A map allows us to understand the Earth's surface and subsurface by illustrating the location of various rock types and the relationships that exist among different types of rocks. Geologic maps have information that we need in order to be able to produce a vast number of consumer goods we use in our daily lives and to assist us in making decisions about the wise use of mineral, fuel, and water resources that are the backbone of our economy. Maps are also essential for many recreational activities in our society; they provide information about the location of trails for hiking, streams and rivers for canoeing, lakes for swimming and boating, and fascinating geologic features in the landscape that are often the focal point of national and state parks.
What is a topographic map and how is it used? A topographic map is a reduced image of the Earth that illustrates the shape of the land surface and provides an important base for the construction of other, more detailed maps, such as geologic maps. Topographic maps typically include information about vegetation (e.g., forested areas), the elevation (depth and height) of hills and valleys, and the location of streams and rivers, lakes, roads, railroads, bridges, towns, and cultural features such as schools, churches, and cemeteries. Topographic maps are used by property owners, land developers, hikers, fishermen, biologists, environmentalists, oil and gas operators, coal miners, engineers, researchers, students, search and rescue workers, and emergency-response personnel for disaster preparedness (for example, flood control, fire fighting). Topographic maps are used by engineers to plan construction; by agricultural scientists to survey soils; by farmers to estimate crop yields; by military forces to plan troop movements on the ground; and by hikers, bikers, hunters, and campers for directions in the field (Mazzullo, 1997).
What is a geologic map? A geologic map illustrates the land surface, as well as describes the type of rock that exists at the surface immediately below the soil. Geologic maps typically include text that describes the rock types; the area covered by the map; the location of faults, mining activities, and quarries; and discusses the mineral resources (for example, oil, natural gas, coal, and limestone) likely to occur in the area.
Why should I use a geologic map? Information on geologic maps can be used to make informed decisions, build safe communities, develop resources, and explore recreational areas. For example, geologic maps can be used to identify areas that are prone to geologic hazards such as earthquakes, landslides, sinkholes, and flooding. Geologic maps can help guide the decisions of engineers and contractors to select locations that will be safe to build tunnels, bridges, dams, quarries, and large buildings (Lambert and the Diagram Group, 1998). Geologic maps provide information required to select safe places to build septic systems and landfill sites to minimize the risk of polluting soils and ground water. Similarly, geologic maps can be used to help farmers, land owners, and municipal officials locate water wells that will yield high volumes of safe drinking water. Geologic maps can be used to help locate mineral resources such as oil, natural gas, coal, and limestone for commercial development. Citizens can use geologic maps to find information about trails for hiking, rivers for canoeing and boating, and lakes for fishing.
What about geologic maps in Kentucky? Kentucky is in an enviably position among the U.S. states. We are one of the few states in the nation to have topographic and geologic maps that cover the entire area of the state. In Kentucky, it took 707 individual maps to cover the entire area of the state. The maps are published at a 1:24,000 scale, which means that one inch on the map represents 24,000 inches on the ground. This map scale provides a great deal of detail and is useful for urban and rural planning. All 707 geologic maps are referred to as geologic quadrangle maps or GQ's. For geologists, a quadrangle is a four-sided tract of land bounded by lines of latitude and longitude. The size of a quadrangle can be given in minutes: a 7.5-minute quadrangle map, at a scale of 1:24,000, has dimensions of 7.5 minutes for both latitude and longitude, and covers 50 to 60 square miles.
The Kentucky Geological Survey is converting the geologic maps of Kentucky from the traditional paper format into computer files. This conversion is important because the value of the information on the maps is greatly increased if it is in a digital format so that it can be used in a wide array of computer programs and applications. If maps are available in digital format, they become powerful research tools for many people, as well as making the information on the map available to any individual who has a computer in his or her office or home.