ABSTRACT
Geological maps show outcrops (where the rocks meet the surface). Shapes of outcrops depend on the shape of the surface and the shape of the rock structure. Surface shape is known (from topographic contours): therefore rock structure can be interpreted. An important rule: where more than one interpretation is possible, the simplest is usually correct. Map interpretation is therefore logical and straightforward if approached systematically. Maps remain the best way of depicting 3-D rock structure on a piece of paper.
