Madison River-Snake River drainage divide area landform origins along the continental divide in western Yellowstone National Park, Wyoming, USA

Authors


Abstract:

This essay uses topographic map evidence to interpret landform origins along the continental divide in western Yellowstone National Park between the Madison River and Snake River. More specifically this essay addresses the continental divide segment west of Yellowstone Lake between the north oriented Firehole River, which flows to the north oriented Madison River, and the south oriented Bechler and Lewis Rivers, with the Lewis River flowing directly to the Snake River and Bechler River flowing to Henrys Fork, which then flows to the Snake River. This continental divide segment crosses the Madison Plateau and is directly north of the Pitchstone Plateau and extends in a south direction around the north oriented Firehole River headwaters before extending in a north direction around the south oriented Lewis River headwaters. Multiple through valleys or passes cross the continental divide and provide evidence of former south oriented flood flow channels that once moved floodwaters to the actively eroding south oriented Snake River tributary valleys. In addition streamlined erosional residuals and anastomosing valley complexes provide further evidence of massive south oriented flood flow. The present day north oriented Firehole River drainage route was established by a reversal of flood flow on the north end of a beheaded south oriented flood flow channel. Northwest oriented Firehole River tributaries were established by reversals of flood flow on northwest ends of beheaded southeast oriented flood flow channels. Floodwaters were derived from the western margin of a melting thick North American ice sheet and were flowing in a south and southeast direction from western Canada. At that time the Yellowstone Plateau did not stand high above regions to the north and floodwaters could cross the study region. Crustal warping related to the thick ice sheet presence raised the Yellowstone Plateau area as floodwaters flowed across the region and contributed significantly to a massive flood flow reversal that was triggered when south oriented flood flow on the Madison River alignment was beheaded and reversed by headward erosion of a much deeper northeast oriented valley in northern Montana, which was eroding headward from space in the deep “hole” the melting ice sheet had occupied and that was being opened up as the ice sheet melted to captured the immense south and southeast oriented melt water flood flow.

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 Madison River-Snake River drainage divide area landform origins along the continental divide in western Yellowstone National Park, Wyoming and 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 Madison River-Snake River drainage divide area landform evidence along the continental divide in western Yellowstone National Park, Wyoming will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Madison River-Snake River drainage divide area location map

Figure 1: Madison River-Snake 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 Madison River-Snake River drainage divide area along the continental divide in western Yellowstone National Park, Wyoming. The northwest corner of Wyoming fills much of the east half of figure 1 and Yellowstone National Park is located in the northwest corner of the northwest corner of Wyoming. Idaho is located west of Wyoming in the southwest quadrant of figure 1 and Montana is north of Idaho and Wyoming. The Madison River originates in western Yellowstone National Park and flows in a northwest direction to Hebgen Lake just west of Yellowstone National Park. From Hebgen Lake the Madison River flows in a southwest direction through Earthquake Lake before turning to flow in a north-northwest direction to the north edge of figure 1. North of figure 1 the Madison River joins the north and northwest oriented Gallatin River and the northeast oriented Jefferson River to form the north oriented Missouri River, which further to the north turns to flow in a northeast and then east direction to North Dakota where it turns to flow in a southeast and south direction with water eventually reaching the Gulf of Mexico. The Gallatin River originates in the northwest corner of Yellowstone National Park (north of Mount Holmes) and flows in a northwest and north direction to the north edge of figure 1 (near Big Sky). Montana drainage routes west of the Madison River seen in figure 1, including the west oriented Red Rock River, flow to the northeast oriented Jefferson River. The Snake River originates in Yellowstone National Park south of Yellowstone Lake and flows in a southwest and south direction to Jackson Lake and the south center edge of figure 1. South of figure 1 the Snake River makes an abrupt turn to flow in a northwest direction to flow back into figure 1 at the town of Lorenzo, Idaho (seen near south edge of southwest quadrant of figure 1) before turning to flow in a south, southwest, and northwest direction across Idaho. In western Idaho the Snake River turns to flow in a north direction with water eventually reaching the Pacific Ocean. The Lewis River is a south oriented Snake River tributary flowing from Shoshone and Lewis Lakes in Yellowstone National Park. The Madison River-Snake River drainage divide is the east-west continental divide and in Yellowstone National is located west of Yellowstone Lake and east of the Yellowstone National Park western boundary.

