Jefferson River-Madison River drainage divide area landform origins in Madison and Gallatin Counties, Montana, USA

Authors


Abstract:

This essay uses topographic map evidence to interpret landform origins between the Jefferson River and the Madison River in Madison and Gallatin Counties, Montana and focuses on areas east of the north-northeast oriented South Boulder River, which flows from the high Tobacco Root Mountains to join the Jefferson River north of the Tobacco Root Mountains. The Jefferson River flows in a north-northeast direction west of the Tobacco Root Mountains and then turns to flow in an east and southeast direction north of the Tobacco Root Mountains and finally turns to flow in a northeast direction to join the north oriented Madison River and the north and northwest oriented Gallatin River at Three Forks to form the north oriented Missouri River. Summit Valley is a large northwest-to-southeast oriented through valley linking the south oriented Boulder River valley, east oriented Jefferson River valley, and the north end of the north oriented South Boulder River valley with the north oriented Madison River valley. Today the through valley is crossed by northeast and north oriented Jefferson River tributaries, but at one time the through valley served as a major southeast oriented flood flow channel delivering floodwaters to a south oriented flood flow channel on the present day north oriented Madison River alignment. Additional through valleys provide evidence of south oriented flood flow channels east of the Tobacco Root Mountains and west of the deep north oriented Madison River valley in Bear Trap Canyon while still additional through valleys or mountain passes can be used to identify former southeast oriented channels crossing what are today the highest Tobacco Root Mountains. Floodwaters are interpreted to have been derived from the western margin of a thick North American ice sheet and were flowing in south and southeast directions from western Canada across Montana to and across the study region. The thick ice created a deep “hole” in the North American continent by a combination of deep glacial erosion and of crustal warping that raised mountain ranges and high plateau areas, including the Tobacco Root Mountains seen in the study area. As the thick ice  melted space in the deep “hole” was opened up and a deep northeast oriented valley north of the study area eroded headward from that open space to capture south and southeast oriented melt water flood flow further to southwest. Aided by the crustal warping that was raising Montana and adjacent region mountains and plateaus floodwaters on north ends of beheaded flood flow channels reversed flow direction to create north oriented drainage routes, including the north oriented Missouri River, Madison River, and Gallatin River drainage routes. Evidence for this massive flood flow reversal is found in numerous barbed tributaries and U-turns made by present day drainage routes.

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

Jefferson River-Madison River drainage divide area location map

Figure 1: Jefferson River-Madison 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 Jefferson River-Madison River drainage divide area in Madison and Gallatin Counties, Montana and primarily illustrates a region in southwest and south central Montana with the northwest corner of Wyoming and Yellowstone National Park in the southeast corner of figure 1 and an area of Idaho located in the southwest corner. The Tobacco Root Mountains are labeled and are located near the center of figure 1. The Jefferson River is formed near Twin Bridges (west side of Tobacco Root Mountains) at the confluence of the north-northeast oriented Beaverhead River and the north, southeast, south, and northeast oriented Big Hole River. From Twin Bridges the Jefferson River flows in a north-northeast, east, and northeast direction to near Three Forks, where it joins the north oriented Madison River and the north and northwest oriented Gallatin River to form the north and north-northwest oriented Missouri River. North of figure 1 the Missouri River turns to flow in a northeast direction and eventually reaches North Dakota where it turns to flow in a southeast and south direction. The Madison River originates in western Yellowstone National Park and flows in a northwest direction to Hebgen Lake and then in a west direction to Earthquake Lake before turning to flow in a north-northeast direction to near Ennis, Montana where it turns to flow in a north-northeast and north direction to near Three Forks where it joins the Jefferson and Gallatin Rivers to form the north oriented Missouri River. The unlabeled northeast oriented stream originating in the Tobacco Root Mountains and joining the Jefferson River near the town of Willow Creek is Willow Creek and the unlabeled north-northeast oriented stream originating in the Tobacco Root Mountains and joining the Jefferson River near the town of Cardwell is the South Boulder River. The north, southeast, and south oriented drainage route joining the Jefferson River near Cardwell is the Boulder River. The Jefferson River-Madison River drainage divide area investigated in this essay is located between the South Boulder River and the Madison River. A separate Jefferson River-South Boulder River drainage divide area essay illustrates and describes topographic map evidence directly west of the South Boulder River.

