Yellowstone River-North Fork Shoshone River drainage divide area landform origins east 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 the North Fork Shoshone River east of Yellowstone National Park along the Absaroka Range crest ridge in Wyoming. The Yellowstone River flows in a north-northwest direction to Yellowstone Lake and then in a northwest, northeast, north and northwest direction to the Yellowstone National Park north boundary and the west and north-northwest oriented Lamar River is an important Yellowstone River tributary. The North Fork Shoshone River originates as a southwest and south oriented stream south of the Lamar River headwaters and then turns to flow in a southeast and east direction to join the northeast oriented South Fork Shoshone River and to form the northeast oriented Shoshone River. Mountain passes or through valleys link Lamar River and Yellowstone River tributary valleys with North Fork Shoshone River tributary valleys. These mountain passes or through valleys are interpreted to be remnants of south oriented flood flow channels that once crossed the region. At that time the Absaroka Range did not stand high above surrounding areas and floodwaters could freely flow across what is today a major mountain range. Floodwaters were derived from the western margin of the thick North American ice sheet and were flowing in south and southeast directions from western Canada to and across the Yellowstone National Park region. Ice sheet related crustal warping raised the Absaroka Range and Yellowstone Plateau as floodwaters flowed across them. At the same time headward erosion of the deep Yellowstone River in Montana (north of the study region) from space in the deep “hole” the ice sheet had occupied and which was being opened up by ice sheet melting systematically beheaded south and southeast oriented flood flow channels in sequence from east to west. Floodwaters on north ends of beheaded flood flow channels reversed flow direction to create the north oriented drainage routes seen today and often captured south and southeast oriented floodwaters from west of the actively eroding Yellowstone River valley head. Barbed tributaries to north oriented Yellowstone River valley segments provide further evidence of these massive flood flow reversals.

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-North Fork Shoshone River drainage divide area landform origins east of Yellowstone National Park, which is located in northwest 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-North Fork Shoshone River drainage divide area landform evidence east of Yellowstone National Park, Wyoming will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Yellowstone River-North Fork Shoshone River drainage divide area location map

Figure 1: Yellowstone River-North Fork Shoshone River drainage divide area location map (select and click on maps to enlarge). National Geographic Society map digitally presented using National Geographic Society TOPO software.

Figure 1 provides a location map for the Yellowstone River-North Fork Shoshone River drainage divide area east of Yellowstone National Park and illustrates a region of northern Wyoming with Yellowstone National Park located in the northwest corner of Wyoming in the south half with Montana being located north of Wyoming. The Yellowstone River originates south of the southeast corner of Yellowstone National Park and flows in a north-northwest direction to Yellowstone Lake and then to Canyon, Wyoming. From Canyon the Yellowstone River flows in a northeast, north, and northwest direction to Gardiner, Montana and then in a northwest, north-northeast, and east-northeast direction to Big Timber, Montana. From Big Timber the Yellowstone River flows in an east-southeast and northeast direction to the north edge of figure 1 (east half) and north and east of figure 1 the northeast oriented Yellowstone River eventually joins the Missouri River. The northwest oriented Lamar River is an important Yellowstone River tributary in the northeast quadrant of Yellowstone National Park. The North Fork Shoshone River originates just east of Sylvan Pass (east of Yellowstone Lake) and flows in an east direction to Buffalo Bill Reservoir where it joins the north-northeast oriented South Fork Shoshone River to form the northeast oriented Shoshone River, which then joins the north and north-northeast oriented Bighorn River, which in turn joins the Yellowstone River near Bighorn, Montana (near north edge of figure 1). The Yellowstone River-Shoshone River drainage divide area east of Yellowstone National Park investigated in this essay begins with Lamar River-North Fork Shoshone River drainage divide area north of Sylvan Pass and extends southward to the drainage divide between the north-northeast oriented Yellowstone River headwaters and the north-northeast oriented South Fork Shoshone River and is located along the crest of the high Absaroka Range.

