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