Bulletin No. 37. Minnesota's Rocks and Waters A Geological Story

with assistance from Peggy harding LoveThis volume has been prepared in an attempt to make available to the citizens of Minnesota a general summary of the major geological features of the state and to stimulate a greater interest in, and appreciation of, their natural surroundings. Ability to interpret the landscape requires knowledge of the forces that produced it. One may admire the beauty of a waterfall or marvel at its grandeur, but to appreciate it fully, one must know how it was formed. Man draws from the earth many materials which are necessary for life and happiness, and he deals with geological conditions in many of his daily activities. For example, he plows the soil, which is composed largely of weathered rock materials, and cuts the surface rocks as he grades roads and railroads and excavates foundation places for his skyscrapers and his great plants in which to exploit the earth's resources. Yet how many of the thousands of citizens of Minnesota employed in these enterprises understand the geological relationships of the materials with which they labor? How much greater would be their interest in their assigned tasks if they knew more about the formation of the materials which occupy their attention? An understanding of geological processes guides us in the search for mineral resources and aids us in understanding the forces which produced them. Soil erosion, one of our most important problems, is closely related to the geology of the area involved. The resources of any region determine to a marked degree the activity of its inhabitants. They are the foundation of our well- being, the hope of our future. Minnesota, though known as an agricultural state, has great mineral wealth, and many of its citizens are engaged in mineral industries. All of the mineral substances produced from the rocks of the state may be classified as industrial minerals even though some are metals and others nonmetals. :Metal mining is restricted to the iron ranges, but the nonmetals include a great variety of materials-such as limestone for agricultural lime. marl, sand and gravel, clays and shales, wool rock, and structural and architectural stone-which are excavated and processed at many places in the state. The authors of this book have had many years of experience in educational work in Minnesota. It is their opinion, based upon observation and experience, that in the curriculums in our schools not enough time is devoted to a study of our own state and its resources. It is hoped that this volume will furnish science teachers 'with accurate information which they can in turn pass on to their students at the appropriate time, and that citizens at large will find it a source of information regarding their state. Technical terms have been held to a minimum in order to make the text intelligible to those unfamiliar with detailed geological terminology. The authors know that this method inevitably results in generalities that may not always take into account all detailed scientific information available to the geologist. We hope, however, that geologists will recommend the book to their friends and that they will not hesitate to explain some of the exceptions that are bound to appear where such broad generalizations are employed for the sake of simplicity. Geology is the science that weaves all the other natural sciences together into a comprehensive whole and this results in great complexity. The authors, with full awareness of the magnitude of the task, have attempted to resolve complex geological details by employing a nonscientific assistant who screened out much of the detail and obtained a residue that is sufficiently free of technicalities to be comprehensible to the general reader