Abstract:

This essay uses topographic map evidence to interpret landform origins in the region between the Boulder River and Buffalo Creek drainage basins in the northern Absaroka Range, which is located in south central Montana. The Boulder River flows in a north and northeast direction from the high Absaroka Range to join the east and northeast oriented Yellowstone River near Big Timber, Montana. Buffalo Creek originates in the Absaroka Range directly south of the Boulder River headwaters and flows in a south direction to join the northwest oriented Lamar River, which then joins the northwest oriented Yellowstone River near Tower Junction, Wyoming. Between Tower Junction and Big Timber the Yellowstone River flows in a northwest, north-northeast, and east-northeast direction around the Absaroka Range northwest end. North oriented Boulder River headwaters and tributary valleys are linked by through valleys (or mountain passes) across high Absaroka Range mountain ridges with south oriented Buffalo Creek headwaters and tributary valleys and with valleys of adjacent south oriented streams. The through valleys (or mountain passes) are evidence of south oriented flood flow channels, which crossed the region prior to Absaroka Range uplift and prior to headward erosion of the deep east and northeast oriented Yellowstone River valley north of the study region. Floodwaters were derived from a rapidly melting thick North American ice sheet, which was located in a deep “hole”, and were flowing in south and southeast directions from the ice sheet’s west Canada margin across Montana and into Wyoming. Absaroka Range and Yellowstone Plateau uplift are interpreted have been caused by ice sheet related crustal warping and occurred as immense south and southeast oriented melt water floods flowed across them. The deep east and northeast oriented Yellowstone River valley is interpreted to have eroded headward from space in deep “hole” being opened up by the ice sheet melting and eroded headward across the southeast and south oriented melt water floods. The northwest oriented Yellowstone River valley segment is interpreted to have been reversed during a massive flood flow reversal caused by Yellowstone Plateau uplift and by beheading of a major southeast oriented flood flow channel on the same alignment by the much deeper east and northeast oriented Yellowstone River valley.

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 Boulder River-Buffalo Creek drainage divide area landform origins in the northern Absaroka Mountains, Montana, USA. Map interpretation methods can be used to unravel many geomorphic events leading up to formation of present-day drainage routes and development of other landform features. While each detailed topographic map feature provides detailed evidence to be explained, the solution must be consistent with explanations for adjacent area map evidence as well as solutions to big picture map evidence puzzles. I invite readers to improve upon my solutions and/or to propose alternate solutions that better explain evidence and are also consistent with adjacent map area and big-picture evidence. Readers may do so either by making comments here or by writing and publishing their own essays and then by leaving a link to those essays in a comment here.

This essay is also exploring a new geomorphology paradigm in which erosional landforms are interpreted as evidence left by immense glacial melt water floods. Implied in that interpretation is the immense floods were derived from a thick North American ice sheet that created a deep “hole” in the North American continent and also melted fast. The previously unexplored paradigm being tested in this and other Missouri River drainage basin landform origins research project essays is a thick North American ice sheet, comparable in thickness to the Antarctic ice sheet, occupied the North American region usually recognized to have been glaciated, and through its weight and erosive actions created a deep North American “hole”. The southwestern rim of that deep “hole” is today preserved in the high Rocky Mountains. The ice sheet through its weight and deep erosion (and perhaps deposition along major south-oriented melt water flow routes) caused significant crustal warping and tectonic change, through its action of melting fast produced immense floods that flowed across the continent, and through its action of melting fast systematically opened up space in the ice sheet created “hole” so headward erosion of newly developed north-oriented drainage systems captured immense south-oriented melt water floods and diverted immense melt water floods north into space the ice sheet had once occupied.

If this previously unexplored paradigm is correct the geographic region explored by this essay should contain evidence of immense floods that were captured by headward erosion of new valley systems so as to cause the floods to flow in a different direction. Ability of this previously unexplored paradigm to explain Boulder River-Buffalo Creek drainage divide area landform evidence in the northern Absaroka Mountains, Montana will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Boulder River-Buffalo Creek drainage divide area location map

