All geologists know that the Earth is not flat; it has landforms, such as rivers, valleys, hills, and mountains. Maps are a two dimensional representation of the three-dimensional Earth. They can be used to show the location of objects or features, their shape (physical characteristics), cultural features (buildings, roads, cities, etc.) and political features, such as state, county, international boundaries, and, most important for geologists, they can be used to show the extent and age of geological units and structures. Geologists use topographic and geologic maps and imagery to study the Earth. The links below can be used to connect to separate pages on maps, geologic maps, imagery and photographs.