A collection of detailed research data based on topographic map evidence
The Missouri River drainage basin landform origins research project introduces a fundamentally new and different geomorphology paradigm by interpreting previously unexplained topographic map evidence to determine origins for all major Missouri River drainage basin drainage divides. Detailed essays illustrating and describing interpreted topographic map evidence for most or all Missouri River drainage basin drainage divides in North and South Dakota, Iowa, Minnesota, Nebraska, Kansas, eastern and central Montana, northeast Wyoming have been written and can be found on this website. Essays illustrating and describing other Missouri River drainage basin drainage divide areas are added as the essays are completed. The Missouri River drainage basin is one of North America’s largest drainage basins and encompasses significant areas in the states of Montana, North Dakota, South Dakota, Wyoming, Colorado, Nebraska, Iowa, Kansas, and Missouri and smaller areas in Minnesota and the Canadian provinces of Alberta and Saskatchewan. The Missouri River drainage basin is bounded on the west by the east-west continental divide and on the north by the north-south continental divide. The Missouri River drains to the south-oriented Mississippi River, which flows to the Gulf of Mexico. This overview essay contrasts the new geomorphology paradigm with the existing geomorphology paradigm by describing how the new geomorphology paradigm uses topographic map evidence to explain the east-west continental divide origin. The east-west continental divide is interpreted to have been the approximate location of an immense southeast and south-oriented melt water river flowing from a rapidly melting thick North American ice sheet. This immense melt water river was dismembered from south to north as deep valleys eroded headward into the region from the east and west and later from the deep “hole” the thick ice sheet had occupied. At the same time regional uplift, including uplift of Rocky Mountain ranges, aided the dismemberment process, which also included massive flood flow reversals. The new geomorphology paradigm explains vast quantities of previously unexplained topographic map evidence and the Missouri River drainage basin landform origins research project is intended to be a demonstration to support that claim.
Missouri River drainage basin location map
Figure 1: Missouri River drainage basin location map (select and click on map to enlarge). National Geographic Society map digitally presented using National Geographic Society TOPO software.
This essay provides an overview of the Missouri River drainage basin landform origins research project, which is a project to use topographic map evidence to describe the origin of all Missouri River drainage divides. The project method is to systematically study drainage divides surrounding each major Missouri River tributary (or tributary to a major Missouri River tributary). Study results are presented in detailed essays illustrating and describing topographic map evidence used in interpreting the drainage divide origins. Detailed essay titles identify drainage divides being illustrated and described. Detailed essays for each of the major Missouri River tributaries (and tributaries of some major Missouri River tributaries) can be found under those tributary names on this website’s sidebar category list. The project began in August of 2009 and probably will not be completed until sometime in 2013. All completed essays are published on this website and new essays are added as those essays are completed.
- The Missouri River drainage basin is one of North America’s largest drainage basins and today drains to the south-oriented Mississippi River near St. Louis, Missouri. The Missouri River drains significant areas in the states of Missouri, Kansas, Nebraska, South Dakota, North Dakota, Montana, Wyoming, northeast Colorado, and western and southern Iowa, and also drains smaller areas in southwest Minnesota, southern Alberta, and southwest Saskatchewan. The Missouri River drainage basin western boundary in Montana, Wyoming, and Colorado is the east-west continental divide. The Missouri River drainage basin northern boundary in Alberta, Saskatchewan, and North Dakota is the north-south continental divide. South of the Missouri River drainage basin in Colorado and Kansas is the southeast-oriented Arkansas River drainage basin, with the Arkansas River eventually flowing across the state of Arkansas to reach the Mississippi River. South of the Missouri River drainage basin in Missouri is the southeast-oriented White River drainage basin, with the White River also flowing across the state of Arkansas to reach the Mississippi River. East of the Missouri River drainage basin in North Dakota is the north-oriented Red River drainage basin, which drains to Hudson Bay. East of the Missouri River drainage basin in northeast South Dakota, southwest Minnesota, Iowa, and northeast Missouri is the Mississippi River drainage basin, with the Mississippi River flowing to the Gulf of Mexico.
