The work of John Bluemle PhD

Monthly Archives: May 2015


Dahlen Esker

Fig. 5-A. Dahlen Esker, junction of Grand Forks, Walsh, and Nelson counties. This view is to the south, in the direction the stream that deposited the esker was flowing. The esker has a generally accordant crest level, which, however, appears irregular because of numerous minor gaps. The esker consists of a mixture of sand, gravel, till, and boulders, a mixture that resulted from a combination of materials deposited by running water, and debris in the glacier sliding from the ice walls into the esker stream. Photo: 6-26-2009.

Eskers and kames are among the best-known of the various features formed by glaciers and by the running water associated with melting glaciers. Eskers come in all sizes: ridges snaking across the countryside ranging from a few hundred feet to several miles long, and up to 50 or 100 feet high. Kames may be cone or pyramidal-shaped hills as high as a hundred feet, or they may be simply small mounds of material. Kames and eskers are found in most parts of North Dakota that were covered by the Late Wisconsinan glacier.

Eskers were deposited by streams and rivers flowing 1)  on the surface of a glacier, 2) in cracks in the glacial ice or, sometimes, 3) in tunnels beneath the ice. Imagine a river flowing in a valley or crack in the glacier. The banks of the river were formed of ice and, in some places, the river floor might also have been on ice. These Ice-Age rivers and streams deposited gravel and sand in their ice-walled valleys, just as a modern stream deposits sediment in its earthen valley. However, the ice banks of esker rivers eventually melted away, leaving the gravel deposits that had been deposited in the ice-walled valleys, standing as ridges above the surrounding countryside.


North Dakota has thousands of esker ridges. Most are small and non-descript, apparent only from a height (air view) or on air photos, but some eskers are impressive.

esker, North Dakota, glaciation, geology

Fig. 5-B. This diagram shows how an esker forms when a stream of meltwater carrying sediment develops beneath a glacier or, in some instances, in an open crack in the glacier. Such a stream may meander a little as it winds its way underneath the glacier, making its way to the front of the ice. The sand and gravel are eventually deposited when the ice melts, and the meltwater flow gradually slows and it drops its sediment load. When the ice melts away, the fluvial sediment is left as a long, narrow, winding ridge, which marks the course of the former subglacial, ice-walled stream.
The stream may be in a crack so that it does not flow in a tunnel, and it may flow on both solid ground in places beneath the glacier and over ice in other places. In places where the stream flowed over ice, the esker ridge may have a gap or dip in its crest because, when the ice beneath the stream bed melted, the overlying stream deposits collapsed.

One of the best examples of an esker in the U.S. is the Dahlen Esker, located midway between Fordville and Dahlen in the northeastern part of the state. It can be seen as a prominent ridge off to the west where State Highway 32 crosses the Grand Forks-Walsh County line. If the weather is dry, you can drive about a mile on a section-line trail to the crest of the Dahlen Esker (if the fields on either side of the trail are being farmed, be careful not to drive on the crops).

Kame, Jack Lake

Fig. 5-C. The Jack Lake kame in eastern Foster County, a mile west of the James River and eight miles east of the town of Bordulac. This is a scan of a photo I took in 1962. Notice that much of the kame (the hill in the center of the photo) has been removed for gravel. Photo scan: 1962.











The Dahlen Esker was deposited by a meltwater stream flowing in an ice-walled channel, or possibly through a tunnel in the ice,  near the edge of the glacier. The stream flowed mainly southward, toward the margin of the glacier. The esker is about four miles long, 400 feet wide, and as high as 50 to 80 feet. In some places, native prairie covers the surface. The Dahlen Esker has been described in various geologic reports dating to the late 19th century, but the best description and discussion of the feature was provided by Jack Kume for the North Dakota Geological Survey (“The Dahlen Esker of Grand Forks and Walsh Counties, North Dakota,” Miscellaneous Series 32, 1966).

Other large eskers include ones near Benedict in northeastern McLean County;  another about ten miles southwest of Carrington in Foster County; one immediately west of Hannaford in Griggs  and Barnes counties; one near Dazey in Barnes and Stutsman counties; and an unusual one in Frankhauser Lake in northern Sheridan County. The Frankhauser esker is particularly interesting because it winds its way through a lake, which floods a depression that was formed by ice-thrusting. The esker formed during the ice-thrusting process.

