A geomorphic history based on topographic map evidence

This essay provides an overview of more detailed essay which illustrate and discuss topographic map evidence pertaining to Judith River drainage basin drainage history. The detailed essays can be found under Judith River on this website’s sidebar category list. The Judith River is a north-oriented Missouri River tributary located in central Montana and drains the Judith Basin. The Little Belt, Judith, and Big Snowy Mountains surround the Judith Basin and the Judith River drainage basin reaches into those Rocky Mountain outlier mountain ranges. Topographic map evidence from drainage divide areas between Judith River tributaries and between the Judith River drainage basin and adjacent drainage basins suggests the Judith Basin was eroded when headward erosion of a deep Judith River valley and tributary valleys captured an immense southeast-oriented flood, which originally moved across a high level topographic surface now represented by the highest ridges in the present day Little Belt, Judith, and Big Snowy Mountains. Captured flood waters were diverted northeast and north to what was then the actively eroding the Missouri River valley, which at that time was eroding headward into the region. Flood waters were derived from a rapidly melting North American ice sheet and were flowing in a southeast direction between the present day Rocky Mountains to the west and the decaying ice sheet’s southwest margin. The ice sheet had been thick and had deep roots, which extended into a deep “hole” created by deep glacial erosion and crustal warping. When ice sheet melting progressed to the point that space in the deep “hole” opened up, deep northeast-oriented valleys, such as the Missouri River valley, eroded headward from the deep “hole” to capture southeast-oriented ice marginal floods and to divert ice marginal floods into the deep “hole”. Headward erosion of the deep Missouri River-Judith River valley beheaded flood flow routes to what was then the newly eroded Musselshell River valley. Emergence of the Little Belt, Judith, and Big Snowy Mountains as high mountain ranges occurred as flood waters crossed the region and may have been caused by deep flood water erosion as flood waters removed easy to erode materials surrounding the mountain ranges and/or by crustal warping related to the ice sheet weight and/or the removal of significant thicknesses of overlying bedrock material. Flood flow into the Judith River drainage basin ended when Missouri River valley headward erosion beheaded and reversed all southeast-oriented flood flow routes into the present day Judith River drainage basin.

Figure 1: Montana Judith River drainage basin location map. National Geographic Society map digitally presented using National Geographic Society TOPO software.

Judith River drainage basin drainage history

This essay provides an overview of more detailed essays which illustrate and describe topographic map evidence used in interpreting Judith River drainage basin drainage history. This overview essay provides a few examples of topographic map evidence seen in the detailed essays. The detailed essays can be found under Judith River on this website’s sidebar category list. The Judith River drainage basin is located in central Montana and the Judith River and its tributaries drain the Judith Basin and northern slopes of the eastern Little Belt Mountains and western Big Snowy Mountains. The Judith River flows in a northeast direction from the Little Belt Mountains into the Judith Basin and then turns to flow in a north direction to join the east-oriented Missouri River. Elevations in the Judith River drainage basin range from more than 2500 meters (more than 8000 feet) to approximately 750 meters (or 2400 feet) where the Judith River joins the Missouri River. South and east of the Judith River drainage basin is the Musselshell River drainage basin. The Musselshell River flows in an east-southeast, east-northeast, and north direction to join the Missouri River east of the Judith River drainage basin. Northeast-oriented Judith River tributaries originating in the Little Belt Mountains are linked by through valleys with south-oriented Musselshell River tributaries. Northwest and north-oriented Judith River tributaries in the Big Snowy Mountains are also linked by shallow through valleys eroded across a high mountain ridge with south-oriented Musselshell River tributary valleys. Between the Little Belt Mountains and Big Snowy Mountains is a deep north-south oriented through valley at Judith Gap linking north-oriented Judith River tributaries with southeast-oriented Musselshell River tributaries. North of the Big Snowy Mountains and south of the Judith Mountains is another somewhat less well-defined through valley linking northwest-oriented Judith River tributary valleys with east-oriented Musselshell River tributary valleys.

