Abstract:

This essay uses topographic map evidence to interpret landform origins along the continental divide between the Red Rock River in Beaverhead County, Montana and Henrys Fork in Clark and Fremont Counties, Idaho. The continental divide segment studied in this essay is located along the Centennial Mountains east end. The Centennial Mountains are a west-to-east oriented mountain range, which forms the Montana-Idaho border west of Yellowstone National Park. The Red Rock River flows in a west direction in the Centennial Valley north of the Centennial Mountains and west of the study region turns to flow in a north-northwest direction with water eventually reaching the north oriented Missouri River at Three Forks, Montana. Henrys Fork originates in Henrys Lake, which is located slightly north and east of the Centennial Mountains east end and flows in a south and southwest direction to join the southwest and west oriented Snake River. North-to-south oriented passes or through valleys cross the Centennial Range in the study region and link north oriented Red Rock River tributary valleys with south oriented Henrys Fork tributary valleys. These through valleys or mountain passes were eroded as flood flow channels at a time when immense south oriented melt water floods flowed across the region. Initially the Centennial Mountains did not stand high above surrounding regions as they do today and the Centennial Valley and west oriented Red Rock River in the Centennial Valley did not exist. As floodwaters flowed across the region the Centennial Mountains began to emerge with the Centennial Valley emerging as a structural basin probably under the weight of flood deposited debris along the north margin of the emerging Centennial Mountains. At first south oriented flood flow eroded deeper and deeper channels into the emerging mountain mass, but eventually was captured by an east-oriented valley in the developing Centennial Valley, which eroded headward from a deep south oriented flood flow channel on the present day Madison River-Henrys Fork alignment, which had formed at the east end of the emerging Centennial Mountains. Floodwaters on north ends of the beheaded flood flow channels in the Centennial Mountains reversed flow direction to form north oriented drainage routes and also captured floodwaters from yet to be beheaded flood flow channels further to the west. Headward erosion of the much deeper Missouri River valley (north and east of the study region) beheaded the south-oriented flood flow channel on the Madison River-Henrys Fork alignment. The resulting massive reversal of floodwaters created the north oriented Madison-Missouri River drainage system north of Henrys Fork and captured the east oriented flood flow in the Centennial Valley. Next south oriented flood flow channels further to the west, which were supplying floodwaters to the east oriented flood flow channel in the Centennial Valley were beheaded and reversed to create the west and north-northwest oriented Red Rock River drainage system. Floodwaters were derived from a melting thick North American ice sheet and the deeper Missouri River valley eroded headward from space being up in a deep “hole” the ice sheet had occupied. The massive reversal of flood flow that created the west and north-northwest oriented Red Rock River and north oriented Madison-Missouri River drainage systems was probably greatly aided by ice sheet related crustal warping that raised the Centennial Mountains and surrounding region.

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 Red Rock River-Henrys Fork drainage divide area landform origins along the continental divide in Beaverhead County, Montana and Clark and Fremont Counties, Idaho 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 Red Rock River-Henrys Fork drainage divide area landform evidence along the continental divide in Beaverhead County, Montana and Clark and Fremont Counties, Idaho will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Red Rock River-Henrys Fork drainage divide area location map

