Agreement on the origin of the name of the “Missouri” River is difficult because too many contradictory explanations exist. The name apparently comes from a Siouan Indian word, “ouemessourita” or “emissourita,” translated by early French explorers as “those who have wooden dugout canoes,” or “river of the large canoes,” or “town of the large canoes,” or any of several other possibilities. One source says the term was the name the Illinois Indians used for the native people who lived in the Mississippi River Valley, probably mainly on the eastern (Illinois) side of the river; another source says they lived in what is now the State of Missouri.
The Missouri River originates near Three Forks, Montana, where the Gallatin, Jefferson, and Madison rivers come together. It flows 2,341 miles to St. Louis, where it joins the Mississippi River. This makes the combined Missouri-Mississippi River, at 3,709 miles, the fourth longest river in the world, after the Nile, Amazon, and Yangtze. The entire length was once riverine environment but, due to the dams that have been built along its route, approximately a third of the length is now reservoirs – lake environment rather than river. Listed from upstream to downstream, the dams are: Fort Peck in Montana, Garrison in North Dakota, Oahe, Big Bend, and Fort Randall in South Dakota, and Gavins Point on the South Dakota-Nebraska border.
Along with its valley, the Missouri River is largely a product of glaciation. Before North America was glaciated, all the drainage in North and South Dakota, eastern Montana, and northern Minnesota was north or northeastward into Canada. There was no “Missouri River” carrying drainage from the northern mid-continent region to the Gulf of Mexico. The way I define the Missouri River requires that its water ultimately reach the Gulf of Mexico as it does today, and that it carry water draining from the Rocky Mountains and northern Great Plains. Prior to glaciation, no such river existed. Why is the situation today so different than it was before the Ice Age?
The modern Missouri River Valley in North Dakota consists of several discrete valley segments that differ markedly from one another. Some of the segments are broad: six to twelve miles wide from edge to edge, with gentle slopes from the adjacent upland to the valley floor. Others are narrow: less than two miles wide, with rugged valley sides – even badlands slopes in places. Most of the wide segments trend from west to east whereas the narrow segments are mainly north-south. The Bismarck-Mandan area is one of only a few exceptions, and I’ll explain why shortly.
The west-east segments of the Missouri River Valley are wide because they coincide with much older valleys that existed long before the area was glaciated. Old, mature river valleys, which formed over long periods of time (hundreds of thousands or millions of years), tend to be broad with gentle slopes. Younger valleys formed more quickly (tens of thousands of years), and are usually narrower with steeper sides. An example of a wide segment is the forty-mile-long, west-east segment of the Missouri River Valley upstream from Garrison Dam. This part of the valley, now flooded by Lake Sakakawea, was once the route of a river that flowed east to Riverdale. However, the river didn’t turn south at Riverdale, as it does today. Rather, it continued eastward past Riverdale, and on past Turtle Lake and Mercer, flowing into northeastern North Dakota. For convenience, I’ll refer to this ancient river as the “McLean River.”
East of U. S. Highway 83, the route of the old McLean River valley is a broad, low area, partly buried beneath tens to hundreds of feet of glacial sediment. Lake Audubon, Turtle Lake, Lake Brekken, Lake Holmes, Lake Williams, Lake Peterson, Pelican Lake, Blue Lake, Brush Lake, and other smaller lakes mark the former route of the McLean River through eastern McLean County. However, continuing farther east, the McLean River valley becomes so deeply buried beneath glacial deposits that it would be nearly impossible to know its route from a study of the surface topography. Fortunately, hundreds of test holes were drilled during studies of the ground water resources of the glacial deposits so we have a good idea of the route the river followed into northeastern North Dakota.
Another wide, west-east trending segment of the modern Missouri River Valley, between Stanton and Washburn, is an eastward continuation of the modern Knife River. Prior to glaciation, the Knife River flowed east in its modern valley to Stanton, but it continued eastward from there, past Washburn. A few miles east of Washburn it turned slightly northeastward. The ancient Knife River joined the McLean River near the town of Mercer and the combined Knife-McLean River continued northeastward to the Devils Lake area. It then flowed north along the east side of Turtle Mountain area into Canada.