• North and west of the Judith River drainage basin is the northeast, southeast, and east-oriented Missouri River drainage basin. A major northeast and north-oriented Missouri River tributary located west of the Judith River is Arrow Creek (shown, but not labeled on figure 1). Arrow Creek also originates in the Little Belt Mountains and flows across the western Judith Basin to join the Missouri River a short distance west of where the Judith River joins the Missouri River (see figure 2 below). In some respects Arrow Creek could be considered a Judith River tributary and the Arrow Creek valley was probably eroded in the same manner and at approximately the same time as the adjacent and parallel Judith River valley. North of the Little Belt Mountains and west of the Arrow Creek valley are the Highwood Mountains and a through valley between the Highwood Mountains and the Little Belt Mountains links east-oriented Arrow Creek tributaries with northwest-oriented Missouri River tributaries. Through valleys in the high Little Belt Mountains also link Arrow Creek tributaries with northwest-oriented Missouri River tributaries. West of the Judith Mountains are the North and South Moccasin Mountains (not labeled on figure 1) and through valleys between those mountains and the Judith Mountains link Judith River tributary valleys with the northeast-oriented Armells Creek valley, with Armells Creek flowing directly to the Missouri River. Essays found under MT Missouri River on the sidebar category list provide evidence related to the development of the Arrow Creek and other central Montana valleys. In addition readers interested in Judith River-Musselshell River drainage divide history are encouraged to also study essays found under Musselshell River on the sidebar category list.

• Drainage history interpretations in this Judith River drainage basin landform origins overview essay and its related detailed essays are based entirely on topographic map evidence. Each of the detailed essays illustrates and describes a specific Judith River drainage divide area and includes location maps and eight or more detailed topographic maps showing examples of landform features found in that region. Evidence interpreted usually includes orientations of valleys present and through valleys linking drainage routes on opposite sides of major drainage divides. Significant through valleys between the Little Belt and Big Snowy Mountains and between the Big Snowy Mountains and Judith Mountains link north-oriented Judith River tributaries with east and south-oriented Musselshell River tributaries. These through valleys can be identified on large region maps such as figure 1 above, although the linkages become much more evident on topographic maps, especially mosaics of detailed topographic maps. Each of the more than 40 detailed topographic maps included in this overview essay and the related detailed essays documents many other smaller scale through valleys providing evidence the deep Judith River valley eroded headward across a massive southeast-oriented flood, which was flowing to what was probably a newly eroded and deep Musselshell River valley. Headward erosion of the deep northeast-oriented Arrow Creek valley subsequently captured flood flow to the newly eroded Judith River valley and its actively eroding tributary valleys. Perhaps what is most intriguing are linkages between Judith River tributaries and Musselshell River tributaries which can be found in the high Little Belt Mountains and Big Snowy Mountains. These linkages suggest flood water flowed across what are today high mountain ranges, which means flood waters deeply eroded the surrounding regions and/or the mountain ranges were uplifted as the flood occurred.