Kames are similar in many ways to eskers. Like eskers, they consist largely of gravel and sand, but they are conical or irregularly shaped hills, rather than long ridges.

Pierce County Kame

Fig. 5-D. The hill in the middle of this photo is a kame two miles southeast of Orrin in Pierce County. Photo 8-20-2010.

Water flowing on the surface of the glacier, or in esker valleys, plunged into holes in the ice, filling the  holes with a mixture of materials. When the ice eventually melted, the water-deposited materials slumped down, resulting in mounds and conical hills. Kames occur in several places, mainly on the Glaciated Plains, usually in association with ground moraine, but they are sometimes found in areas of dead-ice moraine. A few examples include one in southwestern Richland County, one south of Lidgerwood, and one west of Cayuga in Sargent County. A prominent kame, visible from miles away, is located four miles south of State Highway 200 in eastern Foster County along the west side of the James River. About half of the 60-foot-high feature has been mined for sand and gravel.

Most eskers and kames are composed of coarse, poorly sorted materials, a mixture of sedimentary textures ranging from silt and sand, up to large cobbles or boulders. As they were forming, flowing water deposited flat-lying beds of sand and gravel. Later though, when the ice-walls melted and the bedding collapsed, the bedding became contorted. While a stream was flowing in an ice-walled tunnel or valley, or water was flowing into a hole in the glacier (a “moulin”), cobbles and boulders fell from the melting ice into the water-lain deposits, into the stream or down the moulin. Some eskers have a nearly complete covering of boulders on their surfaces. Most kame or esker deposits contain so many cobbles they are not suitable for construction purposes. Some of them consist of materials suitable for rough fill work.

Frankhauser Esker, Sheridan County

Fig. 5-E. This is an air view of the Frankhauser Esker in northern Sheridan County, about eight miles southwest of the Town of Drake. The esker lies in a lowland that is largely flooded by a lake. The lowland is the result of ice thrusting. The glacier excavated material from what is now the lowland and deposited it a short distance to the southeast, forming a prominent hill. The esker formed when large amounts of groundwater were released as the glacier removed material overlying a large aquifer. The water flowed in a tunnel at the base of the glacier, depositing the gravel and sand in the esker ridge. Photo scan: 1979.


Late in the Cretaceous, beginning about 70 million years ago, and continuing through the Paleocene, until about 56 million years ago, western North Dakota’s climate was subtropical. Trees up to 12 feet in diameter and more than 100 feet tall grew in a setting similar to today’s Dismal Swamp in Virginia, or the Florida Everglades, with meandering rivers, swamps, and vast forested floodplains. Modern evidence for this fossil forest includes widespread seams of lignite coal, fossil tree leaves, pollen, and logs and stumps of petrified wood.

Petrified stump

Fig. 4-A. Petrified stump. South Unit, Theodore Roosevelt National Park, Billings County. The badlands topography in the background is carved from the Bullion Creek Formation. Photo: 9-09-2009.

Lignite exposure

Fig. 4-B. Lignite exposure about six miles southeast of Medora, Billings County. The lignite occurs at the top of the Bullion Creek Formation, which appears light gray in the exposure. The Sentinel Butte Formation, more brown in color, overlies the lignite. Photo 9-09-2009

Lignite is a soft coal that underlies much of the western two-thirds of North Dakota. It began as an accumulation of dead plant material in tropical or semitropical basins: swamps, lagoons and marshes. As the basins filled with stagnant water, the plant debris became submerged so that atmospheric oxygen could not reach it. When the plants died and fell into the water, they began to decay, but before all the plant debris could decompose, the bacterial action causing the decay stopped; most of the bacteria “committed suicide” by filling the stagnant swamp water with their own toxins to such an extent that they died. The only bacteria that remained were ones that did not need oxygen for respiration. However, these “anaerobic” (the word means “living without air”) bacteria are less efficient at decomposition. As a result, large amounts of submerged organic materials did not decompose, and thick beds of peat accumulated.

