A geomorphic history based on topographic map evidence
Abstract:
This essay provides an overview of more detailed Loup River drainage basin landform origins essays, which can be found under Loup River on this website’s sidebar category list. Detailed essays illustrate and discuss topographic map evidence for all drainage divides surrounding the Loup River drainage basin and also for drainage divides separating major Loup River tributaries. Interpretations in this overview essay and in more detailed essays are solely based on topographic map evidence. The Loup River drainage basin is entirely located in the state of Nebraska. The Loup River has multiple southeast-oriented tributaries, some of which originate as east oriented streams in the Nebraska Sand Hills region before turning to flow in a southeast direction. These tributaries include the North Loup River and it tributary Calamus River, the Middle Loup River and its tributary Dismal River, and the South Loup River. These and other southeast-oriented tributaries flow to the northeast oriented Loup River, which joins the northeast and east oriented Platte River near Columbus, Nebraska. The northeast-oriented Loup River flows for a considerable distance near the northwest wall of a broad valley shared with the northeast-oriented Platte River, which flows near the valley’s southeast wall. Evidence presented in detailed essays suggests the Loup River drainage basin was eroded during a massive southeast-oriented flood that converged with immense east and south oriented floods. The southeast-oriented flood waters upon entering the broad northeast-oriented Loup-Platte River valley were forced by flood waters from the west to flow along the valley’s northwest wall while flood waters from the west flowed along the valley’s southeast wall. The Nebraska Sand Hills regions is interpreted here to have been subsequently developed on deltaic sediments deposited where the immense converging floods developed temporary lakes in central and western Nebraska prior to headward erosion of the deep Platte River and Loup valleys and their tributary valleys. Headward erosion of the deep northeast-oriented Platte River and Loup River valleys and their tributary valleys drained the ponded flood waters. Headward erosion of the Elkhorn River valley and subsequently the Missouri River-Niobrara River valley beheaded southeast-oriented flood flow to what were then the actively eroding Loup River valley and its tributary valleys.
Loup River drainage basin location map
Figure 1: Loup River drainage basin location map (select and click on map to enlarge). National Geographic Society map digitally presented using National Geographic Society TOPO software.
Loup River drainage basin history
This essay is an overview of more detailed Loup River drainage basin essays, which can be found under Loup River on this website’s sidebar category list. All interpretations presented in this essay and in the more detailed essays is based on topographic map evidence. Approximately 100 topographic maps are included in the more detailed essays to illustrate the types of evidence upon which the interpretations are based. The Loup River drainage basin is located entirely in the state of Nebraska with the Loup River being a Platte River tributary. Major Loup River tributaries originate in the Nebraska Sand Hills region generally as east-southeast oriented streams and upon leaving the Sand Hills region turn to become southeast-oriented streams and flow to the northeast-oriented Loup River, which after flowing for a considerable distance parallel to a northeast-oriented Platte River segment eventually joins the Platte River. Figure 1 above illustrates the Loup River drainage basin relationship to adjacent drainage basins. North of the Loup River headwaters and the Nebraska Sand Hills region is the east-oriented Niobrara River in northern Nebraska. East of the Loup River drainage basin and north of the eastern Loup River drainage basin is the Elkhorn River drainage basin. South of the Loup River drainage basin is the Platte River drainage basin. Essays describing the Niobrara River, Elkhorn River, and Platte River drainage divide areas are found under those river names on the sidebar category list. Loup River drainage basin history is intertwined with origins of other Missouri River tributary drainage basins and to fully understand Loup River drainage basin history it is necessary to view the entire Missouri River drainage basin as a single unit, which can be done using essays published on this website.
- Detailed Essays describing all major drainage divides between Loup River tributaries and between the Loup River drainage basin and adjacent drainage basins have been written. The detailed essays present strong evidence the Loup River valley and its tributary valleys eroded headward to capture an immense southeast-oriented flood and to divert flood waters to what was then the newly eroded Platte River valley. Flood waters entering the Platte River valley converged with a large east-oriented flood already in the Platte River valley. Convergence of two massive floods (or at least floods that had used different routes to reach Nebraska) probably resulted in the ponding of flood waters, which may have covered large regions in central and western Nebraska. The Nebraska Sand Hills located in the Loup River headwaters area probably are formed on deltaic sediments, deposited where flood waters entered ponded flood waters areas. Finer grained sediments may have been deposited east of the Nebraska Sand Hills region. If so the finer grained sediments were subsequently eroded as flood waters continued to flow across the region.
Regional map illustrating central Nebraska drainage routes
Figure 2: Regional map illustrating central Nebraska drainage routes. National Geographic Society map digitally presented using National Geographic Society TOPO software.