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 Missouri, Madison, and Gallatin Rivers are flowing in valleys that originated as south oriented flood flow channels. When floodwaters first flowed across the region the present day mountain ranges did not exist and floodwaters could freely flow in south and southeast directions across the region. The mountain ranges emerged as floodwaters flowed across the region and initially floodwaters flowed across what are today high mountains including the Tobacco Root Mountains. More successful, or deeper, flood flow channels moving floodwaters across mountain ranges first captured floodwaters from adjacent less successful flood flow channels and later floodwaters were captured by flood flow channels moving floodwaters between the emerging mountain ranges. These captures of the south and southeast oriented flood flow channels initially were made by the headward erosion of south-southwest and southwest oriented valleys from the more successful, or deeper, south oriented or southeast oriented flood flow channels. Through valleys or mountain passes crossing present-day drainage divides today provide evidence of the former flood flow channels. Segments of the present day north oriented Jefferson River and South Boulder River valleys probably were initiated by the headward erosion of south-southwest oriented and/or southwest oriented valleys across south and southeast oriented flood flow routes. However, as mountain ranges emerged a massive flood flow reversal occurred, which systematically reversed flood flow in most, but not all of the south oriented flood flow channels to create the drainage routes seen today.

The flood flow reversal that created the present day north oriented Missouri, Madison, Gallatin, and Jefferson Rivers 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 (the northeast oriented Missouri River valley north of figure 1), which beheaded the south oriented flood flow channel supplying floodwaters to a south oriented flood flow channel on the present-day north  and north-northwest oriented Missouri River alignment. At Three Forks, Montana this south oriented flood flow channel had 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 floodwaters 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 and tributary drainage routes seen 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 a deep northeast and east oriented 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 River drainage route, although the history is much more complex than given in this brief description.

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

Figure 2: Detailed location map Jefferson River-Madison 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 Jefferson River-Madison River drainage divide area in Madison and Gallatin 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. County boundaries are shown and Madison and Gallatin Counties are labeled. Jefferson County is located north of Madison County. The Tobacco Root Mountains are located in Madison County in the west half of figure 2. The Jefferson River is formed at the confluence of the northeast oriented Big Hole River, north-northeast oriented Beaverhead River, and northwest oriented Ruby River near the town of Twin Bridges (near west edge of southwest quadrant in figure 2). From Twin Bridges the Jefferson River flows in a north-northeast, east, southeast, and northeast direction to near the town of Three Forks where it joins the north oriented Madison River and north and northwest oriented Gallatin River to form the north oriented Missouri River (the short segment seen in figure 2 north of Three Forks appears to be oriented in a northeast direction). The Madison River flows in a north direction from the south center edge of figure 2 to Ennis Lake) and then in a north-northeast and north direction join the Jefferson and Gallatin Rivers near Three Forks. The South Boulder River originates in the Tobacco Root Mountains and flows in a north-northeast direction to join the Jefferson River near the town of Cardwell (west of Lewis and Clark Cavern State Park). The south oriented drainage route joining the Jefferson River near Cardwell is the Boulder River. Antelope Creek and Willow Creek are northeast oriented Jefferson River tributaries located between the South Boulder River and the Madison River (note North and South Willow Creeks, which join to form Willow Creek). Hot Springs Creek is the unlabeled east-northeast oriented stream joining the Madison River near the town of Norris. North Meadow Creek is the unlabeled east-northeast and southeast oriented stream south of Hot Springs Creek and flowing from the Tobacco Root Mountains to join the Madison River as a barbed tributary at Ennis Lake.

