Preface:

The following interpretation of detailed topographic map evidence is provided as evidence in the Missouri River drainage basin landform origins research project, which is compiling similar evidence for all major drainage divides contained within the Missouri River drainage basin and for all major drainage divides with and within certain adjacent drainage basins. The research project is interpreting evidence in the context of a previously unexplored geomorphology paradigm, which is briefly described in the introduction below. 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 North Dakota’s Knife River drainage basin landform origins. 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 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 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 similar essays is a thick North American ice sheet, comparable in thickness to the present day Antarctic ice sheet, occupied approximately the North American region usually recognized to have been glaciated and through its weight and erosive actions created a “deep” North American “hole”, 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 North Dakota Knife River drainage basin landform evidence will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Knife River drainage basin location

Figure 1: National Geographic reference map illustrating Knife River location in North Dakota and relationship to adjacent rivers (select and click on maps to enlarge).  National Geographic Society map digitally presented using National Geographic Society TOPO software.

The Knife River drainage basin is located in west-central North Dakota, USA. The Little Missouri River and Missouri River drainage basins are immediately north of the east-oriented Knife River drainage basin (see Little Missouri River-Knife River drainage divide essay under Little Missouri River or North Dakota Missouri Slope on sidebar category list). The Little Missouri River drainage basin also bounds the Knife River drainage basin to the west. The Heart River drainage basin is located to the south (see eastern Heart River drainage basin and western Heart River drainage basin essays under North Dakota Missouri Slop on sidebar category list). The Knife River flows in a southeast and then northeast direction to reach the Missouri River near Stanton, North Dakota. North of the Knife River drainage basin the Little Missouri River and the Missouri River flow in what could be considered to be an east-oriented deep valley until the Missouri River makes an abrupt turn to the south near the present-day Garrison Dam location. The Knife River roughly parallels the east-oriented Little Missouri-Missouri River course and is northeast-oriented where it joins the south-oriented Missouri River. South of the Knife River drainage basin the Heart River also flows in an east-southeast oriented direction before abruptly turning north-northeast to join the south-oriented Missouri River (just east of the map area shown). The north-oriented Little Missouri River west of the Knife River drainage basin appears to have beheaded several east and southeast-oriented drainage routes before abruptly turning east to reach the Missouri River. The following map illustrations look at more detailed evidence.

Knife River headcut

Figure 2: Knife River headwaters near Fairfield, North Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

The Knife River headwaters as shown in figure 2 illustrate a typical flood-formed headcut shape indicating the deep Knife River valley was eroded headward in response to large volumes of water coming from the northwest. However, today west and northwest of the deep Knife River valley is a fairly narrow upland with some shallow northwest-southeast oriented valleys cut across it. Northwest of this upland are high-gradient northwest-oriented valleys draining to the north-oriented Little Missouri River. Since the large volumes of water responsible for headward erosion of the deep Knife River valley came from the west and northwest, the Little Missouri River valley did not exist when the deep Knife River valley eroded west, however it is possible, and in fact probable, the deep Little Missouri River valley was being eroded at the same time as the deep Knife River valley was eroding west. The narrow upland between the two deep valleys remains as a remnant of the upland surface the two deep valleys eroded into and the narrow upland survived as the divide between the two deep flood-eroded valleys because headward erosion of the deep Little Missouri valley beheaded and reversed southeast-oriented flood flow that had been moving toward the Knife River valley. Note how east of Fairfield a northeast-oriented unnamed Knife River tributary valley has eroded southwest across what was a southeast-oriented flood flow route to capture southeast-oriented flood flow moving toward the southeast-oriented Crooked Creek valley (Crooked Creek is a Knife River tributary). Also note in northwest corner of figure 2 how a northwest-oriented Little Missouri River tributary, North Creek, begins as a southeast-oriented stream indicating it captured a southeast-oriented stream (today the southeast-oriented North Creek headwaters).

