- © 2008, The Clay Minerals Society
The devastating impact of landslides and secondary instability associated with their unconsolidated debris deposits due to weathering, settlement and groundwater seepage are significant geological threats. Mass movements can impact negatively on urbanisation and represent a critical factor determining landuse zonation during town and regional planning.
Mapping and classification of mass movement deposits in the KwaZulu-Natal Province highlighted the more widespread extent of these Quaternary geomorphic disequilibrium indicators than is commonly appreciated. Many of the largest occurrences mapped are palaeo-landslides located in areas of high relief and steep slopes in the Ukhahlamba-Drakensberg footslopes and the major river valleys. Some of these events temporarily blocked river channels resulting in changed channel and floodplain morphology. However, the majority of the landslides identified are smaller, more recent, localized occurrences associated with high intensity rainfall events. Accelerator Mass Spectrometry (AMS) or radiocarbon dating of bulk organic material derived from ponds on back-tilted surfaces (sag ponds) of the palaeo-landslides has yielded minimum ages for the landslide events.