The Down-Structure Method of Viewing Geologic Maps

Abstract

Most contact lines on geologic maps are surface traces of inclined planes. If the map is viewed down the slope of these planes, it becomes, in effect, a section, and the map patterns are seen as structures. The "down-structure" method of looking into maps rather than at them can be introduced into the most elementary exercise in geologic map interpretation; it helps the student to grasp quickly the structural significance of patterns on maps made by others and increases his sensitivity in laying down lines on his own maps in the field. Used with proper caution and an understanding of its limitations, the method is applicable to a wide range of map patterns, from those of simple monoclinal structures to those of recumbent folds.