South Boulder River-Willow Creek drainage divide area

Figure 3: South Boulder River-Willow 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 South Boulder River-Willow Creek drainage divide area. Hogbacks along the north edge of the Tobacco Root Mountains can be seen near the southwest corner of figure 3. The Jefferson River meanders in a southeast direction from the north edge of figure 3 (near northwest corner) in a deep valley in the London Hills and then turns to flow in an east and northeast direction to the northeast corner of figure 3. The South Boulder River flows in a north-northeast and north direction from the west edge of figure 3 (south half) to join the southeast oriented Jefferson River as a barbed tributary near the north edge of figure 3. North of the northwest corner of figure 3 the Boulder River flows in a south direction to join the Jefferson River at the point where it turns from flowing in an east direction to flowing in a southeast direction and the south oriented Boulder River valley is on the same alignment as the north oriented South Boulder River valley in the northeast quadrant of figure 3. Antelope Creek flows in a north-northeast direction from the south edge of figure 3 (west half) to join the Jefferson River where it turns from flowing in a southeast direction to flowing in an east direction. Willow Creek flows in a north-northeast direction from the south edge of figure 3 (just east of center) and then turns to flow in an east-southeast and northeast direction to the east edge of figure 3 (south half) and east of figure 3 turns to flow in a north direction to join the Jefferson River. Summit Valley is northwest-to-southeast oriented through valley between the Tobacco Root Mountains to the southwest and the London Hills to the northeast and links the north oriented South Boulder River valley with the east-southeast oriented Willow Creek valley segment. The map contour interval for figure 3 is 50 meters and the Summit Valley elevation at the South Boulder River-Antelope Creek drainage divide is between 1450 and 1500 meters. Elevations in the London Hills reach 1928 meters while elevations in the Tobacco Root Mountains to the south and west of figure 3 are much higher suggesting the Summit Valley through valley is as much as 428 meters deep. While probably related to underlying geologic structures the Summit Valley through valley is also a water-eroded valley and was eroded by south and southeast oriented flood flow moving from the south oriented Boulder River alignment (north of figure 3) to a south oriented flood flow channel on the present day north oriented Madison River alignment (east and south of figure 3). Flood flow moving through the Summit Valley was captured by headward erosion of the southeast oriented Jefferson River valley, although it had been previously captured by headward erosion of the northeast and north oriented Willow Creek valley and the north-northeast oriented Antelope Creek valley.

Detailed map of South Boulder River-Dogtown Sewer drainage divide area

Figure 4: Detailed map of South Boulder River-Dogtown Sewer 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 South Boulder River-Dogtown Sewer drainage divide area seen is less detail in figure 3. Hogbacks along the north flank of the Tobacco Root Mountains can be seen in the southwest corner of figure 4. The London Hills are the upland located in the east half of figure 4 north and east of Summit Valley. Summit Valley is a northwest-to-southeast oriented through valley located between the Tobacco Root Mountains to the southwest and the London Hills to the northeast. The South Boulder River flows in a north-northeast and then north direction from near the southwest corner of figure 4 to the north edge of figure 4 (west half). Note South Boulder River tributaries in the north center region of figure 4, which originate as southeast oriented streams and then which turn to flow in northwest directions to join the north oriented South Boulder River. The U-turns made by these tributaries provide evidence of the flood flow reversal that ended south and southeast oriented flood flow through the Summit Valley. Dogtown Sewer originates near the north edge of section 12 and drains in an east, southeast, and east direction to the east edge of figure 4 (near southeast corner) and east of figure 4 joins north-northeast oriented Antelope Creek. The drainage divide between the northwest oriented South Boulder River tributaries and the southeast and east oriented Dogtown Sewer drainage route is located in section 6. The map contour interval for figure 4 is 40 feet. The elevation at the drainage divide is between 4840 and 4880 feet. The high point in the London Hills is 6328 feet and much higher elevations are found in the Tobacco Root Mountains to the south and west, which means the Summit Valley through valley is approximately 1450 feet deep. As described in the figure 3 discussion before being captured by headward erosion of the deeper Jefferson River valley south oriented floodwaters from the south oriented Boulder River valley (north of the present day Jefferson River) flowed in a southeast direction through Summit Valley to a south oriented flood flow channel on the present north oriented Madison River alignment. Headward erosion of the deeper southeast oriented Jefferson River valley captured the south oriented flood flow, beheading the southeast oriented flood flow route through Summit Valley. Floodwaters on the north end of the beheaded flood flow route reversed flow direction to create the north oriented South Boulder River drainage route and the U-turns made by the South Boulder River tributaries seen in the north center area of figure 4. Prior to the flood flow reversal north oriented flow on the South Boulder River alignment in the Tobacco Root Mountains made a sharp turn in the southwest quadrant of figure 4 to enter the Summit Valley flood flow channel. That east oriented flood flow channel was beheaded when the deeper Jefferson River valley beheaded and reversed the Summit Valley flood flow channel.

