Karoo Sequence, South Africa
October 18, 2004
I use this picture in teaching to illustrate the role of horizontal strata in structural control. This large flat-topped hill is near Harrismith in central South Africa and not far from Lesotho. The geology shown consists of the upper units of the Karoo Sequence - Phanerozoic Age. The lighter, underlying material is relatively soft sandstone. This has been capped by an outpouring of basalt. This darker, volcanic material flowed over the existing surface and caps the topographic feature. Note the caving and structural benches evident in the sandstone, the distinctive columnar jointing in the basalt, as well as the talus cones.
This picture was taken in September 2003, just after the extremes of winter and before the rains which soon green-up the frosted landscape