Yellowstone River-Pacific Creek drainage divide area landform origins along continental divide south of Yellowstone National Park, Wyoming, USA

Authors


 

Abstract:

This essay uses topographic map evidence to interpret landform origins in the region between the Yellowstone River and Pacific Creek along the continental divide south of Yellowstone National Park. The Yellowstone River originates in the high Thorofare Plateau region of the Absaroka Range and flows in a northwest and north direction to the Yellowstone National Park south boundary with water eventually reaching the Gulf of Mexico. Pacific Creek is a southwest oriented tributary to the south oriented Snake River (in Grand Teton National Park) with water eventually reaching the Pacific Ocean. Northeast oriented Yellowstone River tributary valleys are linked by deep through valleys or passes across the continental divide with southwest oriented Pacific Creek tributary valleys, the most impressive of which is Two Ocean Pass, which links the southwest oriented Pacific Creek headwaters valley with the northeast oriented Atlantic Creek valley. These through valleys or passes were eroded by southwest oriented flood flow channels diverging from a south oriented flood flow channel on the present day north oriented Yellowstone River alignment. Floodwaters were derived from the western margin of a thick North American ice sheet and were flowing from western Canada in south and southeast directions to and across the study region. At that time the Yellowstone Plateau and Absaroka Range did not stand high above surrounding regions. Ice sheet related crustal warping raised the Yellowstone Plateau and Absaroka Range and contributed to massive flood flow reversals that created the north oriented Yellowstone River drainage system. West of Two Ocean Pass the southwest oriented Pacific Creek valley is linked by north-to-south oriented through valleys with tributaries to west oriented Buffalo Fork, which is located south of Pacific Creek and which also flows to the south oriented Snake River. East and south of Two Ocean Pass the northwest oriented Yellowstone River headwaters are linked by north-to-south oriented through valleys with tributaries to west oriented Buffalo Fork. These north-to-south oriented through valleys or passes cross what are today high mountain ridges and provide evidence the south and southeast oriented melt water floods once flowed on a surface at least as high, if not higher, than the highest Absaroka Range elevations today.

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 Yellowstone River-Pacific Creek drainage divide area landform origins along the continental divide south of Yellowstone National Park, Wyoming. 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 Yellowstone River-Pacific Creek drainage divide area landform evidence along the continental divide located south of Yellowstone National Park, Wyoming will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Yellowstone River-Pacific Creek drainage divide area location map

Figure 1: Yellowstone River-Pacific 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 Yellowstone River-Pacific Creek drainage divide area along the continental divide located south of Yellowstone National Park and illustrates a region of northwest Wyoming with Yellowstone National Park located in the northwest corner of Wyoming. The Yellowstone River originates south of the Yellowstone National Park southeast corner and flows in a north-northwest direction to Yellowstone Lake. From Yellowstone Lake the Yellowstone River flows in a northwest direction to Canyon and then in a northeast and north direction to the north edge of figure 1. North of figure 1 the Yellowstone River flows in a northwest direction into Montana where it turns to flow in a north-northeast, east-northeast, and east-southeast direction before turning to flow in a northeast direction to join the Missouri River with water eventually reaching the Gulf of Mexico. The Snake River originates near the Yellowstone National Park south boundary (south of Yellowstone Lake) and flows in a northwest direction toward Heart Lake and then abruptly turns to flow in a south and west direction before flowing again in a south direction to Jackson Lake in Grand Teton National Park. From Jackson Lake the Snake River continues to flow in a south direction to the south edge of figure 1. South of figure 1 the Snake River turns to flow in a northwest direction into Idaho where it turns to flow in a southwest and northwest direction. In western Idaho the Snake River turns again to flow in a north direction and joins the west oriented Columbia River with water eventually reaching the Pacific Ocean. Pacific Creek is a southwest oriented Snake River tributary originating near Two Ocean Pass and joins the Snake River at Jackson Lake. Buffalo Fork is a west-southwest oriented Snake River tributary directly south of Pacific Creek and originates further east than Two Ocean Pass. The Yellowstone River-Pacific Creek drainage divide area along the continental divide investigated here is south of the Yellowstone National Park boundary, west and south of the Yellowstone River, and north of the west-southwest oriented Buffalo Fork headwaters location.