Figure 2 provides a somewhat more detailed regional drainage map of the Loup River drainage basin and the Nebraska Sand Hills regions is labeled. The east-oriented Niobrara River is located near the figure 2 north edge and joins an east-oriented Missouri River segment at Niobrara, Nebraska near the figure 2 northeast corner. The state of South Dakota is north of the Missouri River in the northeast corner area. The east-southeast oriented North Platte River and the east-northeast oriented South Platte River meet at North Platte, Nebraska (in figure 2 southwest quadrant) to form the Platte River. From North Platte the Platte River flows in a southeast direction to the approximately location of Kearney, Nebraska and then turns to flow in a northeast direction to Columbus (located near figure 2 east edge). The Nebraska Sand Hills region is located north of the Platte River in the figure 2 west half and east and east-southeast oriented Loup River tributary headwaters are located in the Sand Hills region between the Niobrara River in the north and the Platte River in the south. Major Loup River tributaries shown include the North Loup River and its tributary the Calamus River, the Middle Loup River and its tributary the Dismal River, and the South Loup River. As these Loup River tributaries approach the figure 2 center area (and the Sand Hills region eastern margin) the Loup River tributaries all become oriented in a southeast direction and flow almost to the northeast-oriented Platte River, however on approaching the Platte River they turn to form the northeast-oriented Loup River. While not obvious from figure 2 evidence, although obvious on topographic maps (see figure 3 below), between Grand Island and Columbus the Loup River is flowing along the northwest wall of a broad northeast-oriented valley while the parallel Platte River is flowing along the same valley’s southeast wall. Major topographic map evidence needing explanations are the origins of sand deposits which are present in the Sand Hills region, the parallel southeast-oriented Loup River tributary valleys draining to the northeast-oriented Loup River, and the broad northeast-oriented valley in which the Loup River and Platte River are located and why the two rivers are on opposite sides of the valley. Further, topographic maps illustrate more detailed evidence also requiring explanations.
- The Loup River drainage basin was eroded by massive southeast-oriented floods which converged with immense east-oriented floods in the broad northeast-oriented Loup River-Platte River valley. The flood waters were derived from a rapidly melting North American ice sheet and flowed across the entire state of Nebraska. The ice sheet had been large, probably as large if not larger than the present day Antarctic Ice Sheet and was located in a deep “hole.” The deep “hole” had been created by a combination of deep glacial erosion and by crustal warping caused by the ice sheet’s great weight. When fully developed the ice sheet may have stood two kilometers or more above the surrounding non glaciated surface while the ice sheet “roots” may have extended as much as one kilometer or more below the surrounding non glaciated surface. The surrounding non glaciated surface has been completely destroyed by deep melt water flood erosion, which occurred as this giant ice sheet melted, and melt water floods flowed across what are today high Rocky Mountain erosion surfaces. To what extent present day mountain and plateau elevations are the result of deep flood erosion and are the result of localized uplift is difficult to determine, although mountain ranges west and northwest of the Loup River drainage basin probably emerged as the massive ice sheet melted. At the time the Loup River drainage basin was eroded the 300-meter high north-facing Pine Ridge Escarpment (north of the Niobrara River) did not exist and the northern plains were at least as high as the present day southern plains south of the Escarpment. How much material had been stripped from Nebraska prior to this time is difficult to determine, although it is possible hundreds of meters of easily eroded bedrock had previously been removed from the entire region.
- The immense southeast-oriented floods flowing across the Loup River drainage basin were ice-marginal melt water floods and occurred at a time when ice sheet melting had progressed to the point where the ice sheet no longer stood high above the surrounding non glaciated surface. Probably at this time only the decaying ice sheet “roots” remained, at least in the south. Those decaying ice sheet “roots” were located north and east of the Missouri River (see figure 1) and the massive southeast-oriented melt water floods were flowing between the emerging Rocky Mountains and the ice sheet southwest margin. Evidence for these massive southeast-oriented floods is contained detailed essays describing major Missouri River tributary drainage basins north and northwest of the Loup River drainage basin in South Dakota, Wyoming, North Dakota, and Montana. At the same time massive melt water floods were flowing through the present day Rocky Mountain region and were being systematically captured (from south to north) by headward erosion of deep valleys now included in the Platte River drainage basin. These deep valleys were diverting the Rocky Mountain melt water floods in an east direction across what is now the state of Nebraska. Essays illustrating and describing the Rocky Mountain flood flow routes and North and South Platte River drainage basins have not yet been published, although are scheduled to be written before Missouri River drainage basin landform origins research project completion. What is important to understand Loup River drainage basin history is recognize the massive southeast-oriented melt water floods converged with immense east and south-oriented floods in central and eastern Nebraska.