Figure 2: Arrow Creek-Judith River drainage divide area south of Missouri River. Arrow Creek is the north-oriented Missouri River tributary flowing along figure 2 west edge. Judith River flows north along east edge. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Topographic map evidence for massive flood flow and flood erosion is found throughout the Judith River drainage basin. Figure 2 illustrates the Arrow Creek-Judith River drainage divide area south of the east and northeast oriented Missouri River, which flows across the figure 2 north margin. Arrow Creek is the north oriented stream flowing along the figure 2 west edge and the Judith River is the north oriented stream flowing along the figure 2 east edge. The Big Sag is a large northeast and east-oriented through valley eroded across the Arrow Creek-Judith River drainage divide and provides evidence large volumes of flood water once flowed from the Arrow Creek drainage basin to the north oriented Judith River valley. The Little Sag, which is located north of the Big Sag valley, is also a through valley linking the Arrow Creek valley with the Judith River valley, although the linkage is at a much higher elevation. Figure 2 evidence suggests headward erosion of the deep north-oriented Arrow Creek valley beheaded east-oriented flood flow in the Little Sag valley and subsequently beheaded the northeast-oriented flood flow moving through the Big Sag valley. This evidence suggests the deep north-oriented Judith River valley eroded headward first from what was probably the actively eroding deep Missouri River valley head, at a time when the deep Missouri River valley had not yet eroded headward across the figure 2 map area and when there was no deep north-oriented Arrow Creek valley. The evidence also suggests the deep Missouri River valley did erode headward across the entire figure 2 map area and that volumes of flood water moving north in what is today the Arrow Creek drainage basin were so great the flood water spilled across what were the drainage divides between the actively eroding deep Missouri River valley and what was also the actively eroding and deep Big Sag valley and eroded the deep north-oriented Arrow Creek valley. In other words, flood waters responsible for eroding these deep valleys came not only from the west along what is now the Missouri River valley, but also came from the south from what are now the north- and northeast-oriented Judith River and Arrow Creek drainage basins, which means the north-oriented flood waters moved through what is today the through valley between the Highwood Mountains and the Little Belt Mountains and also probably came from what are today the high Little Belt Mountains.

Figure 3: Judith River west of the North and South Moccasin Mountains with Judith Mountains in figure 3 southeast corner. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 3 illustrates the north-northwest and north-northeast oriented Judith River west of the North and South Moccasin Mountains. The North Moccasin Mountains are located just south of the figure 3 center area and the South Moccasin Mountains are located along the figure 3 south center edge. The Judith Mountains are the mountains located in the figure 3 southeast corner area. Wolf Creek is the north-northeast oriented stream in the figure 3 northwest corner and is a Judith River tributary. Note how Judith River tributaries in the figure 3 map area are predominately northwest oriented, although tributaries east of the North Moccasin Mountains flow in south and southwest directions before flowing west and northwest between the North and South Moccasin Mountains. Note also Dog Creek, which flows in an east direction from the North Moccasin Mountains (north of the Judith River tributaries) and then turns to flow in a north direction to the figure 3 north edge. North of the figure 3 map area Dog Creek continues to flow in a north direction until it almost reaches the east oriented Missouri River valley. Instead of continuing north to the Missouri River Dog Creek then turns and flows in a west and west-northwest direction to join the Missouri River near where the deep Judith River valley joins the Missouri River valley. Also note north-oriented Armells Creek and its north- and northeast-oriented Deer Creek tributary, both of which originate in the Judith Mountains. Armells Creek turns to flow in a northeast direction to flow to the figure 3 east edge (north half) and continues to flow in a northeast direction to join the Missouri River. The northwest-oriented Judith River tributary and the west-oriented Dog Creek valleys were eroded by reversals of flood flow on beheaded east and southeast-oriented flood flow channels. The west to east oriented through valley between the North and South Moccasin Mountains was initially by southeast-oriented flood water flowing to what was then the actively eroding deep northeast-oriented Armells Creek valley, which had eroded headward from what was then the actively eroding and deep Missouri River valley. The deep Armells Creek valley initiated erosion of the through valley between the North Moccasin Mountains and the Judith Mountains. Headward erosion of the deep Missouri River valley north of the figure 3 map area next beheaded and reversed flood flow routes to erode the west and west-northwest Dog Creek valley, which then eroded south to capture southeast-oriented flood flow routes flowing to the newly eroded Armells Creek valley. Headward erosion of the deep north-oriented Judith River valley next beheaded and reversed southeast-oriented flood flow routes to the newly eroded Dog Creek and Armells Creek valleys to create the south, west, and northwest-oriented Judith River tributaries seen today. All interpretations begin with flood waters flowing on a topographic surface at least as high as the highest Judith and Moccasin Mountains elevations today.