Today drainage systems seen in figure 1 are oriented in a north direction, however most north and northwest oriented drainage routes seen in figure 1 originated as south and southeast oriented flood flow channels. Floodwaters were derived from the western margin of a thick North American ice sheet and were flowing in south and southeast directions from western Canada across Montana into and across Wyoming. At that time the deep glacial erosion was creating a deep “hole” in the continent under the ice sheet and ice sheet related crustal warping was raising mountain ranges and high plateau areas along the ice sheet rim and elsewhere on the continent. The region seen in figure 1 could be considered to part of the deep “hole’s” deeply eroded southwest rim and mountain ranges and other high areas (e.g. Yellowstone Plateau) seen in figure 1 were being uplifted as immense south and southeast oriented melt water floods flowed across them. Headward erosion of what was then a much deeper northeast and east oriented Yellowstone River valley from space in the deep “hole” being opened up by ice sheet melting captured the south and southeast oriented melt water floods and diverted floodwaters into the south end of the deep “hole” and then initially in a south direction to Gulf of Mexico, although as ice sheet melting continued new northeast and north oriented flood flow routes across the ice sheet floor opened up. Floodwaters on north and northwest ends of flood flow routes beheaded by the northeast and east oriented Yellowstone River valley headward erosion in Montana reversed flow direction to create what are today north oriented Yellowstone River tributary drainage systems and the north oriented Yellowstone River headwaters drainage system seen near the west edge of figure 1. Flood flow channels were beheaded in sequence from east to west and often newly reversed flood flow channels captured floodwaters from yet to be beheaded flood flow channels further to the west. Also aiding in the flood flow reversal process was crustal warping that was raising mountain ranges as floodwaters flowed across them. While this brief description gives a very generalized picture of how the figure 1 drainage system evolved there were many additional complexities and each valley segment has a story to tell. Detailed maps shown in this essay illustrate a few of those stories, although again in a very abbreviated form.

Detailed location map for Yellowstone River-North Fork Shoshone River drainage divide area

Figure 2: Detailed location map Yellowstone River-North Fork Shoshone River 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 Yellowstone River–North Fork Shoshone River drainage divide area east of Yellowstone National Park. A region in eastern Yellowstone National Park is shown with the red-brown color in the west half of figure 2. The Yellowstone River originates in the Thorofare Plateau area south and east of the southeast corner of Yellowstone National Park and flows in a north-northwest direction to Yellowstone Lake. North of Yellowstone Lake the Yellowstone River flows in a northwest direction from Fishing Village (at north end of the lake) to Canyon Junction and then in a northeast and north direction to the north edge of figure 2. The Lamar River (labeled “River” in figure 2) originates near the Yellowstone National Park easternmost extension (near Lamar Mountain) and flows in a north, southwest, and west direction before turning to flow in a north-northwest direction to the north edge of figure 2 and joins the Yellowstone River north of figure 2. Note numerous southwest oriented streams flowing to the north-northwest oriented Yellowstone River and to Yellowstone Lake as barbed tributaries. These barbed tributaries provide evidence the Yellowstone River valley south of Yellowstone Lake probably originated as a south oriented drainage route and was subsequently reversed to form the north-northwest drainage route seen today. The highway from Yellowstone Lake to Buffalo Bill Reservoir (west of Cody, Wyoming) follows the North Fork Shoshone River valley from Pahaska to Buffalo Bill Reservoir where the east oriented North Fork is joined by the northeast oriented South Fork to form the northeast oriented Shoshone River, which then flows to the northeast corner of figure 2. East oriented tributaries forming the North Fork include Jones Creek, Crow Creek, and Middle Creek. Northeast oriented Eagle Creek joins the North Fork east of Pahaska. Note how the southwest and south oriented North Fork Shoshone River headwaters flow to the southeast and east oriented North Fork Shoshone River at Pahaska and drain the region directly south of the Lamar River headwaters. While not obvious from figure 2 the Yellowstone River-North Fork Shoshone River drainage divide is the crest of the high Absaroka Mountains and is today a high mountain region. In spite of this mountain topography many of the North Fork Shoshone River tributaries are aligned with Yellowstone River tributaries, but flow in opposite directions. For example the northeast oriented Eagle Creek drainage route is aligned with an unnamed southwest oriented Yellowstone River tributary (Howell Creek). This alignment suggests the drainage routes originated as a southwest oriented flood flow channel that was dismembered as crustal warping raised the Absaroka Mountains and as headward erosion of the deep northeast oriented Eagle Creek valley beheaded the south-southwest oriented flood flow. This and other similar alignments are illustrated and discussed in the topographic maps illustrated below.

