Abstract:

This essay uses topographic map evidence to interpret landform origins between the north oriented Ruby River and the west oriented Red Rock River in Beaverhead and Madison Counties, Montana. The Red Rock River flows in the east-to-west oriented Centennial Valley at the south end of the study region and further west turns to flow in north-northwest direction to flow to the north-northeast oriented Beaverhead River, which then joins the north and northwest oriented Ruby River to flow to the north-northeast, east, and northeast oriented Jefferson River. The Ruby River originates north of the Centennial Valley and flows in a north direction between the Snowcrest Range to the west and the Gravelly Range to the east before turning to flow in a northwest direction to join the north-northeast Beaverhead River. The Centennial Divide is located in a deep north-to-south oriented through valley linking the north oriented Ruby River valley with south-southeast oriented streams flowing to southwest oriented Long Creek, which flows to the west oriented Red Rock River. Southeast oriented through valleys link the southwest oriented Long Creek valley with southeast oriented tributaries to the west oriented Red Rock River. Further north The Notch is a deep wind gap in the Snowcrest Range, which links north oriented Robb Creek (a Ruby River tributary) with the northeast oriented West Fork Ruby River and with south oriented headwaters of the East Fork Blacktail Deer Creek, which further to the south turn to flow in northwest direction to the Beaverhead River. Further north Ledford Pass is another deep wind gap in the Snowcrest Range linking the south end of the U-turn where south oriented Ledford Creek headwaters turn to flow in a north direction (to join the Ruby River) with the northeast oriented West Fork Ruby Creek valley. Floodwaters were derived from west margin of a melting thick North American ice sheet and were flowing from western Canada in south and southeast direction to the study region. Diverging and converging flood flow channels are interpreted to have eroded the deep through valleys or wind gaps. At first south oriented flood flow moved to an east oriented flood flow channel in the developing Centennial Valley, although the reversals of flood flow that create the north-northeast oriented Beaverhead and Jefferson River drainage routes and north-northwest oriented Red Rock River drainage route also caused a flood flow reversal in the Centennial Valley to create the west oriented Red Rock River drainage route. South oriented flood flow channels in the present day north oriented Ruby River drainage basin were reversed in sequence to produce north oriented drainage routes seen today, although evidence of converging south oriented flood flow channels is found in U-turns made by south oriented headwaters of present day north oriented streams and by through valleys or wind gaps linking south ends of U-turns with valleys further to the south. Crustal warping related to the thick ice sheet presence occurred as south oriented melt water floods flowed across the study region and contributed to the flood flow reversals, which were triggered by headward erosion of deep northeast oriented valleys from space in the deep “hole” the melting ice sheet had occupied.

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 Ruby River-Red Rock River drainage divide area landform origins in Beaverhead and Madison Counties, Montana 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 Ruby River-Red Rock River drainage divide area landform evidence in Beaverhead and Madison Counties, Montana will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Ruby River-Red Rock River drainage divide area location map

Figure 1: Ruby River-Red Rock 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 Ruby River-Red Rock River drainage divide in Beaverhead and Madison Counties, Montana and illustrates in the north a region in southwest and south central Montana with Yellowstone National Park in the northwest corner of Wyoming in the southeast quadrant of figure 1 and an area in eastern Idaho located west of Yellowstone National Park. The Montana-Idaho state line west of Yellowstone National Park is located on the east-west continental divide, which follows the crest of the Beaverhead and Centennial Mountains from the west edge of figure 1 to the Wyoming state line. Upper Red Rock Lake is located north of the Centennial Mountains and drains in a west direction to Lower Red Rock Lake and then to the Red Rock River, which flows in a west direction to Lima, Montana where it turns to flow in a north-northwest direction to join the north-northeast-oriented Beaverhead River. The Beaverhead River joins the north, southeast, south, and northeast oriented Big Hole River near Twin Bridges, Montana to form the north-northeast, east, and northeast oriented Jefferson River. The Jefferson River flows to Three Forks, Montana where it joins the north oriented Madison and Gallatin Rivers to form the north and north-northwest oriented Missouri River. The Ruby River is the unlabeled north and northwest drainage route flowing through Alder, Laurin, and Sheridan, Montana to join the Beaverhead River Ruby River-Red Rock drainage divide area landform origins Beaverhead and Madison Counties, Montana, USA near Twin Bridges, Montana to form the Jefferson River. The Ruby River-Red Rock River drainage divide area investigated in this essay is located south of the Ruby River and north of the Red Rock River and also includes drainage divides between north oriented tributaries to the northwest oriented Ruby River segment and the east oriented West Fork Ruby River (none of which are shown in figure 1).

