, and west direction from the south edge of figure 5 (west of Elk Mountain) to the west edge of figure 5 (near southwest corner). Dana Meadows is located near the northwest corner of figure 5. North of Dana Meadows Saint Marys Creek (unlabeled in figure 5) flows in a west-northwest direction to the north edge of figure 5 (near northwest corner). Saint Marys Creek tributaries include west oriented Percy Creek and north oriented Martinez Creek, Dana Springs Creek, and Kinney Creek. A through valley links the north oriented Dana Springs Creek valley with the Rattlesnake Creek valley at the point where Rattlesnake Creek changes from flowing in a north and northwest direction to flowing in a southwest and west and direction. The through valley floor elevation at its deepest point is between 2220 and 2240 meters. Halleck Ridge to the east rises to more than 2420 meters and Dana Ridge to the west (and west of figure 5) rises to 2410 meters. These elevations suggest the through valley is at least 170 meters deep. Ridges in the region are hogback ridges and their orientations are determined by regional geologic structures, however the through valley is a water-eroded valley and was eroded by south oriented flood flow prior to headward erosion of the west-northwest oriented Saint Marys Creek valley. Headward erosion of the Saint Marys Creek valley beheaded the south oriented flood flow and floodwaters on north ends of the beheaded flood flow routes reversed flow direction to create the north oriented Dana Springs Creek, Martinez Creek, and Kinney Creek drainage routes. Halleck Creek flows in a north direction from the south edge of figure 5 (at Elk Mountain) and then turns to flow in an east and east-southeast direction to join the Medicine Bow River north of the town of Elk Mountain. Rattlesnake Pass (south of Halleck Ridge) links the Rattlesnake Creek valley with the Halleck Creek and Medicine Bow River valleys. Rattlesnake Pass was probably eroded by southwest oriented flood flow moving to the Rattlesnake Creek valley. Mill Creek is the north oriented Halleck Creek tributary located west of the town of Elk Mountain. The north oriented Mill Creek valley and the north-northeast oriented First Sand Creek headwaters valleys are linked by a north to south oriented through valley north of Halleck Creek. The through valley was probably eroded by south oriented flood flow prior to a reversal of flood flow on the First Sand Creek alignment.

Saint Marys Creek-Pass Creek drainage divide area

Figure 6: Saint Marys Creek-Pass Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 provides a topographic map of the Saint Marys Creek-Pass Creek drainage divide area north and east of figure 3 and includes an overlap area with figure 3. The map contour interval for figure 6 is 20 meters. The North Platte River flows in a north, northwest, north, and northwest direction from the south edge of figure 6 (west half) to the west edge of figure 6 (north half). West and north of figure 6 the North Platte River turns to flow in a northeast direction. The north oriented North Platte River has eroded a water gap across the ridge labeled “Hogback”. Pass Creek flows in a north-northwest and southwest direction from the south edge of figure 6 (east half) to join the north oriented North Platte River as a barbed tributary near the south edge of figure 6. Saint Marys Creek flows in a southwest and northwest direction from the north edge of figure 6 (east half) to join the North Platte River near the town of Fort Steele and where the North Platte River turns from flowing in a north direction to flowing in a northwest direction. A northwest to southeast oriented through valley links the northeast oriented North Platte River valley (north of figure 6) with the Saint Marys Creek valley and also with the north-northwest and southwest oriented Pass Creek valley. The through valley is located between the Fort Steele Breaks ridge and Saint Marys Ridge and was eroded by southeast oriented flood flow moving to the present day north oriented Pass Creek valley. The southeast oriented flood flow channel converged with a another southeast oriented flood flow channel on the present day northwest oriented Saint Marys Creek and North Platte River alignments (south of the Fort Steele Breaks ridge) near Walcott Junction. Headward erosion of the northeast oriented North Platte River valley (north of figure 6) from a newly reversed flood flow channel on the north oriented North Platte River alignment in the Seminoe Reservoir area (see figure 2) first beheaded the southeast oriented flood flow channel and next beheaded and reversed the southeast oriented flood flow channel south of Fort Steele Breaks ridge to create the northwest oriented North Platte River and Saint Marys Creek drainage route segments. The reversal of flood flow on the North Platte River segment south of the Fort Steele Breaks ridge also reversed a diverging south oriented flood flow channel on the present day north oriented North Platte River alignment to create the north and northwest oriented North Platte River drainage route segments seen in figure 6. The flood flow reversal that created the present day north oriented North Platte River drainage route occurred in multiple steps of the type described here and did not occur in a single step.