- Topographic maps, while not regarded as “high-tech” tools favored by many modern scientific researchers, provide an excellent source of information for determining erosional landform origins. Detailed topographic maps of most Missouri River drainage basin areas have been available for more than fifty years. Yet, remarkably during the past 50 years research geomorphologists have never undertaken a systematic study of the available Missouri River drainage basin topographic maps to determine Missouri River drainage basin erosional landform origins. One reason geomorphologists have ignored Missouri River erosional landform origins is topographic map evidence cannot be explained in the context of the geologic history constructed by geologists who work with different types of evidence. In other words, Missouri River drainage basin history as determined from topographic map evidence is fundamentally different from the Missouri River drainage basin history geologists would like the geomorphology research community to describe. And, because the topographic map evidence does not support the Missouri River drainage basin history geomorphologists are supposed to describe, the geomorphology research community has avoided a conflict by simply ignoring the topographic map evidence and pretending the erosional landform evidence does not exist.
- Drainage divides, whether in the Missouri River drainage basin or elsewhere, represent some of the most commonly neglected landform types and are almost completely ignored in the geology and geomorphology research literature. The east-west continental divide is a well-known topographic feature, yet a study of the scientific literature suggests the geology and geomorphology research communities do not know when, why, and/or how the east-west continental divide was formed, and even more remarkable the geology and geomorphology research communities appear to have little or no interest in discovering how, why, and when the east-west continental divide was formed. This same lack of knowledge and interest applies to the origin of almost all drainage divides within the Missouri River drainage basin with the exception of the north-south continental divide origin. A commonly accepted origin published for the north-south continental divide north of the Missouri River drainage basin is pre-glacial northeast and north-oriented drainage routes were blocked by a continental ice sheet margin and water from these blocked drainage routes spilled along the ice sheet’s margin to erode the present day Missouri River valley. Advocates of this hypothesis have even published maps illustrating routes the pre-glacial north- and northeast-oriented rivers used prior to glaciation.
- These pre-glacial river valleys, which are traced across the Montana, South Dakota, North Dakota, Alberta, Saskatchewan, and Manitoba plains, are components of the framework of ideas defining what is the commonly accepted geomorphology (and geology) paradigm. Existence of these north and northeast-oriented pre-glacial river valleys implies whatever continental ice sheets covered the region were thin and did not deeply erode the underlying surface, which in much of the northern plains region is easily eroded material. Treating the Missouri River valley as an ice marginal valley eroded by water from blocked north and northeast-oriented drainage routes spilling in a southeast direction along a continental ice sheet’s southwest margin also implies ice sheet melt water did not significantly alter regions south and west of the Missouri River valley. Many of these so-called pre-glacial valleys originate along the present day east-west continental divide, which suggests the east-west continental divide was formed long before continental glaciation. Yet the paradigm in which these pre-glacial north and northeast-oriented valleys exist, is unable to provide a satisfactory explanation as to how, why, and/or when the pre-glacial north and northeast-oriented valleys were eroded, much less a satisfactory explanation as to how, when, and/or why the east-west continental divide was formed.
- A paradigm is a framework of ideas upon which future researchers build new ideas as they flesh out the paradigm. Paradigms by themselves are neither correct or incorrect. Science researchers, who must build paradigms according to definite rules (see table 1 below), find some paradigms highly productive while other paradigms lead to dead ends. The paradigm in which the north and northeast-oriented pre-glacial valleys exist has led geomorphology researchers to repeated dead ends. Not only are geomorphology researchers unable to explain how, why, and/or when the east-west continental divide was formed, they are unable to explain how, why, or when almost all drainage divides were formed. In fact the list of unexplained landforms is almost endless and includes erosional escarpments, water gaps, wind gaps, mountain passes, elbows of capture, aligned drainage routes, barbed tributaries, escarpment-surrounded uplands, escarpment-surrounded basins, and much more. Further, researchers are defying common sense logic when they suggest one or more continental ice sheets covered the northern plains and did not destroy all evidence of whatever pre-glacial valleys existed in the easily eroded underlying bedrock materials. In addition, researchers are defying common sense logic when they imply all continental ice sheet melt water from north of the Missouri River drainage basin flowed south in the present day Missouri River valley. The existing geomorphology (and geology) paradigm is leading geomorphology researchers to dead ends and a new and better geomorphology paradigm is needed.
|1. Scientific research must be based on observable evidence that actually exists.|
|2. Scientific research must be based on a representative sample of all observable evidence.
|3. Scientific research must be based on common sense logic.|
|4. Scientific research must be consistent in its methods and explanations.|
|5. Scientific research almost always prefers the simplest explanations.|
|6. Scientific research must stand the test of time and is always subject to future revision.|
Table 1: Rules science researchers must follow when conducting their research projects.