A brief look at the big picture erosion history will help understand discussions related to detailed maps shown below. Large volumes of south and southeast oriented floodwaters once flowed across the region shown by figure 1. Floodwaters were derived from the western margin of a melting thick North American ice sheet and were flowing in a south and southeast direction from western Canada to and across the figure 1 region. North oriented rivers in figure 1 including the north oriented Madison River are generally flowing in valleys that originated as south oriented flood flow channels. The south oriented Snake River headwaters and south oriented tributaries seen in figure 1 originated as south oriented flood flow channels, as did the present day northwest oriented Snake River segment south of figure 1. When floodwaters first flowed across the region the mountain ranges, deep river valleys, and basins between the mountains did not exist and floodwaters could freely flow across the region. Mountain ranges emerged as floodwaters flowed across the region and initially floodwaters flowed across what are today high mountain ranges and plateau areas including the Yellowstone Plateau, which today form the east-west continental divide. North-to-south oriented through valleys were eroded across the present day east-west continental divide by south and southeast oriented flood flow channels. The Madison River originated as a south oriented flood flow channel, which was subsequently reversed to form the north oriented drainage route. The flood flow reversal was probably indirectly caused by crustal warping that occurred as melt water floods flowed across the region with the crustal warping being related to thick ice sheet presence north and east of figure 1, although the direct cause was headward erosion of a deep northeast oriented valley across northern Montana (north of figure 1), which beheaded south oriented flood flow channels supplying floodwaters to the south oriented Madison River flood flow channel. The deep northeast oriented valley was eroding headward from space in the deep “hole” the melting ice sheet had occupied and which was being opened up by ice sheet melting and was capturing the south and southeast oriented ice-marginal melt water floods and diverting floodwaters into the deep “hole” the ice sheet had formed. This northeast oriented valley was much deeper than the beheaded flood flow channels and floodwaters on the north end of the beheaded flood flow channel reversed flow direction to create the north oriented Madison River and other drainage routes seen in figure 1.

Detailed location map for Madison River-Snake River drainage divide area

Figure 2: Detailed location map Madison River-Snake 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 Madison River-Snake River drainage divide area along the continental divide in western Yellowstone National Park, Wyoming and shows drainage routes not seen in figure 1. Yellowstone National Park is located in the east half of figure 2 with the north-to-south oriented Wyoming state line being shown with a dashed line slightly east of the western Park boundary. Yellowstone Lake is the large lake straddling the east edge of figure 2. The east-west continental divide is shown with a labeled dashed line and extends from the west edge of figure 2 (north of center) in an east and then north direction as it loops around Henrys Lake before it continues in a southeast direction into Yellowstone National Park. Once in the Park the continental divide first loops around the north oriented Firehole River headwaters and then loops around a south oriented stream flowing to Shoshone Lake and continues in a southeast and south direction on the south side of Yellowstone Lake. South oriented drainage south of the continental divide flows to the Snake River with water eventually reaching the Pacific Ocean. North oriented drainage north of the continental divide flows to the Missouri River with water eventually reaching the Gulf of Mexico. The Madison River is formed near Madison Junction (east of West Yellowstone) at the confluence of the north oriented Firehole River and the south and west oriented Gibbon River. From Madison Junction the Madison River flows in a west direction to near the Park west border and then turns to flow in a northwest direction to Hebgen Lake (a large reservoir straddling the north edge of figure 2). North of figure 2 the Madison River makes a southwest jog before turning to flow in a north-northwest direction north of Raynolds Pass (seen north of Henrys Lake). The north oriented Firehole River drains the Madison Plateau area of Yellowstone National Park, including the Old Faithful region. Note north, northeast, and northwest oriented Firehole River tributaries and headwaters originating near the east-west continental divide. South of the continental divide Shoshone Lake drains to Lewis Lake, which is drained by the south oriented Lewis River. South of figure 2 the Lewis River joins the south-southwest oriented Snake River, which originates in the region south of Yellowstone Lake. South of Shoshone Lake is the Pitchstone Plateau and west of the Pitchstone Plateau is the south-southwest and south oriented Bechler River drainage system, which south of figure 2 turns to flows in a southwest direction to join southwest oriented Henrys Fork. Henrys Fork originates at Henrys Lake in Idaho (west of Yellowstone National Park) and flows in a south, southwest, and south direction to the south edge of figure 2. South of figure 2 Henrys Fork turns to flow in a southwest direction to join the Snake River. This essay focuses on the continental divide segment between the Yellowstone National Park west border and Yellowstone Lake.