Figure 1: Boulder River-Buffalo Creek 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 Boulder River-Buffalo Creek drainage divide area in the northern Absaroka Mountains and illustrates a region of southern Montana with northwest Wyoming in the southeast three-fourths of figure 1 and a strip of Idaho seen in the southeast corner. Yellowstone National Park is the yellow shaded area in northwest Wyoming. The Absaroka Range extends from southern Montana across the Yellowstone National Park eastern margin in south-southeast direction. The Yellowstone River flows from Yellowstone National Park in northwest Wyoming in a northwest direction and then turns to flow in a northeast direction to Livingston and Big Timber, Montana. From Big Timber the Yellowstone River flows in an east-southeast direction to the east edge of figure 1. The Boulder River is a labeled north and northeast oriented tributary flowing from the Absaroka Range (north of Yellowstone National Park) to join the Yellowstone River near Big Timber. Buffalo Creek is not shown on figure 1, but is a south oriented stream originating directly south of the Boulder River headwaters and joins the northwest oriented Lamar River near where the Lamar River joins the northwest oriented Yellowstone River (in Yellowstone National Park). As seen in topographic maps illustrated below through valleys or mountain passes link the north oriented Boulder River valley with the south oriented Buffalo Creek valley.

Looking at the big picture erosion history of the figure 1 map area the drainage routes shown developed as immense south and southeast oriented melt water floods flowed across the region and at approximately the same time as crustal warping raised the Yellowstone Plateau and the Absaroka Range and as the deep east and northeast oriented Yellowstone River valley eroded headward from a deep “hole” in which a large North American ice sheet was rapidly melting. The deep “hole” was located north and east of the figure 1 map area, which is located along the deep “hole’s” deeply eroded southwest wall. The east and northeast oriented Yellowstone River valley eroded headward from the deep “hole” to capture immense south and southeast oriented ice marginal floods flowing from western Canada across Montana. At that time mountain ranges in the figure 1 map area, including the Yellowstone Plateau and the Absaroka Range, did not stand high above the surrounding regions and floodwaters could freely flow across the entire figure 1 map area. Over time however uplift of the Yellowstone Plateau and of the regional mountain ranges channeled the huge south and southeast oriented melt water floods into valleys or basins between the rising mountains. One such flood flow channel was between the rising Gallatin and Absaroka mountain ranges along the valley now used by the northwest oriented Yellowstone River. This large south oriented flood flow channel was eventually beheaded and reversed by continued crustal warping and by headward erosion of the much deeper northeast and east oriented Yellowstone River valley (from the deep “hole” the melting ice sheet had once occupied). Beheading of the southeast oriented flood flow channel on the present day northwest oriented Yellowstone River alignment probably took place at the elbow of capture (where the Yellowstone River turns from flowing in a northwest direction to flowing in a northeast direction). The Yellowstone River valley upstream from the elbow of capture was eroded by a massive flood flow reversal as the ongoing Yellowstone Plateau and Absaroka Range uplift continued.

Detailed location map for Boulder River-Buffalo Creek drainage divide area

Figure 2: Detailed location map Boulder River-Buffalo Creek 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 Boulder River-Buffalo Creek drainage divide area in the northern Absaroka Mountains. The northern margin of Yellowstone National Park is the brown shaded area along the south margin of figure 2 with the Montana-Wyoming state line being the west to east oriented dashed line running through the northern margin of Yellowstone National Park. Green shaded areas are National Forest lands, which are generally located in mountainous regions. The Yellowstone River flows in a northwest direction from the south center edge of figure 2 (near Tower Junction) to Miner, Montana (near west center edge of figure 2) and then in a northeast direction to the north edge of figure 2 (west half). The mountainous region (green shaded area) east of the Yellowstone River includes the Absaroka Range, which is labeled. The Boulder River originates near Monument Peak in the Absaroka Range (near center of figure 2) and flows in a north direction to the north center edge of figure 2 and north of figure 2 turns to flow in a northeast direction to join the east and northeast oriented Yellowstone River near Big Timber (see figure 1). Buffalo Creek originates near Iron Mtn., just south of the Boulder River headwaters, and flows in a south-southwest and south direction and to join the Lamar River in Yellowstone National Park, which then flows in a northwest direction to join the northwest oriented Yellowstone River near Tower Junction. Slough Creek is located east of Buffalo Creek and originates east of Monument Peak and then flows in a south and southwest direction to join Buffalo Creek in Yellowstone National Park. Note how south oriented Slough Creek headwaters are located just east of a north oriented Boulder River tributary and the Boulder River headwaters. Adjacent drainage routes, flowing in opposite directions, is usually evidence that one of the drainage routes developed as a result of a reversal of flow. In this case flood flow was reversed when headward erosion of the much deeper Yellowstone River valley north of figure 2 beheaded  south oriented flood flow channels.