Pelican Creek-Jones Creek drainage divide area

Figure 3: Pelican Creek-Jones 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 Pelican Creek-Jones Creek drainage divide area. The northeast shore of Yellowstone Lake can be seen just east of the south half of the west edge of figure 3. The Yellowstone River-North Fork Shoshone River drainage divide serves as the Yellowstone National Park eastern boundary in figure 3 and is shown with a labeled dashed line extending from near the northeast corner of figure 3 to the south center edge of figure 3. Pelican Creek is the south, southwest, and west oriented stream (labeled “Creek”) flowing from the north edge of figure 3 (west half) to the west center edge of figure 3 and west of figure 3 turns to flow in a south direction to enter Yellowstone Lake. Raven Creek is the southwest oriented Pelican Creek tributary flowing from the north center edge of figure 3. Mist Creek is a northeast oriented stream flowing from Mist Creek Pass to the north edge of figure 3 (east of center) and south and east of Mist Creek is northeast and north-northeast oriented Cold Creek. North of figure 3 Mist Creek joins Cold Creek, which turns to flow in a north direction to the north-northwest oriented Lamar River. East oriented streams east of the Park boundary flow to the east edge of figure 3 and from north to south these east oriented streams are Bear, Jones, and Crow Creeks. East of figure 3 Bear, Jones, and Crow Creeks flow to the south oriented North Fork Shoshone River headwaters, which then turn to flow in a southeast and east direction at Pahaska. Note how several labeled and unlabeled passes cross the Yellowstone River-North Fork Shoshone River drainage divide. These include Crow Creek Pass, which links the east oriented Crow Creek valley with the southwest and west oriented Cub Creek valley, and Jones Pass, which links the east oriented Jones Creek valley with the southwest and northwest oriented Bear Creek valley. The map contour interval for figure 3 is 50 meters and, depending on where one measures, these passes are from 100 to 300 meters deep. Even deeper unlabeled passes can be seen near Stonecup Lake linking the Jones Creek headwaters with a northwest oriented Pelican Creek tributary and near Frost Lake linking the southeast oriented Bear Creek valley with a north oriented Cold Creek tributary valley. The pass near Stonecup Lake has an elevation of between 2800 and 2850 meters. Mount Chittenden to the west rises to 3103 meters while Cathedral Peak to the northeast rises to 3280 meters suggesting the pass is at least 250 meters deep. The pass near Frost Lake also has an elevation of between 2800 and 2850 meters. Pyramid Peak to the west rises to 3201 meters while unnamed peaks east of figure 3 rise to more than 3250 meters suggesting the pass is at least 350 meters deep. These passes are water-eroded features and were eroded by southeast and east oriented flood flow moving to the actively eroding east oriented North Fork Shoshone River valley and its tributary valleys. Headward erosion of a deeper south oriented valley on the present day north oriented Yellowstone River alignment beheaded and reversed flood routes across Crow and Jones Passes and perhaps the Stonecup Lake pass while southeast oriented flood flow continued to move across the pass near Frost Lakes. Flood flow across the Frost Lake pass ended when flood flow in the Yellowstone National Park area was beheaded and reversed to create the north oriented Yellowstone River drainage system, which included the north-northwest oriented Lamar River drainage basin.