Streams meandering through western North Dakota during Paleocene time changed course frequently and, when they did so, they sometimes deposited sand and silt on top of the partially decomposed vegetation (peat). The layers of peat were buried beneath thick layers of sediment and the weight of the overlying beds gradually compressed the peat to lignite. Layers of swamp vegetation, some of them over 50 feet thick, were eventually transformed into beds of lignite coal only a few feet thick.

Seams of lignite, horizontal black bands, can be seen eroding out of hillsides today. They range from a few feet to as much as forty feet thick in Slope County and even thicker in Wyoming and Montana. If a peat bog happened to be buried by river sediments before the decay process had progressed very far, and trees were still growing in the swamps, some lignite may have formed, but some of the trees were instead changed into petrified wood. Occasionally, a petrified tree stump, rooted in a lignite bed, can be seen.

Lignified tree trunk

Fig. 4-C. Tree trunk rooted in lignite beds. The tree is buried by silt and sand, which were deposited quickly, thus preserving the tree trunk. The vertical part of the tree grades upward, from lignite at the base, to a combination of lignite and some petrified wood. The pick ax is about four feet long. Photo: 1979

Petrified wood formed when minerals gradually replaced the buried plant material. The petrification process requires rapid burial of the wood to prevent decay. This sometimes happened when rivers shifted course or overflowed their banks, burying a forest floor under a layer of sand and silt. Other times, forests were partially covered by volcanic ash, blown to the area from volcanoes in the rising Rocky Mountains. After burial, ground water seeped through the ash and wood, coating cell walls and filling the intercellular cavities with minerals.

North Dakota, Park, petrified stump

Fig. 4-D. In 1973, along the South Loop Road for Theodore Roosevelt l Park. It was later destroyed by vandals.

Usually, the cellular structure of the wood was destroyed; leaving only a rough cast of the original log, but sometimes growth rings, bark, knots, and even the shapes of the wood’s tiny cells are preserved with remarkable fidelity. This more detailed preservation is possible because some molecules, such as silica and other inorganic materials, are much smaller than organic molecules so, rather than “molecule for molecule” replacement, the organic molecules are coated and surrounded with silica. Cavities in petrified wood may be encrusted with quartz crystals.

Petrified wood ranges from solid, well-silicified specimens to splintery, or “coalified” wood that tends to disintegrate when it is exposed to weathering or it may simply fall apart when you pick it up. The degree of petrification can vary, even within a single specimen. Individual stumps or logs may contain both well-silicified parts and other parts that are still coal. Most of North Dakota’s petrified wood is brown or tan on weathered surfaces and dark brown where freshly broken, but colors can range from white to gray, with streaks of black. Traces of minerals add color to the fossilized wood: yellow, brown and red may indicate iron; black and purple hues suggest carbon or manganese mineralization.

Elgin ND Petrified Wood Bandstand

Fig. 4-E. Elgin ND Park bandstand, Grant County. The wall is constructed of petrified wood collected in the area. This is a good place to see a variety of nice specimens. Photo: 6-23-2010

Petrified wood occurs as entire logs or stumps, some standing upright where they once grew, or as scattered limbs and fragments, strewn over the land surface. A fallen log was probably cylindrical when it fell down, but the petrified logs we find today often have oval cross sections because, after they were buried, they became compressed and flattened by the weight of overlying sediments. Most of North Dakota’s fossil wood is Paleocene in age, but petrified wood is also found in smaller amounts in the older Hell Creek Formation and in some of the younger bedrock units.

Fossil leaves, commonly found along with petrified wood, help us to identify the species of trees that grew in and near the swamps where petrified wood is found. Many specimens belong to the plant genus Metasequoia, the dawn redwood. Fossils of dawn redwood were first discovered in 1941, and the tree was thought to be extinct, but living specimens were discovered in south-central China in 1945. Today, the dawn redwood is widely used as an ornamental tree in warmer climates.

Petrified Wood Park, Lemmon, South Dakota

Fig. 4-F. Petrified Wood Park, Lemmon, South Dakota (about a half mile south of the ND-SD state line). Constructed by Ole S. Quammen, the park covers a city block, and was completed in 1932. The petrified wood was collected in both North and South Dakota. Photo: 6-24-2010

During the Paleocene, while Metasequoia trees were growing in North Dakota, a variety of other kinds of vegetation were also present. We know them primarily through studies of fossil pollen and the delicate imprints of leaves in mudstone, siltstone, and carbonaceous shale. Along with the leaf fossils, we find remarkably preserved petrified cones of Sequoia dakotensis (giant evergreen trees), the leaves of tree ferns, and various kinds of petrified wood.