Boulder River-Hellroaring Creek drainage divide area north of Yellowstone National Park

Figure 3: Boulder River-Hellroaring Creek drainage divide area north of Yellowstone National Park. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 provides a topographic map of the Boulder River-Hellroaring Creek drainage divide area north of Yellowstone National Park, which provides a good staring point for the topographic maps illustrated in this essay. The Absaroka Range high ridge extends in southeast direction from Crow Mountain (slightly west of north center edge of figure 3) to near the southeast corner of figure 3 and is labeled “RANGE”. East of the Absaroka Range high ridge is the north oriented Boulder River, which originates near Sheepherder Mountain in the southeast quadrant of figure 3. Note Boulder Pass just west of Sheepherder Mountain. The south oriented stream originating at Boulder Pass is Buffalo Creek and the Boulder Pass area is illustrated in detail in figure 4 below. The south oriented stream originating near Crow Mountain is Hellroaring Creek, which flows to the south edge of figure 3 and then to join the northwest oriented Yellowstone River near Tower Junction in Wyoming to the south of figure 3. The East Branch originates near the center of figure 3 and flows in a northwest and southwest direction to join Hellroaring Creek. The Middle Branch is located south of the East Branch and flows in a south and southwest direction to join Hellroaring Creek near the south edge of figure 3. The high Absaroka Range ridge appears at first to be an insurmountable barrier, yet a close look reveals mountain passes or through valleys eroded across that high ridge. Boulder Pass linking the north oriented Boulder River valley with the south oriented Buffalo Creek valley is perhaps the most obvious of these through valleys, although a trail from the Middle Fork Hellroaring Creek to both Copper Creek and Sheep Creek in the Boulder River drainage basin identifies another deep mountain pass. Other less deep mountain passes can also be found. These mountain passes or through valleys were eroded by diverging south oriented flood flow channels at a time when the Absaroka Range was just beginning to rise and before headward erosion of the deep east oriented Yellowstone River north of figure 3. At that time the Yellowstone Plateau and surrounding mountain ranges did not stand high above Montana plains, valleys, and basins to the north and floodwaters could freely flow from western Canada across Montana including into and across the figure 3 area. The Boulder River drainage basin was created by a massive flood flow reversal caused by Absaroka Range uplift and by headward erosion of the much deeper Yellowstone River valley to the north.

Detailed map of Boulder River-Buffalo Creek drainage divide area

Figure 4: Detailed topographic map of the Boulder River-Buffalo 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 Boulder River-Buffalo Creek drainage divide area seen in less detail in figure 3 above. Boulder Pass is located near the center of figure 4. Sheepherder Mountain located a short distance south and east of Boulder Pass. Buffalo Creek originates in the southeast corner of section 32 just west of Boulder Pass and flows in a south direction across section 5 to the south edge of figure 4. The Boulder River originates in section 3 (just east of Sheepherder Mountain) and flows in a north-northwest direction to the north edge of figure 4. A northeast oriented tributary flows from Boulder Pass to join the Boulder River. Today Boulder Pass is a high mountain pass with an elevation at the drainage divide of 9678 feet (the map contour interval is 40 feet). The Boulder River valley bench mark (BM) in section 28 reads 8170 feet and the bench mark in the Buffalo Creek valley in section 5 reads 8469 feet. In other words the trail from the Boulder River valley to Boulder Pass climbs 1500 feet while the trail from the Buffalo Creek valley climbs 1200 feet. But follow the ridge both to the northwest and to the southeast and there are peaks with elevations greater than 10,400 feet in both directions. While today Boulder Pass is just a notch in a high mountain ridge it is also a notch almost 800 feet deep. This notch is a water eroded feature and was eroded by south oriented flood flow moving from the Boulder River valley to the Buffalo Creek valley before the flood flow reversal that created the north oriented Boulder River drainage basin. While Boulder Pass is the deepest of these flood-eroded valleys seen in figure 4, other higher elevation water eroded notches in the high ridge can also be seen. For example in section 32 a notch (or through valley) links the Buffalo Creek headwaters with the north oriented South (Fork Sheep Creek), which north of figure 4 flows to Sheep Creek and then to the Boulder River. When viewed as group these through valleys (or notches) provide evidence of a south oriented anastomosing channel complex that was eroded into a landscape equivalent in elevation to the present day elevation of the highest figure 4 mountain peaks. At that time the Absaroka Range did not have its present elevation above surrounding regions and floodwaters could easily flow from western Canada across Montana to and across the figure 4 region.