Firehole River-Bechler River drainage divide area

Figure 3: Firehole River-Bechler River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 provides a topographic map of the Firehole River-Bechler River drainage divide area. Shoshone Lake is located in the northeast quadrant of figure 3 and Shoshone Creek flows in a southwest and south-southeast direction to Shoshone Lake. East of figure 3 Shoshone Lake drains in a south direction to Lewis Lake and the south oriented Lewis River, which then flows to the south oriented Snake River.  The east-west continental divide is shown with a labeled dashed line and extends from the north edge of figure 3 (west half) in a southeast direction to Trischman Knob and then in an east, north, and northeast direction to the north edge of figure 3 (east half). The north-northeast oriented stream in the region north of the continental divide is the headwaters of the Firehole River, which flows to the Madison River. South of Trischman Knob are headwaters of the south-southwest oriented Bechler River, which south and west of figure 3 flows to southwest oriented Henrys Fork, which in turn flows to the Snake River. Quzel Creek is a Bechler River tributary. The map contour interval for figure 3 is 50 meters except along the west edge where the contour interval is 20 meters. The continental divide in this region is crossing the Madison Plateau and there is no sharp drainage divide. A close look at figure 3 reveals some shallow through valleys crossing the continental divide and linking the various drainage systems. Perhaps the deepest and most obvious of these through valleys is located between Trischman Knob and the Pitchstone Plateau and links the Shoshone Lake basin with the south-southwest and southwest oriented Bechler River valley. The floor elevation of this through valley at the drainage divide is between 2550 and 2600 meters. Elevations at Trischman Knob and along the continental divide near the north edge of figure 3 exceed 2600 meters and north of figure 3 rise to about 2700 meters where the continental divide crosses the Yellowstone National Park west border. The high point in the Pitchstone Plateau is shown as 2736 meters, which suggests the through valley is broad and at its deepest points is more than 100 meters deep. Just north of Trischman Knob a deep and narrower channel has been eroded into the floor of this broad northeast-to-southwest oriented through valley and links the north-northeast oriented Firehole River valley with the south-southwest and south oriented Quzel Creek valley. This channel is defined by two contour lines so it must be at least 50 meters deep, although adjacent elevations suggest the channel was exactly that a channel in a larger anastomosing complex of southwest oriented flood flow channels. The flood flow channels were moving large quantities of south oriented flood flow from the Shoshone Lake basin area to the southwest oriented Henrys Fork valley and then to the Snake River valley and at least some of the floodwaters were flowing through the present day north oriented Firehole River drainage basin.

