Library Guides: GEOL 380: Hydrogeology (Information Sources in Hydrology): Geologic Maps

About Geologic Maps

Geologic maps show the distribution of geologic features, including types of rocks and unconsolidated sediment in an area and structural features, such as faults and folds. Geology is shown by colors, lines, and specialized symbols unique to geologic maps. More information about geologic maps is available from:

What is a Geologic Map?
This website developed by the National Park Service provides some basic information about geologic maps and their symbols.
Meeting Challenges with Geologic Maps
This website from the American Geosciences Institute contains basic information about geologic maps, how geologists make them, the value of geologic maps, and examples of how geologic maps have been used to address issues across the United States.
Using Geologic Maps
The Maine Geological Survey has developed a web site that provides information on reading and interpreting geologic maps.

United States Resources

National Geologic Map Database
An index to published geologic and other geology-related maps developed by the U.S. Geological Survey and the Association of American State Geologists
Tapestry of Time and Terrain
A site containing information on the geology of the United States, including a geologic map of the United States superimposed on a digital landform map.
The North American Tapestry of Time and Terrain
A geologic map of North America superimposed on a digitally produced landform map.

Illinois Maps

Bedrock Geology of Illinois (Front Side)
A large pdf file showing the bedrock in Illinois.
Bedrock Geology of Illinois (Back Side)
The back side of the bedrock geologic map of Illinois contains cross-sections of and a stratigraphic column for the state. It includes inset maps showing Quaternary geology, and bedrock maps showing Ordovician, Lower Devonian and Sub-Pennsylvanian geology. The page also includes a bibliography.
Quaternary Deposits of Illinois
A map showing surface materials of Illinois that were deposited by glaciers during the Ice Age.
Wisconsinan End Moraines in Illinois
A map showing end moraines that formed at the edge of the ice sheet when they were stationary as the ice was retreating.
Drift Thickness of Illinois
A map showing the thickness of glacial deposits in Illinois.
Loess Thickness of Illinois
A map showing the thickness of loess in Illinois. Loess is fine-grained sediment that is deposited by wind or water in front of a glacier, although it can also be carried long distances.
Illinois Surface Topography
A computer-generated map showing the surface elevation of Illinois.
Physiographic Divisions of Illinois
A map of Illinois' physiographic regions.
Satellite Image Map of Illinois
A map of Illinois compiled from satellite imagery.
Illinois Oil and Gas Resources Interactive Map Site
An interactive mapping site that allows users to access information about over 180,000 oil and gas wells in Illinois.
Illinois Coal Maps and Data
A site with links to maps and data related to coal in Illinois.