Willow Creek-Madison River drainage divide area

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

Figure 5 illustrates the Willow Creek-Madison River drainage divide area south and east of figure 3 and includes an overlap area with figure 3. Red Bluff is a place-name near the south center edge of figure 5. The Madison River flows in north-northeast and north direction from the south edge of figure 5 (east half) to the north edge of figure 5 (near northeast corner). Note the unnamed south-southeast and east-southeast oriented stream joining the north oriented Madison River as a barbed tributary in the southeast quadrant of figure 5. Also note northwest oriented Cherry Creek near the southeast corner of figure 5. Willow Creek flows in a northeast direction across the northwest corner of figure 5 and then turns to flow in an east-southeast direction to Willow Creek Reservoir where it is joined by north-northeast oriented Norwegian Creek and then turns flow in a northeast direction to the north edge of figure 5 (west half). Note how the north-northeast oriented Norwegian Creek valley is linked by northwest-to-southeast oriented through valleys with the north-northeast oriented Madison River valley. Two of the through valleys parallel the north-northwest oriented highway in the southwest quadrant of figure 5 and the third through valley is north of Red Bluff and links the unnamed south-southeast and east-southeast oriented Madison River tributary valley with a north oriented Willow Creek tributary valley. The map contour interval for figure 5 is 50 meters and the through valleys are defined by at least three contour lines on a side, which means the through valleys are at least 100 meters deep. The through valleys were eroded by diverging southeast oriented flood flow channels moving floodwaters from northwest-to-southeast oriented Summit Valley seen in figures 3 and 4 to a south oriented flood flow channel on the present day north oriented Madison River alignment. The northwest oriented Cherry Creek valley in the southeast corner of figure 5 was initiated by southeast oriented flood flow moving to a south oriented flood flow channel on the present day north oriented Gallatin River alignment and was beheaded and reversed by headward erosion of a deeper south oriented flood flow channel on the Madison River alignment. The south oriented flood flow channels on the Madison River and Gallatin River alignments eroded northward to Three Forks where they received significant south oriented flood flow from points further to the north. South oriented flood flow to the Three Forks area was then beheaded by headward erosion of a much deeper northeast oriented valley from space in the deep “hole” the melting ice sheet had occupied and a major flood flow reversal took place creating the north oriented Missouri River valley segments north of Three Forks and the north oriented Madison River and Gallatin River drainage routes south of Three Forks. The massive flood flow reversal was greatly aided by crustal warping that was raising mountain ranges and high plateau areas, which are now located along the former south oriented flood flow channel routes.