Figure 4: Judith Gap located between Big Snowy Mountains to the east and the Little Belt Mountains to the west. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 4 illustrates the Judith Gap area located between the high Big Snowy Mountains to the east and the high Little Belt Mountains to the west. North-oriented streams flowing to the figure 4 north edge are Judith River tributaries. South and southeast-oriented streams flowing to the figure 4 south edge are Musselshell River tributaries. The drainage divide near the town of Judith Gap along the railroad line is at approximately 1400 meters or 4600 feet. Elevations in the Big Snowy Mountains to the east and in the Little Belt Mountains to the west rise to more than 2500 meters or more than 8000 feet. While the Judith Gap through valley could be considered a tectonically formed valley it is also an erosional feature and was eroded by immense south-oriented floods. Evidence that south-oriented flood waters were beheaded and reversed can be seen in the south-oriented headwaters of north-oriented Ross Fork Creek, a stream which north of Judith Gap flows parallel to the highway to the figure 4 north edge. The present day north-oriented Ross Fork Creek valley was eroded by a massive reversal of south-oriented flood flow that had been flowing through large the Judith Ga valley to what was probably the newly eroded Musselshell River valley. The south-oriented flood flow route was beheaded and reversed by headward erosion of the deep Missouri River-Judith River valley and the reversed flood flow captured some south-oriented drainage routes south of the Big Snowy Mountains.

• Figure 4 evidence also demonstrates the immense south-oriented floods once crossed the Big Snowy Mountains. Note how Ross Fork Creek headwaters flow south on the Big Snowy Mountains south flank adjacent to south-oriented Browns Gulch which drains to south-oriented Niel Creek, which is a Musselshell River tributary and how the two valleys are linked by through valleys (better seen on more detailed maps). The ridge immediately north of the south-oriented Ross Fork Creek and Niel Creek headwaters rises to almost 2300 meters or 7800 feet and shallow north-south oriented through valleys eroded across that ridge link the south-oriented Browns Gulch valley with the north-northeast oriented Dry Pole Creek valley (a tributary to a northwest-oriented Judith River tributary). While it may be difficult to imagine today, the through valley and the linkage provides evidence flood water once flowed south across that high level drainage divide. Either flood water erosion removed almost 900 meters or 3200 feet of easily eroded bedrock material that had been surrounding the Big Snowy Mountains (and also the Little Belt Mountains) or the mountain areas were uplifted as the flood waters eroded the region (or some combination of the two).

• Why would immense southeast-oriented floods be flowing across what is now central Montana on a topographic surface at least as the high Big Snowy Mountains and/or why would the Big Snowy Mountains be uplifted as the flood waters flowed across the region? Judith River drainage basin history important to this discussion began with development of a North American ice sheet comparable in size to the present day Antarctic Ice Sheet, if not larger. The ice sheet was thick, probably several kilometers thick, and was located in a deep “hole”, which the ice sheet formed by a combination of deep glacial erosion and crustal warping caused by the ice sheet’s immense weight. When at its maximum size the ice sheet stood high above the pre-glacial surface, but also had roots that extended well below the pre-glacial surface, which no longer exists. The Judith River drainage basin location was probably located south and west of ice sheet’s southwest margin, although evidence for the ice sheet’s southwest margin has probably been removed by deep melt water flood erosion. The pre-glacial surface under the ice sheet was completely destroyed by deep glacial erosion and the pre-glacial surface adjacent to the ice sheet and elsewhere on the North American continent was deeply eroded by deep melt water flood erosion and was also probably significantly altered by crustal warping caused by the thick North American ice sheet presence.