A brief look at the regional drainage history is needed to understand interpretations given below. Drainage routes shown in figure 1 developed as immense south and southeast oriented melt water floods flowed across the region and later as crustal warping raised the Yellowstone Plateau and Absaroka Range area. Floodwaters were derived from the west margin of a melting thick ice sheet and were flowing from western Canada to and across the region shown in figure 1. As immense south and southeast oriented floods crossed the region the deep east and northeast oriented Yellowstone River valley eroded headward from space being opened in a deep “hole” in which the large North American ice sheet was melting. The deep “hole” was located north and east of the figure 1 map area, which is located along the deep “hole’s” deeply eroded southwest rim. The deep east and northeast oriented Yellowstone River valley eroded headward from the deep “hole” to capture immense south and southeast oriented ice marginal floods and beheaded the much shallower south and southeast oriented flood flow channels crossing the figure 1 map area. Floodwaters on north ends of beheaded flood flow channels reversed flow direction and with the aid of crustal warping that was raising the Yellowstone Plateau and Absaroka Range created the north oriented Yellowstone River drainage route seen in figure 1. Prior to the massive flood flow reversal floodwaters had been flowing to the actively eroding south oriented Snake River valley and its tributary valleys, including the Buffalo Fork and Pacific Creek valleys. The present day northwest oriented Snake River headwaters route was created independently prior to the Yellowstone River flood flow reversal when headward erosion of the deep south oriented Snake River valley beheaded and reversed a much a much shallower southeast oriented flood flow channel.

Detailed location map for Yellowstone River-Pacific Creek drainage divide area

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

Figure 2 provides a more detailed location map for the Yellowstone River–Pacific Creek drainage divide area south of Yellowstone National Park. The east-west continental divide is shown with a labeled dashed line and extends from the north edge of figure 2 (near northwest corner) to Two Ocean Pass (near the center of figure 2) to Togwotee Pass (near south center edge of figure 2). A large region in southeast Yellowstone National Park is shown in a red-brown color in the northwest quadrant of figure 2. Jackson Lake in Grand Teton National Park is located near the southwest corner of figure 2. The Snake River originates west of the continental divide along the Yellowstone National Park south boundary and flows in a northwest direction until south of Heart Lake where it turns to flow in a south, northwest, southwest and south direction to Jackson Lake. From Jackson Lake the Snake River flows in an east direction to Moran and then in a south-southwest direction to the south edge of figure 2. Pacific Creek is a southwest oriented stream originating at Two Ocean Pass and joining the Snake River near Moran. Note how unlabeled west, southwest, and south oriented Pacific Creek tributaries originate almost directly south of the northwest oriented Snake River headwaters. South Buffalo Fork originates east and south of the center of figure 2 and flows in a west-southwest direction to join west and south oriented North Buffalo Fork and then to flow as Buffalo Fork in a west direction to join the Snake River near Moran. The south oriented North Buffalo Fork segment is located south of Two Ocean Pass. The Yellowstone River originates on the northeast side of the continental divide just north of the west-southwest oriented South Buffalo Fork headwaters. From its origin the Yellowstone River flows in a northwest and north-northwest direction to enter the Southeast Arm of Yellowstone Lake (north of Two Ocean Plateau in Yellowstone National Park). Atlantic Creek is the labeled northeast oriented tributary flowing to the north-northwest oriented Yellowstone River from Two Ocean Pass. Discussions of detailed maps below describe linkages between the various drainage routes shown. For example, Two Ocean Pass links the northeast oriented Atlantic Creek valley with the southwest oriented Pacific Creek valley and was eroded by southwest oriented flood flow moving from a south oriented flood flow channel on the present day north oriented Yellowstone River alignment to the actively eroding south oriented Snake River valley.