- Saying a better geomorphology paradigm is needed is easy, developing a better geomorphology paradigm according to the rules of science is much more challenging. While the existing geomorphology (and geology) paradigm is unproductive in terms of determining erosional landform origins, researchers have used the paradigm to construct significant frameworks of ideas related to other types of geology and geomorphology evidence. Any fundamentally new geomorphology paradigm is going to challenge those existing and well established ideas and is not going to be automatically accepted. In fact any fundamentally new geomorphology paradigm to even be seriously considered will have to demonstrate its ability to explain vast quantities of previously unexplainable geomorphology evidence. The Missouri River drainage basin landform origins research project is such a demonstration. The project is introducing a fundamentally different and new geomorphology paradigm to the geomorphology research community by systematically going around the Missouri River drainage basin and interpreting the origins of large numbers of previously unexplainable landform features. Geomorphology research community reviewers not only need to check to make sure the rules of science have been followed, but also need to evaluate the new paradigm by comparing it with the existing paradigm in terms of each paradigm’s abilities to explain unexplained evidence.
The Missouri River drainage basin landform origins research project paradigm
- The new geomorphology paradigm being introduced by the Missouri River drainage basin landform origins research project is here named the “thick ice sheet that melted fast” paradigm. The paradigm name identifies two major differences from the existing paradigm, specifically the new paradigm requires one thick ice sheet, not multiple thin ice sheets as the existing paradigm implies. Further the new paradigm requires rapid ice sheet melting and immense melt water floods, while the existing paradigm implies much more gradual ice sheet melting with much smaller melt water floods. However, there are many other important differences. Among those differences are the following:
- 1. The new paradigm requires the thick ice sheet to have been located in a deep “hole” created by deep glacial erosion (under the thick ice sheet) and by crustal warping caused by the thick ice sheet’s great weight. The existing paradigm implies little or no glacial erosion occurred in the northern plains region and suggests much more limited crustal warping.
- 2. The new paradigm requires the topographic surface upon which the thick ice sheet was originally formed to have been completely destroyed by deep glacial erosion and by deep flood water erosion of regions elsewhere on the North American continent surface. The existing paradigm assumes the pre-glacial topographic surface has been largely preserved south and west of the ice sheet margins and was not significantly altered under the continental sheets (at least in the northern plains region).
- 3. The new paradigm requires the thick North American ice sheet to have triggered crustal warping that raised mountain ranges and high plateau areas while massive melt water floods flowed across them. The existing paradigm requires mountain ranges and high plateau areas to have been uplifted prior to glaciation, making it impossible for melt water floods, no matter how massive, to flow across them.
- 4. The new paradigm requires a single thick ice sheet with one or more ensuing thin ice sheet(s) to explain all topographic map evidence. The existing paradigm, which was constructed from other types of evidence, suggests there were multiple ice sheets, although there is no consensus regarding the number of ice sheets other the requirement that none of the ice sheet’s deeply eroded the northern plains region, nor is the existing paradigm able to explain much of the erosional landform evidence.
- 5. Many additional differences exist and perhaps can best be summarized by saying the new paradigm requires the North American continent surface to have been radically altered by the thick ice sheet’s presence whether by deep glacial erosion, crustal warping triggered by the ice sheet’s tremendous weight, deep melt water flood erosion which eroded most of North America’s present day valleys, or crustal warping triggered by deep melt water flood erosion and the deposition of flood transported sediments. The existing paradigm requires the North American continent surface, prior to whatever Cenozoic ice sheets existed, to have looked very similar to the continent surface seen today.
- 6. While this Missouri River drainage basin landform origins research project is based completely on topographic map evidence and sedimentary deposits are not mentioned or discussed, the new paradigm also requires some or all Middle Cenozoic sedimentary deposits to have been deposited by massive melt water floods. The existing paradigm requires those Middle Cenozoic sediments to have been deposited over a period of thirty or more million years, with most of those sediments being deposited long before any large North American ice sheet(s) existed.
- Differences between the new paradigm and the existing paradigm are significant and the new paradigm challenges many well established geology and geomorphology ideas. The existing geology and geomorphology paradigm has been fleshed out by thousands of researchers over a period of many decades. The “thick ice sheet that melted fast” paradigm to date has been developed by a single researcher, who has worked on the problem for approximately thirty years. The Missouri River drainage basin landform origins research project essays demonstrate how the new paradigm can explain vast quantities of previously unexplainable topographic map evidence. However, like any new paradigm being introduced for the first time, the explanations are not perfect and can probably be significantly improved. Further, this demonstration of how the new paradigm explains topographic map evidence is only a beginning. Much more evidence needs to be explained, and as that additional evidence is explained the new paradigm will be further fleshed out.
