Indiana has great wealth in its mines and quarries, its water supply, and, in spite of waste and misuse, its soil and timber. The mineral wealth is derived largely from the sedimentary rocks consisting of limestone, sandstone, shale, and coal, with large deposits of clay and kaolin in certain parts of the State. Sand and gravel are also plentiful.
The State's best-known mineral resource is an almost unlimited supply of building stone, chiefly obtained from limestone deposits. The most dependable Indiana stone, of which there are several varieties, is quarried from the Mississippian system of rocks. All the varieties are used widely for the manufacture of lime and cement, and locally for building. The Indiana oölitic limestone (so called because of its granular structure, which suggests a mass of fish eggs) is one of the finest building stones quarried in the United States. A medium- to finegrained stone with even texture, it is soft and easily carved when first quarried, but under the action of atmospheric agents becomes hard and durable. From the chief quarries in Monroe and Lawrence Counties, this stone is shipped all over the United States and to foreign countries.
In the area of the Pennsylvanian rocks there are extensive deposits of bituminous coal. Third in value among mineral resources is clay, found largely in the Pennsylvanian rocks, especially in the coal-bearing areas. Thirty years ago the clays were regarded as a detriment to coal mining; today, although not yet fully utilized, they rank in value next to coal and stone.
Because of its fine clay deposits and immense supply of limestone, Indiana ranks high in the manufacture of Portland cement. There are extensive deposits of stone in southern Indiana, at present unused, that are also suitable for cement manufacture. Huge quantities of sand and gravel are extracted from gravel pits every year and used in the manufacture of cement, plaster, and glass, and in the surfacing of roads.
In earlier periods several minerals were more important to Indiana industry than they are today. Iron ore was formerly mined, but in recent years iron of much better quality is imported. Marl, a clay-like substance found at the bottom of some lakes, was formerly an important mineral used in making cement. Immense wells of natural gas were wasted between 1890 and 1910; a little later, in the same area, oil production boomed but declined after a few years. Today another oil boom is developing in many Indiana counties.
Indiana has a great area of rich soil suitable for agriculture. Over most of the northern two-thirds of the State lie deep, silty, light-brown loams, weathered by glaciers from limestone and sandstone. In the 'driftless' area the soils are thinner and less fertile -- heavy clay soils, brown silt loams, or yellowish soils of a silty to sandy character, weathered largely from limestone. Their fertility was depleted by an unvaried succession of corn crops during pioneer times.
Two hundred years ago fully seven-eighths of the State was covered with forests. The only treeless area was the prairie land in the northwest. A century's waste of these forests, however, has meant devastation of many kinds. The trees had stored moisture in the earth, and this served the thirsty plants in time of drought. After the trees were gone, when heavy rains fell, the water (no longer held back by roots and mold) drained swiftly toward the streams and washed the soil off the hillsides. Swollen tributaries rushed into main streams, overflowing their banks and sometimes creating serious floods. In a long dry period, on the other hand, the soil dried quickly to a great depth, since water could no longer be easily retained. Streams ran dry, and moistureless winds blew away the topsoil in clouds of dust. Thus the destruction of the forests brought in its wake floods, drought, and soil erosion.
Despite these tragic losses, the supply of hardwood timber still constitutes a valuable natural resource. Although much of it is of young trees, the remaining first-growth timber is of high quality, including such species as walnut, ash, poplar, elm, hickory, maple, and many kinds of oak, some reaching an exceptionally large size. Throughout southern Indiana and in several northern counties are vast areas that could easily be devoted principally to forests.
In the southern hills the problems of drought, flood, and soil erosion are extremely acute. A suggested solution is the retirement of most of the region from agriculture and the reforestation of the hills. Good drainage and limestone soils in certain areas would make the cultivation of fruit trees profitable, and a gigantic State forest stocked with game is contemplated in the 'driftless' area. Throughout the reforested section, tree roots would nail the soil to the slopes; water would be adequately stored; and streams would not swell toward flood proportions in rainy weather.
Northern Indiana is so low that bogs are common and storage is more than adequate. Hence there is no danger of flood, drought, and soil erosion. But even here natural resources have been misused in the clearing and drainage of submarginal land. Again a suggested solution is to retire this poor land from agriculture and plant extensive forests.
In central Indiana, agriculture is sometimes menaced by drought and flood, since rainfall, although fairly adequate, is irregular. Because of the deep, level soil, however, there is less damage from erosion here than in the south. Since the region is too valuable agriculturally for extensive reforestation, experts particularly recommend the planting of 'riverside forests'; the development of irrigation; and the increased use of the self-controlling dam, allowing an ordinary flow of water to escape but retaining the excess amount in storage ponds. Thus the water table would be lifted and maintained as a precaution against drought. During rainy weather the dams would take the crest off the floods, preventing torrents.