EOLIAN GEOMORPHOLOGY, WIND DIRECTION, AND CLIMATIC CHANGE IN NORTH AFRICA
MASSACHUSETTS UNIV AMHERST
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The North African desert belt is a region of temperature extremes, strong winds, and negligible rainfall. Wind action has been a major geologic process. Erosional effects comprise en closed basins and various residual rock knobs and ridges, commonly elongated parallel to dominant wind direction. Depositional effects comprise sand streamers, drifts, and dunes. Active dunes may be classed as simple, compound, and complex. Compound dunes comprise barchan, transverse, and longitudinal types, and are transitional into simple types on the one hand, and complex types on the other. Complex dunes are the most wide spread, and show extreme diversity in character. They may be grouped as longitudinal, peaked, domal, ridged, and undifferentiated. They are believed to have been formed by vergent winds, and to have had a complicated development history. Stabilized or fossil dunes occur in a broad belt bordering the Sahara on the south, and represent a former expansion or shift of the desert belt. Where original form has not been too greatly modified by non-eolian processes, dune forms similar to those found farther north in the active stage may be recognized, and it is probable that some of the latter passed through a stabilized state at one or more times in their history.