So much fossil wood is strewn over the surface in some places that such areas are referred to as “petrified forests.” North Dakota’s best-known petrified forest is in the South Unit of Theodore Roosevelt National Park, where large numbers of tree stumps have eroded out of the Sentinel Butte Formation. Some stumps are still upright, in the positions in which they grew 60 million years ago. They were preserved when the forest floor was flooded, burying the bases of the trees. The unburied parts of the trunks and branches decayed and disappeared. Petrified stumps may be anchored in a lignite bed or a buried soil horizon, which may mark a former forest or swamp floor.

Petrified wood is often used in landscaping. Many western North Dakota driveways and flower beds are decorated with fine specimens. An outstanding example of a petrified stump, collected in McKenzie County, may be seen in the Long-X Visitor Center in Watford City. The stump, probably bald cypress, is nine feet in diameter and weighs about eight tons. Perhaps the most elaborate use of petrified wood in an ornamental sense is in the Petrified Wood Park in Lemmon, South Dakota. In this park, completed in 1932, O. S. Quammen constructed hundreds of pillars and intricate structures of petrified wood, much of it from North Dakota.

In 1990, the level of Lake Sakakawea was low, revealing several petrified logs weathering out of the Sentinel Butte Formation along the lake shore in Mercer County. Pieces of an 80-foot-long petrified log, collected from the area, along with two stumps from the Amidon area, are displayed on the North Dakota State Capitol grounds. The log and stumps were located southeast of the State Capitol building, in the Centennial Grove for many years, but they were moved to a location east of the Heritage Center in 2014. Still another large petrified log was uncovered during construction of Interstate Highway 94 west of Dickinson, This 120-foot-long, six-foot diameter log (much larger than the one on the State Capitol grounds) was offered to nearby towns as a tourist attraction, but it was reburied when no one wanted it.

Petrified log

Fig. 4-G. Petrified log displayed on the Capitol campus, Bismarck, prior to being relocated. This 80-foot-long log was collected along the shore of Lake Sakakawea in Mercer County when the reservoir level was low. Even though the tree trunk was round when it fell, the cross-sectional shape now is oval rather than round. The weight of the overlying sediment in which it was buried caused the log to assume its oval shape. Photo: 9-26-2009.



Fountain at Crystal Springs

Fig. 3-A. Fountain at Crystal Springs, Kidder County. This field-stone monument was constructed in 1935 by stonemason Art Geisler. It was a Works Progress Administration project intended to replace an old iron pipe from which travelers used to obtain a cool drink of spring water while motoring on U.S. Highway 10. The fountain was listed on the National Register of Historic Places in 2010. The spring was flowing when I took this picture. The water flows from an ice-thrust hole, which intersected a preglacial river valley. Photo: 8-30-2010.

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).

North Dakota, geology, erratics, Forbes, Schulstad House

Fig. 3-B. House built of field stones in Forbes, in Dickey County on the ND-SD state line. An inscription reads “Schulstad House: 1907.” Photo: 7-8-2010.








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.

granite erratic, field stone

Fig. 3-C. Large granitic erratic about ten miles west of Mandan, Morton County. This is one of the largest erratics in North Dakota. Several pieces of granite, some of them rising ten feet above the ground surface, are all part of what was once a single erratic, which weighed at least 350 tons (but I don’t know how much additional rock may be buried beneath the ground surface). Numerous large granite erratics occur in this part of eastern Morton County. They are all that remains of materials deposited during an old (pre-Wisconsinan) glacial advance.
Old Highway 10 can be seen on the right. My wife, Mary (5’7”) shows the scale. Photo: 6-5-09

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.

riprap, Devils Lake

Fig. 3-D. Riprap of erratics along a Devils Lake levee built to protect the town of Minnewaukan, Benson County. Photo: 9-13-2011










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.

erratics, boulders

Fig. 3-E. Field with abundant erratics, about six miles east of Wing, northeastern Burleigh County. Photo: 9-4-10.