East-West Continental Divide origin
- Perhaps the best way to illustrate differences between the new paradigm and the existing paradigm is to describe how the new paradigm explains the east-west continental divide origin in Montana, Wyoming, and Colorado. Today the Montana, Wyoming, and Colorado east-west continental divide is often located along the crests of high Rocky Mountain ranges, although there are places where the continental divide crosses deep mountain passes and other places where the continental divide crosses high intermontane basin areas. As already noted the existing geology (and geomorphology) paradigm implies the Rocky Mountains existed prior to any large Cenozoic ice sheets (in North America at least), which implies the continental divide and major drainage basins, both east and west of the continental divide, had already been formed before ice sheets covered large regions of northern North America. While correlations between Rocky Mountain alpine glaciation and continental glaciation are debated, the existing paradigm implies the two glaciations are in some way related and occurred at about the same time. Further, Rocky Mountain alpine glaciation is often cited as a major erosion agent responsible for carving deep valleys eroded into resistant Rocky Mountain bedrock while advocates of the same paradigm suggest continental ice sheets daintily tip-toed across pre-glacial valleys located in easily eroded northern plains bedrock. Finally there is no agreement as to when, how, or why the Rocky Mountains were uplifted or as to how, why, or when the east-west continental divide was formed.
- The “thick ice sheet that melted fast” geomorphology paradigm on the other hand requires a North American ice sheet which was several kilometers thick and which was located in a deep “hole”. This thick ice sheet was comparable in size, if not larger, to the modern-day Antarctic Ice Sheet and had been formed on a topographic surface which no longer exists, although there is excellent evidence massive melt water floods flowed across what are now high level Rocky Mountain erosion surfaces. In other words, the Rocky Mountains did not stand high above the topographic surface on which the thick ice sheet was formed. Through a combination of deep glacial erosion and crustal warping the ice sheet created a deep “hole” in which the ice sheet was located. The crustal warping included down warping (under the ice sheet) and uplift of mountain ranges and high plateau areas located beyond the ice sheet margins. Crustal warping was not instantaneous and immense melt water floods flowed from the thick ice sheet in whatever directions the topography at that time permitted, although crustal warping raised continent margins, forcing most melt water to flow in south directions. While melt water floods flowed along many routes one of the major south and southeast oriented flood flow routes roughly followed the present day east-west continental divide location. At that time there were no Rocky Mountains and immense south and southeast oriented melt water floods flowed along this route, which is named here the “Great Divide River”. The “Great Divide River” was only one of many south-oriented flood flow routes and more accurately was probably a complex of anastomosing southeast and south-oriented flood flow channels extending across what is now the entire Rocky Mountain region. How far south the “Great Divide River” melt water floods reached has yet to be determined, although the Rio Grande River valley in Texas, New Mexico, and Colorado probably was eroded headward along “Great Divide River” flood flow routes.
Great Divide River dismemberment from the east and west
- The “Great Divide River” was dismembered as headward erosion of deep valleys from both east and west captured the southeast and south oriented flood water. Also aiding in the dismemberment process was uplift of the Rocky Mountain region and adjacent high plateau areas. “Great Divide River” dismemberment began in the south and progressed northward. While outside the Missouri River drainage basin, and not addressed by Missouri River drainage basin landform origins research project essays, topographic map evidence demonstrates the Rio Grande River valley and its major tributary valleys (e.g. Pecos River valley) eroded headward across and along south and southeast-oriented “Great Divide River” flood flow routes. At the same time southeast-oriented Texas river valleys (such as the Colorado and Brazos River valleys) eroded headward from the Gulf of Mexico across and along south-oriented melt water flood flow routes east of the “Great Divide River” route. Headward erosion of the Mississippi River-Red River valley next captured south-oriented melt water flood flow east of the “Great Divide River” routes. Next the Mississippi River-Arkansas River-Canadian River valley eroded headward across south-oriented flood flow to capture large volumes of south-oriented flood flow from the “Great Divide River” eastern edge. South-oriented flood flow to the actively eroding Canadian River valley was subsequently beheaded by Arkansas River valley headward erosion, which also beheaded eastern flood flow routes to the actively eroding Rio Grande River valley.