Figure 1: Red Rock River-Henrys Fork 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 Red Rock River-Henrys Fork drainage divide area along the continental divide in Beaverhead County, Montana and Clark and Fremont Counties, Idaho and illustrates in the north a region in southwest Montana with Idaho to the south and Yellowstone National Park, which is primarily located in the northwest corner of Wyoming, appearing in the southeast quadrant of figure 1. The Montana-Idaho state line west of Yellowstone National Park is located on the east-west continental divide, which follows the crest of the Centennial Mountains from the west edge of figure 1 to the Wyoming state line. The Red Rock River originates as Red Rock Creek east of Upper Red Rock Lake, just north of the Centennial Mountains, and flows in a west direction to near Lima, Montana and then turns to flow in a north-northwest direction to an unnamed lake (Clark Canyon Reservoir). At Clark Canyon Reservoir the Red Rock River is joined by east oriented tributaries to form the north-northeast oriented Beaverhead River, which joins the north, southeast, south, and northeast oriented Big Hole River near Twin Bridges to form the northeast and east oriented Jefferson River. The Jefferson River then joins the north oriented Madison and Gallatin Rivers north of figure 1 to form the north oriented Missouri River. North of figure 1 the Missouri River turns to flow in a northeast and east direction to North Dakota where it turns to flow in a southeast and south direction with water eventually reaching the Gulf of Mexico. East and slightly north of the Centennial Mountains Henrys Fork originates near Henry Lake (just west of Targhee Pass) and flows in a south and southwest direction to the town of Island Pond and then to the south center edge of figure 1 and south of figure 1 joins the Snake River. Note the southeast and east oriented Henrys Fork tributary flowing to Island Pond Reservoir. The Snake River originates in Yellowstone National Park near the south edge of figure 1 and flows in a south direction and south of figure 1 turns to flow in a northwest direction to join southwest oriented Henrys Fork and then flows in a southwest and northwest direction across southern Idaho before turning to flow in a north direction west of figure 1 with water eventually reaching the Pacific Ocean. The Red Rock River-Henrys Fork drainage divide area investigated in this essay is located along the east end of the Centennial Mountains and is generally east of Upper Red Rock Lake and west of Henrys Lake.

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 southwest Alberta and southeast British Columbia to and across the figure 1 region. North oriented rivers in figure 1 are generally flowing in valleys that originated as south oriented flood flow channels. The north oriented drainage routes seen north of the continental divide seen in figure 1 were initially developed as south and southeast oriented flood flow channels. Prior to development of deep flood flow channels adjacent to the emerging mountain ranges floodwaters flowed across what are today high mountain ranges including the Centennial Mountains, 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 before the deep Red Rock River drainage route to the north evolved and before the Centennial Mountains emerged to become the major topographic barrier they are today.

The Red Rock River probably originated as a south-southeast and east oriented flood flow channel, which probably eroded headward from a deep south oriented flood flow channel on the Madison River-Henrys Fork alignment and which was subsequently reversed to form the west and north-northwest oriented drainage route seen today. 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 Montana (north of figure 1), which beheaded south oriented flood flow channels supplying floodwaters to the south-southeast and east oriented Madison River-Henrys Fork and Red Rock River flood flow channels. The deep northeast oriented valley was eroding headward from space in the deep “hole” the melting ice sheet had occupied and was capturing the south and southeast oriented ice-marginal melt water floods in sequence from east to west and diverting the 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 north ends of the beheaded flood flow channels reversed flow direction to create the north oriented drainage routes seen in figure 1. Mountain ranges, including the Centennial Mountains, shown in figure 1 emerged as floodwaters flowed across the region. As the mountains emerged floodwaters eroded deep valleys into and around the emerging mountain masses, with the floodwaters being captured by the most successful of these deep valleys. In time the Centennial Mountains formed an insurmountable topographic barrier that ended all south oriented flood flow into Idaho.