North Platte River-Saint Marys Creek drainage divide area

Figure 7: North Platte River-Saint Marys Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the North Platte River-Saint Marys Creek drainage divide area north and west of figure 6 and includes an overlap area with figure 6. The map contour interval for figure 7 is 20 meters. The North Platte River flows in a north direction from south edge of figure 7 (west of center) to near Fort Steele and then turns to flow in a northwest direction along southwest side of the northwest to southeast oriented Fort Steele Breaks ridge to the west edge of figure 7 (near northwest corner) where the North Platte River flows across the Fort Steele Breaks ridge and then turns in an east-northeast direction to flow to the north edge of figure 7 (west of center). North of figure 7 the North Platte River flows in a north and north-northeast direction to flow around the northwest end of the Laramie Mountains and then to flow in a southeast direction on the east side of the Laramie Mountains. Saint Marys Creek flows in a southwest direction from the east center edge of figure 7 to near Walcott and then turns to flow in a northwest direction along the southwest side of the Fort Steele Breaks ridge to join the northwest oriented North Platte River. A northwest to southeast oriented through valley between the Fort Steele Breaks Ridge and Cedar and Saint Marys Ridges links an east oriented North Platte River segment with the Saint Marys Creek valley (and as seen in figure 6 with the north-northwest oriented Pass Creek valley south of figure 7). What could be a much broader northwest to southeast oriented through valley is located north and east of the Cedar and Saint Marys Ridges and is marked at the southeast end by shallower northwest to southeast oriented through valleys between Taylor Draw and Saint Marys Creek. One of these through valleys is directly north of Saint Marys Hill and has a floor elevation of between 2060 and 2080 meters. Saint Marys Hill rises to 2284 meters and the unnamed hill to the northeast rises to at least 2160 feet suggesting the through valley is at least 80 meters deep. The second shallow through valley is located along the southwest side of Edson Ridge and has a floor elevation of between 2080 meters. Edson Ridge rises to 2145 meters suggesting the through is at least 45 meters deep. Boneside Pass between Cedar Ridge and Saint Marys Ridge is also a water-eroded valley and has a floor elevation of between 2020 and 2040 meters. Cedar Ridge rises to more than 2160 meters suggesting Boneside Pass is at least 120 meters deep. These through valleys were eroded by southeast oriented flood flow prior to headward erosion of the deeper east-northeast oriented North Platte River valley to the northwest, which captured the flood flow and diverted the floodwaters to the newly reversed North Platte River drainage route north of figure 7. Headward erosion of the east-northeast oriented North Platte River valley also beheaded and reversed a southeast oriented flood flow channel on the southwest side of the Fort Steele Breaks ridge to create the northwest oriented North Platte River and Saint Marys Creek drainage route segments seen in figure 7. The reversal of flood flow that produced the northwest oriented North Platte River drainage route segment also beheaded and reversed flood flow on the north oriented North Platte River drainage route segment seen in figure 7 and further captured the southwest oriented flood flow channel on the southwest oriented Saint Marys Creek alignment seen in figure 7 (which had previously been converging with the southeast oriented flood flow channel on the southwest side of the Fort Steele Breaks ridge to flow in a south-southeast direction of the present day north-northwest oriented Pass Creek alignment south of figure 7.

