How Was the Geologic Map Made?
Geologic maps are made by carefully studying the location, age, and identity of geologic materials in a region, as well as the orientation and position of geologic structures. This information is compiled in a Geographic Information System (GIS) that combines a digital map and a database. This data is interpreted to “fill in” areas where the geologic materials and structures are not visible (covered by dense vegetation or thick soil, for example). Learn more about geologic maps and how they are made. The maps that were compiled to make the geologic map of the San Francisco Bay region are listed below: Bezore, Stephen, and others, 2002, Geologic Map of the Cordelia and Fairfield South 7.5′ Quadrangles, Solano and Napa Counties, California: California Geological Survey CD 2002-07 Bezore, Stephen, Randolph, C.E., and Witter, R.C., 2002, Geologic map of the Petaluma 7.5′ quadrangle, Sonoma and Marin counties, California: a digital database: California Geological Survey Preliminary Geologic