Detailed location map for Red Rock River-Henrys Fork drainage divide area

Figure 2: Detailed location map Red Rock River-Henrys Fork 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 Red Rock River-Henrys Fork drainage divide area along the continental divide in Beaverhead County, Montana and Clark and Fremont Counties, Idaho and shows drainage routes not seen in figure 1. The Yellowstone National Park boundary is labeled near the east edge of figure 2 and the Wyoming state line is just east of the National Park boundary. The continental divide serves as the Montana-Idaho state line and is shown with well-marked dashed line extending from the west edge of figure 2 along the Centennial Mountains crest ridge to near Henrys Lake and then north around Henrys Lake and then continues in a southeast direction to near the southeast corner edge of figure 2. Green shaded areas are National Forest lands, which generally are located in mountainous regions. The Madison River is the north-northwest oriented drainage route north of Raynolds Pass (north of Henrys Lake) flowing to the north center edge of figure 2. Henrys Fork originates at Henrys Lake and flows in a southeast, west, and southwest direction to Island Pond Reservoir and then in a south-southwest direction to the south center edge of figure 2. Labeled Henrys Fork tributaries of interest in this essay are southeast, east, and southeast oriented Sheridan Creek, which in spite of what figure 2 shows is a Henrys Fork tributary, and south oriented Willow Creek. An unlabeled east and northeast stream (Duck Creek) originates near the continental divide just west of Henrys Lake and then flows to Henrys Lake. West of the Duck Creek headwaters, on the other side of the continental divide, is north, northwest, and west oriented Red Rock Creek, which originates at the east end of the Centennial Mountains and which flows to Upper Red Rock Lake and then to Lower Red Rock Lake. The Red Rock River originates at Lower Red Rock Lake and flows in a west direction through the Centennial Valley to the west edge of figure 2. Note north and north-northwest oriented Red Rock Creek and Red Rock River tributaries originating near the continental divide in the Centennial Mountains. Several of these north oriented tributaries are aligned with south and southeast oriented streams on the south side of the continental divide suggesting the drainage routes originated at a time when multiple south and southeast oriented flood flow channels crossed the emerging Centennial Mountains, which means at that time the Centennial Mountains did not form the topographic barrier they do today.

Odell Creek-West Dry Creek drainage divide area

Figure 3: Odell Creek-West Dry 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 Odell Creek-West Dry Creek drainage divide area and is located at the west end of the continental divide segment investigated in this essay. The east-west continental divide serves as the state and county line and is shown with a labeled dashed line in the south half of figure 3 extending from the west edge to the east edge of figure 3. Areas in Montana drain to the Red Rock River with water eventually reaching the Gulf of Mexico. Red Rock Creek flows in a west direction from the east edge of figure 3 (north of center) to Upper Red Rock Lake and then to Lower Red Rock Lake where the west oriented Red Rock River is formed. Baldy Mountain is a labeled high point on the continental divide south of Lower Red Rock Lake. Odell Creek is a southeast, north and north-northwest oriented stream originating on Baldy Mountain and flowing to Lower Red Rock Lake. Southeast oriented Odell Creek headwaters provide evidence of a former southeast oriented drainage route between Baldy Mountain and Sheep Mountain (located south of Upper Red Rock Lake). A deep north-to-south oriented gap or through valley is located between the two mountains and links the north oriented Odell Creek valley with the south-southeast oriented West Dry Creek valley. The map contour interval for figure 3 is 50 meters and the through valley floor elevation at the drainage divide is between 2300 and 2350 meters. Elevations on Baldy Mountain exceed 3000 meters and elevations on Sheep Mountain exceed 2950 meters suggesting the through valley or gap could be as much as 600 meters deep. The through valley or gap was eroded by south oriented flood flow prior to the formation of the deep Red Rock valley to the north. Probably the Centennial Mountains were emerging as the south oriented floodwaters flowed across them and the floodwaters eroded a deep valley into the emerging mountain mass. South of figure 3 West Dry Creek flows to and then in the same valley as East Dry Creek (although on opposites sides of the valley) and then West Dry Creek turns to flow in a southwest direction to join south oriented Camas Creek while East Dry Creek turns to flow in an east direction to Sheridan Reservoir and to join Sheridan Creek, which flows to Henrys Fork. West Dry Creek south of figure 3 eventually joins Camas Creek, which disappears as a surface stream, but which is headed toward the Snake River. The divergence of two valleys from the single West and East Dry Creek valley south of figure 3 suggests the valleys were originally channels in an anastomosing channel complex.