Figure 3: Northeast oriented Loup River and Platte River valley with Loup River flowing along northwest wall and Platte River flowing along southeast wall. United States Geological Survey map digitally presented using National Geographic Society TOPO software.
Figure 3 uses a reduced size map to illustrate some of the evidence suggesting a massive southeast-oriented flood converged with a an immense east-oriented flood in the present day northeast-oriented Loup River-Platte River valley. The Platte River is the northeast-oriented river flowing along the large valley’s northwest wall in the figure 3 northwest quadrant. Fullerton is the town located near the figure 3 north center edge and Central City is the town located near the figure 3 south center edge. The grid on figure 3 shows squares one mile on a side and the distance from Fullerton to Central City is approximately 17 miles. As seen in figures 1 and 2 Loup River tributaries are predominately oriented in a southeast direction and are flowing into this broad northeast-oriented valley. The Loup River and Platte River flow on opposites of this broad valley from the Grand Island area (southwest of figure 3) to the Columbus area (northeast of figure 3-see figures 1 and 2). Between the northeast-oriented Loup River and the northeast-oriented Platte River is northeast-oriented Prairie Creek. Prairie Creek originates as a southeast-oriented stream flowing into the northeast-oriented Platte River valley south and east of the South Loup River elbow of capture (where the South Loup River turns from flowing in southeast direction to flowing in a northeast direction). Once in the Platte River valley Prairie Creek flows along the valley’s northwest until the Loup River enters the Platte River valley, at which point the Loup River then begins to occupy the northwest wall position, while Prairie Creek then flows between the Loup River and the Platte River. Prairie Creek joins the Platte River east of the figure 3 map area and near Columbus southeast-oriented Shell Creek enters the broad valley and occupies the northwest and north wall position while the Loup River moves into the center position and then joins the Platte River.
- The present day Prairie Creek, Loup River, Shell Creek, and other Platte River tributary channels in the broad northeast and east-oriented valley are evidence of routes used by southeast-oriented flood water as it entered what was at one time a giant east-oriented flood flow channel. Southeast-oriented flood flow from the South Loup River drainage basin initiated the Prairie Creek channel by flowing into the northeast oriented valley, which was filled with east-oriented flood waters from further to the west. The (South Loup River)or Prairie Creek flood water did not mix with the Platte River water from the west, but instead flowed along the north or northwest valley wall while the Platte River water from further to the west flowed further to the southeast. Southeast-oriented flood waters from the Middle Loup River drainage basin (and from southeast-oriented Loup River tributaries further to the east) then entered the flood filled valley and pushed the Prairie Creek flood waters into the valley center while the Middle Loup River flowed along the valley’s northwest wall. At the same time flood waters spilling from the South Loup River valley to the Middle Loup River valley eroded the present day east-northeast South Loup River valley, which beheaded flood flow to the Prairie Creek route. Further to the northeast southeast-oriented flood flow from the Shell Creek drainage basin entered the broad northeast and east-oriented valley and pushed the Loup River flood water toward the valley center so the Shell Creek flood water could occupy the position near the valley’s northwest and north wall. This evidence suggests the broad valley was completely filled with rapidly moving northeast and east-oriented flood water as the massive southeast oriented flood waters converged with large quantities of east oriented flood waters.
North Loup River-Middle Loup River drainage divide area
Figure 4: North Loup River-Middle Loup River drainage divide area with Ord being the town in the northeast corner located on North Loup River and Comstock being the town near the west edge and Middle Loup River. United States Geological Survey map digitally presented using National Geographic Society TOPO software.