Medicine Bow River-Medicine Bow River drainage divide area

Figure 8: Medicine Bow River-Medicine Bow River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 provides a topographic map of the Medicine Bow River-Medicine Bow River drainage divide north and east of figure 5 and there is a small overlap area with figure 5. The map contour interval for figure 8 is 20 meters. The Medicine Bow River flows in a north-northwest, north-northeast, northeast, and north-northeast direction from the south edge of figure 8 (east half) to be joined by west oriented Rock Creek (unlabeled stream near west edge of figure 8 and east of the town of Medicine Bow) and then turns to flow in northwest direction to flow to the north edge of figure 8 (east of center). North of figure 8 the Medicine Bow River flows in a northwest, west, and northwest direction to join the north oriented North Platte River. Big Ditch is a west oriented drainage route near the highway and railroad in the northwest quadrant of figure 8 and west of figure 8 drains in a southwest and northwest direction to join the north oriented North Platte River. First Sand Creek flows in a northeast, north, northeast, and north direction from near the southwest corner of figure 8 to Allen Lake (west of the town of Medicine Bow and near the Medicine Bow River). Spade Flats and Horne Flats are located on the floor of what was once a southeast oriented flood flow channel that diverged from the south oriented flood flow channel on the present day north oriented North Platte River alignment and that continued to the northeast oriented Rock Creek valley east of figure 8. The northeast oriented Rock Creek drainage route today continues almost to the Laramie Mountains and then turns in a northwest and west direction to join the Medicine Bow River as seen in figure 8. East of figure 8 the northeast oriented Rock Creek drainage is linked through valleys with deep valleys crossing the Laramie Mountains (see Medicine Bow River-Laramie River drainage divide area between the Medicine Bow and Laramie Mountains essay). In other words flood flow moving across the region seen in figure 8 flowed across the Laramie Mountains to what at that time was the actively eroding and much deeper southeast oriented North Platte River valley. At that time the southeast oriented North Platte River valley had not eroded around the northwest end of the Laramie Mountains to behead and reversed south oriented flood flow channels on the present day north oriented North Platte River alignment. When the flood flow channels west of the northwest end of the Laramie Mountains were beheaded and reversed flood flow across figure 8 was also reversed to create the northwest oriented Medicine Bow River drainage route.

Big Ditch-Saint Marys Creek drainage divide area

Figure 9: Big Ditch-Saint Marys Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the Big Ditch-Saint Marys Creek drainage divide area west and slightly south of figure 8 and there is an overlap area with figure 8. The map contour interval for figure 9 is 20 meters. Big Ditch drains in a west, southwest, and west direction from the east edge of figure 9 (near northeast corner and highway) to the west edge of figure 9 (north of center). West of figure 9 Big Ditch drains in a northwest direction to the north oriented North Platte River. Jim Creek flows in a north-northwest direction to join Big Ditch east of the town of Elmo. A northwest oriented Jim Creek tributary originates near Simpson Gap and the southwest oriented Carbon Creek headwaters flow between the Sand Hills to the southwest and Hi Allen Ridge to the northeast before flowing to the east center edge of figure 9. East of figure 9 Carbon Creek turns in a northeast and southeast direction to join First Sand Creek. Simpson Ridge is the large ridge labeled “Ridge” in the southeast quadrant of figure 9.  Simpson Gap and the Carbon Creek drainage route seen in figure 9 were eroded by southeast and east oriented flood flow diverging from a south oriented flood flow channel on the present day north oriented North Platte River alignment and flowing in a southeast and east direction on the present day west and northwest oriented Big Ditch alignment to the flow in an east direction on the present day Carbon Creek alignment to the Spade Flats area and then in an east and northeast direction across the emerging Laramie Mountains to reach the much deeper and actively eroding North Platte River valley on the east side of the emerging Laramie Mountains. Saint Marys Creek flows in a northwest direction north of Dana Meadows in the southwest quadrant of figure 9 to reach the west edge of figure 9 and west of figure 9 flows in a northwest, southwest, and northwest direction to join the northwest oriented North Platte River segment on the southwest side of the Fort Steele Breaks ridge. Percy Creek flows in a southwest and west direction to join north oriented tributaries on the west side of Dana Meadows to form the Saint Marys Creek drainage route. Through valleys link the southwest oriented Percy Creek valley with the west oriented Carbon Creek valley and with the west oriented Big Ditch valley. The through valleys are located between hogback ridges, but are water-eroded valleys and were eroded by east and northeast oriented floodwaters flowing from a south oriented flood flow channel on the present day north oriented North Platte River alignment in a southeast, east, and northeast direction to cross the emerging Laramie Mountains to reach the much deeper southeast oriented North Platte River valley located east of the emerging Laramie Mountains. Floodwaters flowed in southeast, east, and northeast directions across this region to deeply erode the landscape north of the Medicine Bow Mountains and contributed to the emergence of the Medicine Bow Mountains as a high mountain range. Headward erosion of the deep southeast oriented North Platte River valley around the northwest end of the emerging Laramie Mountains beheaded the south oriented flood flow channels (in multiple steps) on the present day north oriented North Platte River alignment. Floodwaters on north ends of the beheaded flood flow routes reversed flow direction to flow to the much deeper southeast oriented North Platte River valley and in the process beheaded and reversed southeast, east, and northeast oriented flood flow channels on the Saint Marys and Big Ditch alignments to create the present day southwest, west, and northwest oriented Saint Marys Creek and Big Ditch drainage systems.