Detailed map of Odell Creek-West Dry Creek drainage divide area

Figure 4: Detailed map of Odell Creek-West Dry 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 Odell Creek-West Dry Creek drainage divide area seen in less detail in figure 3. The east-west continental divide serves as the state and county line and is shown with a labeled dashed line extending from the west edge of figure 4 to the east edge with drainage north of the continental divide to the Gulf of Mexico and drainage south of the continental divide to the Pacific Ocean. Odell Creek flows in a southeast and northeast direction north of the continental divide and has some southeast and northeast oriented tributaries. South of the continental divide West Dry Creek flows in a southeast direction to the south edge of figure 4 (east half). As described in the figure 3 discussion West Dry Creek flows to a valley, which today is used by drainage flowing to both Henrys Fork and to Camas Creek, although both are within the Snake River drainage basin. Note how the West Dry Creek alignment is the same as the alignment of one of the southeast oriented Odell Creek tributaries and that the two southeast oriented valleys are linked by a northwest-to-southeast oriented through valley (near center of figure 4). The map contour interval for figure 4 is 40 feet and the through valley floor elevation at the continental divide is between 7520 and 7560 feet. A second through valley crossing the continental divide can be seen in the southwest quadrant of figure 4 and links a northeast oriented Odell Creek tributary valley with a southwest oriented stream valley seen near the south edge of figure 4 (Scalp Creek). The floor elevation of this second through valley at the continental divide is between 7680 and 7720 feet, which is slightly higher than the first through valley floor elevation. The continental divide near the east edge of figure 4 rises to 8161 feet and further east rises to more than 9600 feet. To the west the continental divide elevation at the west edge of figure 4 is more than 8200 feet and rises to more than 9800 feet further to the west. Based on these elevations the through valleys seen in figure 4 could be considered to be between 500 and 2000 feet deep. South oriented flood flow channels eroded these deep through valleys into what was at that time an emerging Centennial Mountains mass. The valleys were eroded deeper and deeper as the Centennial Mountains emerged until headward erosion of a deeper east oriented valley on the present day west oriented Red Rock River and Red Rock Creek alignment north of the Centennial Mountains captured the south oriented flood flow and diverted the floodwaters first to the south oriented Henrys Fork alignment and later as north oriented flood flow on the Madison River alignment. Floodwaters on the north ends of the beheaded flood channels in the emerging Centennial Mountains also reversed flow direction to create north oriented drainage routes, including the north oriented Odell Creek drainage route.

Tom Creek-Schneider Creek drainage divide area

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

Figure 5 illustrates the Tom Creek-Schneider Creek drainage divide area east and slightly south of figure 3 and includes a significant overlap area with figure 3. The east-west continental divide serves as the state and county line and extends from the west edge of figure 5 to the east center edge and then loops back into figure 5 to continue in a north direction from Mount Jefferson to Red Rock Pass and Squaw Pass before reaching the north edge of figure 5 (near northeast corner). Drainage in Montana (north and west of the continental divide) is to the Gulf of Mexico while drainage south and east of the continental divide is to the Pacific Ocean. Upper Red Rock Lake is located in the northwest quadrant of figure 5. Cole Creek is a northwest and north oriented stream originating near Red Rock Pass and flowing to join west and north oriented Hell Roaring Creek to form west oriented Red Rock Creek, which flows to Upper Red Rock Lake and then continues north and west of figure 5 to Lower Red Rock Lake and the Red Rock River. Tom Creek is a northwest oriented stream originating near the continental divide (near center of figure 5) and flowing to Upper Red Rock Lake. South of the north oriented Tom Creek headwaters are headwaters of south oriented Schneider Creek, which flows to the south center edge of figure 5 with water eventually reaching Henrys Fork. Note how a north-to-south oriented through valley or mountain pass links the northwest oriented Tom Creek valley and the south oriented Schneider Creek valley. A through valley or pass of approximately equal depth is located a short distance to east and links the northwest oriented Tom Creek valley with the south-southeast oriented Myers Creek valley. Still further east a slightly deeper through valley links north oriented Hell Roaring Creek valley with the south-southwest oriented Willow Creek valley. This third through valley has an elevation of between 2400 and 2450 meters at the continental divide. The map contour interval for figure 5 is 50 meters (except along the south margin where the contour interval is 20 meters). The elevation of the first two through valleys at the drainage divide is between 2450 and 2500 meters. Taylor Mountain to the west rises to 2946 meters and Mount Jefferson to the east rises to more than 3000 meters suggesting the through valleys may be as much as 450 to 500 meters deep. These through valleys or mountain passes were eroded by diverging and converging south oriented flood flow channels into what was at that time an emerging Centennial Mountains mass. Headward erosion of a deep east oriented valley (from Red Rock Pass and/or Squaw Pass) to the north first captured the south oriented flood flow. Later flood flow in the valley to the north was reversed so as to create the west oriented Red Rock Creek drainage route. The north oriented drainage routes were created by reversals of flood flow on north ends of beheaded south and southeast oriented flood flow channels.