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, including the north oriented Ruby River and Missouri River, north-northwest oriented Red Rock River, and north-northeast oriented Beaverhead and Jefferson Rivers are generally flowing in valleys that originated as south oriented flood flow channels. The west oriented Red Rock River alignment was at one time used by an east oriented flood flow channel. 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 in south and southeast directions across the region. Mountain ranges emerged as floodwaters flowed across the region and initially floodwaters flowed across what are today high mountain ranges including mountain ranges, which today form the east-west continental divide. More successful, or deeper, flood flow channels captured floodwaters from adjacent less successful flood flow channels. North-to-south oriented through valleys eroded across the present-day east-west continental divide by south and southeast oriented flood flow channels are today preserved as mountain passes.

The present day north oriented Ruby River originated as a south oriented flood flow channel, which was subsequently reversed to form the north 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 the south oriented flood flow channel on the present-day north oriented Missouri River alignment. At Three Forks this south oriented flood flow channel split into several diverging south oriented flood flow channels. The deep northeast oriented valley (now northeast oriented Missouri River valley north of figure 1) 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 and diverting the captured flood flow into space being opened up in the deep “hole” where the melting the ice sheet had been located. This northeast oriented valley was much deeper than the beheaded south oriented flood flow channel and floodwaters on north end of the beheaded flood flow channel reversed flow direction to create the north oriented Missouri River drainage route seen north of Three Forks in figure 1.The reversal of flow in the Missouri River flood flow channel also reversed flood flow in flood flow channels on the Gallatin and Madison River alignments to create the north oriented Madison and Gallatin River drainage routes seen today. Headward erosion of the deep northeast and east Jefferson River valley from this reversed Missouri River flood flow channel next beheaded flood flow channels further to the west and floodwaters on north ends of those beheaded flood flow channels reversed flow direction to create north oriented drainage routes, including the north-northeast oriented Jefferson and Beaverhead Rivers, north and north-northwest oriented Ruby River, and north-northwest oriented Red Rock River (which then reversed the east oriented flood flow north of the Centennial Mountains to create the west oriented Red Rock River headwaters segment seen in figure 1).

Detailed location map for Ruby River-Red Rock River drainage divide area

Figure 2: Detailed location map Ruby River-Red Rock River 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 Ruby River-Red Rock River drainage divide area in Beaverhead and Madison Counties, Montana and shows drainage routes not seen in figure 1. Green shaded areas are National Forest lands, which generally are located in mountainous regions. The continental divide serves as the Montana-Idaho state line and follows the crest of the Beaverhead Mountains in the southwest corner of figure 2 and then follows the crest of the west-to-east oriented Centennial Mountains near the south edge of figure 2 before making a northward jog around Henrys Lake in the southeast corner of figure 2. All areas in Idaho drain to the Snake River with water eventually reaching the Pacific Ocean. Red Rock Creek is a northwest and west oriented stream originating near the continental divide (west of Henrys Lake) and flows to Upper and Lower Red Rock Lakes. The Red Rock River originates at Lower Red Rock Lake and flows in a west direction to Lima, Montana where it turns to flow in a north-northwest direction to Clark Canyon Reservoir where it joins other streams to form the north-northeast Beaverhead River, which north of figure 2 joins the Big Hole River and Ruby River to form the north-northeast, east, and northeast oriented Jefferson River. The Ruby River originates in the south center region of figure 2 (north of the Centennial Valley) and flows in a north direction between the Snowcrest Range (to the west) and the Gravelly Range (to the east) to Ruby River Reservoir and then in a north and northwest direction to the north center edge of figure 2 and north of figure 2 joins the Beaverhead River and Big Hole to form the north-northeast, east, and northeast oriented Jefferson River. Long Creek is a southeast, southwest, and south oriented Red Rock River tributary directly south of the east and north oriented Ruby River headwaters.  The West Fork Ruby River is located in the Snowcrest Range. Note just south of the West Fork Ruby River headwaters the south oriented headwaters of northwest oriented East Fork Blacktail Deer Creek, which flows to northwest oriented Blacktail Deer Creek. Also note north of the West Fork Ruby River north oriented Ledford Creek, which flows to the northwest oriented Ruby River north of the Snowcrest Range. West of Ledford Creek is another unlabeled north oriented Ruby River tributary (Robb Creek) seen in this essay. North and northwest oriented drainage routes seen in figure 2 generally are located on alignments of former south and southeast oriented flood flow channels. The south and southeast oriented flood flow channels were systematically beheaded by headward erosion of much deeper valleys and floodwaters on north and northwest ends of the beheaded flood flow channels reversed flow direction to create the north and northwest oriented drainage routes seen today. Flood flow channels were beheaded one channel at a time and usually from east to west. These systematic flood flow reversals were greatly aided by ice sheet related crustal warping that raised the regional mountain ranges as immense south and southeast oriented melt water floods flowed across the region.