Still another wide segment of the Missouri River Valley in northwestern North Dakota extends from near the modern Missouri River /Yellowstone River confluence, northeastward to Williston.
This six-to-eight-mile-wide section of the valley coincides with the pre-glacial route of the Yellowstone River through that area. Prior to glaciation, the Yellowstone River continued to the north, past Williston, following a route that is now mainly buried. The pre-glacial route coincides with the modern route of the Little Muddy River as far as Zahl, about 30 miles north of Williston. North of Zahl, the old Yellowstone River valley into Canada is so deeply buried that its route is known only through drill-hole data. The river entered Saskatchewan about six miles north of Crosby.
The Missouri River Valley between Williston and New Town, now flooded by Lake Sakakawea, follows the same route as did an east-flowing, mid-Ice Age — but probably not pre-glacial – river. This part of the Missouri River Valley is somewhat narrower than most other east-west segments of the valley in North Dakota, and it is also younger than most of them. It is a continuation of a mid-Ice Age river that flowed east from Montana. In Montana, the route of this river coincides with the modern route of the Missouri River past Wolf Point, Poplar, and Culbertson. The Montana segment of the mid-Ice Age river joined the north-flowing Yellowstone River near Buford.
At Bismarck-Mandan, the Missouri River Valley is about two miles wide at the Interstate Highway 94 crossing, but on the south side of Bismarck the valley broadens to six miles wide. The widening southward seems contrary to my earlier comment that north-south segments of the valley tend to be narrow. There is a reason for this exception though. The valley widens at Bismarck-Mandan because, prior to glaciation, the Heart and Little Heart rivers, which today flow into the Missouri River, joined a few miles east of Bismarck. The combined (preglacial) Heart/Little Heart River continued flowing eastward, joining the Cannonball River in southern Burleigh County, near Moffit. The old, combined Heart/Little Heart valley still exists as a broad lowland south and southeast of Bismarck. It is now a wide spot in the Missouri River Valley.
The Heart/Little Heart river system was probably dammed several times by glacial ice advancing westward. Each time a glacier advanced, a lake formed ahead of – west of – it in the Heart/Little Heart valley. The lake (or lakes) are referred to as glacial Lake McKenzie. At least once, and possibly several times, glacial Lake McKenzie overflowed, carving what is now the Missouri River valley south of the Bismarck-Mandan area.
When the (preglacial?) Heart River flowed eastward, through the Bismarck area, it deposited a thick gravel deposit which now lies buried about 100 feet beneath the Missouri River. Bismarck’s new (2013) water-intake structure withdraws ground water from this old Heart River gravel deposit.
When the McLean River valley was blocked by a glacier in the Riverdale area midway through the Ice Age, a large proglacial lake formed ahead (to the west) of the ice in the valley. This lake might be considered to be the “original” Lake Sakakawea: an early ice-dammed lake that predated the Corps of Engineers version of Lake Sakakawea by thousands of years. When the lake overflowed, near where Garrison Dam is today, the resulting flood quickly carved a narrow spillway trench south to the Stanton area.
Similarly, the Knife River, which flowed past Stanton and on to the Washburn area, was dammed by glacial ice just east of Washburn and the valley was flooded upstream beyond Washburn. The resulting lake overflowed and spilled southward into the Burnt Creek-Square Butte Creek drainage, carving a narrow trench from a few miles east of Washburn to the Bismarck-Mandan area. The modern Missouri River flows in that trench today.
And, as I noted, when the Heart/Little Heart River was dammed by a glacier, which probably advanced as far west as Sterling, glacial Lake McKenzie formed. The lake overflowed southward, forming a new valley, now flooded by the northernmost part of Lake Oahe.