Detailed map of Firehole River-Littles Fork drainage divide area

Figure 4: Detailed map of Firehole River-Littles Fork 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 Firehole River-Littles Fork drainage divide area seen is less detail in figure 3. The Firehole River flows in a north direction from Madison Lake to the north edge of figure 4 (west of center) and north of figure 4 flows to the Madison River. The continental divide is shown with a labeled dashed line and extends from the north edge of figure 4 in south-southeast direction to Trischman Knob and then in an east and north-northwest direction around the north oriented Firehole River valley to the north edge of figure 4. The west end of Shoshone Lake can be seen near the northeast corner of figure 4. Douglas Knob is a labeled high point north of the south center edge of figure 4. Littles Fork is the south-southeast and southwest oriented stream located just west of Douglas Knob and south of figure 4 flows to the south-southwest and southwest oriented Bechler River, which flows to Henrys Fork which in turn flows to the Snake River. Quzel Creek originates near Trischman Knob and flows in a southwest and south-southwest direction to the west edge of figure 4 (south half) and west and south of figure 4 joins the Bechler River. The map contour interval for figure 4 is 20 feet and the elevation at the top of Douglas Knob is 8544 feet while the Trischman Knob to elevation is 8600 feet. Elevations along the continental divide west of the Firehole River near the north edge of figure 4 exceed 8520 feet and just north of figure 4 exceed 8540 feet. A through valley north of Trishman Knob links the north oriented Firehole River valley with the southwest oriented Quzel Creek valley. The through valley floor elevation at the drainage divide is between 8360 and 8380 feet suggesting it is approximately 150 feet deep. Just east of Trischman Knob a somewhat higher-level through valley links the north oriented Firehole River valley with the south oriented Littles Fork valley. The floor of this through valley has an elevation of 8425 feet at the drainage divide. Elevations on the continental divide to the east rise to more than 8600 feet suggesting this second through valley is at least 175 feet deep. These two through valleys cross the present day east-west continental divide and were eroded by south oriented flood flow moving from the present day north oriented Firehole River valley to the south oriented Bechler River valley. Headward erosion of the much deeper west oriented Madison River valley north of figure 4 beheaded the 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 Firehole River drainage route and to create what is today the continental divide.

Firehole River-Shoshone Creek drainage divide area

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

Figure 5 illustrates the Firehole River-Shoshone Creek drainage divide area north and slightly east of figure 3 and includes a significant overlap area with figure 3. The east-west continental divide is shown with a labeled dashed line extending in a south-southeast direction from the northwest corner of figure 5 to Trischman Knob (near south edge of figure 5) and then in an east and northeast direction to Norris Pass (near northeast corner of figure 5) before turning in a northwest direction to the north edge of figure 5. The Firehole River originates near Trischman Knob and flows in a north-northeast and north-northwest direction to Old Faithful, which is located near the north center edge of figure 5. North of figure 5 the Firehole River flows to the west and north oriented Madison River. Spring Creek is a west oriented Firehole River tributary in the northeast quadrant of figure 5. South and east of the northeast oriented continental divide segment is the Shoshone Lake basin, which east of figure 5 drains in a south direction to the Lewis River, which in turn flows to the Snake River. Between the continental divide and Shoshone Lake is southwest and south-southeast oriented Shoshone Creek and in the northeast corner of figure 5 is south oriented De Lacy Creek and its southeast oriented tributary Heron Creek. Norris Pass and to a lesser extent Craig Pass in the northeast corner area of figure 5 link the west oriented Spring Creek valley with the south oriented De Lacy Creek valley. Further to the southwest Grant Pass links the north-northeast oriented Firehole River headwaters valley with the Shoshone Creek valley at the point where it turns to drain in a south-southeast direction. The map contour interval for figure 5 is 50 meters and the Grant Pass elevation at the continental divide is between 2400 and 2450 meters. Elevations along the continental divide to the northeast rise to 2676 meters near Norris Pass while to the southwest elevations rise to more than 2600 meters. These elevations suggest the Grants Pass through valley is at least 150 meters deep. The Grants Pass through valley is a water-eroded feature and was eroded by southeast oriented flood flow channel that diverged from the south-southwest oriented flood flow channel on the present day north-northeast oriented Firehole River alignment. Erosion of a deeper flood flow channel on the Firehole River alignment may have beheaded the southeast oriented channel using the Grants Pass through valley. Another possibility is the flood flow in the Grants Pass through valley ended at the time flood flow in the Firehole River valley was reversed to create a north oriented drainage route.