- At about the same time headward erosion of the southwest-oriented Colorado River valley and its tributary valleys (from the Gulf of California) was beheading western “Great Divide River” flood flow routes to the actively eroding south and southeast-oriented Rio Grande River valley. Also, as the deep southeast-oriented Arkansas River and southwest-oriented Colorado River valleys were eroding headward into the Rocky Mountain region, the Missouri River-Kansas River (Smoky Hill River and Republican River) valleys and later the South Platte River valley eroded headward into the region to behead south oriented “Great Divide River” flood flow routes to the actively eroding Arkansas River valley. Colorado River valley headward erosion next beheaded south oriented flood flow routes to the actively eroding South Platte River valley. As these river valleys were eroding headward into the present day Rocky Mountain region to capture the massive south oriented “Great Divide River” melt water flood flow, the entire region was being uplifted and the Rocky Mountains began to emerge. Dismemberment of the “Great Divide River” from the east continued with headward erosion of the southeast-oriented North Platte River valley into central Wyoming. Headward erosion of this deep valley beheaded south- and southeast-oriented flood flow routes moving flood waters to the newly eroded Colorado River valley. Flood waters on the north and northwest end of one major flood flow route reversed flow direction to create the northwest and north-oriented North Platte River headwaters valley. Rocky Mountain uplift aided this massive flood flow reversal. West of the newly formed northwest and southeast-oriented North Platte River drainage route the massive south-oriented “Great Divide River” flood flow continued to move across the Great Divide Basin to actively eroding south-oriented Colorado River tributary valleys.
Great Divide River dismemberment from the ice sheet created deep “hole”
- North of the newly eroded southeast-oriented North Platte River valley headward erosion of deep east and northeast oriented valleys from the deep “hole” the decaying ice sheet had been located in was capturing south and southeast-oriented flood flow moving to the newly eroded North Platte River valley. Initially these deep east and northeast oriented valleys eroded headward from giant south-oriented ice-walled and ice-floored (later bedrock-floored) canyons carved into the rapidly melting North American ice sheet. The northeast and east-facing Missouri Escarpment is what remains of the one of these giant canyon’s southwest and west wall. Similar escarpments found throughout the northern plains region provide further evidence of these ice-walled and bedrock-floored canyons, which sliced the decaying ice sheet up into many smaller ice sheets and ice masses. The south-southeast oriented Missouri River valley along the present day Nebraska-Iowa border was eroded headward along the south-oriented flood flow emerging from the mouths of giant ice-walled canyons located at that time in southeast South Dakota. Due to Missouri River valley headward erosion the floor of the giant ice-walled canyon located east and northeast of the Missouri Escarpment (named here the “Midcontinent Trench”) was lower in elevation than the non glaciated surface along the ice sheet’s southwest margin. Southeast-oriented ice marginal floods then breached the detached ice sheet margin and flowed onto the ice-walled canyon floor. These breaches enabled deep east-oriented valleys to erode headward across the southeast-oriented ice-marginal floods and divert the flood water in an east direction to the much deeper ice-walled canyon floor. A deep east-oriented White River valley eroded headward from such a breach. Today that deep east-oriented White River valley’s south wall is the north-oriented Pine Ridge Escarpment and the valley’s north wall was removed by flood flow erosion and no longer exists.
- The giant ice-walled and bedrock-floored canyons being carved into the decaying ice sheet’s surface not only chopped the ice sheet up into a series of smaller ice sheets, but also opened up new and shorter melt water flood flow routes to adjacent ocean basins. The giant southeast and south-oriented melt water river flowing on the “Midcontinent Trench” floor (named here the “Midcontinent River”) was systematically captured and dismembered as new and steeper gradient flood flow routes opened up. First the “Midcontinent River” was captured in southeast North Dakota and diverted north and east to the Gulf of Saint Lawrence. Later the “Midcontinent River” was captured in north central North Dakota and diverted north and then east along what is now an east-oriented Assiniboine River valley segment. Next the “Midcontinent River” was diverted in an east direction along the east-oriented Qu’Appele River valley alignment. Still later the “Midcontinent River” was diverted in a northeast direction along the Saskatchewan River alignment to what is now Hudson Bay. As this dismemberment process took place deep valleys eroding headward from breaches in the detached ice sheet southwest margin became oriented in northeast and north directions. Headward erosion of the deep Cheyenne River valley beheaded southeast oriented flood flow to the newly eroded White River valley and eroded headward into eastern Wyoming where southeast oriented flood flow to the North Platte River valley was beheaded. Additional northeast and north-oriented valleys were then eroded across the southeast oriented ice marginal flood flow in sequence including the Moreau, Grand, Cannonball, Heart, Knife, Little Missouri, and Yellowstone River valleys. The northeast-oriented Yellowstone River valley and its northeast-oriented tributary (e.g. Powder and Tongue River) valleys were especially successful in capturing southeast and south-oriented ice marginal flood flow and they eroded headward in the “Great Divide River” flood flow route area.
