Small-Scale Continental Landform Maps

PROPOSAL to portray the surface features of the continents on a new basis at this late date must be deemed presumptuous unless it may reasonably be contended that existing maps are inadequate, at least for some purposes, and that certain advantages may be gained by the specific new approach. The maps of configuration which have been drawn in the past have employed a variety of techniques and have achieved a wide range of effects. If we evaluate them primarily in tern-s of their adequacy for use in the classroom or in small atlas or textbook plates, we must conclude that in varying degrees they have fallen short of the mark. For some the chief deficiency is lack of simplicity or clarity; for others it is misleading representation of the terrain. Much of the problem of adequacy resolves about matters of scale. In the contour map and the relief model we have techniques for representing clearly, accurately, and in detail the surface form of a limited area. As the scale of the representation is increased the completeness of detail may be increased. Carefully drawn contour maps or models constructed at scales no smaller than one inch to a mile are satisfactory representations for the vast majority of purposes. However, if large areas are being studied, the size of map, or alternatively the number of small maps which the use of such large scales necessitates, becomes a serious and often vitiating obstacle. Furthermore, the use of large scale maps for showing very large areas compounds such a staggering total of individual features that the eye and the mind become lost in the welter of detail and one begins to grope for some means of simplification and generalization. One obvious measure for meeting these difficulties is reduction of the scale of representation, but this in turn raises additional problems of its own. No longer is it possible to show all significant features. The sacrifice of detail at scales below 1: 500,000 or 1: 1,000,000 becomes tremendous, and contour maps or models on such scales are no longer faithful reproductions of the actual terrain. Individual ravines, ridges, and benches must be omitted, and the distinctive texture of the topography is thereby lost. A mountain range is no longer a picturesque or forbidding maze of spurs, gullies and jagged crests, but simply a featureless protruding rib, its character generalized out of existence. On maps of entire continents, drawn on scales of 1: 5,000,000 or less, even individual ranges or major valleys on plains may be lost, only broad mountain systems and extensive plains being distinguishable. This loss of detail with decreasing scale of mapping is in large measure inevitable, but the relative value of different small-scale representations depends upon the degree to which they retain the distinctive character of the terrain without undue sacrifice of simplicity. The generalization made to accompany reduction of scale of any map must be planned at least partly in terms of visual clarity. It may be achieved principally through reduction in the number of separate features or areas distin-