East Fork Boulder River-Slough Creek drainage divide area

Figure 5: East Fork Boulder River-Slough Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the East Fork Boulder River-Slough Creek drainage divide area east of figure 3 and includes overlap areas with figure 3. The north oriented Boulder River is located in the west half of figure 5 and flows from near Sheepherder Peak (in southwest quadrant of figure 5) to the north edge of figure 5 (west half). Buffalo Creek is the south oriented stream located south of Boulder Pass and flows to the south edge of figure 5 (west half). The East Fork Boulder River originates east of Sheepherder Peak and flows in a north and northwest direction to join the Boulder River near the north edge of figure 5. Rainbow Creek is a southwest and west oriented East Boulder River tributary located in the north center region of figure 5 and Columbine Creek is a north oriented Rainbow Creek tributary. Slough Creek is the south oriented stream south of the Columbine Creek drainage basin and flows to the south edge of figure 5 (east of center). Wounded Man Creek is a west and southwest oriented Slough Creek tributary (in southeast quadrant of figure 5). South of figure 5 Slough Creek joins Buffalo Creek. Note near the center of figure 5 a through valley linking the north oriented East Fork Boulder River valley with the south oriented Slough Creek valley. A trail uses the through valley to cross the drainage divide and is labeled “PACK” in the through valley. The map contour interval for figure 5 is 50 meters. At the drainage divide the trail elevation is between 2600 and 2650 meters. Elevations to the north rise to 3118 meters and to the south elevations are higher meaning the through valley is almost 500 meters deep. This 500-meter deep through valley linking a north oriented drainage system with a south oriented drainage system is a water eroded feature and for a time was a primary south oriented flood flow channel crossing what was probably a rising Absaroka Range. South oriented flood flow to what was at that time the actively eroding Slough Creek valley ended when Absaroka Range uplift combined with headward erosion of the deep Yellowstone River valley to the north caused a gradual but massive flood flow reversal that eventually created the north oriented Boulder River drainage basin. I say gradual because south oriented flood flow routes were beheaded and reversed in sequence from east to west, with each newly reversed flood flow route capturing yet to be reversed flood flow from flood flow routes further to the west. Study of the Boulder River-East Boulder River drainage divide reveals several though valleys (or mountain passes), which were eroded by this captured flood water which was moving eastward to the newly reversed East Boulder River valley. This captured flood flow supplied the volumes of flood water required to erode the deep north and northwest oriented East Boulder River valley.

Detailed map of East Fork Boulder River-Slough Creek drainage divide area

Figure 6: Detailed map of East Fork Boulder River-Slough 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 East Fork Boulder River-Slough Creek drainage divide area seen in less detail in figure 5 above. The East Boulder River flows in a north-northeast direction from section 35 (southwest quadrant of figure 6) across the northwest corner of section 36 and into section 25. In section 25 the East Boulder River turns to flow in a north direction through section 24 to the north edge of figure 6 (west half). Slough Creek flows in a southwest direction from the southeast corner of section 20 (near east edge of figure 6) across section 29 and the southeast corner of section 30 to section 31 where it turns to flow in a south-southeast direction to the south edge of figure 6 (east half). The through valley linking the East Boulder River valley with the Slough Creek valley is located in section 25. The map contour interval for figure 6 is 40 feet and the through valley floor elevation at the drainage divide is between 8520 and 8560 feet. The high point in section 19 to the north is 10,230 feet. Elevations in the southwest corner of section 36 rise to more than 9400 feet, although a high ridge with elevations greater than 10,200 feet is located south of figure 6. Based on these elevations the through valley is approximately 1600 feet deep and is almost three miles across in width (sections are one square mile in size). Note how unlike Boulder Pass, where there is a steep climb from the Boulder River to the drainage divide, there is almost no climb from the East Fork Boulder River valley to the drainage divide in this through valley. The through valley was eroded by massive south oriented flood flow moving from the present day north oriented Boulder River drainage basin to the present day south oriented Slough Creek valley. Flood flow in the through valley ended when floodwaters in the East Fork Boulder River valley reversed flow direction so as to flow in a north direction. The flood flow reversal was probably caused by Absaroka Range uplift, which was occurring as floodwaters flowed across the region, and by headward erosion of the deep east and northeast oriented Yellowstone River valley, which was eroding headward from the space in the deep “hole” being opened up by ice sheet melting, both of which were occurring as immense south and southeast oriented melt water floods flowed across Montana.

