Earthscapes: The Red River Valley Buffalo Trails and Iceberg Tracks by Don McCollor   Click on highlighted words for images and additional information Nature builds in curves. Consider a meandering river, the shapes of a tree, the gentle elevations superimposed on the nearly flat Valley floor. Man does not. The mark of human activity in the Valley is geometric: the straight lines of roads, the squares of fields, the marching lines of planted shelter belt trees. This is especially evident on maps and aerial photographs. To see the course English Coulee in Brenna township abruptly abandon its meandering and flow due north, then east instantly betrays the hand of man at work on the landscape. Natural features are not expected to be straight or round. It is precisely for this reason that occasional geometric natural features attract curiosity. They stand out --regular order where none should be. Although not of great consequence in the geological scheme of the Valley, features like the buffalo trails are interesting because they are items of curiosity. The trail of the buffalo trails begins with features left on the Agassiz lake bed and surrounding shores by the ices sheets of the Pleistocene glaciers. Like today's alpine (mountain) glaciers and the ice sheets of Greenland and Antarctica, deep crevasses opened in the ice due to the flow of the ice. Such crevasses tend to occur in fairly straight parallel lines. Often these developed into a core of ice covered by fluvial (river) deposits of sand and gravel. As the supporting ice core melted, linear depressions formed in the fluvial sediment on level terrain, changing to ridges where depressions were crossed. Such disintegration ridges are overlain on the underlying topography, and can be used to estimate flow direction of the glacier ice. Very similar looking linear depressions like the depression ridges, several feet wide and deep are often seen extending for hundreds of feet on aerial photographs. Again, they become ridges where depressions are crossed. However, these are etched into the local topsoil rather than in river sediments and usually run northwest to southeast, parallel to the prevailing wind. First identified by Clayton (see reference) as buffalo trails, they are aimed at right angles directly at permanent rivers but do not cross them and do not traverse difficult terrain. The disintegration ridges, being dropped from above so to speak, tend to ignore the current local terrain obstacles. The buffalo (properly the American bison) locate water by smell, follow a more or less direct course upwind. The deep watering trails were formed by the hooves of countless bison herds traveling to watering places, probably over centuries. Another interesting feature particularly noticeable on aerial photographs is low ridges and grooves found on the flat bed of Lake Agassiz. Like the buffalo trails, they are oriented northwest and southeast. In form, the ridges are three to ten feet ( 1 to 3 meters) high, 75 to 100 feet (22 to 30 meters) wide, and extend as far as six miles (10 kilometers) across the lake bed. However, the ridges lead from nowhere to nowhere, and most curve to the east or southeast. At ground level, they are not easily noticed, unless one is specifically looking for them, map in hand. Perhaps furrows made by very large plows? Skid marks left when Paul Bunyon logged off the Dakotas? The suggestion of furrows left by gigantic plows is not far wrong. The most plausible explanation was advanced by (once again) Clayton, who suggested that the ridges and grooves are the track of wind-driven ice sheets and blocks scraping along the lake bottom. The curved track is explained as the result of prevailing winds shifting from southeast to northwest as the ice is sailing and dragging the lake bed. Very similar tracks are seen on the bottom of the shallow waters of the modern-day Great Slave Lake in northern Canada. Normally, flat sheets of lake ice would not ride deep enough to groove the lake bottom. Rather, the ridges were formed by the edge of ice sheets as one side touched bottom in shallower water than the rest of the ice mass. However, thick pressure ridges form from ice movement in large modern-day lakes, possibly forcing ice deep enough to touch bottom. to explored was the possibility that, if Lake Agassiz extended right against the ice face, actual icebergs might split off (calve) from the glacier ice.   Bison Trails and Their Geologic Significance, Clayton, Lee, Abstracts with Programs, Vol. 2, No. 6, North Central Section Fourth Annual Meeting, The Geological Society of American, 1970, p. 381. Intersecting Minor Lineations on Lake Agassiz Plain, Clayton, Lee, Laird, Wilson M., and Kupsch, W. O., Journal of Geology, Vol 73, 1965, pp. 652-656. Another natural feature which attracts attention is an almost perfectly round feature such as a lake. This may be indicative of volcanic origins, such as Crater Lake in Oregon or of meteor impact like the Clearwater Lakes in northern Quebec. Such a curiously round feature is Roseau Lake in northwestern Minnesota. The steep-sided, flat bottomed lake is a little over 3 miles (5 kilometers) in diameter and 10 feet (3 meters) deep. From the round form and higher ground northwest of the lake, it was thought to be a possible impact crater. Alas, a 1975 gravity survey did not show the lower readings indicative of a sediment-filled impact crater. Further, bedrock in only 150 feet (45 meters) below the glacial drift. This is far shallower than the depth expected to be evacuated by an impact event of that size. the study concluded that the lake is a kettle lake (formed by the burial of a large ice block in drift, with the lake in the depression resulting after the ice finally melts away.)   