Figure 4 illustrates topographic map evidence in the Loup River drainage basin north and west of the broad northeast-oriented Loup River-Platte River valley. The North Loup River is the southeast-oriented river in the figure 4 northeast corner and Ord is the town located there. The Middle Loup River is the south-southeast oriented river near the figure 4 west edge and Comstock is the town located in the Middle Loup River valley near the figure 4 west edge (north half). Dane Creek is the north-oriented North Loup River tributary near Ord. Note how the Dane Creek headwaters are oriented in a southeast direction and are linked with the valley of another north-oriented North Loup River tributary. Also note how southeast-oriented Dane Creek headwaters are linked by a large through valley with southeast-oriented headwaters of east-oriented Mira Creek, which flows to the figure 4 east edge and then east to join the North Loup River. Further note higher level through valleys linking south and southeast-oriented Middle Loup River tributary valleys with North Loup River tributary valleys. The through valleys linking Middle Loup River tributary valleys with North Loup River tributary valleys provide evidence the deep Middle Loup River valley eroded headward into the figure 4 map area at a time when south and southeast-oriented flood water was flowing across the entire figure 4 map area on a surface at least as high as the highest figure 4 elevations today. The Middle Loup River valley tributary valleys were eroded headward from the newly eroded Middle Loup River valley. North Loup River valley headward erosion occurred shortly after and was preceded by headward erosion of the east-oriented Mira Creek valley which captured south- and southeast-oriented flood flow which then eroded the region where the southeast-oriented Dane Creek and Mira Creek headwaters are located today. Next headward erosion of the deep North Loup River valley beheaded south-oriented flood flow routes to the newly eroded Mira Creek valley. Flood waters on the north ends of the beheaded flood flow routes reversed flow direction to flow in a north direction to the newly eroded North Loup River valley. Reversed flood flow on the present day north-oriented Dane Creek segment alignment first captured southeast-oriented flood flow on the southeast-oriented Dane Creek segment alignment. Next North Loup River valley headward erosion beheaded and reversed south-oriented flood flow to the southeast-oriented Dane Creek headwaters valley and the reversed flood flow eroded the north-oriented tributary valley west of the north-oriented Dane Creek valley.
North Loup River-Middle Loup River drainage divide area
Figure 5: North Loup River-Middle Loup River drainage divide area in Nebraska Sand Hills region. Thedford is the town in the figure 5 south center located on Middle Loup River. United States Geological Survey map digitally presented using National Geographic Society TOPO software.
Figure 5 uses a reduced size topographic map to illustrate the North Loup River-Middle Loup River drainage divide area in the Nebraska Sand Hills region. Thedford is the town located in the figure 5 south center area. The Middle Loup River flows in an east-southeast direction across the figure 5 south half and is the river flowing next to Thedford. The North Loup River flows in a southeast direction across the figure 5 northeast quadrant. West of the figure 5 map area the Middle Loup River flows in more of an east direction and south and east of the figure 5 map area the Middle Loup River flows in a south-southeast direction as seen in figure 4. North and west of the figure 5 map area the North Loup River flows in an east direction as seen in figure 2 above. Sand hills have obscured most drainage history evidence in the figure 5 map area, although the presence of surface materials suitable for sand dune development is evidence of flood deposition. As previously mentioned southeast and south-oriented ice-marginal melt water floods converged in what is now the state of Nebraska with giant east-oriented melt water floods flowing from the Rocky Mountain region. While not included in the Loup River drainage basin south-oriented flood waters moving on a third melt water flood flow route also converged with the southeast-oriented ice-marginal melt water floods and the melt water floods flowing east from the Rocky Mountains along the present day Platte River route. This third melt water source was from giant south-oriented supra-glacial melt water rivers flowing off the decaying ice sheet surface. These supra-glacial melt water rivers carved large ice-walled and ice-floored canyons (later bedrock-floored canyons) into the ice sheet surface and at the time of Loup River drainage basin erosion one or more of these giant rivers emerged from the decaying ice sheet’s margin in southeast South Dakota. Prior to Missouri River valley headward erosion these giant melt water rivers flowed in a south direction across eastern Nebraska.
- Ponding of flood waters would have been a logical consequence of the convergence of these three immense floods and deposition of whatever sediments the flood waters were carrying would be expected as incoming flood waters flowed into the ponded flood water regions. The large south-oriented floods emerging from the ice sheet margin would have formed a temporary barrier to the east oriented floods moving along the present day Platte River valley alignment. And the east oriented floods moving along the present day Platte River alignment would have formed a barrier to the southeast-oriented floods coming in from the northwest (see figure 3 for evidence of this barrier). South-oriented floods emerging from the giant ice-walled canyons may have moved large icebergs into eastern Nebraska and those icebergs may have rafted large boulders, which the ice sheet had transported from regions still further to the north. While topographic map evidence alone is not adequate to determine ice sheet margin positions, such ice rafted debris could give the impression that eastern Nebraska was glaciated, when in fact it was south of the glacial margin. Evidence for the south-oriented floods is illustrated and discussed in essays found under Elkhorn River on the sidebar category list. At the same time deep melt water flood erosion has probably destroyed all evidence of the thick ice sheet margins, especially in regions to the south. The Nebraska Sand Hills region is located in a region where incoming east and southeast oriented flood waters would have deposited sandy deltaic sediments and flood deposits further east would have been finer grained flood transported materials because the sand sized materials would have settled out first with the finer grained materials continuing further east into the ponded flood water regions. Again, to properly understand this interpretation it is necessary to view the Missouri River drainage basin as a single unit.
Introduction to Missouri River drainage basin research project essay series
- This Nebraska Loup 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 Nebraska Loup River drainage basin 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.
Missouri River drainage basin landform origins research project 
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