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.

boulder pavement

Fig. 3-F. Road cut along State Highway 32 north of Niagara, Grand Forks County, exposing a boulder pavement lying on Cretaceous Pierre Formation shale (dark gray beneath the stones) and overlain by till deposits. Scanned photo: 1968

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.

buffalo boulder

Fig. 3-G. “Buffalo boulder” rubbing stone, about five miles southeast of Napoleon, Logan County. This boulder is about four feet in diameter. Photo: 5-30-2010

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.

Standing Rock monument

Fig. 3-H. Standing Rock monument along State Highway 46 in Ransom County. The monument is placed on top of Standing Rock Hill, a prominent ice-thrust hill. Photo: 7-17-2009.

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?”


Turtle Mountain erratics

Fig. 2-A. Slopes on the south side of Turtle Mountain in Bottineau County, in an area where glacial erratic boulders are abundant. Erosion by running water, flowing on the surface along the slope of the Turtle Mountain upland has removed much of the fine materials, leaving erratics concentrated on the surface. Photo: 8-31- 2010.

Glaciation was the main geologic influence on much of North Dakota’s landscape. The Ice Age, a time geologists also refer to as the Pleistocene Epoch, includes most of the past three million years of geologic time. Glaciers advanced over the northern plains several times during the Ice Age,  reaching northern and eastern North Dakota. When it wasn’t glaciated, the state had a climate much like the one we enjoy today or possibly even milder at times. the Ice Age wasn’t one long “deep-freeze.”

Little Missouri River, wind canyon

Fig. 2-B. Badlands along the Little Missouri River in Billings County. Rapid erosion by the river causes the poorly consolidated sandstone and siltstone layers of the Bullion Creek Formation to slide downward, resulting in steep, freshly exposed slopes. The water carries these materials away when they fall into river, starting them on their way to the Gulf of Mexico. Photo: Photo: 9-16- 2009.






During their studies of the geology of the state, geologists have found evidence for at least seven separate glaciations, but there may have been more. The most recent of these glaciations is known as the Wisconsinan (because deposits typical of that glaciation are widespread in Wisconsin). The Wisconsinan glaciation began about 100,000 years ago and ended about 11,000 years ago. Some geologists debate whether the Ice Age has really ended yet. After all, large areas of the earth’s surface are still covered by extensive glaciers (Greenland, Antarctica, etc.). It’s likely that we are currently enjoying a lull between major glaciations.

Even though North Dakota was glaciated many times during the Ice Age, it is the Wisconsinan glacial deposits, the most recent ones, that are most obvious to us. These are the ones that form the hills and valleys in eastern and northern North Dakota and they are the ones in which our prairie potholes and wetlands are developed. Most of our richest farmland is developed on the Wisconsinan glacial surface.

Early glaciers, which advanced into North Dakota before the Wisconsinan glacier, also had a profound effect on the state. The materials they deposited have been largely eroded away, and about all that remains of them are occasional boulders  — “erratics.” I will discuss erratics elsewhere. It was an early glacier that diverted the course of the Little Missouri River eastward more than 640,000 years ago (possibly earlier). Before that time, the Little Missouri River flowed northward into Canada. In fact, all of North Dakota used to be drained by rivers that flowed into Canada. When it was diverted, the Little Missouri River began to carve the badlands we see today.

Blue Buttes, near Keene ND.

Fig. 2-C. Blue Buttes area of McKenzie County, near Keene. This butte, and others near the south end of a grouping known as the “Blue Buttes,” is capped by a sandstone layer of the Eocene Golden Valley Formation (the caprock is barely visible, along the top of the butte). Many of the larger buttes in this part of the State are capped by the same sandstone bed. The view is toward the west, with a thunderstorm approaching. Photo: 7-27- 2010.

All of us who have traveled around North Dakota know that the landscape varies considerably from place to place. Southwestern North Dakota, with its badlands, buttes, and broad vistas is largely the result of hundreds of thousands of years of erosion. The landscape there is not glacial. It has been carved from layers of flat-lying sandstone and other materials.