• Events important to Judith River drainage basin history began as the ice sheet was rapidly melting and had melted to the point it no longer stood high above the surrounding non-glaciated surface, which had probably already been significantly lowered by deep melt water erosion. Immense melt water floods were flowing in a southeast direction along the ice sheet’s southwest margin and were deeply eroding the region between the Rocky Mountains and the ice sheet’s southwest margin, which at that time was located north and east of today’s Judith River drainage basin. Also at that time immense southeast and south-oriented supra-glacial melt water rivers were flowing across the ice sheet’s surface to the ice sheet’s southern margin and carving giant ice-walled and ice-floored (later bedrock floored) canyons into the decaying ice sheet surface. A huge southeast and south-oriented ice-walled and ice-floored (later bedrock-floored) canyon was carved north and east of the ice sheet southwest margin and the Missouri Escarpment is today what remains of that giant canyon’s west and southwest wall. The ice floor of that giant southeast and south-oriented ice-walled canyon was significantly lower in elevation than the bedrock surface south and west of the decaying ice sheet margin and the huge melt water river flowing in that southeast and south-oriented ice-walled canyon represented the region’s major drainage route, which proceeded to capture the immense southeast-oriented ice-marginal floods by eroding deep northeast-oriented tributary valleys headward across the ice sheet’s southwest margin and then headward into the adjacent bedrock surface. These deep northeast-oriented valleys diverted the immense southeast-oriented ice-marginal floods into space the ice sheet had once occupied.

• Melting of what had been the thick ice sheet roots, which may have extended many hundreds of meters deep (perhaps more than one thousand meters deep) below the surrounding bedrock surface, progressively lowered both the ice sheet surface, the ice-walled canyon floor, and the surrounding bedrock surface, creating a situation where new and even deeper northeast-oriented valleys repeatedly eroded headward to capture immense southeast-oriented ice-marginal melt water floods. The deep northeast-oriented Yellowstone River, Missouri River, and Musselshell River valleys (and other northeast-oriented valleys) we see today were probably eroded very late in the ice sheet melt down history and were probably preceded by earlier, but similar higher level northeast-oriented valleys which diverted massive southeast-oriented ice-marginal floods onto the decaying ice sheet surface. How much the region between the high Rocky Mountain outlier mountain ranges and the former ice sheet margin was lowered by melt water erosion is difficult to determine, especially from topographic map evidence alone. However, topographic map evidence presented in this Judith River drainage basin landform overview essay and its related detailed essays demonstrates the immense ice-marginal melt water floods at one time did flow across what are today high Rocky Mountain outlier mountain ranges. Either the melt water floods removed whatever material was located between those mountains or the mountains were uplifted as the ice-marginal floods were underway. If flood water erosion removed bedrock material between the mountain ranges the amount of bedrock material removed would have been tremendous, suggesting some of the removed material may have been stagnant ice, which simply melted as flood waters flowed across the region.

Figure 5: Judith River-Musselshell River drainage divide area in Little Belt Mountains. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 5 illustrates a Judith River-Musselshell River drainage divide area in the high Little Belt Mountains west of the figure 4 map area. The northeast oriented Lost Fork Judith River is located in the figure 5 northwest corner. The South Fork Judith River flows from the figure 5 west edge (north half) in an east and northeast direction to the figure 5 north center edge. Mount High is the mountain peak located just east of the figure 5 center and rises to 2513 meters (8242 feet). Antelope Creek is the east-northeast and north oriented stream originating near Mount High and north of the figure 5 joins the Judith River. All other streams flowing to the figure 5 north edge are Judith River tributaries and all streams flowing to the figure 5 south edge are Musselshell River tributaries. East Fork Haymaker Creek is the northeast, east, and southeast-oriented stream located directly south of Mount High and flows to the figure 5 southeast corner and the Musselshell River. Daisy Dean Creek is the south-oriented stream flowing to the figure 5 south center edge and located in a valley linked by through valleys to the East Fork Haymaker Creek valley and the valleys of two north-oriented South Fork Judith River tributaries. The north-south oriented through valley is located just east of Daisy Peak, which is located near the Daisy Dean Creek headwaters. East of Daisy Peak and on the east side of Daisy Dean Creek are two well-developed west-to-east oriented through valleys linking the Daisy Dean Creek valley with the south-oriented Nevada Creek valley. These through valleys represent just a few of the through valleys eroded across drainage divides in the figure 5 map area. The through valleys describe a complex pattern of southeast-oriented flood flow channels, which was carved into the underlying bedrock and which almost certainly was influenced by bedrock resistance to erosion. The Judith River drainage basin landform origins overview essay and detailed essays provide clues on how to unravel these drainage history puzzles. In all cases it is necessary to assume flood waters first flowed across a high level surface at least as high as the highest present day Little Belt Mountains highest ridges. This assumption requires deep flood water erosion of regions surrounding the Little Belt Mountains and/or uplift of the Little Belt Mountains as flood waters eroded the region.