Ruby River-Long Creek drainage divide area

Figure 3: Ruby River-Long 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 Ruby River-Long Creek drainage divide area. The Snowcrest Mountains are located in the northwest quadrant of figure 3. The Centennial Divide is located near the center of figure 2 and the Ruby River flows in a north direction from the Centennial Divide to the north center edge of figure 2. North of figure 2 the Ruby River flows in a north and northwest direction to join the north-northeast oriented Beaverhead River. Divide Creek is an east oriented stream joining the Ruby River a short distance north of the Centennial Divide. Jones Creek flows in south-southeast direction from near the Centennial Divide to southwest oriented Long Creek, which flows to the south edge of figure 3. South of figure 2 Long Creek turns to flow in a south direction to join the west oriented Red Rock River, which further west turns to flow in a north-northwest direction to join the north-northeast oriented Beaverhead River, which flows to the north-northeast oriented Jefferson River. In other words, water both sides of Centennial Divide eventually ends up in the Jefferson River, although water on the south side of Centennial Divide makes a much longer journey than water on the north side of Centennial Divide. Centennial Divide is located in a major north-to-south oriented through valley linking a present day north oriented drainage route with a present day south oriented drainage route. The map contour interval for figure 3 is 50 meters and the Centennial Divide elevation low point is between 2200 and 2250 meters. Elevations to the east rise to more 2500 meters while elevations to the west rise even higher suggesting the through valley is at least 250 meters deep. The Centennial Divide through valley is a water-eroded feature and was eroded as a south oriented flood flow channel prior to the reversal of flood flow that created the north and northwest oriented Ruby River drainage route. The southeast and south oriented flood flow channel was beheaded north of figure 3 by headward erosion of a much deeper north-northeast oriented Beaverhead River valley and floodwaters on the north and northwest end of the beheaded flood flow channel reversed flow direction to create the north oriented Ruby River drainage route. The flood flow reversal was probably greatly aided by ice sheet related crustal warping that was raising the Snowcrest Mountains and other regional mountain ranges as immense south oriented melt water floods flowed across the region.

Detailed map of Ruby River-Jones Creek drainage divide area

Figure 4: Detailed map of Ruby River-Jones 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 Ruby River-Jones Creek drainage divide area seen is less detail in figure 3. Centennial Divide is located near the center of figure 4 in sections 13 and 18. The Ruby River originates in section 18 and flows in a north direction to the north center edge of figure 4. Divide Creek flows in a southeast direction from the west edge of figure 4 (north half) to the Divide Creek Guard Station in section 13 and then turns to flow in a northeast direction to join the Ruby River in section 7 near the north edge of figure 4. Jones Creek flows in a southeast direction from the west edge of figure 4 (north of center) to the southwest corner of section 13 and then turns to flow in a south-southeast direction to the south edge of figure 4 (west of center). South of figure 4 Jones Creek flows to southwest and south oriented Long Creek, which flows to the west and north-northwest oriented Red Rock River. Note how the Centennial Divide is located on the floor of a major north-to-south oriented through valley linking the north oriented Ruby River valley with the south oriented Jones Creek valley. The map contour interval for figure 4 is 40 feet and the low point on Centennial Divide in section 18 is between 7320 and 7360 feet while the low point in section 13 is between 7440 and 7480 feet. The elevation in section 17 to the east rises to 8084 feet and elevations greater than 8200 feet can be found east of figure 4. Elevations to the west rise much higher with elevations greater than 8200 feet visible in the northwest corner of figure 4. The through valley was eroded as a major south oriented flood flow channel, which initially flowed to an east oriented flood flow channel on the present day west oriented Red Rock River alignment. However, the east oriented flood flow channel on the Red Rock River alignment reversed flow direction (perhaps to flow toward a south oriented flood flow channel on the present day Monida Pass alignment before being captured by reversed flood flow on the present day north-northwest oriented Red Rock River valley segment). This reversal of east oriented flood flow on the Red Rock River alignment to create a west oriented flood flow channel enabled the southwest oriented Long Creek valley to erode headward to capture the south-southeast oriented flood flow on the Jones Creek alignment (south of figure 4). Shortly after that capture the south oriented flood flow channel on the present day north and northwest oriented Ruby River alignment was beheaded by headward of the much deeper north-northeast oriented Beaverhead River valley. The resulting flood flow reversal created the north and northwest oriented Ruby River drainage route and also created Centennial Divide.