Detailed map of Tom Creek-Schneider Creek drainage divide area

Figure 6: Detailed map of Tom Creek-Schneider 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 Tom Creek-Schneider Creek drainage divide area seen in less detail in figure 5. The east-west continental divide serves as the state and county boundary and extends from the west edge of figure 6 (near center) to the east edge of figure 6 (north of center). Drainage north of the continental divide is to the Red Rock River with water eventually reaching the Gulf of Mexico. Drainage south of the continental divide is to Henrys Fork with water eventually reaching the Pacific Ocean. Tom Creek originates in section 4 just north of the continental divide near the center of figure 6 and flows in a northwest direction to the north edge of figure 6 (west half). Schneider Creek originates in section 9 on the south side of the continental divide and just west of the Clark-Fremont County line and flows in a south-southwest direction to the south edge of figure 6 (west half). Myers Creek originates near the east edge of section 10 (south of the continental divide) and flows in a southeast, south-southwest, and south-southeast direction to the south edge of figure 6 (east half). Willow Creek is not labeled, but originates in section 12 near the east edge of figure 6 and flows in a south direction to the south edge of figure 6 (near southeast corner). The map contour interval for figure 6 is 40 feet. Blair Lake near the east edge of figure 6 and just north of the continental divide drains to north oriented Hell Roaring Creek, which flows in a west direction in the region east of figure 6. The through valleys linking the north oriented Tom Creek valley with the south oriented Schneider Creek valley and with the south oriented Myers Creek valley have elevations at the continental divide of between 8080 and 8120 feet. A through valley linking the north oriented Hell Roaring Creek valley with the south oriented Willow Creek valley is east of figure 6 and has an elevation at the continental divide of between 7920 and 7960 feet. Reas Peak (east of Willow Creek drainage basin and of figure 6) reaches an elevation of more than 9120 feet while elevations greater than 9400 feet can be seen along the continental divide in figure 6. These elevations suggest the through valleys could be as much 1000 feet deep. The through valleys provide evidence of multiple south oriented flood flow channels on the floor of what was once a much broader south oriented valley eroded into the emerging Centennial Mountains mass. The multiple channels suggest the presence of diverging and converging south oriented flood flow channels such as are found in an anastomosing channel complex.