• Commonly accepted Montana drainage history interpretation imply the Missouri River, Judith River, Musselshell River, and other north and northeast-oriented valleys are pre-glacial valleys. Further such commonly accepted interpretations of Montana drainage history do not recognize massive southeast-oriented flood events, such as those described in this Judith River drainage basin overview essay or in the more detailed essays illustrating and describing topographic evidence along Judith River drainage divides. Most of the topographic map evidence illustrated and described in the Judith River drainage basin landform origins essays has never been previously interpreted. While readers familiar with the commonly accepted interpretations of Montana drainage history may want to disagree with the interpretation presented here, I encourage such readers to first take the time to study the evidence. Can commonly accepted interpretations explain how and when the present day valleys were eroded? What is the explanation for the northwest-southeast orientation of many Judith River tributaries? How were the through valleys linking rivers flowing in opposite directions eroded? For example, how was the large Judith Gap valley eroded and why does north-oriented Ross Fork Creek have south-oriented headwaters on the Big Snowy Mountains south flank?  And the list of questions could go on. The  geomorphology research community needs to interpret Montana drainage history in a way that explains obvious evidence seen on published and easily accessed topographic maps.

Introduction to Missouri River drainage basin research project essay series

• This Judith River drainage basin landform origins overview essay and its related detailed essays is one of a series of overview essays and related detailed essays in the Missouri River drainage basin landform origins research project. The research project goal is to use topographic map evidence to describe the evolution of drainage divides separating each significant present day Missouri River tributary valley and also to describe the evolution of drainage divides separating the present day Missouri River drainage basin from adjacent drainage basins. Each overview essay and its related detailed essays pertains to a specific Missouri River tributary, tributary to a present day Missouri River tributary, or a present day Missouri River valley segment. Each detailed essay illustrates and discusses detailed topographic map evidence describing the evolution of a secondary drainage divide separating specified Missouri River tributary valleys.

• The Missouri River drainage basin research project introduces a new regional geomorphology paradigm. An essay titled “About the ‘thick ice sheet that melted fast’ geomorphology paradigm” provides a brief introduction to the new paradigm and how the new paradigm emerged. Detailed evidence illustrated and discussed in the Missouri River drainage basin research project builds a strong case for (1) deep glacial erosion of the North American continent by a thick North American ice sheet that created and occupied a deep “hole”, (2) rapid melting of that thick North American ice sheet, (3) immense floods of south-oriented melt water, (4) headward erosion of deep east, northeast and north-oriented valley systems to capture the south-oriented melt water floods and to divert the melt water further and further northeast into space the ice sheet had once occupied, (5) deep flood water erosion of the North American continent surface, and (6) crustal warping that resulted in uplift of mountain ranges as flood waters were deeply eroding what are now high mountain regions. This interpretation is fundamentally different from most previous interpretations. The Judith River drainage basin landform origins evidence in this overview essay and its related detailed essays is presented for review and discussion by qualified research geomorphologists and geologists.

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.