Little Knife River and Charlie Bob Creek headcuts

Figure 3: Little Knife River headcut and north-oriented Charlie Bob Creek headcut. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

North of the deep Knife River valley is the parallel and adjacent deep Little Knife River headcut as shown in figure 3. The deep north-oriented Charlie Bob Creek valley and several tributary valley have eroded south from the deep east-oriented Little Missouri River valley to the north and a narrow upland separates the deep Charlie Bob Creek valley from the Little Knife River valley. The narrow upland has a southwest-northeast orientation while a narrow upland separating the deep Little Missouri River valley (to the west) from the deep Charlie Bob Creek valley has a southeast-northwest orientation. Upland remnants are also present between the deep north-oriented Charlie Bob Creek valley tributaries. This relationship is best explained if large southeast-oriented floods eroded the deep Little Knife River valley westward at the same time the deep Little Missouri River valley (to the north) was also being eroded west and the deep Charlie Bob Creek valley was being eroded south to capture southeast-oriented flood water moving toward the deep Little Knife River valley. Southeast-oriented flood flow to the deep Charlie Bob Creek valley was in turn captured by continued headward erosion of the deep Little Missouri River valley, which first eroded west and then eroded south to capture flood flow moving toward the deep Little Knife River valley and the adjacent deep Knife River valley further to south. Note the southeast oriented tributary to north-oriented Charlie Bob Creek and northwest-southeast alignment of tributaries in all three major valleys. Also note the northwest-southeast orientation of the Little Knife River headwaters and tributaries indicating erosion from a northwest water source. Evidence the flood water came from northwest of the present day Little Missouri River valley is provided in the Yellowstone River-Little Missouri River drainage divide essay (found under Little Missouri River or Yellowstone River). The source of the flood water cannot be determined from evidence presented in this essay, nor can the reason why headward erosion of a northeast-oriented valley captured southeast-oriented flood flow in the present day Knife River drainage basin be determined from evidence presented here. However, rapid melting of a thick North American ice sheet, which through its weight and erosive actions created a “hole” in the North American continent and caused significant crustal warping elsewhere, would be a logical flood water source and ice sheet melting that permitted meltwater floods to flow northeast into the “hole” that had previously been filled by ice would be a logical reason why deep northeast-oriented valleys might erode headward into the region.

Killdeer Mountain area Knife River-Little Missouri River drainage divide

Figure 4: Killdeer Mountain area Knife River-Little Missouri River drainage divide. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

The Killdeer Mountains represent the Knife River drainage basin’s highest elevations and are composed of resistant lacustrine sediments providing evidence of a higher regional topographic surface. Today the Killdeer Mountains form the Knife River (Spring Creek)-Little Missouri River (Charlie Bob Creek) drainage divide. A northwest-southeast drainage alignment prevails even within the higher Killdeer Mountains and suggests Knife River and adjacent drainage basin erosion was initiated when immense southeast-oriented floods flowed on a preexisting topographic surface at least as high in elevation as the highest Killdeer Mountain elevations. If so the Killdeer Mountains southeast facing wall may represent all that remains of a deep southeast-oriented headcut face. In any case easier-to-erode bedrock in which resistant Killdeer Mountain lacustrine sediments were embedded was completely removed by southeast-oriented floods to produce the present-day prevailing regional topographic surface. The immense floods then eroded the deep Missouri, Little Missouri and Charlie Bob Creek valleys into this newly formed regional topographic surface. Note how Jim Creek (a Little Missouri River tributary) has eroded a deep northeast-oriented valley to capture southeast oriented drainage that originally was moving toward Spring Creek (a Knife River tributary). Southeast-oriented flood waters flowed north around the resistant Killdeer Mountain barrier which is why the deep Little Missouri River valley eroded west where it did and the north-oriented Charlie Bob Creek valley eroded south where it did.