Falcon Creek-Mink Creek drainage divide area

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

Figure 3 provides a topographic map of the Falcon Creek-Mink Creek drainage divide area. The Yellowstone National Park southern boundary is shown with a labeled west-to-east oriented dashed line slightly north of the center of figure 3. The east-west continental divide is shown with a labeled dashed line and extends from the north edge of figure 3 (west of center) in an east direction to near the north center edge of figure 3 and then in a south direction to the south center edge of figure 3. The Yellowstone River flows in a northwest and north direction from the east edge of figure 3 (near southeast corner) to the north edge of figure 3. Labeled northeast oriented tributaries from the west are Lynx Creek in Yellowstone National Park, Falcon Creek, and Atlantic Creek near the south edge of figure 3. Falcon Creek originates near Phelps Pass. West of the continental divide at Phelps Pass Mink Creek flows in a west, southwest, and south direction to the south edge of figure 3 (west half) and south of figure 3 joins southwest oriented Pacific Creek. The Snake River  (labeled “River” in figure 3) originates along the Yellowstone National Park boundary just west of the continental divide and flows in a west and southwest direction before turning to flow in a northwest direction to the west edge of figure 3 (north half). Note the unlabeled southeast and north oriented tributary joining the northwest oriented Snake River in the west center area of figure 3. The valley of that north oriented Snake River tributary is linked by a through valley with a south-southeast oriented Mink Creek tributary valley. The map contour interval for figure 3 is 50 meters and the through valley floor elevation at the drainage divide is between 2550 and 2600 meters. Elevations along the continental divide to the east rise to more than 3000 meters and some small areas greater than 3000 meters in elevation can be seen near the west edge of figure 3. These elevations suggest the through valley is at least 400 meters deep. Phelps Pass is another deep through valley seen in figure 3 and has an elevation at the continental divide of between 2700 and 2750 meters. Elevations on the continental divide both to the north and to south rise to more than 3000 meters suggesting the Phelps Pass through valley is at least 250 meters deep. The north-to-south oriented Snake River-Mink Creek through valley was eroded by a south oriented flood flow channel moving floodwaters from the present day northwest oriented Snake River alignment to the southwest oriented Pacific Creek valley. The Phelps Pass through valley was eroded by a southwest flood flow channel that diverged from a south oriented flood flow channel on the present day north oriented Yellowstone River alignment and first moved the floodwaters to the south oriented Mink Creek flood flow channel and , after the flow direction in the Snake River valley was reversed to flow in a northwest direction, may have moved floodwaters to the northwest oriented Snake River flood flow channel.

Detailed map of Falcon Creek-Mink Creek drainage divide area

Figure 4: Detailed topographic map of the Falcon Creek-Mink 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 Falcon Creek-Mink Creek drainage divide area seen in less detail in figure 3 above. The continental divide is shown with a labeled dashed line and extends from the north center edge to the south center edge of figure 4. Phelps Pass is labeled and is located near the center of figure 4. Falcon Creek flows in a northeast direction from Phelps Pass to the north edge of figure 4 (near northeast corner) and north and east of figure 4 joins the north oriented Yellowstone River with water eventually reaching the Gulf of Mexico. Mink Creek flows in a west, south, and southwest direction from Phelps Pass to the west edge of figure 4 (south of center) and west and south of figure 4 joins southwest oriented Pacific Creek, which flows to the south oriented Snake River. The Snake River flows in a southwest direction across the northwest corner of figure 4 and west of figure 4 turns to flow in a northwest and later a south direction with water eventually reaching the Pacific Ocean. The map contour interval for figure 4 is 40 feet and the Phelps Pass elevation at the continental divide is between 8880 and 8920 feet. South of Phelps Pass in section 33 elevations rise to 10,164 feet with elevations greater than 10,000 feet being located just north of the north edge of figure 4. These elevations suggest the Phelps Pass through valley is approximately 1100 feet deep. The through valley is a water-eroded feature and was eroded by southwest oriented flood flow moving from the present day north oriented Yellowstone River valley to the southwest oriented Pacific Creek valley and then to the south oriented Snake River valley. The southwest oriented Phelps Pass flood flow channel converged with a southeast and south oriented flood flow channel moving from the present day northwest oriented Snake River alignment (north and west of figure 4). A reversal of flood flow direction in the Yellowstone River valley created the north oriented Yellowstone River drainage route and northeast oriented Falcon Creek drainage route and the drainage divide at Phelps Pass. A reversal of flood flow in the present day northwest oriented Snake River valley segment created the northwest oriented Snake River drainage route and ended southeast and south oriented flood flow to the south oriented Mink Creek valley and the southwest oriented Pacific Creek valley.