Buffalo Creek-Bull Creek drainage divide area

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

Figure 7 illustrates the Buffalo Creek-Bull Creek drainage divide area south of figure 5, south and east of figure 3, and includes significant overlap areas with figure 5 and a small overlap area with figure 3. Buffalo Creek is labeled in figure 7 and flows in a south-southwest direction from the north edge of figure 7 to the south edge of figure 7 (west half of figure 7). Slough Creek is also labeled and flows in a south-southwest direction in the figure 7 east half (with a southeast oriented segment near the north edge of figure 7). Bull Creek is a south and southeast oriented Slough Creek tributary originating in the north center region of figure 7. Note how a through valley links the southeast oriented Bull Creek valley with the north and northwest oriented East Fork Buffalo Creek valley. The map contour interval for figure 7 is 50 meters and the through valley floor elevation at the drainage divide is between 2650 and 2700 meters. To the north the Absaroka Range ridge rises to more than 3200 meters and Roundhead Butte to the south reaches an elevation of 3113 meters. In other words the through valley is more than 400 meters deep. A 300-meter deep through valley is located between Roundhead Butte and Lookout Mountain directly to the south. Other shallower through valleys can be seen elsewhere in figure 7. These through valleys are water eroded features and provide evidence of anastomosing south oriented flood flow channels that once crossed the region. At the time floodwaters flowed across the region the Absaroka Range did not stand high above surrounding regions as it does today and the deep east and northeast oriented Yellowstone River valley north of figure 7 did not exist. Floodwaters were free to flow in a south and southeast direction from the western Canada ice margin across Montana, including figure 7, and to flow to and across what is today the high Yellowstone Plateau to the south.

Detailed map of East Fork Buffalo Creek-Bull Creek drainage divide area

Figure 8: Detailed map of East Fork Buffalo Creek-Bully 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 East Fork Buffalo Creek-Bull Creek drainage divide area seen in less detail in figure 7. Buffalo Creek is labeled and flows in south and south-southwest direction from the north edge of figure 8 (west half) to the west edge of figure 8 (south half). The East Fork Buffalo Creek originates in section 21 and flows in a north and northwest direction to join south oriented Buffalo Creek as a barbed tributary. Bull Creek originates near the corner of sections 10, 11, 14, and 15 and flows in a south, southeast, and east direction to the southeast corner of figure 8. The through valley linking the northwest oriented Buffalo Creek valley with the southeast oriented Bull Creek valley is located in section 15. The map contour interval for figure 8 is 40 feet and the through valley floor elevation at the drainage divide is between 8720 and 8760 feet. Roundhead Butte in section 21 near the south edge of figure 8 has an elevation of 10,212 feet. Higher elevations are found on the ridge to the north, which means the through valley is at least 1400 feet deep. While not as broad as the East Boulder River-Buffalo Creek through valley seen in figures 5 and 6 this East Fork Buffalo Creek-Bull Creek through valley is a significant erosional landform and was eroded by southeast oriented flood flow moving from the south oriented Buffalo Creek drainage basin (and the north oriented Boulder River drainage basin to the north) to the southeast oriented Bull Creek valley and the south oriented Slough Creek valley. The northwest oriented East Fork Buffalo Creek valley was eroded by a reversal of flow when headward erosion of a much deeper south oriented Buffalo Creek valley or flood flow channel beheaded southeast oriented flood flow to the actively eroding Bull Creek valley. The north oriented East Fork Buffalo Creek headwaters valley was probably eroded during a much earlier capture event when the deep southeast oriented Bull Creek valley eroded headward along what is now the northwest oriented East Fork Buffalo Creek alignment. Prior to that earlier capture event floodwaters were flowing in a south direction on an erosion equivalent in elevation to the present day top of Roundhead Butte, although considerable regional uplift has probably occurred since that time.

