Prickly Pear Creek-Missouri River drainage divide area landform origins in Jefferson and Broadwater Counties, Montana, USA

Authors


Abstract:

This essay uses topographic map evidence to interpret landform origins in the region between Prickly Pear Creek and the Missouri River in Jefferson and Broadwater Counties, Montana. The Missouri River flows in a north-northwest direction in the study area while Prickly Pear Creek is a west-northwest and north-northeast oriented Missouri River tributary west of the Missouri River, which originates in the Elkhorn Mountains. The Spokane Hills are located on the west side of the Missouri River and are separated from the Elkhorn Mountains by a major north to south oriented through valley linking the Missouri River valley and Prickly Pear Creek valley north of the Spokane Hills with the Missouri River valley south of the Spokane Hills. The north end of the through valley is drained by northeast north oriented Spokane Creek while the through valley south end is crossed by northeast oriented Antelope and Beaver Creeks, with all three creeks originating in the Elkhorn Mountains. Of the three creeks Beaver Creek extends the furthest into the Elkhorn Mountains and is linked by through valleys with north and northwest oriented tributaries to north-northeast oriented Prickly Pear Creek. Northwest oriented Dutchman Creek, which is a Prickly Pear Creek tributary, and the west-northwest oriented Prickly Pear Creek headwaters are linked by through valleys in the Elkhorn Mountains with the southeast oriented Crow Creek valley, with Crow Creek flowing in a southeast direction to join the north-northwest oriented Missouri River as a barbed tributary. The through valleys were eroded by southeast and south oriented floodwaters and were derived from a thick North American ice sheet and were flowing from western Canada across Montana. The thick ice sheet was located in a deep “hole” and the ice sheet weight was causing crustal warping that raised Montana and Wyoming mountain ranges and massive melt water floods carved deep valleys into what were emerging mountain ranges. A major south-southeast oriented flood flow channel on what is today the north-northwest oriented Missouri River segment was reversed in flow direction when headward erosion of the much deeper northeast oriented Missouri River valley north of the study area beheaded the south-southeast oriented flood flow channel. The deep northeast oriented Missouri River valley had eroded headward from space in the deep “hole” being opened up by the ice sheet melting. Headward erosion of the deep north-northeast oriented Prickly Pear Creek valley next beheaded and reversed southeast oriented flood flow channels in what were then the emerging Elkhorn Mountains to erode the northwest and north oriented Prickly Pear Creek tributary valleys. The flood flow reversals were greatly aided by ice sheet related crustal warping that was raising mountain ridges which became topographic barriers.

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

Prickly Pear Creek-Missouri River drainage divide area location map

Figure 1: Prickly Pear Creek-Missouri 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 Prickly Pear Creek-Missouri River drainage divide area in Jefferson and Broadwater Counties, Montana and illustrates a region in central and western Montana. The Missouri River is formed at the confluence of major tributaries near Three Forks (near south center edge of figure 1) and flows in a north and north-northwest direction to Holter Lake and then in a northeast direction to Great Falls and the north edge of figure 1 (east half).  North and east of figure 1 the Missouri River turns to flow in an east direction to North Dakota where it turns to flow in a southeast and south direction with water eventually reaching the Gulf of Mexico. The unnamed north oriented tributary flowing just east of Helena to Lake Helena is Prickly Pear Creek, which has west-northwest oriented headwaters not shown on figure 1. The unnamed southeast oriented stream south of Prickly Pear Creek and flowing to the north-northwest oriented Missouri River (near Toston) as a barbed tributary is Crow Creek. The Prickly Pear Creek-Missouri River drainage divide area investigated in this essay is located east of Prickly Pear Creek, west of the Missouri River and includes the Crow Creek headwaters.

Before focusing on detailed maps of the Prickly Pear Creek-Missouri River drainage divide area a brief look at the big picture erosion history is appropriate. 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 rapidly melting thick North American ice sheet and were flowing in a south and southeast direction from southwest Alberta and southeast British Columbia to and across the figure 1 region. At that time (at least initially) there were no high mountains in western and central Montana and floodwaters could freely flow across locations that are today blocked by high mountain ranges. Mountain ranges in western Canada, Montana, Wyoming, and elsewhere were formed by ice sheet related crustal warping and occurred as massive melt water floods flowed across them. In addition, deep flood water erosion of valleys and basins surrounding the rising mountain masses contributed to the emergence of present day mountain ranges.