Atlantic Creek-Pacific Creek drainage divide area at Two Ocean Pass

Figure 5: Atlantic Creek-Pacific Creek drainage divide area at Two Ocean Pass. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the Atlantic Creek-Pacific Creek drainage divide area ay Two Ocean Pass south and slightly east of figure 3 and includes an overlap area with figure 3. The east-west continental divide is shown with a labeled dashed line and extends from the north edge of figure 5 (at Phelps Pass-west of center) to the near the southeast corner of figure 5. The Yellowstone River flows in a north and northwest direction from the east edge of figure 5 (south half) to the north edge of figure 5 (east half) and north of figure 5 flows in a north direction as seen in figure 3. Two Ocean Pass is located near the center of figure 5 and Atlantic Creek flows in a northeast direction from Two Ocean Pass to join the Yellowstone River near the north edge of figure 5. Pacific Creek originates at Two Ocean Pass and flows in a southwest and west direction to be by joined by west, south, southwest, and south oriented Mink Creek near the west edge of figure 5 and then to flow in a south and southwest direction to the west edge of figure 5 (near southwest corner). Two Ocean Pass is a deep northeast-to-southwest oriented through valley linking the present day north oriented Yellowstone River valley with the southwest oriented Pacific Creek valley and the south oriented Snake River valley. The map contour interval for figure 5 is 50 meters. The continental divide elevation at Two Ocean Pass is between 2450 and 2500 meters. Elevations north of Two Ocean Pass rise to more than 3050 meters while elevations to the south rise to more than 3200 meters. These elevations suggest Two Ocean Pass is at least 550 meters deep. Two Ocean Pass is a water-eroded feature and was eroded by a southwest oriented flood flow channel diverging from a south and southeast oriented flood flow channel on the present day north oriented Yellowstone River alignment. Floodwaters eroding the deep Two Ocean Pass through valley were flowing to the south oriented Snake River valley west and south of figure 5. The drainage divide at Two Ocean Pass was created when a flood flow reversal created the north oriented Yellowstone River drainage route. The flood flow reversal was caused by crustal uplift raising the Yellowstone Plateau and Absaroka Range region along the southwest rim of the deep “hole” in which the melting thick ice sheet was located and by headward erosion of the much deeper northeast oriented Yellowstone River valley from space in the deep “hole” being opened up by the melting ice sheet.