Long Creek-Red Rock River drainage divide area

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

Figure 5 illustrates the Long Creek-Red Rock River drainage divide area south and east of figure 3 and includes a significant overlap area with figure 3. The Red Rock River can be seen meandering in a west direction along and across the south edge of figure 5 and is flowing on the floor of the east-to-west oriented Centennial Valley. South of the Centennial Valley is the west-to-east oriented Centennial Mountain range, which is crossed by several high-level north-to-south oriented through valleys (or mountain passes). The through valleys (or mountain passes) provide evidence of south oriented flood flow channels that flowed across the Centennial Mountains, before the Centennial Mountains became the major topographic barrier they are today. The Centennial Valley probably was developed by the same crustal warping that was raising the Centennial Mountains and probably was a place where south oriented floodwaters became ponded before flowing across the emerging Centennial Mountains and most likely the Centennial Valley contains significant thicknesses of flood deposited debris. Long Creek originates near the north center edge of figure 4 and flows in a southwest and south direction to near the southwest corner of figure 4 and south of figure 5 joins the west oriented Red Rock River. Centennial Divide is located near the north edge of the northwest quadrant of figure 4. Note how Jones Creek flows in a south-southeast direction from near Centennial Divide to join southwest oriented Long Creek near Lone Butte. Also note Fish Creek, which originates at Fish Creek Lake and then flows in a west direction to a southeast oriented through valley where it turns to flow in a southeast direction to join southeast and south oriented Metzel Creek. The southeast oriented Long Creek-Fish Creek through valley is on almost the same alignment as the south-southeast oriented Jones Creek valley suggesting the southwest oriented Long Creek valley eroded headward across a southeast oriented flood flow channel. Further evidence supporting this hypothesis is found to the west of Fish Creek in the somewhat higher-level through valley linking the southeast oriented Brundage Creek valley with the Long Creek valley. The map contour interval for figure 5 is 50 meters and the Long Creek-Fish Creek through valley elevation at the drainage divide is between 2200 and 2250 meters. The Long Creek-Brundage Creek through valley at the drainage divide is between 2300 and 2350 meters. Antelope Peak (west of Brundage Creek) rises to 2524 meters and elevations near Fish Lake rise to 2529 meters suggesting the Long Creek-Fish Creek through valley is at least 270 meters deep while the Long Creek-Brundage Creek through valley is at least 170 meters deep. These through valleys were eroded by southeast oriented flood flow at a time when floodwaters in the developing Centennial Valley were probably flowing in an east direction. The southwest oriented Long Creek valley probably eroded headward from floodwaters in the Centennial Valley that had been reversed in flow direction and which were flowing in a west direction. Apparently the south oriented flood flow ceased a short time after headward erosion of the southwest oriented Long Creek valley captured the south oriented flood flow channel on the present day north oriented Ruby River alignment.

