The theory of scree slope development with particular reference to its application in the Western Desert, Egypt.

This thesis is concerned with the characteristics and development of scree slopes; theoretically from a range of climatic environments, and practically from the Western Desert in Egypt. The account is in two parts, each comprising three Chapters. The first part is an integrated review of the theory of the major gecmorphic processes and variables which influence scree development and is based on available published material. The second part involved detailed field measurement in the New Valley Province of Egypt. This part presents the results of surveying the characteristics of thirty screes situated within the El Kharga and El Dakhla depressions. At present this is an area of extreme aridity, although during late Pleistocene times there were several significant pluvial phases. From the survey of thirty profiles, three classes of scree form were identified. A basal concavity was present on all screes varying in degree and length of curvature from site to site due to the form of the accumulation surface and the evolutionary stage. Dpper straight segments of the profiles ranged between 30 and 37 with the greatest frequency between 31 and 33 . The steepest measured angle was 39.5 . Sampling of debris size and shape revealed two types of distribution; on seme screes an identifiable downslope sorting is attributed to rockfall processes, whilst on others a lack of well defined sorting patterns is ascribed to localized avalanching. Potential mechanisms of particle movemeit were examinei by studies of scree fabric and by field experiments.Late Pleistocene processes induced landslides, rockfalls and the undermining of cliffs. At present, insolation is significant in its effect on both bedrock and scree surfaces. Rockfall still occurs at all rates but at a much slower rate than during the wetter Pleistocene periods. Other processes currently active include dry avalanching, aeolian action and wild animal movement