In time the ice sheet related crustal warping combined by deep glacial erosion under the ice sheet created a deep “hole” in which the ice sheet was located. Eventually as the ice sheet melted there came a time when elevations on the ice sheet surface (at least in the south) were lower than elevations along the deep “hole” southwest rim where the immense south and southeast oriented ice marginal melt water floods were flowing. Deep northeast oriented valleys then eroded headward from space in the deep “hole” being opened up by the ice sheet melting to capture the south and southeast oriented melt water floods in present day Montana. The northeast oriented Missouri River valley segment seen in figure 1) and its east and northeast oriented tributary valleys eroded headward from space in the deep “hole” being opened up by ice sheet melting across the south and southeast oriented melt water flood flow. Northwest and north oriented Missouri River tributary valleys and the north-northwest oriented Missouri River valley segment seen in figure 1 were eroded by reversals of flood flow on north and northwest ends of beheaded flood flow channels.

Detailed location map for Prickly Pear Creek-Missouri River drainage divide area

Figure 2: Detailed location map Prickly Pear Creek-Missouri 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 Prickly Pear Creek-Missouri River drainage divide area in Jefferson and Broadwater Counties, Montana. County boundaries are shown and Jefferson and Broadwater Counties are labeled. Green shaded areas are National Forest lands, which generally are located in mountainous regions. Helena is the largest city in figure 2 and is located in the northwest quadrant of figure 2 near the south edge of Lewis and Clark County. Canyon Ferry Lake in the east half of figure 2 floods the north-northwest oriented Missouri River valley with the Missouri River flowing in a north-northwest direction from the south edge of figure 2 to the north edge of figure 2. The Spokane Hills, located on the west side of Canyon Ferry Lake, are seen in the topographic maps below. The unlabeled north-northwest oriented stream on the west side of the Spokane Hills and flowing to the Lake Helena outlet is Spokane Creek. South of the Spokane Hills Beaver Creek flows in a northeast direction to Canyon Ferry Lake. Lake Helena is located between East Helena and the north edge of figure 2 and is west of the Missouri River. Prickly Pear Creek originates near Bullock Hill (south and slightly west of the center of figure 2) and flows in a west-northwest direction to near Jefferson City where it turns to flow in a north-northeast direction to East Helena and then in a north direction to Lake Helena. The unlabeled north and north-northwest oriented tributary originating near Lava Mountain and joining Prickly Pear Creek just south of the county line is McClelland Creek, which is seen in the topographic maps below. Crow Creek originates near Bullock Hill and flows in a southeast direction to join the north-northwest oriented Missouri River as a barbed tributary near the south edge of figure 2. South oriented Missouri River tributaries seen on both sides of the Missouri River provide evidence that the valley now used by the north-northwest oriented Missouri River was initiated by south oriented flood flow.

Prickly Pear Creek-Spokane Creek drainage divide area

Figure 3: Prickly Pear Creek-Spokane Creek drainage divide area, Montana. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 provides a topographic map of the Prickly Pear Creek-Spokane Creek drainage divide area. Canyon Ferry Lake is the large lake straddling the east edge of figure 3 and is a large reservoir flooding the north-northwest oriented Missouri River valley upstream from Canyon Ferry Dam. Hauser Lake is located downstream from Canyon Ferry Dam and the Missouri River valley makes a jog to the northeast near the north edge of figure 3 before resuming its northwest orientation. Hauser Dam is located north of figure 3. The Spokane Hills are located on the west side of Canyon Ferry Lake and appear to be a ridge linked to the upland region seen north and east of the Missouri River in the northeast corner of figure 3. Canyon Ferry Dam is located in a deep water gap the Missouri River has eroded across this upland ridge. West of the Spokane Hills is north-northwest oriented Spokane Creek, which flows along the west flank of the Spokane Hills. The forested area in the southwest corner of figure 3 is the edge of the Elkhorn Mountains. Prickly Pear Creek flows in a north, north-northwest, and north direction from the south edge of figure 3 (west half) to East Helena and then to Lake Helena, which north of figure 3 drains to the Missouri River. While not completely seen in figure 3 (but much better seen in figure 4), a large through valley between the Elkhorn Mountains and the Spokane Hills links the Missouri River valley north of Spokane Hills with the Missouri River valley south of the Spokane Hills. The through valley and the Missouri River valley were eroded as diverging and converging south oriented flood flow channels prior to the flood flow reversal that created the present day north oriented Missouri River drainage system seen in figure 3. The flood flow reversal occurred when headward erosion of the much deeper northeast oriented Missouri River (north of figure 3) from space in the deep “hole” the melting ice sheet was opening up beheaded large south oriented flood flow channels. Floodwaters on north ends of the beheaded flood flow channels reversed flow direction to erode north oriented valleys. Headward erosion of these much deeper north oriented valleys captured south and southeast oriented floodwaters moving in flood flow channels west of figure 3. The newly reversed and much deeper north oriented Missouri River valley was especially successful in capturing yet to be beheaded flood flow moving west of figure 3 and developed a significant tributary system south and west of figure 3. The north oriented Spokane Creek valley was eroded by a reversal of flood flow on the north end of a beheaded south oriented flood flow channel. The north and north-northwest oriented Prickly Pear Creek valley segments were also eroded by reversals of flood flow, although as seen in the topographic maps below the Prickly Pear Creek history is somewhat more complex.