Hell Roaring Creek-Yale Creek drainage divide area

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

Figure 7 illustrates the Hell Roaring Creek-Yale Creek drainage divide area east of figure 5 and includes a significant overlap area with figure 5. The east-west continental divide is shown with a dashed line and extends from near the west center edge of figure 7 to Reas Peak and around the west oriented Hell Roaring Creek headwaters before reversing direction to Mount Jefferson and then continuing in a north direction to Red Rock Pass and to the north edge of figure 7 (west of center). Drainage north and west of the continental divide flows to the Red Rock River and water eventually reaches the Gulf of Mexico. Drainage south and east of the continental divide flows to Henrys Fork and water eventually reaches the Pacific Ocean. Henrys Lake can be seen straddling the north edge of the northeast quadrant of figure 7. Henrys Fork flows in a south-southeast direction from Henrys Lake to the east center edge of figure 7 and then in a west and south direction near the southeast corner of figure 7. Cole Creek originates near Red Rock Pass and flows in a northwest and north direction to join west and north oriented Hell Roaring Creek and to form Red Rock Creek, which then flows in a west direction to the west edge of figure 7 (near northwest corner). Hell Roaring Creek originates south and east of Mount Jefferson and flows in a west, northwest, and north direction to join Cole Creek and to form west oriented Red Rock Creek slightly north and west of Squaw Pass. East of Red Rock Pass are headwaters of northeast oriented Duck Creek, which flows to Henrys Lake. North of the Hell Roaring Creek headwaters, and east of Mount Jefferson is Rock Creek Basin, and Rock Creek flows in an east and north direction to join northeast oriented Duck Creek. East of the west oriented Hell Roaring Creek headwaters and south of the north oriented Rock Creek valley are headwaters of southeast and south-southwest oriented Yale Creek, which flows to the south edge of figure 7 (east of center). Note how through valleys link the southeast and south oriented Yale Creek valley with the north oriented Rock Creek valley and the west oriented Hell Roaring Creek valley. The map contour interval for figure 7 is 50 meters except along the south edge where the contour interval is 20 meters. The Hell Roaring Creek-Yale Creek through valley has a floor elevation of between 2450 and 2500 meters at the continental divide. Arange Peak to the south rises to 2738 meters and Reas Peak south of Mount Jefferson rises to 2834 meters. Mount Jefferson rises to more than 3000 meters. The Rock Creek-Yale Creek through valley between Mount Jefferson and Sawtell Peak is slightly higher with an elevation of between 2500 and 2550 meters at the drainage divide. Sawtell Peak to the east rises to 2807 meters. These elevations suggest the through valleys could be from 250 to 350 meters deep. The Rock Creek-Yale Creek through valley was eroded by a south oriented flood flow while the Hell Roaring Creek-Yale Creek through valley was eroded by a converging south and east oriented flood flow channel. At that time the deep south-oriented Henrys Fork valley to the east did not exist, although it was probably being eroded by south oriented flood flow. Headward erosion of the deep south-oriented Henrys Fork valley, probably with the help of crustal warping and of the deep Duck Creek valley, beheaded the south oriented flood flow on the Rock Creek-Yale Creek alignment. Floodwaters on the north end of the beheaded flood flow channel reversed flow direction to create the north oriented Rock Creek drainage route. Somewhat later headward erosion of a deep valley north of the Centennial Mountains beheaded the south and east oriented flood flow channel on the Hell Roaring Creek-Yale Creek alignment and floodwaters on the north and west end of the beheaded flood flow channel reversed flow direction to create the west and north oriented Hell Roaring Creek drainage route.