Detailed map of Firehole River-Shoshone Creek drainage divide area

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

Figure 6 provides a detailed topographic map of the Firehole River-Shoshone Creek drainage divide area seen in less detail in figure 5. The continental divide is shown with a labeled dashed line and extends in a north, northeast, and east direction from the south edge of figure 6 (west half) to the east edge of figure 6 (near northeast corner). Shoshone Creek flows in a southwest and southeast direction from the east edge of figure 6 (north half) to the west end of Shoshone Lake. West and south of figure 6 Shoshone Lake drains in a south direction to the south oriented Lewis River, which flows to the Snake River. The Firehole River flows in a north and north-northeast direction from the south edge of figure 6 (west of the continental divide) to the north edge of figure 6 (slightly west of center) and north of figure 6 flows to the west and north oriented Madison River. Grants Pass is located near the center of figure 6 and links a north-southwest oriented Firehole River tributary valley with a southeast oriented Shoshone Creek tributary valley. The map contour interval for figure 6 is 20 feet and the Grants Pass elevation at the drainage divide is between 8000 and 8020 feet. Elevations along the continental divide west and south of Grants Pass rise to almost 8600 feet (they exceed 8600 feet a short distance south of figure 6) and elevations along the continental divide northeast of Grants Pass rise to 8324 in the region seen in figure 6. These elevations suggest Grants Pass is a 300-foot deep through valley linking the north oriented Firehole River valley with the south oriented Shoshone Lake basin. The Grants Pass through valley was eroded by south oriented flood flow moving from the present day north oriented Firehole River valley to the Shoshone Lake basin and then to the south oriented Lewis River. Other shallower northwest-to-southeast oriented through valleys or passes can be seen crossing the continental divide north and east of Grant Pass suggesting the Grants Pass flood flow channel eroded a deeper valley and beheaded the shallower southeast oriented flood flow channels in the process. Flood flow in the Grants Pass flood flow channel ended by the time south oriented floodwaters in the Firehole River valley were beheaded and reversed. The deep Firehole River canyon north of Grants Pass suggests large volumes of floodwaters were reversed and eroded the much deeper north oriented Firehole River valley headward into the region seen in figure 6.

Firehole River-Shoshone Lake drainage divide area

Figure 7: Firehole River-Shoshone Lake drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the Firehole River-Shoshone Lake drainage divide area east and slightly north of figure 5 and includes a significant overlap area with figure 5. Trischman Knob is located near the southwest corner of figure 7. The Firehole River originates near Trischman Knob and flows in a north-northeast and north-northwest direction to the north edge of figure 7 (near Old Faithful). The east-west continental divide extends in roughly a northeast direction from Trischman Knob to Norris Pass and then in a northwest and north direction to the north center edge of figure 7. Drainage west of the continental divide in figure 7 eventually reaches the Gulf of Mexico, while drainage east of the continental divide eventually reaches the Pacific Ocean. The south oriented Lewis River can be seen draining from Shoshone Lake in the southeast quadrant of figure 7. North of Shoshone Lake and east of Norris Pass De Lacy Creek is the south oriented inlet stream with Heron Creek being the southeast oriented De Lacy Creek tributary. West of Norris Pass are headwaters of west oriented Spring Creek, which flows to the north oriented Firehole River. Norris and Craig Passes are additional passes crossing the present day continental divide. The map contour interval for figure 7 is 50 meters and the Norris Pass elevation at the drainage divide is between 2450 and 2500 meters. Elevations south of Norris Pass rise to 2676 meters and elevations along the continental divide to the north rise to more than 2600 meters suggesting that Norris Pass is at least 100 meters deep. Craig Pass is slightly higher in elevation, but is at least 50 meters deep. The history of Norris and Craig Passes may be more complex than the Grants Pass history in that floodwaters probably initially flowed in a southeast direction from the present day north oriented Firehole River drainage basin to the south oriented De Lacy Creek-Lewis River alignment. However, headward erosion of a deeper flood flow channel on the present day north-northeast oriented Firehole River alignment may have captured the southeast oriented flood flow and in the process captured some of the south oriented flood flow on the De Lacy Creek alignment to create a west-southwest oriented flood flow channel on the Spring Creek alignment. Eventually headward erosion of a still deeper south oriented flood flow channel on the Lewis River-De Lacy Creek alignment beheaded the west-southwest oriented flood flow channel. Shoshone Lake is a natural lake and the map evidence is not adequate to determine how Shoshone Lake was formed. Geyser Basins and hot springs in the region suggest the region is an active volcanic region and the Shoshone Lake basin may have been formed by volcanic lava flows blocking earlier drainage routes. If so it is possible and even probable that floodwaters were flowing across the region before and after the emplacement of the lava flows and the regional drainage history may be much more complex than described here.

