ABSTRACT
Theoretical considerations had been used to argue both for parallel slope retreat and for the decline of slope angle with age. The potential for active surface processes is therefore very high. But rates of erosion depend upon the number of rainfalls affecting a particular slope. In fact, there may be no rain for several years, even if an area as a whole is classified as semi-arid and not hyper-arid. Changing slope form and slope processes have been used to assist in the dating of relatively recent sites of occupation in the Oaxaca Valley of Mexico and to explain the pattern of scatter of artefacts. The material was carefully placed in appropriate attitudes within the talluvium on the 30° straight steep slope along with 2011 basalt particles, whose movements have already been described. Since the archaeological and palaeontological material is moving in general at half the rate of the rest of the talluvium it is obviously being concentrated.