Crooked Creek headcut and Russian Springs Escarpment west end

Figure 5: Crooked Creek headcut with Knife River headcut to the north. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

South of the deep Knife River valley is the deep Crooked Creek drainage basin. Crooked Creek is a Knife River tributary and the two join just east of the map area illustrated. The deep Crooked Creek valley did not erode as far westward as the deep Knife River valley in part because a Knife River valley tributary eroded in a southwest direction to capture southeast-oriented flood flow moving toward the deep Crooked Creek valley (note in figure 5 how Knife River headwaters flow in a northeast direction before turning east and southeast). Figure 5 also illustrates how the deep Knife River valley eroded southwest to capture southeast-oriented flood flow moving to unnamed southeast-oriented drainage basins on the upland west and south of the Crooked Creek valley head (note how upland rim extends eastward along the map area south edge). Those unnamed upland drainage basins are headwaters regions of the southeast-oriented Green River that flows on the upland topographic surface to join the east and southeast-oriented Heart River. The Crooked Creek valley head is the western end of the Russian Springs Escarpment that separates the Knife River drainage basin on the north from the Green River-Heart River drainage basin on the south. The Russian Springs Escarpment is one of southwest North Dakota’s most prominent topographic features and in general represents the deep Knife River flood-formed headcut south wall, although some complications exist. Maps shown and discussed next will illustrate this remarkable Russian Springs Escarpment drainage divide as it progresses eastward from the Crooked Creek valley head.

Deep Creek headcut and Russian Springs Escarpment

Figure 6: Deep Creek headcut and Russian Springs Escarpment. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Proceeding east and southeast from the Crooked Creek headcut along the Russian Springs Escarpment the Deep Creek flood-eroded valley is encountered next. The Deep Creek valley has not eroded as far west as the adjacent Crooked Creek valley to the north (Crooked Creek flows in an east oriented direction, see extreme northwest corner of figure 6) and the northwest-southeast oriented Russian Springs Escarpment in figure 6 represents the Deep Creek valley head. Just west of the Deep Creek drainage basin the north-oriented Lightning Creek flows to Crooked Creek and the deep Lightning Creek valley appears to have eroded south to capture southeast-oriented flow moving toward the Deep Creek valley head. Headward erosion of the deep Crooked Creek valley then captured that southeast-oriented flow and reversed flow moving to the deep Lightning Creek valley to create present-day northwest-oriented Crooked Creek tributaries (visible in the northwest corner of figure 6). The upland surface south and west of the Deep Creek valley head is today drained by the southeast oriented Russian Springs Creek, which flows to the parallel Green River drainage basin located south and west of Russian Spring Creek drainage basin. The southeast-oriented Green River flows to the parallel east and southeast-oriented Heart River located south and west of the Green River drainage basin. The northwest to southeast oriented Russian Springs Escarpment rim in figure 6 is the drainage divide between the Knife River drainage basin to north and east and the adjacent Heart River-Green River-Russian Springs Creek drainage basin to the south and west.

North-oriented Deep Creek tributary headcut and Russian Springs Escarpment

Figure 7: North-oriented Deep Creek tributary headcut and Russian Springs Escarpment. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Just northeast of Gladstone a deep north-oriented headcut has cut a major indentation into the Russian Springs Escarpment face. Today a north-oriented Deep Creek tributary drains the deep north-oriented flood-eroded headcut (Deep Creek in turn is a Knife River tributary). The deep north-oriented abandoned headcut is a short distance northeast of the Heart River-Green River confluence near Gladstone. A shallow northeast-southwest oriented valley connects the Heart River-Green River confluence area with the north-oriented headcut face (an unnamed southwest-oriented stream drains that shallow valley). These landforms suggest the north-oriented Deep Creek tributary headcut eroded south to capture large volumes of southeast-oriented flood waters spilling north out of the Heart River valley and that capture of the western Heart River drainage basin almost took place. However, the capture did not take place probably because the deep Knife River valley eroded west and beheaded southeast-oriented flood flow moving toward the Green River (see figure 5). When volumes of southeast moving Green River flood waters were greatly reduced flood water no longer spilled over to flow northeast to the north-oriented Deep Creek valley head and flood water moving toward the Deep Creek valley head in the shallow valley and elsewhere drained back toward the Heart River to create the southwest-oriented Heart River tributary present today. Figure 5 illustrates how headward erosion of the Knife River valley beheaded the Green River drainage basin, and this beheading probably was the event responsible for ending downstream flood spillover to the deep north-oriented Deep Creek tributary headcut (and in turn prevented the imminent capture).

