Chronicles of America 

The Plains

The plains of North America form the third of the four main physical divisions of the continent. For the most part they lie between the great western cordillera on one side and the Laurentian and Appalachian highlands on the other. Yet they lap around the southern end of the Appalachians and run far up the Atlantic coast to New York. They remained beneath the sea till a late date, much later than the other three divisions. They were not, however, covered with deep water like that of the abysmal oceans, but only with shallow seas from which the land at times emerged. In spite of the old belief to the contrary, the continents appear to be so permanent that they have occupied practically their present positions from the remotest geological times. They have moved slowly up and down, however, so that some parts have frequently been submerged, and the plains are the parts that remained longest under water.

The plains of North America may be divided into four parts according to the character of their surface: the Atlantic coastal plain, the prairies, the northwestern peneplain, and the southwestern high plains.


peneplain (PEE-nuh-playn, pee-nuh-PLAYN) noun

An area of nearly flat, featureless land formed by a long period of erosion.

[From pene- (almost), from Latin paene + plain, from Latin planus.]

The Atlantic coastal plain lies along the Atlantic coast from New York southward to Florida and Alabama. It also forms a great embayment up the Mississippi Valley as far as the Ohio River, and it extends along the shore of the Gulf of Mexico to the Rio Grande. The chief characteristic of this Atlantic and Gulf coastal plain is its belted nature. One layer of rocks is sandy, another consists of limestone, and a third of clay. When uplifted and eroded each assumes its own special topography and is covered with its own special type of vegetation. Thus in South Carolina and Georgia the crystalline Piedmont band of the Appalachian province is bordered on the southeast by a belt of sandstone. This rock is so far from the sea and has been raised so high above it that erosion has converted it into a region of gentle hills, whose tops are six hundred or seven hundred feet above sea-level. Its sandy soil is so poor that farming is difficult. The hills are largely covered with pine, yielding tar and turpentine. Farther seaward comes a broad band of younger rock which forms a clayey soil or else a yellow sandy loam. These soils are so rich that splendid cotton crops can be raised, and hence the region is thickly populated. Again there comes a belt of sand, the so-called "pine barrens," which form a poor section about fifty miles inland from the coast. Finally the coastal belt itself has emerged from beneath the sea so recently and lies so nearly at sea-level that it has not been greatly eroded, and is still covered with numerous marshes and swamps. The rich soil and the moisture are good for rice, but the region is so unhealthy and so hard to drain that only small parts are inhabited.

Everywhere in the coastal plain this same belted character is more or less evident. It has much to do with all sorts of activities from farming to politics. On consulting the map showing the cotton production of the United States in 1914, one notices the two dark bands in the southeast. One of them, extending from the northwestern part of South Carolina across Georgia and Alabama, is due to the fertile soil of the Piedmont region. The other, lying nearer the sea, begins in North Carolina and extends well into Alabama before it swings around to the northwest toward the area of heavy production along the Mississippi. It is due to the fertile soil of that part of the coastal plain known as the "cotton belt." Portions of it are called the "black belt," not because of the colored population, but because of the darkness of the soil. Since this land has always been prosperous, it has regularly been conservative in politics.

