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Aerial mapping tools, Paonia Quadrangle, Colorado, August, 2013. Photo credit: Dave Noe for the CGS.

Geologic Mapping


Much of the CGS website is under heavy re-construction and will be for some time. The Publications area is working normally, but there is a lot of content from our original site that was in desperate need of updating. Please bear with us as we gather new information and rewrite hundreds of pages of material, gather and properly caption high-resolution images and otherwise bring you some very cool new and archival material never before seen! Stay in touch by subscribing to the >RockTalk< blog where we will announce new items periodically.


Geologic mapping involves plotting the location and attitude of the various rock units, faults, and folds on a base map. Geologic maps are used to investigate geologic hazards, mineral resources, groundwater aquifers, and just plain science. Our extensive geologic mapping program is conducted under the STATEMAP part of the National Cooperative Geologic Mapping Program (NCGMP). To learn more about geologic mapping, view our RockTalk: Mapping Colorado.

A geologic map depicts the aerial distribution of various rock types of different ages. Rocks are broken out into mappable units or formations. A formation is a rock type that is distinct enough to separate from the other rocks in the area, and thick enough to show accurately on the map. Each formation is represented by a unique symbol and color on the geologic map. The symbol indicates the rock’s age and formation name.The geologic pattern and symbol for each formation are usually overprinted on a topographic map