Detailed map of Atlantic Creek-Pacific Creek drainage divide area

Figure 6: Detailed map of Atlantic Creek-Pacific Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 illustrates a detailed topographic map of the Atlantic Creek-Pacific Creek drainage divide area at Two Ocean Pass seen in less detail in figure 5. The east-west continental divide is shown with a labeled dashed line and extends from the figure 6 north edge (slightly west of center) to the south center edge of figure 6. Two Ocean Pass is a remarkable through valley and is located near the center of figure 6. Note south and south-southeast oriented North Two Ocean Creek, which flows to Two Ocean Pass and then splits to flow in two different directions and to two different oceans. Atlantic Creek flows in a northeast direction from Two Ocean Pass to the north edge of figure 6 (near northeast corner) and then to the north oriented Yellowstone River with water eventually reaching the Gulf of Mexico. Pacific Creek flows in a southwest direction from Two Ocean Pass to the southwest corner of figure 6 with water flowing to the Snake River and eventually reaching the Pacific Ocean. The map contour interval for figure 6 is 40 feet and the Two Ocean Pass elevation at the continental divide is between 8120 and 8160 feet. South of Two Ocean Pass, near where the continental divide crosses the south edge of figure 6, elevations rise to 10,258 feet (even higher further to the south). North of Two Ocean Pass in section 4 elevations rise to 10,136 feet (even higher further to the north). These elevations indicate that Two Ocean Pass is approximately 2000 feet deep if not deeper. Two Ocean Pass is a water-eroded feature and was eroded by a southwest oriented flood flow channel diverging from a south and southeast oriented flood flow channel on the present day north oriented Yellowstone River alignment. Floodwaters were flowing to the deep south oriented Snake River valley, which was being eroded headward in the Grand Teton National Park area seen in figures 1 and 2. A reversal of flood flow direction in the Yellowstone River valley ended flood flow in the Two Ocean Pass through valley and created the present day drainage divide.

Pacific Creek-Buffalo Creek drainage divide area

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

Figure 7 illustrates the Pacific Creek-Buffalo Creek drainage divide area south and west of figure 5 and includes an overlap area with figure 5. The east-west continental divide is shown with a labeled dashed line and crosses the northeast corner of figure 7. Except in the northeast corner all regions in figure 7 drain to the Snake River with water eventually reaching the Pacific Ocean. Pacific Creek flows in a southwest, west, south, and southwest direction from the north edge of figure 7 (east of center) to the west edge of figure 7 (north of center) and west and south of figure 7 joins the south oriented Snake River. Trail Creek is a west and north oriented tributary joining Pacific Creek slightly north of figure 7 (east half). Enos Creek originates at Enos Lake (in north center of figure 7) and flows in a southwest and northwest direction to join Pacific Creek at the point where it turns from flowing in south direction to flowing in a southwest direction. North Buffalo Fork flows in a west direction from the east edge of figure 7 (north half) and then turns to flow in a south direction to the south edge of figure 7 (east of center). South of figure 7 the North Buffalo Fork joins the west oriented South Buffalo Fork to flow in a west direction as Buffalo Fork and to eventually join the south oriented Snake River. The southwest oriented stream flowing to the southwest corner of figure 7 is Lava Creek, which flows to west oriented Buffalo Fork. Box Creek is a south oriented Buffalo Fork tributary originating south of Enos Creek and flows to the south edge of figure 7 (west of center). Note how the southwest and northwest oriented Enos Creek valley is linked by through valleys with the south oriented Box Creek valley and the southwest oriented Lava Creek valley. The map contour interval for figure 7 is 50 meters and through valley floor elevations are between 2500 and 2550 meters. Gravel Mountain to the west rises 2922 meters and Soda Mountain to the east rises to more than 3300 meters suggesting the through valleys are as much 370 meters deep. The through valleys were eroded by south oriented flood flow moving from what were at that time a south and southwest oriented flood flow channel on the Enos Creek headwaters alignment and a south and southeast oriented flood flow channel on the present day northwest oriented Enos Creek alignment and south oriented Pacific Creek alignment. North of Gravel Ridge the flood flow split with one of the diverging flood flow channels using the south oriented Box Creek alignment while the other diverging flood flow channel used the southwest oriented Lava Creek alignment. Headward erosion of the deeper southwest oriented Pacific Creek valley beheaded the southeast oriented flood flow channel on the present day northwest oriented Enos Creek alignment and floodwaters on the northwest end of the beheaded flood flow channel reversed flow direction to create the northwest oriented Enos Creek drainage route. Headward erosion of the northwest oriented Enos Creek valley then captured the south and southwest oriented flood flow channel on the present day Enos Creek headwaters alignment. Next headward erosion of the west oriented Pacific Creek valley north of present day Enos Lake captured the southwest oriented flood flow channel moving floodwaters through the Enos Lake area, which was moving in a southwest direction on the present day northeast oriented Atlantic Creek alignment to Two Ocean Pass and then along the southwest oriented Pacific Creek headwaters alignment (see figure 5). Diverging flood flow channels once crossed other drainage divides in the region seen in figure 7. For example, a north-to-south oriented through valley links the north oriented Trail Creek valley segment with the south oriented North Buffalo Fork segment and is better illustrated in figure 8.