Detailed map of Hell Roaring Creek-Yale Creek drainage divide area

Figure 8: Hell Roaring Creek-Yale 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 Hell Roaring Creek-Yale Creek drainage divide area seen in less detail in figure 7. The east-west continental divide serves as the state and county line and surrounds the west oriented Hell Roaring Creek drainage basin in the west half of figure 8. Hell Roaring Creek flows to Red Rock Creek with water eventually reaching the Gulf of Mexico. Yale Creek originates in section 11 just east of the continental divide and flows in a southeast direction to the southeast corner of figure 8 and then to Henrys Fork, with water eventually reaching the Pacific Ocean. Other south oriented streams in sections 14, 15, and 16 south of the continental divide flow to Henrys Fork. Rock Creek originates in section 3 near the north edge of the northwest quadrant of figure 8 and flows in an east direction to near the north center edge of figure 8 where it turns to flow in a north direction to join northeast oriented Duck Creek, which flows to Henrys Lake with water then flowing to south oriented Henrys Fork. Note the north-northwest oriented Rock Creek tributary just west of Sawtell Peak. A west-to-east oriented through valley near the center of figure 8 links the west oriented Hell Roaring Creek valley with the southeast oriented Yale Creek valley. The map contour interval for figure 8 is 40 feet and the through valley floor elevation at the continental divide is between 8920 and 8960 feet. Through valleys with similar elevations also cross the Hell Roaring Creek drainage divide with south oriented streams in sections 14 and 15. Sawtell Peak rises to 9866 feet and Mount Jefferson (just west of figure 8) rises to more than 10,000 feet while Reas Peak, south of Mount Jefferson and south of Hell Roaring Creek, rises to more than 9320 feet suggesting the through valleys may be as much 360 feet deep. While insignificant when compared with depths of the surrounding valleys these through valleys are water-eroded valleys and were eroded by south and east oriented flood flow moving on the present day west and north oriented Hell Roaring Creek alignment. That south and east oriented flood flow probably converged with south oriented flood flow moving on the present day north oriented Rock Creek alignment in the region where Hell Roaring Creek originates (section 3 in Montana). Note a north-to-south oriented through valley linking the Hell Roaring Creek headwaters valley with a north and northeast oriented Rock Creek tributary valley. The through valley floor elevation at the continental divide is between 9000 and 9040 feet, which is more than 400 feet lower than peak just to the east and more than 800 feet lower than Sawtell Peak further to the east (elevations to the west are much higher). The south oriented flood flow channel on the present north oriented Rock Creek alignment probably diverged in the north center region of figure 8 with one diverging flood flow channel going in a southeast direction to the southeast oriented Yale Creek valley alignment while the other diverging flood flow channel flowed across the present day west oriented Hell Roaring Creek headwaters area to the south oriented valleys in sections 14 and 15. Subsequently the south oriented flood flow channel on the present day north oriented Rock Creek alignment was beheaded and floodwaters on the north end of the beheaded flood flow channel reversed flow direction to create the present day north oriented Rock Creek drainage route.

Red Rock Creek-Duck Creek drainage divide area

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

Figure 9 illustrates the Red Rock Creek-Duck Creek drainage divide area north and west of figure 7 and includes a significant overlap area with figure 7. The east-west continental divide can be seen near the south edge of the southwest quadrant of figure 9 and then extends around the Hell Roaring Creek drainage basin before extending in a north direction from Mount Jefferson to the north edge of figure 9 (east half). Henrys Lake straddles the east edge of figure 9 and drains to south oriented Henrys Fork with water eventually reaching the Pacific Ocean. Cole Creek originates near Red Rock Mountain (north of Mount Jefferson) and flows in a northwest and north direction to join west and north oriented Hell Roaring Creek to form west oriented Red Rock Creek, which flows to the west center edge of figure 9. Red Rock Pass is located just east of Cole Creek and north of Red Rock Mountain. Squaw Pass is located north of Red Rock Pass. East of Red Rock Pass is Duck Creek, which has a north oriented South Fork and a south oriented North Fork and which flows in an east and northeast direction to Henrys Lake. The map contour interval for figure 9 is 50 meters and the Red Rock Pass elevation at the continental divide is between 2150 and 2200 meters (the Squaw Pass elevation is slightly higher). North and east of Henrys Lake and of figure 9 continental divide elevations exceed 3000 meters, as do elevations on Mount Jefferson south of Red Rock Pass (and seen in figure 9). These elevations suggest Red Rock Pass and the region north of Red Rock Pass are part of a broad through valley crossing the present day continental divide. North of Henrys Lake and west of the 3000-meter high mountains is Raynolds Pass (elevation between 2050 and 2100 meters), which links the south oriented Henrys Fork valley with the north oriented Madison River valley. The Red Rock Pass and Squaw Pass through valleys seen in figure 9 link that north-to-south oriented through valley with the west oriented Red Rock River valley. As seen in earlier figures in this essay at one time south oriented flood flow channels crossed the present day Centennial Mountains. At that time the deep west oriented Red Rock Creek and Red Rock River valley north of the Centennial Mountains did not exist and the deep south-oriented Henrys Fork valley must have been in the process of being formed. As a deep south oriented flood flow channel on the present day north oriented Madison River and south oriented Henrys Fork alignment was formed it began to capture south oriented flood flow moving across the east end of the emerging Centennial Mountains. In doing so a deep east-oriented valley eroded headward from the Henrys Lake area into the Centennial Valley area. However, a massive reversal of flood flow reversal beheaded the south oriented Madison River-Henrys Fork flood flow channel and created the north oriented Madison River drainage route. South oriented flood flow from flood flow channels further to the west was at that time still moving to the east oriented valley on the present day west oriented Red Rock River alignment, which was then captured to flow in a northeast and north direction on the newly reversed Madison River alignment. Later the south oriented flood flow channels feeding the east oriented flood flow channel in the Centennial Valley were captured and floodwaters on the north ends of the beheaded flood channels reversed flow direction to create the west and north-northwest oriented Red Rock River drainage route seen today. Crustal warping contributed to the flood flow reversals and probably further complicated drainage routes seen in figure 9.