The youngest and narrowest segment of the Missouri River Valley in North Dakota is at New Town, between Four Bears Bridge and Van Hook Bay. As recently as 13,000 years ago, a glacier blocked the Missouri River from its route around the north and east side of New Town. The old river route (prior to 13,000 years ago) is now a broad valley, known as the “Van Hook Arm,” flooded by Lake Sakakawea. The glacier dammed the valley, causing a lake to form upstream (to the west) of the point of blockage. Thick layers of lake sediment, known as the “Crow-Flies-High silt,” were deposited in the ice-dammed “Crow-Flies-High Lake.” Crow-Flies-High Lake extended westward from the New Town area to near Williston. In many places between these two cities, exposures of the bedded lake silt deposits occur at elevations as high as 70 feet above the modern, maximum reservoir level (1850 feet) of Lake Sakakawea. The lake rose until it overflowed southward, cutting the channel now spanned by the Four Bears Bridge.
Other “Missouri” River Routes
Up to now, I’ve tried to explain the origin of the modern route of the Missouri River. That’s not the end of the story though. The modern route of the Missouri River is only the most recent of many routes that earlier “Missouri” rivers followed through North Dakota at various times during the Ice Age. These rivers also carried runoff water from as far away as the Rocky Mountains, through North Dakota, on its way to the Gulf of Mexico. However, most of these routes, mainly in northern and eastern North Dakota, are now buried beneath thick accumulations of glacial sediment. Whatever routes these rivers followed, they had to have flowed generally eastward and southward because their original, northerly and northeasterly routes into Canada were blocked by ice each time glaciers advanced into the state. Test drilling, done to study ground water resources, has helped us identify least least some parts of the old “Missouri” River routes. There are dozens of them.
One of several early routes of the Missouri River, determined by test-hole drilling, took the river southward past Cooperstown and Valley City to the southeastern corner of the state. Another route took the river southeastward past Jamestown. In the northern part of the state, rivers like the Yellowstone were diverted from their northerly routes to easterly and southeasterly routes, past places like Columbus, Kenmare, and Minot. These buried valleys can be considered to be early “Missouri” River routes. The array of buried river valleys is really amazing – and so complicated – and such a great number of possible routes exist, that it is impossible to work them all out. All of them are now buried beneath hundreds of feet of glacier sediment, and most of them have no surface evidence whatsoever.
However, not all of the early “Missouri River” routes through North Dakota are deeply buried. In the western part of the state, a version of a Missouri River formed when an early glacier advanced at least as far southwest as the Hebron area. The margin of that glacier coincided with what is now a prominent, broad valley, known as the Killdeer-Shields channel. The channel extends southeastward from the Killdeer Mountains, past Hebron and Glen Ullin, to the Fort Yates area, crossing the modern Missouri River Valley, and continuing through southwestern Emmons County into South Dakota. No river flows through the Killdeer-Shields channel today, but an early Missouri River flowed in it, perhaps for a longer period of time than the current Missouri River has flowed in its modern route. Interstate Highway 94 crosses the valley about half way between Dickinson and Mandan. Good views of the Killdeer-Shields channel can be seen just north of Richardton and between Hebron and Glen Ullin. Old U.S. Highway 10 and the Burlington Northern Santa Fe Railroad follow the old channel from Hebron to Glen Ullin.
I realize that my description of the changes in the routes the various “Missouri” Rivers have followed since the Ice Age began is complicated. Even so, it doesn’t begin to account for the evolution of all of the changes in the vast array of routes that rivers followed during the Ice Age in North Dakota.
Most of the narrow, north-south segments of the modern Missouri River Valley correspond to places where glaciers diverted then-existing rivers southward. Glaciers in the central part of the state diverted northeast-flowing rivers, like the Knife, McLean, and Heart-Little Heart, and Cannonball, forcing them to flow southward from the points of diversion, forming the north-south segments of the modern Missouri River. Glaciers advancing into northwestern North Dakota diverted mainly north-flowing rivers, like the Yellowstone and Little Missouri, away from their routes into Canada, forcing them to flow to the east and south.
