Geologic mapping is a highly interpretive, scientific process that can produce a range of map products for many different uses, including assessing ground-water quality and contamination risks; predicting earthquake, volcano, and landslide hazards; characterizing energy and mineral resources and their extraction costs; waste repository siting; land management and land-use planning; and general education (National Cooperative Geologic Mapping Program - USGS).
The distinctive characteristic of a topographic map is the use of elevation contour lines to show the shape of the Earth's surface. Elevation contours are imaginary lines connecting points having the same elevation on the surface of the land above or below a reference surface, which is usually mean sea level. Contours make it possible to show the height and shape of mountains, the depths of the ocean bottom, and the steepness of slopes (What Is a Topographic Map?).
“National Cooperative Geologic Mapping Program - USGS.” Introduction to Geologic Mapping, National Cooperative Geologic Mapping Program, https://www.usgs.gov/programs/national-cooperative-geologic-mapping-program.
“What Is a Topographic Map?” What Is a Topographic Map? | U.S. Geological Survey, U.S. Geological Survey, https://www.usgs.gov/faqs/what-topographic-map.
Sources/Usage: Public Domain.
When recording observations, geologists use descriptive terms and rock names that are in common use or unique to an area. These terms are then synthesized and rewritten into formal map unit descriptions that are published with the map (National Cooperative Geologic Mapping Program - USGS).
Geologic information such as rock composition and texture are being standardized at the national and international levels. This standard language can then be used in the field or in the office to organize and interpret field observations. Geologic terrains and geologic mapping agencies require multiple standard classifications to accommodate regional variations in terminology.