Spokane Creek-Antelope Creek drainage divide area

Figure 4: Detailed map of Spokane Creek-Antelope Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 provides a topographic map of the Spokane Creek-Antelope Creek drainage divide area south and east of figure 3 and includes overlap areas with figure 3. Canyon Ferry Lake floods the north-northwest oriented Missouri River valley in the east half of figure 4. The Spokane Hills are the upland area just west of Canyon Ferry Lake. The northeast flank of the Elkhorn Mountains is the upland area in the southwest quadrant of figure 4. Spokane Creek flows in a northeast direction from the south edge of figure 4 (west of center and from the Elkhorn Mountains northeast flank)) to the Spokane Hills southwest flank and then flows in a north-northwest direction along the Spokane Hills west flank to the north edge of figure 4 (west of center). Antelope Creek flows in a northeast direction just east of the northeast oriented Spokane Creek segment and then turns to flow in an east direction to join northeast and east oriented Beaver Creek, which flows to Canyon Ferry Lake. Beaver Creek flows in a northeast direction from the south edge of figure 4 (near highway) and after being joined by Antelope Creek turns to flow in an east-northeast direction to join the north-northwest oriented Missouri River. Note the large through valley linking the north oriented Spokane Creek valley with the east oriented Antelope and Beaver Creek valley. The map contour interval is 50 meters and the through valley floor elevation at the drainage divide is between 1300 and 1350 meters. The high point near the south end of the Spokane Hills is shown as being 1831 meters. Elevations greater than 2000 meters can be found in the Elkhorn Mountains to the southwest suggesting the through valley is approximately 500 meters deep. While the through valley may be related to geologic structures it is also a water-eroded valley and was eroded as a south oriented flood flow channel, which was one of multiple diverging and converging flood flow channels carved into the regional landscape. Floodwaters were flowing in south and southeast directions along and near the present day north-northwest oriented Missouri River alignment and then further south along alignments of what are today north oriented Missouri River tributaries (e.g. Gallatin River, Madison River). Headward erosion of the much deeper northeast oriented Missouri River valley and tributary valleys (north of figure 4) beheaded the south oriented flood flow channels, which caused massive flood flow reversals that created the north oriented Missouri River drainage system upstream from figure 4 and which created the Spokane Creek-Antelope Creek drainage divide seen today.