Detailed map of Red Rock Creek-Duck Creek drainage divide area

Figure 10:Detailed map of Red Rock Creek-Duck 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 Red Rock Creek-Duck Creek drainage divide area seen in less detail in figure 9. The east-west continental divide serves as the state and county line and extends from the north edge of figure 10 (east half) to the south edge of figure 10 (east of center). At this figure 10 location water west of continental divide flows to the Red Rock River and eventually reaches the Gulf of Mexico and water east of the continental divide flows to Henrys Fork and eventually reaches the Pacific Ocean. The north margin of the east end of the west-to-east oriented Centennial Mountains can be seen along the south edge of figure 10. North of the Centennial Mountains the continental divide follows the crest of the much lower north-to-south oriented Henrys Lake Mountains. West of the Henrys Lake Mountains and north of the Centennial Mountains is the Alaska Basin, which forms the east end of the much larger west-to-east oriented Centennial Valley. The Alaska Basin appears to be a structural basin and appears to have been partially filled by a northwest sloping alluvial fan. North oriented Hell Roaring Creek and Cole Creek emerge near the alluvial fan’s head and flow in a north direction along the fan’s east edge before joining to form west oriented Red Rock Creek, which then flows along the fan’s north edge. Drainage routes on the alluvial fan post date flood events that eroded what are today deep north-to-south oriented through valleys across the Centennial Mountains because the Centennial Valley and Alaska Basin did not exist when south oriented flood flow channels crossed what were then the emerging Centennial Mountains. As the Centennial Mountains emerged the Centennial Valley and Alaska Basin also subsided, perhaps under the weight of flood deposited debris accumulating along the north side of the emerging Centennial Mountains. In time the deep south oriented Henrys Fork valley eroded around the east end of the emerging Centennial Mountains and deep east oriented valleys were able to erode headward along the north margin of the emerging Centennial Mountains. Red Rock Pass seen in figure 10 was probably initiated as an east oriented valley, which captured south oriented flood flow routes across the Centennial Mountains. Floodwaters on north ends of the beheaded flood flow channels then reversed flow direction to create north oriented drainage routes in the Centennial Mountains (e.g. Corral Creek, Hell Roaring Creek and Cole Creek in figure 10). Later the east oriented flood flow channel was reversed in the Alaska Basin to first flow to a northeast oriented flood flow channel (north and west of figure 10) to the newly reversed Madison River flood flow channel and still later to flow to the reversed flood flow channel on the present day west and north-northwest oriented Red Rock River alignment. Continued subsidence probably further lowered the Alaska Basin while continued uplift probably further raised the Centennial Mountains.

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.