Detailed map of Lamar River-Bear Creek drainage divide area

Figure 4: Detailed topographic map of the Lamar River-Bear 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 Lamar River-Bear Creek drainage divide area seen in less detail in figure 3 above. The Lamar River-North Fork Shoshone River drainage divide serves as the Yellowstone National Park eastern boundary and is shown with well-marked line extending from the east edge of figure 4 (north half) to the south edge of figure 4 (west half). Areas north and west of the drainage divide drain to the north-northwest oriented Lamar River. Areas south and east of the drainage divide drain to the North Fork Shoshone River. Bear Creek flows in a northeast direction across section 12 (just east of the Park boundary) and then turns to flow in an east and southeast direction to the south edge of figure 4 (near southeast corner) and south of figure 4 joins the south, southeast, and east oriented North Fork Shoshone River. The unnamed southeast oriented stream flowing to the east edge of figure 4 flows to southwest oriented North Fork Shoshone River, which then turns to flow in a south direction before turning again to flow in a southeast and east direction. The north oriented stream originating west of Frost Lake north of figure 4 joins Cold Creek, which then flows in a north direction to join the north-northwest oriented Lamar River. Note how a well-defined north-to-south oriented through valley (near center of figure 4) links the north-oriented stream valley with the southeast oriented Bear Creek valley. The map contour interval for figure 4 is 40 feet and the through valley floor elevation at the drainage divide is between 9200 and 9240 feet. Pyramid Peak to the east rises to more than 10,480 feet. The Lamar River-North Fork Shoshone River drainage divide near the east edge of figure 4 rises to more than 10,440 feet and further east rises even higher. These elevations suggest the north-to-south oriented through valley is approximately 1200 feet deep. The through valley is a water-eroded valley and was eroded by south oriented flood flow moving from the present day north-northwest oriented Lamar River valley to the southeast oriented Bear Creek valley and then to the south oriented North Fork Shoshone River valley. Headward erosion of the deep east and southeast oriented North Fork Shoshone River probably captured the south oriented flood flow and diverted the floodwaters in an east direction to deeper south oriented flood flow channels in the present day north oriented Big Horn Basin. Reversals of flood flow in the Big Horn Basin were followed by reversals of flood flow in the Yellowstone National Park region and created the north oriented drainage systems seen today and the Lamar River-North Fork Shoshone River drainage divide seen in figure 4.

Clear Creek-Middle Creek drainage divide area

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

Figure 5 illustrates the Clear Creek-Middle Creek drainage divide area south and slightly east of figure 3 and includes a significant overlap area with figure 3. The Yellowstone National Park east boundary is shown with a dashed line and extends in a south-southeast direction from the north edge of figure 5 (west of center) to Hoyt Peak (just north of highway near center of figure 5) and then in an east-northeast direction almost to the east edge of figure 5, but turns in a south direction as a straight line before turning in a southwest direction to Plenty Coups Peak (near south edge of figure 5, east of center). North of Hoyt Peak the Yellowstone River-North Fork Shoshone River drainage divide serves as the Yellowstone National Park boundary. South of Hoyt Peak the drainage divide continues in a south and southeast direction to Sylvan Pass, Top Notch Peak, Mount Langford, and Plenty Coups Peak. The Yellowstone Lake eastern shore is seen along the west edge of figure 5. From south to north named streams flowing to Yellowstone Lake are southwest oriented Columbine Creek; northwest, southwest, and northwest oriented Clear Creek; and southwest oriented Cub Creek. East oriented streams flowing to the east edge of figure 5 are North Fork Shoshone River tributaries and from south to north are east oriented Cabin Creek, east-northeast oriented Middle Creek, and east oriented Crow Creek. Sylvan Pass near the center of figure 5 is a through valley linking the northwest and southwest oriented Clear Creek valley with the east-northeast oriented Middle Creek valley, which east of figure 5 drains to the southeast and east oriented North Fork Shoshone River valley (see figure 2).  The map contour for figure 5 is 50 meters and the Sylvan Pass elevation at the drainage divide is between 2550 and 2600 meters. Hoyt Peak to the north rises to more than 3150 meters and Top Notch Peak to the south rises to more 3121 meters suggesting Sylvan Pass is approximately 500 meters deep. Sylvan Pass is a water-eroded valley and was eroded by southeast oriented flood flow moving from the present day north oriented Yellowstone River drainage basin to the east-northeast oriented Middle Creek valley, which had eroded headward from the actively eroding North Fork Shoshone River valley to capture south and southeast oriented flood flow moving across the region. At that time floodwaters were flowing on a surface equivalent in elevations to the highest points now seen in figure 5, although the region has probably been significantly uplifted since.