Antelope Creek-Missouri River drainage divide area

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

Figure 5 illustrates the Antelope Creek-Missouri River drainage divide area south and east of figure 4 and includes an overlap area with figure 4. Canyon Ferry Lake floods the north-northwest oriented Missouri River valley along the east edge of figure 5. The Elkhorn Mountains are the forested upland in the west half of figure 5. Spokane Creek originates in Montgomery Park (in northwest quadrant of figure 5) and flows in a northeast direction to the north edge of figure 5 (west half). Antelope Creek originates a short distance south and east of the Spokane Creek headwaters and flows in a northeast direction (adjacent to and parallel to Spokane Creek) almost to the north center edge of figure 5 and then turns to flow in an east direction to join Beaver Creek, which then flows in an east-northeast direction to Canyon Ferry Lake. Beaver Creek originates in the southwest quadrant of figure 5 and flows in a northeast direction to near the north edge of figure 5 where it is joined by Antelope Creek and then flows in an east-northeast direction. Note the northwest to southeast oriented through valley near the town of Winston linking the northeast oriented Beaver Creek valley with the north-northwest oriented Missouri River valley. The through valley was eroded by southeast oriented flood flow moving to what at that time was a south-southeast flood flow channel on the present day Missouri River alignment. The northeast oriented Beaver Creek valley eroded headward into what at that time was probably a rising Elkhorn Mountains mass to capture southeast oriented flood flow moving across the rising mountain mass. Note southeast-oriented Beaver Creek tributaries in the region of High Peak, Casey Peak, Sheep Park, and Horsethief Park and how those southeast oriented tributary valleys are linked by shallow through valleys with northwest oriented valleys draining to west edge of figure 5.  Streams in the northwest oriented valleys flow to north and northwest oriented McClelland Creek, which flows to Prickly Pear Creek. In other words, the southeast oriented flood flow was not restricted to the Spokane Creek-Antelope Creek through valley seen in figure 4, but also moved across the Elkhorn Mountains. At least initially the elevation differences seen in figure 5 today did not exist and the Elkhorn Mountains emerged as floodwaters deeply eroded the surrounding valleys and as crustal warping raised the mountain masses. South oriented flood flow in what is today the north-northwest oriented Missouri River valley was reversed when headward erosion of the much deeper northeast oriented Missouri River (north of figure 5) from space in the deep “hole” being opened up by ice sheet melting beheaded the south-southeast oriented flood flow channel. However, crustal warping of regions south of figure 5 probably also contributed to the massive flood flow reversal that created the north oriented Missouri River drainage system upstream from figure 5.

Detailed map of Beaver Creek-Missouri River drainage divide area

Figure 6: Detailed map of Beaver Creek-Missouri 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 Beaver Creek-Missouri River drainage divide area seen in less detail in figure 5. Canyon Ferry Lake is located along the east edge of figure 6. Beaver Creek flows in a north-northeast direction across the northwest corner of figure 6. A segment of the northeast flank of the Elkhorn Mountains can be seen in the southwest quadrant of figure 6. Note the well-defined northwest to southeast oriented through valley linking the north-northeast oriented Beaver Creek valley with the north oriented Missouri River valley. The map contour interval for figure 6 is 40 feet and the through valley elevation at the drainage divide just south of Winston is between 4360 and 4400 feet. The unnamed hill in the southeast corner of section 6 rises to more than 4600 feet while the Elkhorn Mountains to the southwest rise much higher. The through valley is at least 200 feet deep and provides evidence of southeast oriented flood flow, which once moved across the region. At that time the shallow north-northeast oriented Beaver Creek valley west of Winston did not exist and floodwaters moved in a southeast direction from the Spokane Creek-Antelope Creek through valley seen in figures 3 and 4. The floodwaters at that time were moving to the south oriented flood flow channel on the present day north oriented Missouri River alignment. The reversal of flood flow that created the north oriented Missouri River drainage system and the north-northeast oriented Beaver Creek drainage route across the northwest to southeast oriented through valley probably occurred shortly after the through valley seen in figure 6 was eroded. The shallow north-northeast oriented Beaver Creek valley west of Winston suggests the Beaver Creek valley has not been significantly eroded since the flood flow reversal occurred.

Prickly Pear Creek-Beaver Creek drainage divide area

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

Figure 7 illustrates the Prickly Pear Creek-Beaver Creek drainage divide area west of figure 5 and includes an overlap area with figure 5. The mountains seen in figure 7 are the Elkhorn Mountains. Prickly Pear Creek flows in a northwest direction across the southwest corner of figure 7 and then in a north-northeast direction from the west edge of figure 7 (near Jefferson City) to Alhambra and Clancy and finally to the north edge of figure 7 (west half). Note the northwest oriented Prickly Pear Creek tributaries from the east. McClelland Creek originates near the center of figure 7 between Lava Mountain and High Peak and flows in a north and northwest direction to the north edge of figure 7 (east of Shingle Butte) and joins Prickly Pear Creek north of figure 7. The northwest and north oriented Prickly Pear Creek tributary valleys were eroded by reversals of south and southeast oriented flood flow channels, which were beheaded by headward erosion of the much deeper north-northeast oriented Prickly Pear Creek valley. Evidence for the higher level south and southeast oriented flood flow channels can be found in the numerous through valleys linking the north and northwest oriented Prickly Pear Creek tributary valleys with stream valleys further to the east. For example, northwest oriented Strawberry Creek in the northwest quadrant of figure 7 is linked by a through valley between Strawberry Butte and Burnt Mountain with the north oriented Maupin Creek valley, which drains to northwest oriented McClelland Creek near the north center edge of figure 7. As the deep north-northeast oriented Prickly Pear Creek valley eroded headward it first beheaded and reversed flood flow on the McClelland Creek alignment. The reversed flood flow on the McClelland Creek alignment then captured southeast oriented flood flow from south of the actively eroding Prickly Pear Creek valley head. That captured flood flow eroded the through valley between Strawberry Butte and Burnt Mountain and helped erode the Maupin Creek valley north end as the water moved to the northwest oriented McClelland Creek valley. Captured southeast oriented flood flow from a flood flow channel on the present day Warm Springs Creek alignment eroded the Maupin Creek valley south end and what is today the valley used by southwest oriented North Fork Warm Springs Creek between Burnt Mountain and Lava Mountain. Prior to being captured by the McClelland Creek flood flow reversal southeast oriented flood flow on the Strawberry Creek alignment had been flowing to the Beaver Creek headwaters using the previously described through valley between High Peak and Casey Peak. In other words the through valleys and the present day valleys can be used to reconstruct a logical sequence of flood flow erosion and capture events that carved the figure 7 landscape features.