- Another significant “Great Divide River” flood flow reversal and flood flow capture occurred when headward erosion of the deep northeast-oriented Yellowstone River valley beheaded and reversed south oriented flood flow routes moving through the present day Bighorn Basin and then to the newly eroded North Platte River valley in central Wyoming. One of these flood flow routes was located along the alignment of the present day Wind River Canyon, which at that time was being eroded into what were then the emerging Owl Creek Mountains. That flood flow reversal created the north-oriented Bighorn River located north of Wind River and the north-oriented Wind River route through Wind River Canyon. The flood flow reversal also captured a major southeast oriented “Great Divide River” flood flow route located between what were then the emerging Wind River Mountains and the emerging Owl Creek and Absaroka Mountains. This major flood flow capture created the present day southeast and north-oriented Wind River route to and through Wind River Canyon and beheaded all “Great Divide River” flood flow routes to the newly formed North Platte River drainage basin. Shortly before the Wind River capture event Sweetwater River valley headward erosion from the newly eroded North Platte River valley beheaded south oriented “Great Divide River” flood flow routes moving flood waters across the present day Great Divide Basin to what were then actively eroding south oriented Colorado River tributary valleys. Yellowstone River valley headward erosion continued and ultimately beheaded and reversed south and southeast oriented “Great Divide River” flood flow routes flowing across the Yellowstone Plateau. The resulting flood flow reversals created northwest and north-oriented Yellowstone River headwaters.
- North of the actively eroding Yellowstone River valley additional north and northeast oriented valleys eroded headward from another deep ice sheet margin breach located in the Montana northeast and North Dakota northwest corners. The northeast oriented Redwater River and the Missouri-Musselshell River valleys eroded headward from this major ice sheet margin breach and beheaded southeast and south-oriented flood flow routes to the newly eroded Yellowstone River valley. East-oriented valleys eroded headward from the newly eroded Missouri River-Musselshell River valley on both sides of what were then emerging Little Rocky Mountains and Bear Paw Mountains. The southern valley (now the Missouri River route) beheaded and reversed southeast-oriented flood flow moving to the newly eroded Musselshell River valley. The northern valley (now the Milk River valley) captured significant southeast-oriented ice marginal flow from the northwest and west and beheaded and reversed flood flow routes to the newly eroded Missouri River valley. These valleys probably eroded headward as channels in what was then a giant east and northeast oriented anastomosing channel complex with the emerging Rocky Mountain outliers located between the flood flow channels. Headward erosion of a deep northeast-oriented valley segment from what were then the interconnected and newly eroded east-oriented Missouri River and Milk River valleys beheaded and reversed a major southeast-oriented “Great Divide River” flood flow route west of the emerging Big Belt Mountains and created what is today the northwest-oriented Missouri River valley segment located in that region. The resulting flood flow reversal also created the north-oriented Gallatin and Madison River valleys, which had originated as south-oriented “Great Divide River” flood flows to and across the Yellowstone Plateau.
