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 Hasn't It Been Mapped Before?Title Page Depending on their scale, geologic maps vary in detail. A map where one mile on the ground is represented by 2.6 inches on the map shows more detail than one where a mile on the ground is represented by just 0.6 inch on the map. These two map scales are the most common scales used for what is considered large- and intermediate-scale mapping, respectively. Map scales are also expressed as a dimensionless ratio, such as 1:24,000, which means one unit of length on the map equals 24,000 of the same units on the ground. The 7.5-minute map - which covers 7.5 minutes of latitude by 7.5 minutes of longitude, or about 55 square miles in Utah - is the standard scale for detailed geologic mapping, where one inch on the map represents 24,000 inches, or 2,000 feet, on the ground. Maps of this larger resolution are needed today to respond to a variety of environmental, resource-availability, geologic-hazard, and planning questions. It is also important to note that geologic maps are not a commodity that can be ordered up in a short period of time. The geology of many areas is very complex and commonly requires years of study to understand and map. Geologic maps are built on a long history of previous geologic investigations and typically take months or even years to produce. Geology, like other sciences, is evolving. Geologic maps can become obsolete over time, not because the geology changes, but because our understanding of it increases. Mapping often is refined as new geologic information becomes available.
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While
Utah has been mapped at small scales (big areas with limited detail),
large- (1:24,000) and intermediate- (1:100,000) scale mapping is
lacking for many areas. The UGS's Geologic Mapping Program focuses
its efforts on publishing large- and intermediate-scale geologic
maps, the same scales as the popular U.S. Geological Survey 7.5-minute
and 30 x 60-minute topographic maps.
