1. Morphographical information: The forms should be identified from a geomorphological point of view, for in- stance: river terrace, erosion surface, etc., which is not the case on a topographical map. Since the identification of forms is often based on their mode of formation, the morphographical aspect is closely related to the morphogenesis mentioned under heading 2. 2. Morphogenetical information: The forms should be represented in such a way that their origin and development is immediately clear. In the legend accompanying the map descriptive indications like 'sandy piain' should be avoided and genetical descriptions ('sandy alluvial piain; sandy pro-glacial piain') should be used instead. Since forms are the out- come of the effect of geomorphological processes, these should also be mapped. Lithology and geological structure also merit füll attention, because of their often profound effect on forms and processes. 3Morphometrical information: Topographical (contour) maps give much essential information in this respect and thus the geomorphological map can best be printed on an orohydrographical base, but certain geomorphologically important data, such as height of trough Shoulders or river terraces have, however, to be added. Slope steepness is another important element that will be dealt with in paragraph b. 4. Morphochronological information: Since every form is characterized by the period of its formation and further development, it is essential to make a distinction between forms of different ages, in particular between recent forms and those forms inherited from earlier periods when different climatic conditions prevailed. It is essential to keep the indications for age flexible since it is the part of the map that is most apt to need revision with the advance of geomorphological knowledge. It should be stressed here that with a few exceptions (e.g. USSR) the attention in the beginning was devoted almost completely to large Scale mapping in scales ranging from 1 10,000-1 100,000. Considerable (though not completely success- ful) efforts were given to unify the legends used in various countries or at least to make them more comparable. Particularly the Sub-Commission on Geomorpho logical Mapping of the IGU Commission on Applied Geomorphology was active in this field, and ultimately a Special Committee of this Sub-Commission made an attempt to arrive at an unified key to the detailed geomorphological map of the world (1968). One may question whether any key, elaborated into the smallest detail, can really be applied all over the world but the attempt in itself is already valuable. Of particular importance is the fact that coloured area symbols are used for the large morphogenetic groups of landforms. Various hues of these colours are then used to indicate classes of slope steepness. Lithology and structure are mapped, but receive less emphasis. The newly (Delhi, 1968) established IGU- Commission on Geomorphological Survey and Mapping has selected the com- pilation of a small-scale 1 2,500,000 geomorphological map of Europe as one of its principal aims. 86 Introduction to the ITC system of geomorphological survey K.N.A.G. Geografisch Tijdschrift IV (1970) Nr. 1

Digitale Tijdschriftenarchief Stichting De Hollandse Cirkel en Geo Informatie Nederland

Kartografie | 1970 | | pagina 14