Russian Springs Escarpment at Richardton and anastomosing channels

Figure 8: Russian Springs Escarpment at Richardton and anastomosing channels. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Richardton, North Dakota is located at the Russian Springs Escarpment crest. Just east of Richardton is another Russian Springs Escarpment indentation eroded by headward erosion of a deep north-oriented headcut. That deep north-oriented flood-eroded headcut beheaded and captured southeast-oriented flood flow moving toward the east oriented Branch Knife River located in the southeast corner of figure 8. Note how the Branch Knife River turns northwest (the figure 9 discussion will further comment on this Branch Knife River abrupt direction change). North of figure 8 the Branch Knife River turns north and flows to the east and northeast-oriented Knife River. Beheading of the east oriented Branch Knife River drainage basin by headward erosion of a deep north-oriented Knife River tributary valley illustrates how the Knife River and tributary valley systematically eroded headward into the upland surface to capture east and southeast-oriented flood water. Once captured the east and southeast-oriented flood water flowed on the deep Knife River drainage basin floor as is evident by the anastomosing channel complex found at the Russian Springs Escarpment base (see figure 9 and related discussion for evidence those east and southeast-oriented floods flowed to the downstream Heart River drainage basin and perhaps across the present-day Heart River drainage basin). Shape and orientation of the anastomosing channel complex suggests the channels were carved by a large east or southeast-oriented flood, however the present-day drainage network indicates headward erosion of the deep northeast-oriented Knife River valley captured those large east or southeast-oriented floods and diverted flood waters to the northeast.

Branch Knife River capture evidence and Curlew Valley

Figure 9: Branch Knife River capture evidence and Curlew Valley. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 8 illustrated how Branch Knife River headwaters begin at the Russian Springs Escarpment crest and flow east in a progressively deepening valley to reach a large northwest-southeast oriented valley just east of the Hebron, North Dakota. The large valley is known as the Curlew Valley and southeast of Hebron is drained by southeast-oriented Big Muddy Creek, which flows to the southeast-oriented Heart River. Further downstream the Heart River makes an abrupt turn to the north-northeast and a through valley continues to the southeast, both suggesting southeast-oriented flood water was captured by headward erosion of a deep north-northeast-oriented valley. The Branch Knife River does not flow to the southeast-oriented Big Muddy Creek and Heart River, but instead makes an abrupt turn to drain the northwest end of the northwest-southeast oriented valley and then turns north to join the east and northeast-oriented Knife River. This evidence suggests the Curlew Valley was eroded headward by flood waters coming from the western Knife River drainage basin and going southeast across the Heart River drainage basin. Headward erosion of the northeast-oriented Knife River valley then captured the floods and reversed flow to create the present-day north-oriented Branch Knife River. Downstream capture of the southeast-oriented Curlew Valley-Heart River flood flow by a north-northeast oriented valley and subsequent upstream capture of the southeast-oriented Curlew Valley flood flow by the east and northeast oriented Knife River suggests deep northeast-oriented valleys were able to erode headward to capture the immense southeast-oriented floods.

Hans Creek-Goodman Creek through valley

Figure 10: Hans Creek-Goodman Creek through valley. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

One interesting link between the Little Missouri River and the Knife River is the Hans Creek-Goodman Creek through valley. This through valley is characteristic of flood spillways described by Kehew and Lord[1].  North of Halliday the Little Missouri River before entering the east-oriented Missouri River first flows in a southeast direction (from north of the Killdeer Mountains), then abruptly turns north and finally turns east (see figure 1). Hans Creek flows in northwest direction in its large northwest southeast oriented valley to join the southeast-oriented Little Missouri River valley where the abrupt turn north is located. This evidence suggests flood flow moving around the Killdeer Mountain north end first moved southeast to carve what became the southeast-oriented Little Missouri River-Hans Creek-Goodman Creek spillway. Headward erosion by the deep Missouri-Little Missouri River valley subsequently captured that southeast-oriented flood flow. At that time the east-oriented Missouri River valley was probably eroding west from what may have been an ice-free area located east of the Missouri Escarpment (and the stagnant ice-covered Missouri Coteau). Capture of southeast-oriented flood flow in the Little Missouri River-Hans Creek-Goodman Creek spillway resulted in a reversal of flow on the Hans Creek (or northwest) end of the Hans Creek-Goodman Creek spillway.