Detailed map of Willow Creek-Madison River drainage divide area

Figure 6: Detailed map of Willow Creek-Madison River 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 Willow Creek-Madison River drainage divide area seen in less detail in figure 5. The Madison River flows in a north and northeast direction in the southeast corner region of figure 6. The north oriented stream in section 19 (northwest quadrant of figure 6) flows to Willow Creek, which flows to the northeast oriented Jefferson River. Note the well-defined southeast, south-southeast, and east-southeast oriented through valley linking that north oriented Willow Creek tributary valley with the north oriented Madison River. The southeast end of the through valley is drained by a south-southeast and east-southeast oriented Madison River tributary. The map contour interval for figure 6 is 20 feet except in the southeast quadrant where the contour interval is 40 feet. The through valley elevation at the Willow Creek-Madison River drainage divide is between 5060 and 5080 feet. Elevations to the northeast rise to 5702 feet while elevations to the southwest rise to more than 5660 feet (and even higher west and south of figure 6). These elevations suggest the through valley is at least 580 feet deep. The through valley is a water-eroded feature and was eroded by south and southeast oriented flood flow moving floodwaters to a south oriented flood flow channel on the present day north oriented Madison River alignment, although the direction of flood flow on the Madison River alignment was probably reversed while south and southeast oriented flood flow was still coming from the northwest. Headward erosion of the deep northeast oriented Jefferson River valley north of figure 6 beheaded the south oriented flood flow channels on the present day north oriented Willow Creek alignment, which caused a reversal of flood flow on the north end of that beheaded flood flow channel to create the north oriented Willow Creek and the north oriented Willow Creek tributary drainage routes.

Hot Springs Creek-North Meadow Creek drainage divide area

Figure 7. Hot Springs Creek-North Meadow Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the Hot Springs Creek-North Meadow Creek drainage divide area south and west of figure 5 and includes an overlap area with figure 5.  The Madison River flows in a north-northeast direction through Bear Trap Canyon from the south edge of figure 7 (east half) to near the northeast corner of figure 7. The eastern slopes of the Tobacco Root Mountains are seen along the west margin of figure 7. Hot Springs Creek is formed at the confluence of its North, Middle, and South Forks and flows in an east-northeast and east direction to the towns of Sterling, Norris, and Red Bluff and then to join the north oriented Madison River near the northeast corner of figure 7. Note north oriented Burnt Creek, which joins Hot Springs Creek near Norris, and also north and south-southwest oriented Bradley Creek, which flows to north oriented Burnt Creek. North Meadow Creek flows in a southeast direction from near the west center edge of figure 7 to the south center edge of figure 7 and joins the north oriented Madison River as a barbed tributary at Ennis Lake south of figure 7. The map contour interval for figure 7 is 50 meters. High points along the west side of Bear Trap Canyon are more than 1900 meters for a considerable distance in the east center area of figure 7. Elevations in the Tobacco Root Mountains near the west edge of figure 7 exceed 2500 meters and rise even higher to the west of figure 7. Between the Tobacco Root Mountains and the ridge along the west side of Bear Trap Canyon elevations drop to less than 1750 meters where the highway crosses the Hot Springs Creek-North Meadow Creek drainage divide. Study of the drainage divide reveals elevations of less than 1800 meters across a distance of approximately four sections (each section is one mile square) suggesting there is a major north-to-south oriented through valley linking the north oriented Burnt Creek valley with the valleys of south oriented tributaries to southeast oriented North Meadow Creek. The through valley was eroded by south oriented flood flow prior to the flood flow reversal that eroded the north oriented Madison River valley. It is possible south oriented flood flow moving west of Bear Trap Canyon was captured at the south end of Bear Trap Canyon and then flowed in a north direction along the present day Madison River alignment and in the process eroded the deep Bear Trap Canyon. If so the floodwaters would have made a U-turn in the Ennis Lake area south of figure 7. The east oriented Hot Springs Creek valley eroded headward from the north end of Bear Trap Canyon to capture the south oriented flood flow west of the deeper north oriented valley on the present day Madison River alignment. Floodwaters on the north end of the beheaded flood flow channel (west of Bear Trap Canyon) reversed flow direction to create the north oriented Burnt Creek drainage route. The Bradley Creek-Burnt Creek S-curve certainly deserves an explanation and the south-southwest oriented Bradley Creek alignment is a relic of the south oriented flood flow direction. Headward erosion of the deep east oriented Hot Springs Creek valley beheaded and reversed a south oriented flood flow channel to create the north oriented Burnt Creek drainage route. Headward erosion of the deeper south-southwest valley from that newly reversed Burnt Creek drainage route beheaded and reversed a former south oriented flood flow channel further to the east  to create the north oriented Bradley Creek headwaters drainage route.