Detailed map of Long Creek-Fish Creek drainage divide area

Figure 6: Detailed map of Long Creek-Fish 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 Long Creek-Fish Creek drainage divide area seen in less detail in figure 5. The map contour interval for figure 6 is 40 feet in the north half and 20 feet in the south half. Fish Lake straddles the east center edge of figure 6 and Fish Creek flows in west direction before turning to flow in a southeast direction through section 3 to the south edge of figure 6 (near southeast corner). South of figure 6 Fish Creek flows to the west oriented Red Rock River. Long Creek flows in a southwest direction from the north edge of figure 6 (east half) to the east edge of figure 6 (near southwest corner) and south and west of figure 6 turns to flow in a south direction to join the west oriented Red Rock River. Jones Creek flows in a south-southeast direction from near the northwest corner of figure 6 to join Long Creek in the northeast corner of section 31. Note in the northeast quadrant of section 33 how a through valley links a west oriented Long Creek tributary valley with the southeast oriented Fish Creek valley. The through valley floor elevation at the drainage divide is between 7340 and 7360 feet. Elevations to the east rise to more than 8000 feet in figure 6 and to 8298 feet a short distance east of figure 6. Elevations to the west rise to more than 7800 feet in figure 6 and to more than 8200 feet south of figure 6. These elevations suggest the through valley is between 450 and 1000 feet deep. The through valley is a water-eroded feature and was eroded by southeast oriented flood flow prior to headward erosion of the deeper southwest oriented Long Creek valley and its west oriented tributary valley. The southeast oriented flood flow was probably moving to east oriented flood flow in what was then the developing Centennial Valley. The Long Creek valley probably eroded headward from west oriented flood flow in the Centennial Valley, which suggests a flood flow reversal was occurring in the Centennial Valley to the south of figure 6.

Robb Creek-West Fork Ruby River drainage divide area

Figure 7: Robb Creek-West Fork Ruby River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the Robb Creek-West Fork Ruby River drainage divide area west and north of figure 3 and includes a significant overlap area with figure 3. The Ruby River flows in a north direction near the east edge of figure 7 and north of figure 7 turns to flow in a northwest direction to join the north-northeast oriented Beaverhead River and to form the north-northeast oriented Jefferson River. The Snowcrest Range is the mountain range west of the Ruby River and extending in a south-to-north direction across the center of figure 7. The Notch is a labeled location near the center of figure 7 and the West Fork Ruby River originates near The Notch and flows in a northeast, east, and northeast direction to join the north oriented Ruby River. North of The Notch is Hogback Mountain and south of The Notch is Olson Peak. South of the West Fork Ruby River headwaters and east of Olson Peak are south oriented headwaters of the East Fork of Blacktail Deer Creek, which turns to flow in a southwest and then northwest and west direction to the west edge of figure 7 (north of center). West of figure 7 the East Fork joins northwest oriented Blacktail Deer Creek, which flows to the north-northeast oriented Beaverhead River. West of Hogback Mountain is north oriented Robb Creek, which north of figure 7 joins the northwest oriented Ruby River. Note the deep through valley between Olson Peak and Hogback Mountain linking the northeast oriented West Fork Ruby River valley with the north oriented Robb Creek valley and the deep north-to-south oriented through valley linking the northeast oriented West Fork Ruby River valley with the south oriented East Fork Blacktail Deer Creek valley. The map contour interval for figure 7 is 50 meters and the Robb Creek-West Fork Ruby River through valley elevation at the drainage divide is between 2450 and 2500 meters. Hogback Mountain to the north rises to more than 3200 meters and Sunset Peak to the south rises to 3225 meters suggesting the through valley may be as much as 700 meters deep. The West Fork Ruby River-East Fork Blacktail Deer Creek through valley floor elevation at the drainage divide is between 2700 and 2750 meters. Stonehouse Mountain to the east rises to 3071 meters suggesting this north-to-south oriented through valley is as much as 320 meters deep. To understand these through valleys it is necessary to view the present day north oriented valleys as diverging and converging south oriented flood flow channels, which were being eroded into an emerging Snowcrest Mountains mass. South oriented flood flow on the Robb Creek alignment converged with southwest oriented flood flow on the West Fork Ruby Creek alignment to form a south oriented flood flow channel on the present day south oriented East Fork Blacktail Deer alignment, which south of Sunset Peak converged with a southeast oriented flood flow channel on the present day northwest oriented East Fork Blacktail Deer Creek alignment. With the exception of the south oriented East Fork Blacktail Deer Creek segment all of these south oriented flood flow channels have since been reversed to form north oriented drainage routes. The reversals of flow occurred as floodwaters were flowing across the region and were indirectly caused by ice sheet related crustal warping that was raising the Snowcrest Mountains and surrounding region and was caused more directly by headward erosion of deep valleys from space in the deep “hole” the melting ice sheet had occupied and which was being opened up. These deep valleys beheaded the south oriented flood flow channels and systematically reversed the south oriented flood flow channels, with newly reversed flood flow channels capturing floodwaters from yet to be beheaded and reversed flood flow channels. The deep through valley at The Notch was eroded by south oriented flood flow on the Robb Creek alignment that was captured by reversed flood flow on the West Fork Ruby River alignment.