Golden Valley flood spillways

The southeast oriented Spring Creek valley joins the northeast-oriented Knife River valley just west of Beulah.  Further west, the southeast and south oriented through valley joins the Knife River valley from the north and barbed or north-northwest oriented tributaries join the Knife River valley from the south. Evidence the northwest-oriented tributaries are reversals of drainage in what were once parallel south and southeast-oriented flood routes can be found by following the northwest-oriented valleys headward to observe well-defined through valleys where there they are linked to headwaters of southeast-oriented oriented Heart River and Missouri River tributaries. The aligned barbed tributaries suggest the deep northeast-oriented Knife River valley eroded headward across a south-southeast oriented flood to capture the south- and southeast-oriented flood waters and divert them to the northeast. Apparently the northeast-oriented Knife River valley first captured flow moving southeast and south along the Golden Valley dry valley and headward erosion of the Spring Creek valley then beheaded that flow to create the present-day dry through valley. The Knife River valley, the dry through valley and the Spring Creek valley are all characteristic of flood spillways. Valley sizes can be used to make very rough estimates of flood water volumes involved.

Otter Creek-Sweet Briar Creek divide

• The Russian Springs Escarpment does not continue east of Hebron. East of the Curlew Valley the Knife River-Heart River drainage divide follows a hilly upland region that is crossed by several northwest to southeast oriented through valleys (not illustrated here, but easily visible on detailed topographic maps). Through valley northwest ends drain today as north-northwest tributaries flowing to the northeast-oriented Knife River while southeast ends drain as southeast-oriented tributaries flowing to the Missouri River or the Heart River. The through valley linking the north-northwest oriented Otter Creek (a Knife River tributary) with the southeast-oriented Sweet Briar Creek (a Heart River tributary) is a good example. While not as large as the through valley extending south from Golden Valley this Otter Creek-Sweet Briar Creek through valley is a significant erosional feature. The Otter Creek-Sweet Briar Creek through valley was eroded headward by southeast-oriented flood water moving into what is today the Heart River drainage basin. The presence of multiple southeast-oriented through valleys crossing the Knife River-Heart River divide suggests immense quantities of southeast-moving water. Headward erosion of the deep northeast-oriented Knife River valley systematically captured water flowing in these parallel southeast-oriented flood flow routes, and caused reversals of flood flow to create northwest-oriented tributaries. Apparently enough flood water from the west continued to spill into the beheaded flood route to erode the Otter Creek valley headward toward the present-day Otter Creek-Sweet Briar Creek drainage divide.

Antelope Valley through valley complex

Figure 12: Antelope Valley through valley complex north of Beulah, North Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

The southeast-oriented Spring Creek valley joins the northeast-oriented Knife River valley just west of Beulah. Both valleys display flood spillway characteristics described by Kehew and Lord [1]. North of Beulah is the Antelope Valley through valley complex, which suggests a flood formed anastomosing channel complex. A large dry valley extends from the southeast-oriented Spring Creek valley and is joined by a large dry valley extending south from the Missouri River valley (north of figure 12) and then continues east and southeast to join the Knife River valley near Hazen. This through valley complex suggests a flood-formed valley eroded northwest and west from the Knife River valley at Hazen while the Knife River headcut eroded southwest. Northwest of Hazen the northern valley split again with one branch eroding north to capture east-oriented flood flow in the present-day Missouri valley area and the other branch eroded southwest to what is today the southeast-oriented Spring Creek valley. Apparently flood water volumes were so great the Knife River spillway valley also split (near Beulah) with one branch eroding northwest to behead the northern spillway route while the other branch eroded southwest to form the present-day Knife River valley. At the same time western erosion of a deep Missouri River valley headcut beheaded the spillway leading south from the Missouri River valley (although it may also have temporarily captured flood flow from the southwest).