Detailed map of McClelland Creek-Beaver Creek drainage divide area

Figure 8: Detailed map of McClelland Creek-Beaver 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 McClelland Creek-Beaver Creek drainage divide area seen in less detail in figure 7. McClelland Creek originates in section 29 near the south edge of figure 8 (west half) and flows in a north direction to the north edge of figure 8. Tepee Creek is a northwest oriented McClelland Creek tributary originating in section 27. East Fork McClelland Creek originates in the north center area of figure 8 and flows in north and northwest direction to the north edge of figure 8 and joins McClelland Creek north of figure 8. Beaver Creek originates in section 26 and flows in an east-northeast and east direction to the east edge of figure 8 (south of center). High Peak is located in section 34 and Casey Peak is located in section 23. Note the northwest to southeast oriented through valley between High Peak and Casey Peak linking the northwest oriented Tepee Creek valley with a southeast oriented Beaver Creek tributary valley. The map contour interval is 40 feet and the through valley floor elevation at the drainage divide is between 7880 and 7920 feet. Casey Peak reaches an elevation of 8512 feet and High Point reaches an elevation greater than 8520 feet suggesting the through valley may be more than 600 feet deep. The through valley is a water eroded feature and was eroded by southeast oriented flood water at a time when the deep McClelland Creek did not exist and when the deep Prickly Pear Creek valley further to the northwest did not exist. At that time floodwaters were flowing on a surface equivalent in elevation to the tops of High Peak and Casey Peak, although the Elkhorn Mountains may have been uplifted since. A similar northwest to southeast oriented through valley north and east of Casey Peak in section 24 links the northwest oriented East Fork McClelland Creek valley with the valley of a south-southeast oriented Beaver Creek tributary. This second through valley has an elevation at the drainage divide of between 7600 and 7640 feet, more than 200 lower than the first through valley. This second through valley probably carried more flood flow than the first through valley, but also provides evidence of multiple southeast oriented flood flow channels. A look at the McClelland Creek-Beaver Creek drainage divide in figure 8 reveals at least three other through valleys suggesting that one time five or more southeast oriented flood flow channels crossed the figure 9 map area. Floodwaters were initially flowing to a south oriented flood flow channel on what is now the deep north oriented Missouri River alignment and then continued to flow in a south direction on the alignments of what are today north oriented Missouri River tributaries, although the northeast oriented Beaver Creek route east of figure 8 suggests the flood flow reversal that created the north oriented Missouri River drainage basin in southwest Montana and northwest Wyoming occurred as floodwaters were flowing across the McClelland Creek-Beaver Creek drainage divide.

