The Effects of Erosion

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Rock structure

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Fine-grained, homogeneous tuffs of highly compact structure

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Medium-grained pumice-like tuffs of loose structure

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Medium-grained tuffs of compact structure, with oblique cracks cutting across stratification

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Disintegration

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Aeolian and thermoclastic erosion

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Erosion due to pre-existing cracks, precipitationsand frost action

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Erosion due to rain-wash, with wearing away ofbase

The long winding sides of these valleys have offered scope, in suitable places, for the hewing out by man of complex systems of dwellings, one on top of the other, occupying almost the whole of the rock face, as at Göreme, Ürgüp, Çavuşin and Uçhisar.

Near the mouths of the valleys, where the erosional processes have produced a fully graded profile and sometimes a complete levelling, the rock faces lose their continuity and give place to isolated residual pinnacles, the characteristic "fairy chimneys". These pinnacles are conical in shape, with rounded sides rising at an angle usually greater than 60º, topped by a cap of harder tufaceous rock which retards for a time the continuing process of mechanical disintegration. The pre-existing cracks in the rock, usually running more or less vertically, open the way to thermoclastic processes and rain-wash which gradually carve out polygonal blocks of tuff with a bulk of several cubic metres (Ph. 16, Fig. 16), the sides of which are then rounded by aeolian action.
 

1. Vertical cracks
2. Group of cones
3. Isolated cones
4. Levelling-down

The "canyon" of the Melendiz Suyu, near Ihlara, offers a different pattern of erosional activity in which the dominant morphological feature is a narrow valley with sub-vertical walls. This result is due partly to the characteristics of the catchment area of the river and partly to the hardness of the rock and the existence of a system of fractures running in the same direction. The river is continuing to cut ever deeper into the valley, seeking to reduce the difference in level between its drainage basin and the plain into which it emerges near Aksaray.

The valley cuts through beds of reddish and brown tufaceous rock, the lower levels of which are fairly soft. This leads to undercutting and the collapse of large masses of rock, as can be observed near Ihlara.

Throughout most of the region, however, the erosional processes have been able to operate only to a limited extent, producing morphological structures intermediate between the extremes represented by the valleys of the Kızılırmak and the Melendiz Suyu. As a rule these structures have no very marked distinctive characteristics: they may consist of small-scale features like those in the Derinkuyu area, or of a combination of a canyon-type valley with isolated residual pyramids as at Selime, or of relatively shallow erosion by scouring action, as at Soğanlı Dere.

Since water is one of the principal agents in the development of land forms, this process will operate more rapidly in areas situated close to drainage basins, and will be slower in level areas where the only movement of water is that resulting from atmospheric precipitations.

Future Prospects

Although from the human point of view these activities represent a particular manifestation of the creative process, they are of purely negative effect from the geological or geomorphological point of view, serving merely to accelerate the processes of disintegration and erosion. And these processes have of course operated most intensively in the areas where the scale and density of human settlement is greatest.

An effort to preserve the various forms and structures in their present aspect does not mean halting the development and transformation of the landscape; for this would merely lead to further distortions and in effect speed up the destructive action. The object should rather be, after careful study of the operation of these processes, both on a regional scale and in detail, to slow down the erosional action which can be observed at work. For any hydrogeological event, even one of catastrophic proportions, is merely the sum of a series of actions and reactions, which may escape the eye of the ordinary observer but nevertheless add up in the course of time to a major transformation. What is wanted, therefore, is a plan of action which takes account of the pattern of erosional activity, involving the proper regulation of the catchment area, with provision for the necessary drainage works and the stabilising of the valley sides. For the preservation of particular features (isolated pinnacles, towers, and so on) it will be necessary to work out the solution appropriate to the particular circumstances: this may involve, for example, repairing and consolidating the rock, sealing up cracks or fissures, using cramps to hold the structure together, and so on.

It is important to realise the urgency of this restoration work. The processes of erosion are now operating at such a rate as to constitute a grave threat to this remarkable landscape which, as a result of the presence and the varied activities of man, has been in process of continual change and development since prehistoric times.