Detailed map of Trail Creek-North Buffalo Fork drainage divide area

Figure 8: Detailed map of Trail Creek-North Buffalo Fork drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 illustrates a detailed topographic map of the Trail Creek-North Buffalo Fork drainage divide area seen in less detail in figure 7. The east-west continental divide is shown with a labeled dashed line and extends from the north edge of figure 8 (in section 22) to the east edge of figure 8 (in section 31). Jay Creek is the northwest and north oriented stream north and east of the continental divide and north of figure 8 flows to northeast oriented Atlantic Creek, which then flows to the north oriented Yellowstone River. Pacific Creek flows in southwest direction across the northwest corner of figure 8 and west and south of figure 8 joins the south oriented Snake River. Trail Creek originates at the unnamed lake in the southwest corner of section 25 and flows in a west direction to the southeast corner of section 28 where it turns to flow in a north direction to join Pacific Creek in section 21. North Buffalo Fork flows in a west direction from the east edge of figure 8 (near southeast corner) across sections 1, 2, 3, and 4 before turning to flow in a southwest direction to the south edge of figure 8 (west half). South of figure 8 North Buffalo Fork turns to flow in a south direction to join west oriented South Buffalo Fork and then to flow as Buffalo Fork in a west direction to join the south oriented Snake River. Note how in the east half of section 33 and along the west edge of section 34 a north-to-south oriented through valley links the north oriented Trail Creek valley with the southwest and south oriented North Buffalo Fork valley. The map contour interval for figure 8 is 40 feet and the through valley floor elevation at the drainage divide is between 8480 and 8520 feet. West of the through valley in section 32 elevations rise to 9522 feet while east of the through valley along the continental divide elevations are greater than 10,000 feet. These elevations suggest the through valley is at least 1000 feet deep. The through valley is a water-eroded valley and was eroded by south oriented flood flow diverging from a southwest oriented flood flow channel on the present day northeast oriented Atlantic Creek alignment, which was moving floodwaters to a south oriented flood flow channel on the south oriented North Buffalo Fork alignment and then probably in west direction to a south oriented flood flow on the Snake River alignment. Headward erosion of a much deeper southwest oriented Pacific Creek valley beheaded this south oriented flood flow channel and floodwaters on the north end of the beheaded flood flow channel reversed flow direction to create the north oriented Trail Creek drainage route.

