DEFINING THE RATES OF AND CONTROLS ON SLOPE DEVELOPMENT IN SANDSTONE DESERT LANDSCAPES

Abstract

This thesis aims to look afresh at the key characteristics of near-vertical arid land rock slopes, their genesis and evolution, and their association with near horizontal pediment slopes beneath. Such landscapes are by no means unique to arid climates, but they are a defining characteristic throughout the desert regions worldwide. Their universality suggests they are generated and maintained in arid conditions and therefore merit an explanation which still eludes geomorphological investigation. Since deserts are largely free of vegetation, and associated soil and regolith, steep hillslopes display the rock they comprise. Contemporary evidence of what appear to be rockfall provide clear evidence of geomorphological change, as evidenced by the long-lasting scars that such detachments leave behind on desert cliff faces. It is through the detailed examination of these scars that this study seeks evidence of their occurrence in time to ascertain how active rockslopes are under current arid conditions. The research combines the creation of a rockfall scar database and its analysis, the use of 3D photogrammetry to quantify surface roughness as a proxy for surface weathering and hence age, and surface exposure dating to provide a temporal constraint on rockfall occurrence. Evidence is provided on contemporary rockfall, with clear evidence from rockfall scars for extensive cliff face change. The study is conducted in Wadi Rum, S Jordan, and combined aims to adopt again a more holistic view and reopen the discussion on the development of steep rock slope dominated desert landscapes.