The differences in aggregate strength between fan surfaces can be
attributed to the time that has elapsed since last flooding and, therefore,
the degree of weathering. Young or active fans are subjected to periodic
flooding, hence unweathered and relatively fresh sediments and boulders are deposited across the fan surfaces, which provide a source of
higher strength aggregates. The surfaces of older and relict fans (especially the relict one) have remained above the active channel, so that
they do not get recharged by younger, fresher sediments. This has
allowed for the development of weathering features such as pitting of
carbonate clasts and the formation of varnish on stable rock surfaces.
Hence, the strength of aggregates on these surfaces is lower than on
younger ones (Table 3). Apart from differences in weathering characteristics between relict, old and young fans, the degree of weathering also
vary between the apex and toe of the fans.