The modern Missouri River Valley is a “composite” feature, consisting of older, wide pre-glacial segments, formed over long periods of time prior to the Ice Age, along with younger, narrow segments that were cut relatively quickly at various times during the Ice Age. The parts of the Missouri River Valley that extend mainly from west to east are wider and much older than are the narrower segments that extend from north to south. Many of the early “Missouri” River routes followed for varying periods of time during the Ice Age in northern and eastern North Dakota were later buried beneath thick deposits of glacial sediment.
The current route of the modern Missouri River Valley is only the latest in a continuing series. After the next glacier has come and gone, a new version of the Missouri River will likely follow a different route than does the river today.
Field stones are common in parts of North Dakota that have been glaciated. Early settlers used the stones for the foundations of their homes and farm buildings and some people built entire structures with them. Today, field stones are used in landscaping, as rip rap along the faces of dams and shorelines, or as decorations in front yards in towns like Bismarck and Minot (less so in places like Fargo and Grand Forks, where they are much less common).
Geologists use the term “erratic” to refer to field stones left behind by glacial ice. The term “erratic,” with reference to rocks, dates to 1779, when Horace de Saussure, a Swiss geologist, described granite boulders lying on top of limestone in the Jura Mountains in Switzerland. He recognized that the boulders were out of place. His term, “terrain erratique,” comes from the Latin erratus, “to wander,” and means, literally, “ground that has wandered.”
In some instances, the source-area of an erratic can be pinpointed. North of Winnipeg, for example, several Paleozoic carbonate limestone formations are quarried. We can determine from which area and formation a North Dakota boulder was derived by matching it to the Manitoba limestone exposures. Several years ago, Bob Biek, then a North Dakota Geological Survey geologist, found a number of unusual erratics along Lake Sakakawea — dark-colored stones known as “omars.” The name “”omar” is short for the Omarolluk Formation, a 1.76 billion-year-old greywacke formation. The rocks are found in-place (where they originally formed) today only in the Belcher Islands in southeastern Hudson Bay, so it is possible that the Lake Sakakawea omars originated in the Belcher Islands, or near there. The Belcher Islands are located nearly 1,000 miles northeast of Lake Sakakawea.
Erratics have been used as exploration tools in the search for ore deposits. Copper mines were opened in Finland after copper-bearing erratics were traced back to their source. Analysis of gold-bearing erratics in Maine resulted in the discovery of gold ore deposits in Quebec. I have found occasional erratic boulders in North Dakota containing traces of gold. Such erratics were probably transported to North Dakota from the metal mining districts of Manitoba and Saskatchewan, about 700 miles to the north.
Glacial erratics represent the oldest geologic materials found on the surface in North Dakota. Those composed of limestone or dolomite are mainly from 300 to 500 million years old, while some of the igneous or metamorphic erratics may be three or four billion years old. In contrast, the land surface they are lying on could be as young as 12,000 years old in places where erratics lie directly on glacial deposits.
In contrast to the long-distance travelers, boulders of sandstone were moved no more than a few miles by a glacier from nearby locations within the State. Sandstone is less well consolidated than granite or limestone and any extensive glacial transport of sandstone boulders would break them down into smaller fragments, or reduce them to sand. Occasionally, boulders of shale are included in layers of glacial sediment. Most such boulders are quite fragile and have probably been moved only a few tens or hundreds of feet from their original source.
The larger erratics, those three feet or more in diameter, tend to be igneous or metamorphic rocks, such as granite or gneiss. Such rocks are hard and much more resistant to abrasion and fracturing than are sedimentary rocks such as limestone. In some places, especially large granite or quartzite erratics, ten feet or more in diameter are numerous (some are car-sized, measuring up to 20 feet across). A few examples include the walls of the Sheyenne River Valley near Fort Ransom; many of the high bluffs along the Missouri River; along the White Earth River Valley in Mountrail County; and in the valley walls along the Souris River in and near Minot and Velva. Both large and small erratics are particularly abundant near Venturia and Zeeland in McIntosh County. The largest erratic I have seen is located eleven miles south of Calgary, Alberta. Composed of quartzite, and known as the Okotoks Erratic (aka “Big Rock”), it weighs 16,500 tons, stands 30 feet above the surrounding area and is billed as the world’s largest glacial erratic.