The Missouri River marks an approximate boundary between the eroded landscape of southwestern North Dakota and the entirely different glacial landscape north and east of the river, where we see small hills – small at least compared to large buttes like Sentinel Butte and Bullion Butte found in southwestern North Dakota. Eastern North Dakota is characterized by thousands of potholes, poorly developed drainage in places, and remarkably fertile farmland.

When the glaciers advanced over the state, they picked up some of the materials over which they flowed. The glaciers contained a variety of kinds of soil and rock, which they eventually deposited as thick layers of sediment. The exposed surface of these sediments has been weathered for the past several thousand years (since the glaciers melted) and it forms the rich soils our farmers work today.

Lake Sakakawea till, glacial deposits

Fig. 2-D. Glacial deposits (till) exposed in bluffs along Lake Sakakawea near Riverdale. This 40-foot-high cliff exposes boulders incorporated in a mass of finer material – the overall mixture is referred to as “till” by geologists. Most of the till shown here – the part that is characterized by vertical partings – was deposited by a glacier during Early Wisconsinan time, about 70,000 years ago. Younger, Late Wisconsinan till, about 16,000 years old, lies on top lighter color, lacking vertical partings and immediately beneath the grass cover. Photo: 6-27-2009.

Over much of eastern North Dakota, the glacial sediments were laid down as an undulating plain (think of the Carrington, Finley or Kenmare areas, for example). In other places, a more hilly landscape resulted (think of Turtle Mountain or the Missouri Coteau — places like Belcourt, Hurdsfield, Max, Ryder and countless others). In still other places, water from the melting glacier became ponded, forming huge lakes. Today, most of these areas are flat. Examples of the flat topography may be seen in places like Fargo, Hillsboro, Grand Forks or Grafton. The old floor of Glacial Lake Agassiz (the Red River Valley) is the classic example of flat. Hundreds of smaller glacial lake plains are found in North Dakota too.

Dead-ice moraine on Missouri Coteau

Fig. 2-E. Dead-ice moraine topography on the Missouri Coteau, about five miles north of Palermo, Mountrail County. The road helps to show the relief. Photo: 7-2-2010.






As the glaciers flowed over North Dakota, they tended to smooth off and wear down the hill tops and fill in the lower areas with sediment. The overall result is a fairly level landscape. The layers of glacial sediment underlying that landscape are extremely complex, containing buried river channels, blocks of sandstone and shale, old landscapes that were covered many times by fresh glacial sediments. Buried layers of gravel and sand, deposited by water flowing from the melting glacial ice, constitute aquifers. They contain some of our best sources of fresh water.

As the ice flowed, in some places it picked up large chunks of material and moved them short distances before setting them down again. A good example of this is at Devils Lake, where a large amount of material was picked up and moved southward a few miles. Today, Devils Lake lies in a broad lowland. South of the lake is a high range of hills, including Sully’s Hill. The hills consist of materials that were once in the lowland where Devils Lake is now.

In some places, huge floods of water from melting glaciers carved deep river channels. Countless small meltwater valleys, along with some large ones too, are found throughout eastern and northern North Dakota. The Sheyenne, Souris, and James River valleys are good examples of large meltwater valleys. Valley City, Minot, and Jamestown are nestled in meltwater valleys. The Missouri River valley is another example of a glacial river channel, but it had such a complicated history that I’ll plan on writing a special article about it.

How thick were the glaciers that covered North Dakota? Certainly, they were more than a thousand feet thick in the east and north, so thick that the Earth’s crust beneath the ice buckled and sagged downward, eventually rebounding when the ice melted.

Baldhilll Creek, glacial meltwater channel

Fig. 2-F. Baldhill Creek in its meltwater valley about three miles south-southeast of Hannaford in southern Griggs County. This is an example of a very small stream flowing in a valley that is much too large for the size of the stream (an “underfit stream”). The valley was formed by a much larger flow of water from melting glacial ice. Photo: 6-29-2011.

Who or what lived in North Dakota during the Ice Age? Mastodons and wooly mammoths lived along the edge of the glacier. Elk, caribou, and horses were common. Horses became extinct in North Dakota  and in  North America at the end of the Ice Age, They survived, worldwide, because they had migrated to Asia via the land bridge between North America and Asia prior to then. During my field work over the years, I’ve found mastodon teeth, caribou bones and, in the Lake Agassiz deposits, fossil fish bones, mainly perch. It’s likely that early humans also lived here while the most recent glacier was still melting.

