The three-dimensional aspect: structure contours

Abstract

The problem of representing three-dimensional things on a flat piece of paper has exercised minds for many years, nowhere more so than with regard to maps. Many atlases begin by discussing the question of how to represent the spherical earth in a book. A similar problem is the portrayal of the undulations — the relief — of the earth’s surface. Early map-makers attempted to depict relief by drawing humpy little hills, often wildly exaggerated in height and steepness. Better pictorial methods gradually evolved, such as shading and hachuring, but in general these are unsuited to geological maps. By far the most successful means yet devised are topographic contour lines. These are now common on larger scale geological maps, say 1:100 000 or larger. Figures 1.4 and 1.5 illustrated the concept of topographic contours, and Fig. 1.6 showed how to construct topographic profiles from them. It is important that you are completely familiar with topographic contours.