JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. This content downloaded from 128.235.251.160 on Wed, 11 Mar 2015 23:16:48 UTC All use subject to JSTOR Terms and Conditions ASYMMETRICAL VALLEYS OF THE CHILTERN HILLS THE interpretationof slope is one of the fundamental problems of geomorphology, and the problem is nowhere more evident than in asymmetrical valleys, where closely related slopes have obviously had different developmental histories. In the course of a soil survey of part of the Chiltern Hills it was noticed that many valleys were asymmetrical, not only in relief but also in soil pattern, and the study of these valleys has thrown light on both the geomorphology and pedology of the region. The geomorphic results will be given here. Although this paper is mainly concerned with the Chiltern valleys and a hypothesis of their mode of formation, the discussion is extended to the general problems of slope development, and it is hoped that some of the conclusions reached may have applications elsewhere.The literature on asymmetrical valleys shows that they have a wide distribution, and that many causes of asymmetry have been postulated. It also brings out the nature of the problem clearly; reveals how little is known about slope development, and indicates what sort of information is required before real understanding of the processes involved will be achieved. It is unnecessary to discuss the type of asym? metrical valley that is due to structurally controlled uniclinal shifting. However, many valleys are asymmetrical where there is no such control. In western Europe, where these valleys have often been described, the southand west-facing slopes are usually steeper than those facing east or north. Many of the valleys are in chalk country (Geukens, 1947;Pinchemel, 1954), but examples have also been found on Pleistocene gravels in southern Germany (Biidel, 1944), and glacial outwash sands in the Nether?
lands (Edelman and Maarleveld, 1951). Similar vaileys have been found in the arid west of the United States (von Engeln, 1942), in Wyoming (Walker, 1948), and in areas of permanently frozen subsoil in Siberia (Shostakovitch, 1927).Explanations of these differences in degree of slope can be grouped under a number of headings. Insolation, wind direction and vegetation cover have all been cited by various writers as affecting the rate of erosion and weathering on opposite slopes, and until further evidence is forthcoming it is impossible to attribute asymmetrical valleys over such a wide range of climatic regions to any one factor. More important, how? ever, is the lack of agreement as to the effect of different rates of erosion. Does intense erosion cause a slope to steepen or decline? Until this question is answered either slope ...