Columbia River valley and tributary valleys behead Great Divide River flood flow
- The Jefferson River-Beaverhead River valley then eroded headward and beheaded and reversed additional major southeast-oriented “Great Divide River” flood flow routes. Perhaps the most obvious of the beheaded flood flow routes was along the alignment of the present day Clarks Fork valley (northwest of Butte, Montana) and then continued (probably as an anastomosing complex of channels) in a south, southeast, and east direction to the Yellowstone Plateau. The resulting flood flow reversal created the west and northwest-oriented Red Rock River. The northwest, north, northeast, southeast, south, and northeast oriented Big Hole River valley was captured by Beaverhead River valley headward erosion and had initially eroded headward from the south oriented “Great Divide River” flood flow route beheaded by the Beaverhead River valley capture. At that time there were south and southeast-oriented “Great Divide River” flood flow routes west of the Beaverhead Mountains (located along the Idaho-Montana border). These south and southeast-oriented “Great Divide River” flood flow routes west of the Beaverhead Mountains were being beheaded and reversed by headward erosion of the west oriented Salmon River valley, which eroded headward from a newly beheaded and reversed north and northwest-oriented “Great Divide River” flood flow route, which is today a Snake River valley segment. The north and northwest-oriented Snake River valley segment was created when headward erosion of a west and southwest-oriented Snake River valley segment beheaded and reversed another south oriented “Great Divide River” flood flow route. The west and southwest-oriented Snake River valley segment eroded headward from the deep Columbia River valley, which eroded headward from the Pacific Ocean across additional south-oriented melt water flood flow routes further to the west. Subsequently Columbia River valley headward erosion beheaded and reversed the southeast-oriented “Great Divide River” flood flow route to the newly eroded Beaverhead-Jefferson River valley and created the northwest-oriented Clark Fork valley.
- “Great Divide River” flood waters were derived from immense west and southwest-oriented supra glacial melt water rivers flowing to the ice sheet western margin in Alberta. In time these huge supra glacial rivers carved deep ice-walled canyons into the ice sheet surface. At that time the Canadian Rocky Mountains in western Alberta and eastern British Columbia were just beginning to emerge and did not present a barrier to west-oriented flood flow as they do today. However, crustal warping had raised the continent’s western margin, which forced the west-oriented melt water floods to flow in south and southeast directions (and perhaps in north and northwest directions) once in British Columbia. Initially the south and southeast-oriented “Great Divide River” flood flow routes were located on a topographic surface as high as erosion surfaces preserved near crests of present day eastern British Columbia and western Alberta mountain ranges. However, as the “Great Divide River” was progressively dismembered headward erosion of deep valleys gradually lowered the floors of the “Great Divide River” flood flow channels so as to develop the deep south and southeast-oriented valleys presently located between the eastern British Columbia and western Alberta mountain ranges. The southeast-oriented Rocky Mountain Trench is one of these valleys and served as a major southeast-oriented “Great Divide River” flood flow route to western Montana. Flood waters moving on the Rocky Mountain Trench alignment at one time flowed across western Montana to the Yellowstone Plateau and then across Wyoming. This flood flow route supplied much of the melt water flood flow responsible for eroding the Missouri River drainage basin. Southeast-oriented flood flow from this “Great Divide River” flood flow route to the Missouri River drainage basin ended when headward erosion of the Columbia River valley and tributary valleys beheaded and reversed flood flow in the present day Clarks Fork valley. Subsequently headward erosion of Columbia River tributary valleys and of the other valleys associated with the Fraser River further dismembered the Rocky Mountain Trench “Great Divide River” flood flow route. Further north, a major flood flow reversal on what had been a major west-oriented melt water river created the east-oriented Peace River, which today flows across the Canadian Rocky Mountains from the Rocky Mountain Trench onto the Alberta plains.
Climate Change and a thin ice sheet replaces the thick ice sheet
- “Great Divide River” melt water flood flow routes supplied much of the water that eroded the present day Missouri River drainage basin. When the thick ice sheet melted to the point that it no longer stood high above the surrounding non glaciated surface, the ice-walled and ice-floored “Midcontinent Trench” canyon, which was being carved by the supra glacial “Midcontinent River”, sporadically captured southeast-oriented “Great Divide River” flood flow. I mention the possibility of these captures because they may explain alluvium covered uplands in southeast Alberta, southwest Sakatchewan, and northeast Montana (e.g. Cypress Hills, Wood Mountain, and Flaxville uplands), although confirmation of the captures requires information from sources other than topographic maps. Such captures could have helped erode the northeast-oriented regional slope and initiated many of the deep north and northeast-oriented Rocky Mountain valleys found in the Missouri River and tributary river headwaters areas at a time when most melt water was flowing in a south direction. In any case, melt water floods throughout most of the ice sheet melt history were oriented in south directions, with much of the flood water east of the present day east-west continental divide flowing to the Gulf of Mexico and much of the flood water west of the continental divide flowing to Gulf of California. Movement of immense melt water floods into the Gulf of Mexico displaced warm Gulf of Mexico waters and established oceanic circulation patterns that generally warmed the Northern Hemisphere. Similar ocean circulation patterns may have been established in the Pacific Ocean as well. These ocean circulation patterns probably contributed to the ice sheet’s rapid melt down and continued as long as melt water floods moved in a south direction.
