Detail from the 1:250,000-scale geologic map of the Newark quadrangle, New Jersey, Pennsylvania, and New York.

A geologic map shows the distribution, composition, and age of the rocks and sediments in a specific geographic area. "Geologic maps are the single most important and valuable tool we have for understanding and living with the Earth around us.

Their usefulness is so broad that geologic maps are the most requested scientific product produced by state and federal geological surveys" (Meeting Challenges with Geologic Maps an American Geological Institute Environmental Awareness Series).

Because geologic maps contain such a wealth of information, they are used to solve diverse land-use problems, such as finding, developing, and preserving mineral, energy, and water resources; reducing losses from natural hazards, including earthquakes, volcanoes, landslides, and other ground failures; evaluating and planning for land management and environmental protection; mitigating the effects of coastal and stream erosion; locating waste repositories, highways, pipelines; and planning for basic Earth science research.

National Geologic Map Database (NGMDB)

The NGMDB is the primary source for geologic map information of the United States and is organized into four searchable parts:

Geoscience Map Catalog

Access to geologic maps and other information and data developed under the FEDMAP, STATEMAP, and EDMAP components of the NCGMP. Links to other organizations' data and information on general geology, natural hazards, earth resources, geophysics, geochemistry, geochronology, stratigraphy, paleontology, and marine geology.

Geologic Names

Lexicon of lithologic and geochronologic rock units used in geologic maps and scientific reports. Includes unit names recognized by the USGS Geologic Names Committee.

New Mapping

Information about geologic mapping currently being conducted by FEDMAP, STATEMAP, and EDMAP.

The NGMDB site also provides access to standards and guidelines for the creation and publication of geologic maps as well as digital mapping techniques.