Yellowstone River–Lake Creek drainage divide area

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

Figure 9 illustrates the Yellowstone River-Lake Creek drainage divide area south and east of the figure 5 and includes an overlap area with figure 5. The east-west continental divide is also the Park County-Fremont County line and extends from the north to the south edges of figure 9. North Buffalo Fork is the west, north-northwest, and west oriented stream flowing to the west edge of figure 9 near the northwest corner. Soda Fork (Buffalo Fork) is the west-southwest oriented stream flowing to the west edge of figure 9 (south of center). The Yellowstone River is formed near the north edge of figure 9 (east of center) at the confluence of its (northwest and) southwest oriented North Fork and its southwest and north oriented South Fork. Woodard Canyon is a north-northeast oriented valley draining to the Yellowstone River near the north center edge of figure 9. South of the Yellowstone River headwaters and of the continental divide South Buffalo Fork originates on the Buffalo Plateau and flows in west-northwest and then west-southwest direction to the southwest corner of figure 9. Lake Creek is a southwest oriented South Buffalo Fork tributary and originates west of Ferry Lake. Lost Creek is the west, south, and southwest oriented tributary originating near Marston Pass and joining Lake Creek south of Ferry Lake. Drainage divides seen in figure 9 are generally higher than 3000 meters (the map contour interval for figure 9 is 50 meters) and there are no deep through valleys such as the Two Ocean Pass through valley located in figure 9 (Two Ocean Pass in north and west of figure 9 and the relationship can be seen in figure 5). However a close look at the drainage divides in figure 9 reveals through valleys or passes do link north oriented valleys with south oriented valleys. One such through valley or pass is located north of Ferry Lake and links the south oriented Ferry Lake valley with the north-northeast oriented Woodard Canyon valley. A trail crosses the continental divide in that through valley or pass. The elevation of that through valley or pass at the continental divide is between 3100 and 3150 meters. Elevations west of the through valley rise to more than 3250 meters while east of the through valley elevations rise to 3358 meters. These elevations suggest the through valley or pass is at least 100 meters deep. Similar through valleys or passes cross the South Fork Yellowstone River-Lost Creek drainage divide and  other drainage divides seen in figure 9. These through valleys were eroded by south oriented flood flow channels, which flowed on a surface equivalent in elevation to the highest elevations seen in figure 9. Since that time the region has been uplifted and deep valleys have eroded headward into it to capture the massive south oriented melt water floods flowing across the area.

Detailed map of Woodard Canyon-Ferry Lake drainage divide area

Figure 10: Detailed map of Woodard Canyon-Ferry Lake 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 Woodard Canyon-Ferry Lake drainage divide area seen in less detail in figure 9. The South Fork Yellowstone River flows in a west and north direction from the east edge of figure 10 (south half in section 14) to join the southwest oriented North Fork Yellowstone River in section 3 and to form the west oriented Yellowstone River, which flows along the north edge of figure 10 before turning to flow in a northwest direction to the north edge of figure 10 (west of center). North and west of figure 10 the Yellowstone River flows in a north direction with water eventually reaching the Gulf of Mexico. Woodard Canyon originates in the region where sections 7, 12, 13, and 18 come together and drains in a north-northeast direction to join the Yellowstone River near the north edge of figure 10. Lake Creek originates in section 16 and flows in a southwest direction to the south center edge of figure 10. South and west of figure 10 Lake Creek flows to west-southwest and west oriented South Buffalo Fork with water eventually reaching the Pacific Ocean. Ferry Lake is located in section 17 and drains in a south direction to join southwest oriented Lake Creek near the south edge of figure 10. Note in the northwest corner of section 17 a through valley or pass linking the north-northeast oriented Woodard Canyon valley with the south oriented Ferry Lake valley. The map contour interval for figure 10 is 40 feet and the through valley or pass elevation at the continental divide is 10,315 feet. The continental divide in section 18 to the west rises to 10,782 feet while in section 8 to the northeast the elevation rises to 11,009 feet. These elevations suggest the through valley or pass is approximately 460 feet deep. This through valley or pass was eroded by a southeast oriented flood flow channel at a time when floodwaters were flowing across a surface as high, if not higher, than the highest elevations seen in figure 10 today. At that time the region had not yet been uplifted and deep valleys had not been eroded across Montana to the north and the massive south and southeast oriented melt water floods could freely flow across what is today a high mountain region. Regional uplift was caused by crustal warping related to the thick ice sheet presence north and east of this essay’s study region with the study region being located along what became the southwest rim of the deep “hole” the massive North American ice sheet was creating by crustal warping of regions surrounding it and by deep erosion of regions underneath it.

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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