Detailed map of Clear Creek-Middle Creek drainage divide area

Figure 6: Detailed map of Clear Creek-Middle 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 Clear Creek-Middle Creek drainage divide area seen in less detail in figure 5. The Yellowstone National Park east boundary is the well-marked line extending in a southeast and south direction from the north edge of figure 6 (west of center) to Avalanche Peak and Hoyt Peak and then in a northeast and east direction to near the northeast corner of figure 6. Sylvan Pass is near the center of figure 6. Clear Creek flows in a northwest and east direction from Sylvan Pass to the west edge of figure 6 (near northwest corner). Top Notch Peak is located south and west of Sylvan Pass and Middle Creek originates on the southeast side of Top Notch Creek as a southeast oriented stream, but then turns to flow in a northeast and east-northeast direction to the east edge of figure 6 (north of center). A southeast oriented tributary flows from near Sylvan Pass to northeast oriented Middle Creek. Sylvan Pass is an impressive through valley eroded across the Absaroka Mountains crest ridge. The map contour interval for figure 6 is 40 feet and the Sylvan Pass elevation is between 8500 and 8550 feet. Hoyt Peak to the north rises to more than 10,480 feet while Top Notch Peak to the south rises to more than 10,200 feet suggesting Sylvan Pass is approximately 1650 feet deep. While lakes and cirques seen in figure 6 (north side of Top Notch Peak) suggest the region was glaciated at some point in time the Sylvan Pass through valley is a water-eroded feature and was eroded by southeast oriented flood flow moving to the northeast and east-northeast oriented Middle Creek valley, which had eroded headward from the North Fork Shoshone River valley, and which had probably eroded headward from deep south oriented flood flow channels in the present day north oriented Big Horn Basin. The Sylvan Pass through valley was eroded as crustal warping raised the Absaroka Range and for a time the concentrated flood flow was able to erode the water gap deeper and deeper. However headward erosion of what was probably a south oriented flood flow channel on the present day north oriented Yellowstone River alignment beheaded and reversed the southeast oriented flood flow channel to create the northwest and west oriented Clear Creek drainage route and to create the Clear Creek-Middle Creek drainage divide at Sylvan Pass. Glaciation of the region occurred after all melt water flood flow across the region had ended.