Knife River-Missouri River confluence area

• Today the Knife River joins the Missouri River as a barbed tributary. In other words, the Knife River flows northeast to join a south-oriented river. A large shallow valley extends east and northeast from the Missouri Valley east-oriented segment downstream from Stanton and has been considered to be the former Knife River route (to east of the Missouri Escarpment) and that route was blocked by ice forcing water to flow south along an ice-sheet margin. How the route got blocked can be debated, but the deep south-oriented Missouri River valley did erode headward to capture the northeast-oriented Knife River. Both the Knife River and the Missouri River valleys exhibit flood spillway characteristics  so the capture probably took place during a major flood event. Map evidence suggests Knife River flood waters may have flowed north in what is today a segment of the south-oriented Missouri River valley. Such northward flood flow would be possible if a deep valley eroded west from what may have been an ice-free area north and east of the Missouri Escarpment. This deep valley may have carved a deep ice-walled and bedrock floored valley across the present-day Missouri Coteau (just east and north of the present-day Missouri River valley) to capture southeast-oriented flood flow southwest of the Missouri Coteau stagnant ice region and in the process to erode the present-day Knife River and upper (east-oriented Missouri River) drainage basins. Northward erosion of the deep south-oriented Missouri River valley next captured flood waters from the combined Knife River and upper (east-oriented) Missouri River drainage areas.

Summary

• The earliest Knife River drainage basin history event determinable from topographic map evidence was a topographic surface at least as high as the present-day Killdeer Mountains tops. Age of the resistant Killdeer Mountain bedrock mass can be debated although there is general agreement the bedrock mass represents lacustrine sediments. Presence of lacustrine sediments indicates the Killdeer Mountain area was once a lake basin and the surrounding region was higher in elevation. The fact lacustrine sediments remain while surrounding material is gone implies the surrounding material was more easily eroded than the lacustrine sediments. Yet existence of a lacustrine bedrock mass indicates regional erosional history began from a topographic surface at least as high as the Killdeer Mountains tops. Also, the regional aligned drainage extending across the Killdeer Mountains (see figure 4) suggests the same northwest to southeast oriented floods that produced present-day Knife River drainage basin landforms also stripped surrounding rock layers to leave the Killdeer Mountains as a modern-day monadnock.

• Stripping of regional rock layers to leave the Killdeer Mountains as an isolated monadnock probably was done when southeast-oriented flood waters eroded adjacent large and deep valleys in a northwest direction across the region. While much stripping probably occurred prior to erosion events for which there is good evidence, initial stripping was probably just an earlier stage in what were a progressive and continuing series of flood caused erosion events. Earlier flood erosion events probably were similar to later flood caused erosion events for which there is good topographic map evidence, although most earlier flood erosion evidence has been completely eroded away.

• Topographic map evidence indicates the present-day deep western Knife River drainage basin erosion began when a large southeast oriented valley eroded headward along what is today the Curlew Valley route (see figure 9). As tributary valleys, including the Crooked Creek and Little Knife River valleys, eroded west and northwest from this deep southeast oriented valley another deeper valley eroded southwest. This second northeast-oriented valley eroded along what is today the northeast-oriented Knife River route and systematically beheaded and reversed what were multiple southeast oriented flood flow routes crossing the present-day Knife River drainage basin until it reached, beheaded, and reversed what was south-oriented flood flow on what was then a south-oriented Deep Creek-Branch Knife River route moving flood waters to the southeast-oriented Curlew Valley route. Beheading south-oriented flood flow to the Curlew Valley route and reversing that flood flow to become north-oriented flood flow enabled the deep northeast-oriented Knife River valley to capture all flood flow moving into what is today the entire western Knife River drainage basin. Headward erosion of the deep Little Missouri River valley then systematically beheaded and reversed southeast- and east-oriented flood flow that had been moving to the Knife River drainage basin and rapid erosion of the Knife River drainage basin ceased. [Note: the Knife River drainage basin history given here differs substantially from geomorphic histories provided by previous workers. Murphy [2] provides a summary of the previous and more commonly accepted interpretations.]

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 the detailed 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 were created using National Geographic 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.