Devil's Peak (Cape Town) - Geology

Geology

The upper, rocky parts of Devil's Peak, Table Mountain and Lion's Head consist of a hard, uniform and resistant sandstone commonly known as the Table Mountain sandstone or TMS. (This is, however, no longer used as a formal geological name). The tough sandstone rests conformably upon a basal shale that in turn lies unconformably upon a basement of older (Late Precambrian) rocks (Malmesbury shale/slate and the Cape Granite). The basal shale and the older rocks below it weather much faster than the TMS and for this reason the lower slopes are everywhere smoother, with few outcrops and deeper soil. Millions of years of erosion have stripped all of the TMS from Signal Hill and that is why it looks very rounded compared to its sister peaks. There is a road that runs almost on the contour from the lower cable station on Table Mountain along the mountain to Devil's Peak. As it turns east around the bulk of Devil's Peak the road cuttings expose a few famous geological unconformities, which illustrate very clearly that the Malmesbury rocks were folded, baked, intruded by granite and planed down by millions of years of erosion before the area sank below the ocean and a new sequence of sediments, including the TMS, began to accumulate.