Detailed map of Bradley Creek-North Meadow Creek drainage divide area

Figure 8: Detailed map of Bradley Creek-North Meadow 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 Bradley Creek-North Meadow Creek drainage divide area seen in less detail in figure 7. The map contour interval for figure 8 is 20 feet in the north half and 40 feet in the south half. The Madison River flows in a north direction through Bear Trap Canyon near the east edge of figure 8. North Meadow Creek flows in a southeast direction across the southwest corner of figure 8 and joins the north oriented Madison River as a barbed tributary at Ennis Lake south of figure 8. Note the south-southeast oriented barbed stream in section 18 flowing to the Madison River as a barbed tributary near the southeast corner of figure 8. Bradley Creek flows in a south-southwest direction from the north edge of figure 8 (slightly east of center) to make its second U-turn and to join north oriented Burnt Creek, which flows to the north edge of figure 8 (slightly west of center) with Burnt Creek flowing to east oriented Hot Springs Creek north of figure 8. The north oriented Bradley Creek headwaters can be seen flowing through the small pond in section 6 in the northeast quadrant of figure 8 and Bradley Creek makes its first U-turn north of figure 8 to flow in a south-southwest direction back into figure 8. The drainage divide between north oriented drainage to east oriented Hot Springs Creek and south oriented drainage to southeast oriented North Meadow Creek is crossed by numerous north-to south oriented through valleys, which are remnants of former south oriented flood flow channels. One of the deeper through valleys is located in section 11 where the highway crosses the drainage divide and has an elevation of 5707 feet at the drainage divide. A through valley of similar depth can be seen in section 10 just to the west. Elevations along the drainage divide near the edge of Bear Trap Canyon to the east rise to more than 6200 feet while elevations along the drainage divide near the west edge of figure 8 rise to more than 6000 feet with elevations greater than 6200 feet found a short distance west of figure 8. These elevations suggest the deeper north-to-south oriented through valleys crossing the drainage divide are at least 500 feet deep. The through valleys are water-eroded features and were eroded by diverging and converging flood flow channels moving floodwaters to the southeast oriented North Meadow Creek valley. It is quite possible reversed flood flow on te Madison River alignment had captured the southeast oriented flood flow on the South Meadow Creek alignment and south and southeast oriented floodwaters from west of Bear Trap Canyon were making a U-turn at the Ennis Lake location and then flowing in a north direction along the Madison River alignment and in the process were eroding the deep north oriented Madison River valley in Bear Trap Canyon seen today.

South Boulder River-North Meadow Creek drainage divide area

Figure 9: South Boulder River-North Meadow Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the South Boulder River-North Meadow Creek drainage divide area north and west of figure 7 and includes an overlap area with figure 7 and shows a region in the high Tobacco Root Mountains. Beall Creek is the unlabeled north-northwest oriented stream flowing to the northwest corner of figure 9 and north of figure 9 Beall Creek turns to flow in a northwest direction to join the Jefferson River. The South Boulder River originates south of the Beall Creek headwaters (near Synders Mine) and flows in a northeast and north-northeast direction to the north edge of figure 9 (west half) and north of figure 9 joins the Jefferson River near the point where the south oriented Boulder River also joins the Jefferson River and where the Jefferson River turns to flow in a southeast direction (see figures 1, 2, and 3). North Willow Creek originates at Hollow Top Lake (north of Potosi Peak) and flows in a northeast direction to the north center edge of figure 9. South Willow Creek originates north of Lonesome Peak and flows in a northeast, east-southeast, northeast, and north direction to the north edge of figure 9 (east half) and north of figure 9 joins North Willow Creek to form Willow Creek, which was seen in figures 3 and 5. North Meadow Creek flows in a northeast direction from the south edge of figure 9 (east half) and then turns to flow in a southeast direction to the southeast corner of figure 9. The map contour interval for figure 9 is 50 meters and the Tobacco Root Mountains as seen in figure 9 reach elevations greater than 3000 meters, which is more than 1500 meters higher than Summit Valley elevations seen in figure 3, the Madison River elevation in Bear Trap Canyon seen in figure 7, and the Jefferson River valley to the northwest of figure 9 and not seen in this essay. Today the Tobacco Root Mountains form a 1500-meter high barrier that would prevent southeast oriented floodwaters from flowing from the Beall Creek valley in the northwest corner of figure 9 to the southeast oriented North Meadow Creek valley in the southeast corner of figure 9. Yet study of intervening drainage divides reveals northwest-to-southeast oriented through valleys or passes that cross the high drainage divides along such a southeast oriented flood flow channel route. Some of the through valleys or passes are illustrated and discussed in the Jefferson River-South Boulder River drainage divide area essay. Figure 10 below illustrates the through valley or mountain pass crossing the South Willow Creek-North Meadow Creek drainage divide near Upper and Lower Sureshot Lake (in southeast quadrant of figure 9). Evidence of this former southeast oriented flood flow channel crossing the highest Tobacco Root Mountain regions suggests the Tobacco Root Mountains did not exist when floodwaters first flowed across the region and were uplifted as floodwaters flowed across the region. As the Tobacco Root Mountains were uplifted the southeast oriented flood flow channel was repeatedly captured by deeper northeast oriented valleys eroding headward into the rising mountain mass and finally was beheaded and reversed by headward erosion of the deep Jefferson River valley north and west of figure 9.

