Geologic maps show the types and ages of rocks that occur at or near the Earth’s surface. They show the locations of faults and folds, landslides, glacial deposits, and other regional or local features, depending on the scale of the map. Geologic maps are the most fundamental and important tool of earth scientists.
Most geologic mapping done by companies and universities is for a specific purpose and covers a small irregular area. The job of the Geology and Earth Resources Division as the state survey is to produce maps that cover whole areas of the state at various scales. We compile mapping done by others and add our own mapping to complete the coverage.
Our geologic maps are used for a broad range of practical applications, including growth-management planning, dam safety, hazard and risk assessment, water-resource appraisals, resource use and protection, education, recreation, and scientific research.
Virtually every Environmental Impact Statement (about 50 each year) begins with a geologic map. Without our geologic maps, EIS originators would be required to generate their own information at significant cost.
Recent storm-water runoff mitigation in the West Plains area of Spokane was based on findings of our geologic mapping program, which discovered permeable rock into which storm water could be drained, thus preventing frequent flooding.
Our current mapping focuses on 7.5-minute quadrangles at a scale of 1:24,000. This work is partially supported by grants from the U.S. Geological Survey STATEMAP Program. A state geologic mapping advisory committee, with members from industry, government, and the geotechnical consulting community, directs our mapping to areas of highest need.
Sometimes Division geologists can gather enough subsurface data to create maps and cross sections that can be used for ground-water resource planning and evaluation. For instance, our subsurface mapping of the Spokane aquifer was critical in planning new development to make the best use of available water. Subsurface mapping also aids in hazard assessment and environmental cleanup.