Minnesota's Geology, Ojakangas, Richard W., and Matsch, Charlers L., University of Minnesota Press, Minneapolis, 1982, pp. 207-208. Crater or Kettle? A Geophysical Study, Hammer, Sigmund, and Ervin, C. Patrick, Geology (Boulder), Vol 3, No. 3, 175, pp. 145-146. Images provided by the U.S.G.S. Back The buffalo come in two species, the Plains Bison (Bison bison) and their cousins the Woods Bison (Bison athabascae), although the "buffalo" of popular image is the Plains Bison. Between them, they once roamed from the Rockies to the Appalachians in staggering numbers. In Kansas a Col. Dodge wrote of traveling thirty-five miles (56 kilometers) between two military posts, at least 25 miles (40 kilometers) of which was through one huge buffalo herd. General Sheridan, also in Kansas, attempted to estimate their numbers. He came up first with a figure of ten billion, somewhat arbitrarily whittled it down to one billion, and finally to one hundred million buffalo. Even the final figure was kept quiet, for fear of no one believing it. With the coming of railroads and the settlements of the plains, the buffalo were vigorously hunted for meat, hides, the tongues (a delicacy of the time), sport, to discommode the plains Indians, and just to remove the nuisance. On the continent their numbers decreased precipitously, surviving in a few isolated herds by the turn of the century. The last carload of hides was shipped from Dickinson in western ND in 1884.   The Buffalo Book, Dary, David A., Avon Books, New York, 1974. Buffalo-Back Home on the Range, Hodgson, Bryan, National Geographic Magazine, Vol 186, Nov. 1994, pp 64-89. Picture provided by EMAN of Canada. Back The buffalo apparently can smell water at some distance. For all its shaggy, ungainly looks, a buffalo can run nearly as fast (reportedly up to 38 miles/hour [ 60 kilometers/hour]) as a horse and be able to sustain the pace for many miles. Several pioneers saw the potential of the powerful animals to act as beasts of burden. One German farmer in Montana had trained two cow buffalo to draw a wagon like oxen. According to the account, he set out one hot day with a wagon load of potatoes heading for town. Somewhere along the way, the thirsty buffalo scented the water of the Tongue river and made a beeline for it at a thundering gallop. At the river, they roared straight over the bank into the water, along with farmer, wagon, and what potatoes, remained after the bone-jarring journey across the rough prairie. The Buffalo Book, Dary, David A., Avon Books, New York, 1974. Back One of the troubling questions as a child reading about the buffalo was the question of their remains. If there were so many buffalo and they were all killed off, where were the bones--particularly the potentially decorative skulls. It turns out that the buffalo bones were a "cash crop" for homesteaders and for the local Indians, with great quantities collected and sold for producing bone black (bone charcoal used to remove color and impurities in sugar refining) and fertilizer. The horns were sold for things like knife handles and the hooves for producing glue. One lumber company in northern Dakota recorded shipping a thousand carloads of bones each year from 1884 to 1891, representing an estimated nearly six million buffalo. Today it is a rarity for buffalo bones to be unearthed.   The Buffalo Book, Dary, David A., Avon Books, New York, 1974. Buffalo Bone Days, McCreight, Major. Israel., Nupp Printing, Sykesville, PA, 1939. Back The logging off of North Dakota was reputedly done by the legendary Paul Bunyon and faithful companion, Babe the Blue Ox. The latter was a magnificent beast "forty-two ax handles and a plug of Star tobacco between the eyes". The peculiar coloration was the result of standing outside in the savagely cold Winter of the Blue Snow. Logging of North Dakota (with Babe stomping the stumps out of sight) was performed at the request of the King of Sweden to permit the Swedes to settle and farm there. To answer the inevitable skeptic with irrefutable evidence, one need only point out the total absence of trees or stumps in North Dakota. Great American Folklore, Batton, Kemp E., ed, Barnes and Noble Books, NY, 1992, pp. 623-625. Photo courtesy of Ethan Haslett.Back Freshwater ice is 91.7% the density of water at the freezing point. A regular block of ice projecting three feet (1 meter) above the water surface would have its bottom approximately 27 feet (9 meters) below the surface. Back Disclaimer and Copyright