| Summary: | 532 NORTH DAKOTA CENTENNIAL BLUE BOOK GEOGRAPHICAL AND GEOLOGICAL FEATURES Many people do not realize the extent to which their activities depend upon their geological and geographical environment. Better than half the state's fertile soil depends upon continental glaciation; the great coal resources of the western half of the state are the result of geological processes which operated millions of years ago. Briefly, rocks of four great eras of geological time are known to be present in North Dakota, although not all are exposed at the surface. Cryptozoic crystalline rocks are deeply buried and provide the " basement" rocks upon which all other rocks were deposited. Upon these crystalline rocks were deposited marine sandstones, shales, and the limestones of the Paleozoic era. These Paleozoic rocks offer the best possibilities for oil in the state. After the deposition of the Paleozoic rocks, a great erosion interval intervened and much of the Paleozoic rocks were worn away, particularly in the eastern part of the state. Upon this eroded prehistoric landscape were later deposited rocks of the Mesozoic era. Some of these rocks, like famous artesian water- bearing Dakota sandstone, were deposited on land or under terrestrial conditions, while others were deposited in a vast seaway which extended from the Arctic to the Gulf. Following the deposition of the Mesozoic rocks, continental conditions prevailed rather largely in North Dakota. During the Cenozoic era, conditions were apparently more moist than now and great swamps and forests of conifers and other trees prevailed over much of the state. In these swamps accumulated great thicknesses of partially decayed vegetable matter which has been changed through the action of the overlying rocks and subsequent heat into our great lignite coal beds. Long after the deposition of the coal, many of these beds were exposed at the surface through the stripping action of erosion by running water. Through spontaneous combustion or by accidental ignition by lightning or prairie fires, some of these beds started to burn, producing the famous ash and " scoria" beds so familiar in southwestern North Dakota. The " scoria" can be attributed to the " clinkering" or baking and fusing together of the overlying shale and sand due to the heat of the burning lignite. This so- called " scoria" is not true scoria in the geological sense. In comparatively recent geological time, much of the northern and eastern parts of the state were covered by the glacial ice which was many hundreds of feet thick. This ice brought down from Canada much fertile soil, as well as rocks. It also blocked the northward flowing Red River, forming the famous glacial Lake Agassiz. whose old lake bed now forms the beautiful and fertile Red River Valley. In addition, the ice forced the old north flowing Missouri River into its present course. Physiographically, North Dakota can be divided into three plains rising like steps from the east to the west. The easternmost plain is the old lake bed of glacial Lake Agassiz, the Red River Valley. This plain is present on both sides of the river, and the North Dakota portion is from 30 to 40 miles wide. At the southern end at Wahpeton, the elevation of the plain is 965 feet, declining northward at the approximate rate of one foot per mile to 789 feet above sea level at the Canadian line near Pembina. Bordering the Red River Valley plain on the west is an escarpment which is prominent in the northeastern part of the state, but much less so in the southeastern part of North Dakota. This escarpment, known as the Pembina Mountains in Cavalier County ( 300- 500 feet above the Red River Valley), marks the eastern boundary of the plain called the Drift plain that is intermediate in elevation between the Red River plain on the east and the Missouri Plateau on the west. It is known as the Drift plain as its surface is covered entirely by glacial drift to a considerable depth in some cases. However, glacial drift is not limited to the Drift plain. but is also found on the Missouri Plateau. Topographically, the Drift plain consists of rolling land excellently suited to farming. A number of lakes, the largest of which is Devils Lake, are also found here. Devils Lake is a lake with no outlet and thus, is quite salty. The Drift plain varies in elevation from 1,300- 1,650 feet above sea level and is 70 miles wide on the southern border of the state and over 200 miles wide at the Canadian boundary. On the west, rising above the Drift plain, is the Missouri Coteau, an escarpment 300- to 400- feet high, that marks the eastern boundary of the Missouri Plateau. The Missouri Plateau extends from the Missouri Coteau westward to the Rocky Mountains. It has considerable variation in elevation; east of the Missouri River it is 1,800- 2,000 feet above sea level, but in the northwestern part of the state it is 2,200 to nearly 2,400 feet above tide. The Missouri Plateau reaches its greatest elevation in the southwestern part of the state where it has an elevation of from 2,800 to better than 3,100 feet. A number of buttes in the southwestern part of the state rise above the general elevation of the plain, and one of these buttes, White Butte in Slope County, has an elevation of 3.506 feet above sea level, the highest elevation in the state. No description of the scenery of the Missouri Plateau would be complete without mention of the picturesque badland country along the Little Missouri. Cannon ball, and other rivers in the southwestern part of the state. Here, immediately adjacent to the rivers, rapid erosion of the relatively soft shales and sands has created an intricate maze of sharp gullies. On the steep sides of the buttes, the
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