Sedentary Soils

In a general way the soils in that part of Northern United States which was covered by the great glacier are mostly transported, while the soils farther south, and east of the Mississippi River, are mostly sedentary. Sedentary soils are usually not deep, because the mother rock beneath weathers very slowly, being largely protected by the soil above it. The red clay soils of Tennessee, Georgia and other parts of the South, and the famous "blue grass soil" of Kentucky, derived from limestone, are excellent illustrations of a sedentary soil. They are usually very fertile. Other examples of a sedentary soil are muck and peat, which are made almost entirely by the decay of plants, together with the little mineral material that is blown in. The plant that accomplishes the most in this direction is sphagnum moss. It is a semi-aquatic plant and grows with great luxuriance, making a thick carpet over the water. Eventually the whole surface of a shallow pond may be covered with sphagnum.

Other plants get a foothold upon this — rushes, sedges, cattails, cranberries, and the like. "Floating" cranberry bogs are quite common on the freshwater marshes of Cape Cod. Finally the covering of plants is solid enough and has decayed sufficiently for small water-loving shrubs, as huckleberries and alders, to get established. The floating carpet gets thicker and heavier from the decay of plants; finally it either breaks and sinks at once to the bottom of the stream or lake, or sinks into it gradually and is covered with water. Then begins the formation of peat. This process of pond, swamp, and stream filling is going on in all parts of the United States, mostly on a small scale but sometimes on large areas. One million acres of soil in the Kissimmee Valley of Florida have been made in this way. The Great Dismal Swamp of Virginia is another illustration. When drained these swamps may be very fertile.