Detailed map of Robb Creek-West Fork Ruby River drainage divide area

Figure 8: Robb Creek-West Fork Ruby River 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 Robb Creek-West Fork Ruby River drainage divide area seen in less detail in figure 7. The Snowcrest Range is the labeled high mountain ridge extending from Sunset Peak near the south edge of figure 8 (west of center) to Olson Peak and then to Hogback Mountain, which straddles the north center edge of figure 8. The Notch is a deep through valley in sections 17 and 18 between Olson Peak to the south and Hogback Mountain to the north. East of The Notch is the northeast oriented West Fork Ruby River, which originates east of Olson Peak and which flows to the east edge of figure 8 (near northeast corner). South of the West Fork Ruby River headwaters along the west margin of section 20 are south oriented headwaters of East Fork Blacktail Deer Creek, which flow to the south center edge of figure 8. Note the north-to-south oriented through valley linking the north oriented West Fork Ruby River valley with the south oriented East Fork Blacktail Deer Creek valley. The map contour interval for figure 8 is 40 feet and the through valley floor elevation at the drainage divide is between 8960 and 9000 feet. Olson Peak to the west rises to 10,482 feet and the high point in section 20 to the east is 9783 feet while south of figure 8 Stonehouse Mountain rises to 10,076 feet. Depending on which elevations are chosen the through valley is between 780 and 1075 feet deep. The Notch is an even more intriguing through valley as it links the northeast oriented West Fork Ruby River valley with the north oriented Robb Creek valley, which is located west of Olson Peak and of Hogback Mountain. Note how a Robb Creek tributary, which originates in the southwest corner of section 8, flows in a southwest and northwest direction through a deep water gap between Olson Peak and Hogback Mountain. Elevations in The Notch at the drainage divide are between 8640 and 8680 feet and in the northwest oriented stream valley in the water gap are below 8600 feet. Hogback Mountain to the north rises to more than 10,560 feet while as already noted Olson Peak to the south rises to 10,482 feet, which means the water gap is at least 1800 feet deep. The Notch was eroded by a southeast oriented flood flow channel, which diverged from a south oriented flood flow channel on the present day north oriented Robb Creek alignment. East of the water gap the southeast oriented flood flow channel converged with a southwest oriented flood flow channel to form a south oriented flood flow channel on the East Fork Blacktail Deer Creek alignment. Systematic reversal of the south oriented flood flow channels first reversed flood flow in the West Fork Ruby River flood flow channel, which captured the southeast oriented flood flow channel moving through the water gap and which then eroded The Notch through valley deeper than the through valley in section 20. Continued reversal of flood flow channels next reversed flood flow on the Robb Creek alignment, which resulted in a reversal of flood flow in the water gap. But there was no opportunity to capture floodwaters from the already reversed West Fork Ruby River flood flow route so the newly formed northwest oriented drainage route could only capture local drainage.