Detailed map of South Willow Creek-North Meadow Creek drainage divide area

Figure 10:Detailed map of South Willow Creek-North Meadow 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 South Willow Creek-North Meadow Creek drainage divide area seen in less detail in figure 9. South Willow Creek flows in a southeast and northeast direction from the west edge of figure 10 (north of center) to the north edge of figure 10 (east of center) with water eventually reaching the northeast oriented Jefferson River. North Meadow Creek flows in a north and southeast direction in sections 31, 32, and 33 near the southeast corner of figure 10 and south and east of figure 10 flows to the north oriented Madison River as a barbed tributary. A southeast oriented stream flowing from Upper and Lower Sureshot Lakes joins North Meadow Creek where North Meadow Creek turns to flow in a southeast direction. North of Upper Sureshot Lake is a through valley or pass linking the South Willow Creek valley with the southeast oriented North Meadow Creek valley. The map contour interval for figure 10 is 40 feet and the through valley floor elevation at the drainage divide is between 7520 and 7560 feet. Elevations in the northwest quadrant of section 29 to the east rise to 8426 feet and elevations greater than 9400 feet can be seen to the west suggesting the through valley is at least 850 feet deep. The through valley was eroded by southeast and south oriented flood flow moving from the South Willow Creek valley location to the southeast oriented North Meadow Creek valley. At that time the deep northeast oriented South Willow Creek valley did not exist and floodwaters could easily flow across what is today a high drainage divide (the floor of the South Willow Creek valley today is almost 900 feet lower than the through valley drainage divide elevation). While it is possible some of flood flow was moving in a south direction along the Tobacco Root Mountains east flank it is more probable that some of the flood flow was moving in a southeast direction on the present day southeast oriented South Willow Creek alignment seen near the west edge of figure 10. As seen in figure 9 this southeast oriented South Willow Creek valley segment is linked by a series on passes or through valleys across drainage divides in the high Tobacco Root Mountains to the northwest with the north-northwest and northwest oriented Beall Creek valley, which flows today to the north-northeast Jefferson River west of the Tobacco Root Mountains. The highest pass on that alignment has an elevation of 9476 feet and the Jefferson River valley where Beall Creek enters it has an elevation today of approximately 4500 feet. If the aligned valley segments and through valleys (or passes) were initiated as a southeast oriented flood flow channel the Tobacco Root Mountains have risen almost 5000 feet since that time. Study of drainage divides in the Tobacco Root Mountains area shows flood flow capture and reversal events were taking place as the Tobacco Root Mountains were rising, suggesting there was a relationship between the huge floods crossing the region and the tectonic activity causing the Tobacco Root Mountains uplift.

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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