I’ve mainly been discussing North Dakota’s glacial landscape. Part of the state, the southwest quarter, was not glaciated, but the glaciers also left their mark there. The badlands along the Little Missouri River owe their existence to early glaciers that diverted the river eastward from its northerly route into Canada. This diversion triggered greatly increased erosion by the Little Missouri River, which resulted in the formation of badlands.  Some places that were not glaciated are marked by polygons, formed when permafrost froze the land beyond the limit of the glaciers.

Sheyenne River; meltwater channel, erratics

Fig. 2-G. Sheyenne River meltwater channel (a small part of the valley) about six miles southeast of Cooperstown in southern Griggs County. Notice the large number of glacial erratic boulders on the slopes of the valley wall. Erratics remain behind when erosion by the running water removes the finer materials (silt, clay, etc.). Photo: 6-29- 2011.


During my 42 years with the Geological Survey (1962 – 2004), I worked on nearly every facet of North Dakota geology: the rocks that produce oil, gas, coal, gravel, ground water and our other mineral resources. My studies of the glacial sediments near Devils Lake helped me to gain detailed insights into North Dakota’s past climate changes. However, I was always most interested in the origin of the hills and valleys I saw every day as I traveled around the state. I’ve spent a lifetime trying to understand how the land that is North Dakota came to be the way it is. My wife, Mary, and our three children as they came along, lived with me in about 25 North Dakota towns over the years. Our oldest son, Bill, was born in Park River while I was mapping Walsh County, and our daughter, Irene, arrived in Lisbon while I was mapping Ransom County. Paul, the youngest, was born in Grand Forks on the first day of January, when it was too cold to map anywhere. Over the years, we lived, up to six months each, in places like Carrington, Cooperstown, Harvey, Hazen, Mayville, McClusky, Washburn, White Shield, Fort Totten, Fort Yates, Rock Lake, and Turtle Lake. Our summer homes were in towns in about 30 counties, and on four Indian Reservations. We enjoyed every one of them.

Fig. 1-A. Mose is one town we never stayed in. On July 12, 1943, a tornado moved west from the town of McHenry toward Mose, twisting trees out of the ground as it went. As it came, it developed into one of the biggest storms in North Dakota’s history. Twenty-one-year-old Helen Johnson stood in the north window of her home and watched the driveway go, along with a bridge over the ditch at the front of her house. Mose actually survived for another 12 years before the post office finally closed. Mose was located about six miles west of Banford in Griggs County. Photo: 9-10-2009.

Each place was special in some way. North Dakota people are open and friendly, and often interested in geology. When we arrived at a new place, we asked locally if anyone had an apartment for rent and, usually, someone did. In Harvey we rented from the owner of the town bakery—a great choice! In Enderlin, our landlady’s son, a hunter, kept us supplied with pheasants and geese that autumn. In another town, our landlady’s son provided us with wild turkeys (some of them may have been poached—we didn’t ask). In another place, we shared a rental house with some bats. In Fort Yates, the brand-new nursing home was not yet filled and still had room, so that became our home. Our little kids were a hit with the elderly residents. I worked in every part of the state. A “field season” for me usually lasted from sometime in May, beginning when it was dry enough to get around, and ending in November, when the ground was frozen too hard to auger a hole. Just before Thanksgiving, we would move back to our own home in Grand Forks. The day after we got home one year, I raked the yard and put up the storm windows. The next day a blizzard blew, and the snow stayed until spring. Our neighbor, an elderly Norwegian man, commented, in his wonderful accent, “that Bluemle, he always times things right.” Well, I don’t “always time things right,” but I was glad I had that year. For the nearly 25 years that we spent our summers “in the field,” throughout North Dakota, we tended to visualize Grand Forks as a white and snowy “winter wonderland” because we weren’t around much to enjoy it in the summer time. Mary and I claim some important knowledge and understanding of North Dakota, apart from the geology. While mapping, I noted stands of chokecherries, wild plums, buffalo berries and juneberries. That valuable information went on my field maps, right along with the geology, as did the locations of the best places to buy sausage and kuchen.