Detailed map of Spring Creek-De Lacy Creek drainage divide area

Figure 8: Spring Creek-De Lacy Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 provides a detailed topographic map of the Spring Creek-De Lacy Creek drainage divide area seen in less detail in figure 7. The east-west continental divide is shown with a labeled dashed line in the east half of figure 8. In this figure 8 areas west of the continental divide drain to the Madison River with water eventually reaching the Gulf of Mexico and areas east of the continental divide drain to the Snake River with water eventually reaching the Pacific Ocean. The Firehole River flows in a north and northwest direction from the south edge of figure 8 (near southwest corner) to the west center edge of figure 8 and north and west of figure 8 joins the west and north oriented Madison River. Spring Creek flows in a south and west-southwest direction from the southeast quadrant of figure 8 (west and south of the continental divide) to join the north oriented Firehole River near the southwest corner of figure 8. De Lacy Creek is the south oriented stream flowing from the east edge of figure 8 (north half) to the south edge of figure 8 (near southeast corner) and south of figure 8 flows to Shoshone Lake, which drains to the south oriented Lewis River, which in turn flows to the Snake River. Norris Pass and Craig Pass are located in the southeast quadrant of figure 8 and link the west oriented Spring Creek drainage basin with the south oriented De Lacy Creek drainage basin. These passes are located in water-eroded valleys. The map contour interval for figure 8 is 20 feet and the Norris Pass valley has an elevation of between 8240 and 8260 feet and Craig Pass is approximately 20 feet higher. North of the passes elevations on the continental divide rise to 8725 feet while an elevation of 8725 feet can also be seen south of Norris Pass. These elevations suggest the passes may be almost 500 feet deep. What is particularly interesting about the Norris Pass region is the multiple valleys surrounding what appear to be streamlined erosional residuals. Larger scale streamlined erosional residuals can be seen near the center of figure 8 and are also surrounded by northwest-to-southeast oriented valleys. These diverging and converging valleys, with streamlined erosional residuals between them, suggests the presence of a southeast oriented anastomosing channel complex, which is a characteristic of flood-eroded landscapes. Floodwaters in the region were flowing in a southeast direction to the south oriented De Lacy Creek valley prior to the erosion of the Firehole River valley. Headward erosion of a south oriented flood flow channel on the present day north oriented Firehole River alignment captured the southeast oriented flood flow, which ended flood flow to the De Lacy Creek valley. Subsequently flood flow on the Firehole River alignment was reversed to create the north oriented Firehole River drainage route seen today.

