HOW DO GEOLOGIC MAPS DIFFER FROM OTHER MAPS?
Geologic maps differ from many other maps in important ways: (1) Our maps are commonly of entities that are observed with difficulty. Identification of a municipal boundary, or an interstate highway, is easier than the identification of many (most?) geologic map units. Uncertainties about classification of the mapped object are greater than with other types of maps. Misclassification errors are correspondingly more common. (2) Our maps are more sensitive to scale than other types of maps. The nature of a contact on a political map does not change with map scale: it is commonly defined, and observed, with much greater precision than it is plotted at a wide range of scales. Geologic objects are commonly defined and observed with a resolution that is near the intrinsic resolution of the map — indeed, we choose our map scale or our observation method so that this is true, and we then use symbols to denote whether an object is located as well as or more poorly than can be depicted at that