Hawley Creek-Rainbow Creek drainage divide area

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

Figure 9 illustrates the Hawley Creek-Rainbow Creek drainage divide area north and slightly east of figure 5 and includes overlap areas with figure 5. The Boulder River flows in a north and north-northeast direction in the west half of figure 9. Hawley Creek is a northwest, north, and northwest tributary joining the Boulder River near the north edge of figure 9. The East Fork Boulder River flows from the south edge of figure 9 in a north and northwest direction to join the Boulder River in the southwest quadrant of figure 9. Rainbow Creek originates at Rainbow Lake in the Lake Plateau region and flows in a south, southwest, and west direction to join the East Fork Boulder River near the point where it turns from flowing in a north direction to flowing in a northwest direction. Note how the northwest oriented Hawley Creek headwaters valley is linked on the Lake Plateau by a through valley with the south oriented Rainbow Creek valley. The map contour interval for figure 9 is 50 meters. The through valley floor elevation at the drainage divide is between 2950 and 3000 meters. Mount Douglas on the northeast side rises to 3441 meters while the unnamed mountain to the southwest rises to an elevation greater than 3250 meters. In other words the northwest and north oriented Hawley Creek valley is linked by a 250-meter deep through valley on the high Lake Plateau with the south and southwest oriented Rainbow Creek valley. This high through valley is a water eroded feature and was eroded by south oriented flood flow at a time when the Absaroka Range and its Lake Plateau area did not stand high above surrounding regions as they do today. Absaroka Range uplift, which was occurring as floodwaters flowed across the region, combined with headward erosion of the deep east and northeast oriented Yellowstone River valley to the north of figure 9, resulted in the beheading and reversals of the south oriented flood flow routes in sequence from east to west. During flood flow reversal events south oriented floodwaters from yet to be beheaded flood flow routes in the west were captured by newly reversed flood flow routes further east. Such captured floodwaters may have flowed in a northwest direction from the Rainbow Creek valley to the Hawley Creek valley before the present day Hawley Creek-Rainbow Creek drainage divide was established.

Detailed map of Hawley Creek-Rainbow Creek drainage divide area

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

Figure 10 illustrates the Hawley Creek-Rainbow Creek drainage divide area seen in less detail in figure 9 above. Hawley Creek flows in a northwest direction in the northwest quadrant of figure 10. Rainbow Creek originates in section 29 and flows in a south direction to the south edge of figure 10 (east half). The northwest to southeast through valley linking the northwest oriented Hawley Creek valley with the south oriented Rainbow Creek valley is located in section 29. The map contour interval for figure 10 is 40 feet and the through valley floor elevation at the drainage divide is between 9720 and 9760 feet. Mount Douglas in section 17 to the north rises to 11,282 feet and a spot elevation of 10,713 feet is found along the south margin of section 19 to the southwest of the through valley. These elevations suggest the through valley is approximately 1000 feet.

There is evidence in figure 10 (and in figure 9) of glacially eroded landforms, although the alpine glaciers probably only modified preexisting valleys. In other words the through valley is a water-eroded feature and was eroded prior to the alpine glaciation. Floodwaters from the rapidly melting thick North American ice sheet flowing across the Absaroka Range did so as the Absaroka Range was being uplifted and as the deep east and northeast oriented Yellowstone River valley to the north eroded headward across south central Montana. Prior to the alpine glaciation a combination of ice sheet related crustal warping and deep melt water flood erosion (probably caused by erosion of the deep Yellowstone River valley and its deep tributary valleys around the rising Absaroka Range) caused the Absaroka Range to emerge as the high mountain range it is today.

About the same time as the Absaroka Range was emerging as a high mountain range the thick ice sheet melting progressed to the point where melt water floods, which had been flowing to the Gulf of Mexico, were captured by north oriented drainage routes opening up on the former ice sheet floor between the decaying thick ice sheet remnants. The result was immense melt water floods started flowing to the North Atlantic Ocean and even the Arctic Ocean. This melt water flow direction change also changed North American climates. Climatic conditions responsible for the thick ice sheet rapid melt down were replaced by climatic conditions that caused the north oriented melt water floods to freeze around rejuvenated thick ice sheet remnants and to form a thin ice sheet. The changed climatic conditions also were ideal for formation of alpine glaciers in newly emerged mountain ranges, such as the Absaroka Range. In time climatic conditions moderated and the thin ice sheet and many alpine glaciers melted, although in figure 1 some permanent snow fields still exist in the Mount Douglas region.

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.