- Late during the thick ice sheet melt down history giant south-oriented ice-walled and bedrock-floored canyons carved into the decaying ice sheet’s surface began to intersect with similar east, west, and north oriented ice-walled canyons. Intersection of these ice-walled and bedrock-floored canyons not only chopped the decaying ice sheet up into many smaller ice sheets, but it also opened new and shorter routes to adjacent ocean basins. At the same time crustal warping in the form of mountain and plateau uplift was opening up new outlets to adjacent ocean basins and causing massive flood flow reversals, which diverted south-oriented melt water floods in alternate directions (e. g. no longer could south-oriented melt water flood flow reach the Gulf of California). In other words, late during the thick ice sheet melt down history the massive south-oriented melt water floods were diverted to flow in a northeast and north directions (and in west and in northwest directions) and no longer displaced warm Gulf of Mexico (and Gulf of California waters) and instead displaced colder North Atlantic, North Pacific, and even Arctic Ocean water. The result was a significant change in ocean circulation patterns, which significantly changed Northern Hemisphere climates. Climatic conditions responsible for the thick ice sheet’s rapid melt down were replaced by climatic conditions that froze north oriented melt water floods on the floors of the giant ice-walled and bedrock-floored canyons. Freezing of the north oriented melt water floods in turn caused incoming north and northeast oriented flood waters to also freeze and in time the floors of the ice-walled and bedrock-floored canyons were filled with frozen melt water and a thin ice sheet evolved. The resulting thin ice sheet was composed of rejuvenated thick ice sheet remnants surrounded by frozen melt water located on floors of the former ice-walled and bedrock-floored canyons.
- Development of the thin ice sheet ended the massive melt water floods, however the north and northeast-oriented drainage in the valleys the previous melt water floods had eroded continued to flow toward the former thick ice sheet southwest margin. Upon reaching the ice sheet margin the north and northeast-oriented valleys were blocked and the north and northeast-oriented drainage was forced spill over drainage divides until it reached south and southeast-oriented valleys. This spillage of north and northeast-oriented drainage across drainage divides between north and northeast-oriented valleys resulted in the present day North Dakota and northeast Montana Missouri River route. Unlike the previous thick ice sheet the thin ice sheet did not deeply erode the underlying bedrock, although the thin ice sheet did move bedrock materials around. Melt water floods froze from the top down, which meant where water was deep there was still liquid water under the ice. At the same time where water was shallow freezing also included water saturated bedrock under the ice. The liquid water under some ice sheet segments provided lubrication enabling relatively easy movement of those ice sheet segments. Such movements often included bedrock masses which were frozen solid with the overlying ice. Evidence for such ice thrust bedrock masses can be seen on topographic maps, especially on floors of the former ice-walled and bedrock-floored canyons. The climatic change that resulted in the thin ice sheet was probably also responsible for formation of alpine glaciers in the newly emerged Rocky Mountains.
- Finally, in time the thin ice sheet melted, as did many of the alpine glaciers. Thin ice sheet melt water floods also locally altered landscape features, although the thin ice sheet melt water floods did not significantly alter the previously established drainage routes. It is possible thin ice sheet melting also caused oscillating climates and there may have been more than one thin ice sheet. Like with the thick ice sheet, the thin ice sheet melt water initially flowed south to the Gulf of Mexico and later flowed in northeast and north directions. The history of the thick ice sheet final melt down stages may have been repeated one or more times before all ice sheet remnants disappeared from the North American continent. Probably the final ice sheet remnants to melt were the thick ice sheet remnants, which had been embedded in the frozen melt water floods. In the Missouri River drainage basin area these thick ice sheet remnants were located in the present day Missouri Coteau region, located between the North and South Dakota Missouri River valley and the northeast and east-facing Missouri Escarpment, and the Prairie Coteau upland region, located between the west-facing Prairie Coteau Escarpment in eastern South Dakota and northeast-facing Prairie Coteau Escarpment in northeast South Dakota and southwest Minnesota. On topographic maps these regions are poorly drained, and have numerous lakes and depressions, low hills, and other evidence of glacial deposition. Floors of the former ice-walled and bedrock-floored canyons are much better drained and while evidence of glacial features can be found on topographic maps, the evidence is quite different from that found in the Missouri and Prairie Coteau areas.
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.