Erratics tend to be abundant in places where the ground surface has been washed by the winnowing action of waves along the shores of glacial lakes and modern reservoirs. Wave action removes the finer materials, leaving a lag of cobbles and boulders behind. Examples include areas along the wave-worn shore of glacial Lake Agassiz, near Pisek in Walsh County and Hankinson in Richland County. Erratics are sometimes concentrated along the shores of modern lakes, such as Lakes Addie and Sibley, near Binford in Griggs County and along Devils Lake in Benson County (but many of the erratics along Devils Lake are now submerged). A good place to see erratics is along the levees and causeway roads that have been constructed in response to Devils Lake flooding. Great numbers of erratics have been brought to the area to serve as rip rap along shorelines subject to wave erosion.
Most erratics are rounded and worn, but some of them have beveled or faceted surfaces. During the course of their journey, the rocks were jostled against one another while in the glacial ice, or against the rock over which the glacier was flowing. As a result of this rubbing, the surfaces were planed smooth. Glacial transport fractured some boulders, producing fresh, angular edges. Some erratics are grooved or polished, a result of abrasion by the moving ice. Coarse sand and gravel within the ice scraped against the boulders, scratching or “striating” them, sometimes as the boulder moved along with the advancing glacial ice or when the glacier flowed over a hard, stationary rock.
In some places where the more-easily eroded glacial deposits have been largely eroded away, erratics may be concentrated on the land surface (eastern Burleigh and western Kidder counties are examples), resulting in a very bouldery landscape. If such a landscape was then glaciated again, and covered by fresh glacial deposits (Late Wisconsinan glacial deposits lying over Early Wisconsinan glacial deposits, for example), the erratics may occur as a buried boulder zone, known as a “boulder pavement.” Boulder pavements are common, but not often discovered, unless an excavation cuts though the boulder zone. This is most likely to happen during road construction. Striated boulders with straight grooves are sometimes found in such “boulder pavements.” If the boulders have not moved, the striations can sometimes be used to determine the direction of glacial flow.
Single large, isolated erratics are sometimes surrounded by depressions, a result of animals such as bison or cattle using them as rubbing stones. Such “buffalo boulders” form as animals rub against the stone, loosening the soil with their hooves. The wind blows the loose soil away, leaving a depression surrounding the rock. Many buffalo boulders are polished from repeated rubbing by the animals.
Erratics aren’t restricted to the surface. They occur throughout the entire thickness of glacial sediments, which averages between 150 and 250 feet thick throughout the northern and eastern parts of North Dakota. Seasonal freezing and thawing causes rocks to work their way upward to the surface from below the plow zone. Every farmer knows that, each spring, a new “crop” of stones has to be removed from the fields. The smaller rocks can be picked up with rock-picking equipment and carried away. Larger erratics are sometimes blasted with explosives and the pieces hauled away. Some of the very largest are simply left in place and avoided.
Some erratics are famous. Everyone has heard of Plymouth Rock where the Pilgrims first set foot in the New World on December 21, 1620. In North Dakota we have the Standing Rock, where Highway 46 crosses the Sheyenne River Valley near Fort Ransom. The explorers Nicollet and Fremont, in 1839, noted Standing Rock Hill on their maps. In northwestern North Dakota, near Alkabo in Divide County, is Writing Rock, which was known by the Sioux as Hoi-waukon or Spirit Rock.
In his book, Blue Highways, a Backroads Tour of Rural America, William Least Heat Moon captured the resignation of farmers to a continual crop of boulders:
East of Fortuna, North Dakota, just eight miles south of Saskatchewan, the high moraine wheat fields took up the whole landscape. There was nothing else, except piles of stones like Viking burial mounds at the verges of tracts and big rock pickers running steely fingers through the glacial soil to glean stone that freezes had heaved to the surface; behind the machines, the fields looked vacuumed. At a filling station, a man who long had farmed the moraine said the great ice sheets had gone away only to get more rock. “They’ll be back. They always come back. What’s to stop them?”