Ledford Creek-West Fork Ruby River drainage divide area

Figure 9: Ledford Creek-West Fork Ruby River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the Ledford Creek-West Fork Ruby River drainage divide area north and east of figure 7 and includes a significant overlap area with figure 7. The Snowcrest Mountain Range is the ridge of high mountains extending from Hogback Mountain in the southwest quadrant of figure 9 to Snowcrest Mountain near the north center edge of figure 9. The Ruby River flows in a north-northeast direction in the east half of figure 9 and north of figure 9 turns to flow in a northwest direction through a deep water gap, which serves as the boundary between the Snowcrest Range to the south and the Greenhorn Range to the north. The West Fork Ruby River is located near the south center edge of figure 9 and flows in a northeast, east, and northeast direction to join the north oriented Ruby River. West of Hogback Mountain in the southwest quadrant of figure 9 is north oriented Robb Creek, which flows to the north edge of figure 9 (west half) and which north of figure 9 joins the northwest oriented Ruby River. East of north oriented Robb Creek, but west of the Snowcrest Range, is north oriented Ledford Creek, which originates as a southwest oriented stream near Spur Mountain and Sliderock Mountain and which then makes a U-turn to flow in a north direction to the north edge of figure 9 and which joins the northwest oriented Ruby River north of figure 9. On the north side of the ridge between Spur Mountain and Sliderock Mountain are headwaters of north oriented Spring Creek, which north of figure 9 turns to flow in a northwest direction to join north oriented Ledford Creek. Note how there is a pass between Spur Mountain and Sliderock Mountain linking the north oriented Spring Creek headwaters valley with the south oriented Ledford Creek headwaters valley. The map contour interval for figure 9 is 50 meters and the pass is defined by three contour lines on the Spur Mountain side and five contour lines to the east. Next note south of the Ledford Creek U-turn a north-to-south oriented through valley (Ledford Pass in figure 10) linking the Ledford Creek U-turn with the northeast oriented West Fork Ruby River valley. The elevation of the floor of that through valley is between 2450 and 2500 meters at the drainage divide, Hogback Mountain to the west rises to more than 3200 meters while Sliderock Mountain to the northeast rises to 3182 meters suggesting the through valley may be 700 meters deep. The Ledford Creek U-turn is evidence of two converging south oriented flood flow channels, which formed a south oriented flood channel that flowed to a southwest oriented flood flow channel on the present day northeast oriented West Fork Ruby River headwaters alignment and then to the south oriented flood flow channel on the present day south oriented East Fork Blacktail Deer Creek alignment (which was seen in figures 7 and 8). Again the flood flow channels were beheaded and reversed in sequence to create the present day north oriented drainage routes seen in figure 9 and the southwest oriented Ledford Creek headwaters preserve evidence of the earlier south oriented flood flow direction.

Detailed map of Ledford Creek-West Fork Ruby River drainage divide area

Figure 10:Detailed map of Ledford Creek-West Fork Ruby River 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 Ledford Creek-West Fork Ruby River drainage divide area seen in less detail in figure 9. Hogback Mountain is located near the west edge of the southwest quadrant of figure 10. The West Fork Ruby River flows in a northeast direction into section 9 (east of Hogback Mountain) and then turns to flow in an east and east-northeast direction to the east edge of figure 10 (near southeast corner). Ledford Creek flows in a southwest and northwest direction near the north center edge of figure 10. East of the southwest oriented Ledford Creek valley segment is the high Snowcrest Mountain ridge with Sliderock Mountain being north of figure 10. Ledford Pass is located in the northwest quadrant of section 3 near the center of figure 10 and is a deep wind gap eroded across the high Snowcrest Mountains crest ridge. The map contour interval for figure 10 is 40 feet and the Ledford Pass elevation at the drainage divide is between 8160 and 8200 feet. North of Ledford Pass is a north oriented Ledford Creek tributary and south of Ledford Pass is a southeast oriented West Fork Ruby River tributary. Hogback Mountain to the southwest of Leford Pass rises to more than 10, 560 feet while Sliderock Mountain to the northeast of Ledford Pass (and of figure 10) rises to 10,439 feet. These elevations suggest the Ledford Pass depth may be as much as 2200 feet. Ledford Pass was eroded by a south oriented flood flow channel, which was formed by a southeast oriented flood flow channel and a southwest oriented flood flow channel on the alignment of the present day Ledford Creek U-turn and which first flowed to a southwest oriented flood flow channel on the present day northeast oriented West Fork Ruby River alignment (south of figure 10). However, while floodwaters were still eroding the Ledford Pass wind gap flood flow in the West Fork Ruby River valley was reversed to flow in a northeast, east, and northeast direction. The flood flow reversal caused south oriented floodwaters moving through what was then the Ledford Pass water gap (now wind gap) to flow in a southeast direction as they approached what had become a northeast, east, northeast oriented flood flow channel. This southeast oriented flood flow eroded the southeast oriented West Fork Ruby River tributary valley seen in sections 3 and 10. The reversal of flood flow in the Ledford Creek valley west of the Snowcrest Range next beheaded and reversed the south oriented Ledford Pass flood flow channel to create the north oriented Ledford Creek tributary and to change the Ledford Pass water gap to a wind gap.

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.