Middle Creek-Beaverdam Creek drainage divide area

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

Figure 7 illustrates the Middle Creek-Beaverdam Creek drainage divide area south and east of figure 5 and includes a significant overlap area with figure 5. The Yellowstone National Park east boundary is shown with a dashed line extending in a southwest direction from the north edge of figure 7 (near northeast corner) to Plenty Coups Peak and then in a south direction to Atkins Peak, Mount Schultz, and the south edge of figure 7. The Yellowstone Lake Southeast Arm straddles the west edge of figure 7. The north-northwest oriented Yellowstone River enters the Southeast Arm south of figure 7. Mount Langford is located near the center of figure 7. Beaverdam Creek originates on the southeast side of Mount Langford and flows in a south and southwest direction to enter the Yellowstone Lake Southeast Arm just south of the south edge of figure 7. Rocky Creek is a south-southwest oriented Beaverdam Creek tributary. Sylvan Pass is located near the north center edge of figure 7 and Top Notch Peak is located south and west of Sylvan Pass. Middle Creek originates south and east of Top Notch Peak and flows in a northeast direction to the north edge of figure 7 (east half). A north-northeast oriented Middle Creek tributary originates east of Mount Langford and joins Middle Creek near the north edge of figure 7 (east half).  Note how there is a deep notch, gap, or pass between Mount Langford and Plenty Coups Peak linking the north-northeast oriented Middle Creek tributary valley with the south and southwest oriented Beaverdam Creek valley. The map contour interval for figure 7 is 50 meters and the pass elevation is between 2950 and 3000 meters. Mount Langford rises to more than 3250 meters and Plenty Coups Peak rises to 3334 meters suggesting the pass is at least 325 meters deep. While located today on what is a high mountain ridge the pass is a remnant of what was once a water-eroded valley and was eroded by south-southwest oriented flood flow moving to a south oriented flood flow channel on the present day north oriented Yellowstone River alignment. Headward erosion of the much deeper northeast oriented Middle Creek valley from the North Fork Shoshone River valley beheaded and reversed the south-southwest oriented flood flow channel to create the north-northeast oriented Middle Creek tributary drainage route and to create the Middle Creek-Beaverdam Creek drainage divide.

Detailed map of Middle Creek-Beaverdam Creek drainage divide area

Figure 8: Detailed map of Middle Creek-Beaverdam Creek 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 Middle Creek-Beaverdam Creek drainage divide area seen in less detail in figure 7. The Yellowstone National Park eastern boundary is shown with a well-marked line in the east half of figure 8. Beaverdam Creek originates near the center of figure 8 and flows in a south direction to the south edge of figure 8 (west of center). The north-northeast oriented stream flowing to the north edge of figure 8 (east of center) is a Middle Creek tributary. Note the gap or pass linking the north-northeast oriented Middle Creek tributary valley with the south oriented Beaverdam Creek valley. Mount Langford is to the northwest of the pass and Plenty Coups Peak is to the southeast. The map contour interval for figure 8 is 40 feet and the pass elevation is between 9680 and 9720 feet. Mount Langford reaches an elevation of more than 10,760 feet while Plenty Coups Peak reaches an elevation of 10,940 feet suggesting the pass is approximately 1100 feet deep. The northeast side of the pass appears to be a cirque suggesting glaciation has altered valley shapes. What is important to remember is the valleys seen in figure 8 were eroded by water and any glacial erosion occurred after all flood flow across the region in figure 8 had ended. The pass was eroded by south-southwest oriented flood flow moving from the present day north-northeast oriented Middle Creek tributary valley alignment to the south and southwest oriented Beaverdam Creek valley and then to a south oriented flood flow channel on the present day north oriented Yellowstone River alignment. At that time south oriented floodwaters were eroding diverging and converging flood flow channels into a surface equivalent in elevation to the high mountain ridges seen in figure 8. Headward erosion of the much deeper northeast oriented Middle Creek valley (north of figure 8) beheaded the south-southwest oriented flood flow channel between Mount Langford and Plenty Coups Peak. Floodwaters on the north-northeast end of the flood flow channel reversed flow direction to create the north-northeast oriented Middle Creek tributary drainage route.