Mallard Creek-Heron Creek drainage divide area

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

Figure 9 illustrates the Mallard Creek-Heron Creek drainage divide area north and slightly east of figure 7 and includes a significant overlap area with figure 7. The Firehole River flows in a north and northwest direction from the south edge of figure 9 to the Upper Geyser Basin and then in a north direction to the north edge of figure 9 (at the Lower Geyser Basin). South and west oriented Spring Creek joins the Firehole River near the south edge of figure 9. Mallard Creek flows in a northwest direction from Mallard Lake to join the Firehole River near the Midway Geyser Basin and White Creek flows in a north and northwest direction to join the Firehole River in the Lower Geyser Basin area. Northwest and north oriented Juniper Creek flows to the north edge of figure 9 (east of center) and north of figure 9 joins west and southwest oriented Nez Perce Creek, which joins the Firehole River north of figure 9. The west edge of Yellowstone Lake can be seen in the southeast corner of figure 9 and drains to the north and northwest oriented Yellowstone River, which north of Yellowstone National Park turns to flow in a northeast, east, and northeast direction to eventually join the Missouri River. De Lacy Creek originates at the De Lacy Lake (south of the center of figure 9) and flows in a southeast and south direction to the south center edge of figure 9. South of figure 9 De Lacy Creek flows to Shoshone Lake and the south oriented Lewis River, which then flows to the Snake River. The east-west continental divide is shown with a dashed line surrounding the south oriented De Lacy Creek drainage basin. Note how the south oriented De Lacy Creek drainage basin is located in a region higher in elevation than the north oriented drainage basins on either side and to the north. Also note how east of the south oriented De Lacy Creek valley there are what appear to be west and southwest oriented erosional residuals while west of the De Lacy Creek valley there is evidence of northwest-to-southeast oriented linear features some of which were seen in figure 8 and more of which will be seen in figure 10. Based on this evidence it appears that southeast and southwest oriented floodwaters converged at a deeper south oriented flood flow channel on the present day south oriented De Lacy Creek alignment. Northwest oriented Firehole River tributary drainage routes were established when headward erosion of a much deeper oriented flood flow channel on the Firehole River alignment beheaded the southeast oriented flood flow. Northeast oriented drainage routes in the east half of figure 9 probably were created by reversals of southwest oriented flood flow channels while the north oriented Juniper Creek drainage route was created by a reversal of south oriented flood flow. The map in figure 9 lacks many desired details, although more detailed topographic are available as seen in figures 8 and 10.

Detailed map of Mallard Creek-Heron Creek drainage divide area

Figure 10:Detailed map of Mallard Creek-Heron 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 Mallard Creek-Heron Creek drainage divide area seen in less detail in figure 9. Mallard Lake is located west of the center of figure 10. Mallard Creek flows in a northwest direction from Mallard Lake to the west edge of figure 10 (near northwest corner). West and north of figure 10 Mallard Creek flows to the north oriented Firehole River, which then flows to the west and north oriented Madison River. The De Lacy Lakes are located in the east center area of figure 10. De Lacy Creek flows in an east and southeast direction from the De Lacy Lakes to the east center edge of figure 10 and then flows in a south-southwest direction across the southeast corner of figure 10. Heron Creek is a southeast oriented stream flowing to the south edge of figure 10 and joins De Lacy Creek south of figure 10. South of figure 10 De Lacy Creek flows to the south oriented Lewis River, which in turn flows to the Snake River. The east-west continental divide is shown with a labeled dashed line and surrounds the south oriented De Lacy Creek drainage basin in the east half of figure 10. North of the De Lacy Lakes are headwaters on north-northwest oriented White Creek, which north of figure 10 turns to flow in a northwest direction to join the north oriented Firehole River. North oriented drainage routes east of White Creek flow to north oriented Juniper Creek, which north of figure 10 joins west oriented Nez Perce Creek to flow to the north oriented Firehole River. Note how a north-to-south oriented through valley links the north-northwest oriented White Creek valley and the south oriented De Lacy Creek valley. The map contour interval for figure 10 is 20 feet and the drainage divide elevation north of the De Lacy Lakes is between 8580 and 8600 feet. An elevation of 8785 feet is found west of the through valley and an elevation of 8728 is located just east of figure 10 and north of the southeast oriented De Lacy Creek segment. These elevations suggest the through valley is at least 125 feet deep. An even deeper and more impressive northwest-to-southeast oriented through valley links the northwest oriented Mallard Creek valley with the southeast oriented Heron Creek valley. The through valley floor elevation at the continental divide is between 8460 and 8480 feet. To the north elevations rise to 8785 feet and to the south elevations rise to 8725 feet suggesting the through valley may be as much as 250 feet deep. These through valleys are water-eroded features and were eroded by south-southeast and southeast oriented flood flow moving to an actively eroding south oriented valley on the De Lacy Creek alignment. Further evidence of anastomosing flood flow channels and streamlined erosional residuals can be seen along the flood flow channel route linking the northwest oriented Mallard Creek valley with the southeast oriented Heron Creek valley.

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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