The Atlantic coastal plain is by no means the only part of the United States where the fertility of the soil is the dominant fact in the life of the people. Because of their rich soil the prairies which extend from western Ohio to the Missouri River and northward into Canada are fast becoming the most steadily prosperous part of America. They owe their surpassing richness largely to glaciation. We have already seen how the coming of the ice-sheet benefited the regions on the borders of the old Laurentian highland. This same benefit extended over practically the whole of what are now the prairies. Before the advent of the ice the whole section consisted of a broadly banded coastal plain much older than that of the Atlantic coast. When the ice with its burden of material scraped from the hills of the north passed over the coastal plain, it filled the hollows with rich new soil. The icy streams that flowed out from the glaciers were full of fine sediment, which they deposited over enormous flood plains. During dry seasons the winds picked up this dust and spread it out still more widely, forming the great banks of yellow loess whose fertile soil mantles the sides of many a valley in the Mississippi basin. Thus glaciers, streams, and winds laid down ten, twenty, fifty, or even one hundred feet of the finest, most fertile soil. We have already seen how much the soil was improved by glaciation in Wisconsin and Ohio. It was in the prairie States that this improvement reached a maximum. The soil there is not only fine grained and free from rocks, but it consists of particles brought from widely different sources and is therefore full of all kinds of plant foods. In most parts of the world a fine-grained soil is formed only after a prolonged period of weathering which leaches out many valuable chemical elements. In the prairies, however, the soil consists largely of materials that were mechanically ground to dust by the ice without being exposed to the action of weathering. Thus they have reached their present resting-places without the loss of any of their original plant foods. When such a soil is found with a climate which is good for crops and which is also highly stimulating to man, the combination is almost ideal. There is some justification for those who say that the north central portion of the United States is more fortunate than any other part of the earth. Nowhere else, unless in western Europe, is there such a combination of fertile soil, fine climate, easy communication, and possibilities for manufacturing and commerce. Iron from that outlier of the Laurentian highland which forms the peninsula of northern Michigan can easily be brought by water almost to the center of the prairie region. Coal in vast quantities lies directly under the surface of this region, for the rock of the ancient coastal plain belongs to the same Pennsylvanian series which yields most of the world's coal. Here man is, indeed, blessed with resources and opportunities scarcely equaled in any other part of the world, and finds the only drawbacks to be the extremes of temperature in both winter and summer and the remoteness of the region from the sea. Because of the richness of their heritage and because they live safely protected from threats of foreign aggression, the people who live in this part of the world are in danger of being slow to feel the currents of great world movements.

The western half of the plains of North America consists of two parts unlike either the Atlantic coastal plain or the prairies. From South Dakota and Nebraska northward far into Canada and westward to the Rocky Mountains there extends an ancient peneplain worn down to gentle relief by the erosion of millions of years. It is not so level as the plains farther east nor so low. Its western margin reaches heights of four or five thousand feet. Here and there, especially on the western side, it rises to the crest of a rugged escarpment where some resistant layer of rocks still holds itself up against the forces of erosion. Elsewhere its smooth surfaces are broken by lava-capped mesas or by ridges where some ancient volcanic dike is so hard that it has not yet been worn away. The soil, though excellent, is thinner and less fertile than in the prairies. Nevertheless the population might in time become as dense and prosperous as almost any in the world if only the rainfall were more abundant and good supplies of coal were not quite so far away. Yet in spite of these handicaps the northwestern peneplain with its vast open stretches, its cattle, its wheat, and its opportunities is a most attractive land.

South of Nebraska and Wyoming the "high plains," the last of the four great divisions of the plains, extend as far as western Texas. These, like the prairies, have been built up by deposits brought from other regions. In this case, however, the deposits consist of gravel, sand, and silt which the rivers have gradually washed out from the Rocky Mountains. As the rivers have changed their courses from one bed to another, layer after layer has been laid down to form a vast plain like a gently sloping beach hundreds of miles wide. In most places the streams are no longer building this up. Frequently they have carved narrow valleys hundreds of feet deep in the materials which they formerly deposited. Elsewhere, however, as in western Kansas, most of the country is so flat that the horizon is like that of the ocean. It seems almost incredible that at heights of four or five thousand feet the plains can still be so wonderfully level. When the grass is green, when the spring flowers are at their best, it would be hard to find a picture of greater beauty. Here the buffalo wandered in the days before the white man destroyed them. Here today is the great cattle region of America. Here is the region where the soul of man is filled with the feeling of infinite space.

To the student of land forms there is an ever present contrast between those due directly to the processes which build up the earth's surface and those due to the erosive forces which destroy what the others have built. In the great plains of North America two of the divisions, that is, the Atlantic coastal plain of the southeast and the peneplain of the northwest, owe their present form to the forces of erosion. The other two, that is, the prairies and the high plains, still bear the impress of the original processes of deposition and have been modified to only a slight extent by erosion.