Eagle Creek-Howell Creek drainage divide area

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

Figure 9 illustrates the Eagle Creek-Howell Creek drainage divide area east and south of the figure 7 and includes a significant overlap area with figure 7. The Yellowstone National Park eastern boundary is shown with a dashed line that extends in a south direction from the north edge of figure 9 (west half) to Mount Humphreys and then in an east direction to Eagle Peak and finally in a south direction (as a straight line) to the south center edge of figure 9, The Yellowstone River flows in a north-northwest direction across the southwest corner of figure 9. Beaverdam Creek flows in a southwest direction across the northwest corner of figure 9. Mountain Creek flows in a west-southwest direction from the southeast quadrant of figure 9 to join the Yellowstone River south of figure 9. Howell Creek is a south and south-southwest oriented tributary originating near Eagle Pass and joining Mountain Creek near the south edge of figure 9 (west half). Eagle Creek is a northeast oriented stream originating north of Eagle Peak and flowing to the north center edge of figure 9. North of figure 9 Eagle Creek continues to flow in a northeast direction to join a southeast oriented segment of the North Fork Shoshone River. Note the northeast and north oriented Eagle Creek tributary located north of Eagle Pass. Eagle Pass is a north-to-south oriented through valley linking the north oriented Eagle Creek tributary valley with the south and south-southwest oriented Howell Creek valley. The map contour interval for figure 9 is 50 meters and the Eagle Pass elevation is between 2900 and 2950 meters. Eagle Peak to the west rises to 3462 meters and the unnamed mountain to the east rises to 3299 meters suggesting that Eagle Pass is at least 350 meters deep. Eagle Pass is another example of a water-eroded valley, which was eroded by a south oriented flood flow channel moving floodwaters to a south oriented flood flow channel on the present day north oriented Yellowstone River alignment. Headward erosion of the much deeper northeast oriented Eagle Creek valley from the southeast oriented North Fork Shoshone River valley beheaded the south oriented flood flow channel. Floodwaters on the north end of the beheaded flood flow channel reversed flow direction to create the north oriented Eagle Creek tributary drainage route. Prior to eroding the south-southwest oriented flood flow channel floodwaters flowed on a surface equivalent in elevation to the highest points seen in figure 9, although the region has probably been significantly uplifted by ice sheet related crustal warping since that time.

Detailed map of Eagle Creek-Howell Creek drainage divide area

Figure 10: Detailed map of Eagle Creek-Howell Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 provides a detailed topographic map of the Eagle Creek-Howell Creek drainage divide area seen in less detail in figure 9. Eagle Pass is located near the center of figure 10. The Yellowstone National Park east boundary extends in an east-southeast and east-northeast direction from Mount Humphreys near the west edge of figure 10 to Eagle Pass and then in a south direction to the south center edge of figure 10. Howell Creek is the south oriented stream originating near Eagle Pass and flowing to the south center edge of figure 10. The northeast oriented stream in section 36 near the northwest corner of figure 10 is Eagle Creek, which north of figure 10 joins the southeast and east oriented North Fork Shoshone River. The northeast oriented stream originating in section 6 and flowing to the north center edge of figure 10 north of figure 10 flows in a north direction to join northeast oriented Eagle Creek. Note the west and northwest oriented tributary to that northeast and north oriented Eagle Creek tributary in sections 4 and 5, which is located directly north of Eagle Pass. While it is a significant climb from either direction to reach Eagle Pass, Eagle Pass is a remnant of what was once a north-to-south oriented flood flow channel moving floodwaters to a south oriented flood flow channel on the present day north oriented Yellowstone River alignment. The map contour interval for figure 10 is 40 feet and the Eagle Pass elevation is 9628 feet. Eagle Peak to the west rises to more than 11,320 feet and the unnamed mountain to the east rises to 11,497 feet. These elevations suggest Eagle Pass is as much as 1,690 feet deep. Small ice masses can be seen on north sides of the higher mountain peaks and north facing valley heads have cirque shapes suggesting glaciation, which occurred after flood flow across the region had ended, has further modified valleys heads, especially north facing valley heads. Valleys seen in figure 10 are water-eroded valleys and while glaciation has steepened valley walls the primary erosion agent that produced the landscape seen in figure 10 was water with immense south oriented melt water floods responsible for much of the erosion.

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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