Medicine Bow River-Big Ditch drainage divide area

Figure 10: Medicine Bow River-Big Ditch drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 provides a topographic map of the Medicine Bow River-Big Ditch drainage divide area north and slightly east of figure 9 and includes an overlap area with figure 9. The map contour interval for figure 10 is 20 meters. The Medicine Bow River flows in a west-northwest and west direction from the east edge of figure 10 (north half) to the west edge of figure 10 (north half) and west of figure 10 turns to flow in a northwest direction to join the north oriented North Platte River at Seminoe Reservoir. Big Ditch flows in a west and southwest direction from near Como Lake (near southeast corner of figure 10) to the south edge of figure 10 (east of center). South and west of figure 10 Big Ditch drains in a southwest, west, and northwest direction to join the north oriented North Platte River. Pine Draw is an east oriented drainage route draining to the east center edge of figure 10 and east of figure 10 joins the northwest oriented Medicine Bow River as a barbed tributary. Dixie Draw is an east-northeast oriented Pine Draw tributary and Missouri John Draw is a northeast oriented Pine Draw tributary while South Pine Draw is a north and east-northeast oriented Pine Draw tributary. These and other unlabeled Pine Draw tributaries make up an extensive east oriented drainage system in a region drained today by west oriented tributaries to the north oriented North Platte River. The east oriented Pine Draw drainage system is a relic of the southeast, east, and northeast oriented flood flow routes that diverged from the south oriented flow channels on the present day north oriented North Platte River alignment and that then flowed to and across the emerging Laramie Mountains to reach the much deeper southeast oriented North Platte River valley on the east side of the emerging Laramie Mountains. Hanna Draw in a north-northeast oriented tributary draining to the west oriented Medicine Bow River from the north end of the strip mine area. The north-northeast oriented Hanna Draw valley eroded headward across numerous northwest to southeast oriented flood flow channels supplying floodwaters to what was at that time the actively eroding Pine Draw valley system. Headward erosion of the deeper north-northeast oriented Hanna Draw valley beheaded the southeast oriented flood flow channels and diverted the floodwaters to what was then an actively eroding east oriented Medicine Bow River valley. Floodwaters on northwest ends of the beheaded flood flow routes reversed flow direction to create the northwest oriented Hanna Draw tributary drainage routes seen today. Next headward erosion of the deeper east oriented valley on the present day west oriented Medicine Bow River alignment beheaded and reversed the southeast oriented flood flow routes to the newly eroded north-northeast oriented Hanna Draw valley. Floodwaters on northwest ends of the beheaded flood flow routes reversed flow direction to create the northwest oriented Medicine Bow River tributary drainage routes seen today. Reversal of flood flow on the North Platte River alignment created the north oriented North Platte River drainage route west of figure 10 and also reversed flood flow on the Medicine Bow River alignment to create the west oriented Medicine Bow River drainage route seen in figure 10.

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.