Prickly Pear Creek-Crow Creek drainage divide area

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

Figure 9 illustrates the Prickly Pear Creek-Crow Creek drainage divide area south and slightly west of figure 7 and includes an overlap area with figure 7. High Peak is located in the northeast quadrant of figure 9 and northeast oriented drainage routes in the northeast corner of figure 9 are headwaters of Beaver Creek. The north oriented stream west of High Peak is the headwaters of McClelland Creek. Bullock Hill is located near the center of figure 9 and Prickly Pear Creek originates just south of Bullock Hill. From the Bullock Hill area Prickly Pear Creek flows in a west-northwest direction to near Jefferson City where it joins north-northeast oriented Beavertown Creek and then flows in a north-northeast direction to Jefferson City and the north edge of figure 9 (west half).  Dutchman Creek is a northwest oriented tributary joining Prickly Pear Creek near the north edge of figure 9. North of Bullock Hill is Wilson Creek, which originates as a northeast oriented stream, but which then turns to flow in a southeast direction to join northeast oriented Tizer Creek and to form southeast oriented Crow Creek. Remember from figures 1 and 2 that Crow Creek flows in a southeast direction to join the north-northwest oriented Missouri River as a barbed tributary. Note the northwest to southeast oriented through valley between Bullock Hill and Elk Park linking the northwest oriented Dutchman Creek valley with the southeast oriented Wilson Creek and Crow Creek valleys. The map contour interval for figure 9 is 50 meters and the through valley floor elevation at the drainage divide is between 2200 and 2250 meters. High Peak to the north rises to 2601 meters and Elkhorn Peak to the south of Bullock Hill rises to more than 2800 meters suggesting the through valley north of Bullock Hill may be as much as 350 meters deep. Between Bullock Hill and Elkhorn Peak is an equally deep through valley linking the west-northwest oriented Prickly Pear Creek valley with northeast and east oriented Tizer Creek valley and the southeast oriented Crow Creek valley. Bullock Hill between these two through valleys rises to more than 2400 meters and is an erosional residual between what were once diverging and converging southeast oriented flood flow channels in what was a major southeast oriented anastomosing channel complex. Floodwaters were flowing to a major south-southeast oriented flood flow channel on the present day north-northwest oriented Missouri River alignment. At that time the deep north-northeast oriented Prickly Pear Creek valley did not exist and the Elkhorn Mountains had not yet emerged as a major topographic barrier so the southeast oriented floodwaters could freely flow across the region seen in figure 9.

Detailed map of Prickly Pear Creek-Tizer Creek drainage divide area

Figure 10: Detailed map of Prickly Pear Creek-Tizer 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 Prickly Pear Creek-Tizer Creek drainage divide area seen in less detail in figure 9. Bullock Hill is located in the northwest corner of section 20 near the center of figure 10. Prickly Pear Creek originates south of Bullock Hill and flows in a west-northwest direction to the west edge of figure 10 (north of center). Wilson Creek originates in section 18 west of Bullock Hill and flows in a north and northeast direction before turning to flow in an east-southeast and southeast direction to join northeast oriented Tizer Creek near the east edge of figure 10 (north of center). Tizer Creek flows from the south center edge of figure 10 in a northeast and north direction to the southwest corner of section 21 where it turns to flow in an east-northeast and then southeast direction before joining northeast oriented Little Tizer Creek and then flowing in a northeast direction to join Wilson Creek and to form southeast oriented Crow Creek. Note the through valley in section 20 just south of Bullock Hill linking the west-northwest oriented Prickly Pear Creek valley with the east-northeast, southeast, and northeast oriented Tizer Creek valley and the southeast oriented Crow Creek valley. The map contour interval for figure 10 is 40 feet and the through valley floor elevation at the drainage divide is between 7280 and 7320 feet. Bullock Hill rises to 7928 feet or at least 500 feet above the through valley floor. Elkhorn Peak south of figure 10 rises to at least 9360 feet. High Peak north of figure 10 rises to more than 8520 feet. In other words the through valley is at least 500 feet deep and could be at least 1200 feet deep or even more. The through valley was eroded by southeast oriented flood flow moving to the actively eroding Crow Creek valley. The southeast oriented flood flow was moving along what is now the west-northwest oriented Prickly Pear Creek alignment and then to the actively eroding Tizer Creek valley. At the same flood flow was moving in a southeast direction along what is now the northwest oriented Dutchman Creek valley (north and west of figure 10) to the east-southeast oriented Wilson Creek valley and then to the actively eroding Crow Creek valley. Numerous other through valleys cross other drainage divides in figure 10 and provide evidence of diverging and converging flood flow channels that once moved floodwaters across the region shown by figure 10. Headward erosion of the much deeper north-northeast Prickly Pear Creek valley and its tributary north-northeast oriented Beavertown Creek valley beheaded and reversed the southeast oriented flood flow to erode the west-northwest oriented Prickly Pear Creek valley and the northwest oriented Prickly Pear Creek tributary valleys.

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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