This witch hit the road sign at the end of the driveway into the Davis Ranch in Slope County, October 23, 2009. She represents my own pondering as I tried to decide “which way to turn” as I constructed this website.

Fig. 1-B. This witch hit the road sign at the end of the driveway into the Davis Ranch in Slope County, October 23, 2009. She represents my own pondering as I tried to decide “which way to turn” as I constructed this website. Photo: 9-10-2009.

Most of the photos I will post on this website will illustrate landforms. I hope they will help readers appreciate and understand the geologic processes that shaped our modern landscape. I took most of them during the summers of 2009, 2010, and 2011 while we traveled throughout the state. The notion to travel around the state in the summer as kind of a “post-retirement” project turned out to be a great decision. To provide purpose, I took photos of geologic features. During some of our trips around the state we got a little more “off the beaten path” than I intended. One day, I drove along a road on the Missouri Coteau that became a trail, and eventually a narrow, mostly washed-out path with no place to turn around easily, so I kept going. Finally, we came to a barricade, so I stopped and walked around it to read the hand-printed sign: “Do Not Enter: Road Impassible.” The seven miles I had just driven were Longhorn cattle.IMG_1789_webimpassible! I dug out a couple of the steel fence posts, drove to the “good” side of the barricade, and replaced the posts and sign. Another day, I walked over to a fence line, took a picture, and stepped in a badger hole and broke my foot. Still another time, we stopped to admire a herd of longhorn cattle, standing on the road, surrounding us. I thought one was particularly handsome so I took his picture through the open window on the passenger side of our van. I felt something cold, turned around, and found myself nose to nose with a cow that had gotten her head in through the open window as far as her horns allowed. I presumed she probably wanted her picture taken too, so I snapped her as well.

Top photo shows the "handsome" Longhorn. Lower photo shows the cow that got her head inside our van. Notice that the bark has been scraped off some trees. Billings County, September 10, 2009

Figs. 1-C & 1-D. Top photo shows the “handsome” Longhorn. Lower photo shows the cow that got her head inside our van. Notice that the bark has been scraped off some trees. Billings County, 9-10-2009.

Many geologists move from country to country around the world; we moved from county to county around the state of North Dakota. Unspoiled prairies and buttes, rivers and lakes, wildflowers and wild fruit are everywhere. Wildlife abounds. Gravel trails lead to broad horizons. Late afternoon summer

This "gravel road leading to broad horizons" shows an area of dead-ice moraine topography with a crop-dusting airplane spraying a weed-infested slough area. About six miles south of Hurdsfield, Wells County, August 8, 2009.

Fig. 1-E. This “gravel road leading to broad horizons” shows an area of dead-ice moraine topography with a crop-dusting airplane spraying a weed-infested slough area. About six miles south of Hurdsfield, Wells County. Photo: 8-8-2010.

showers are followed by spectacular sunsets. The prairie landscapes are multi-dimensional. Their breadths, elevations and depths reflect geologic events and processes I’ll explore on this website. And the geology is always there. Geology opens the door to another world just beneath the familiar scenes of our everyday lives. It takes us outdoors as we explore the intricacies of our Earth’s history. Mary and I have traveled beyond North Dakota–to most of the states and Canadian provinces and about 20 other countries. Much of our travel has been to enjoy geology. We’ve seen a lot of spectacular geology in places like Montana, Alberta, and Sweden. Scotland is my favorite destination for geology and for the history of the science of geology. Our geology, here in North Dakota, may be more subtle than the places I just mentioned, but it is just as interesting. My career has been satisfying, my work interesting and rewarding. Every day on the job was different for me. Whether it was the glorious summer days in the field, mapping geology, or wintry days I spent in my office, piecing together and trying to understand what I had mapped the previous summer, it was always fascinating.

Fig. 1-F. “A Tree Grows in Hatton.” This tree in the park has its roots in the air. I don’t think it represents one of the intricacies of our earth’s history, just someone with a backhoe, a sense of humor, and some extra time. This part of Traill County, which includes the Hatton area, is part of the Elk Valley Delta in which sandy silt was deposited by streams flowing into Glacial Lake Agassiz. I took this photo on May 31, 2010.

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