There are many attractive and interesting parts to the Karoo National Park which will attract visitors, but the one thing that is the most conspicuous is the geology. The rock formations, mountains and general landscape is so beautiful it will leave you speechless.
180 million years ago hot magma (dolerite) intruded into the layers of sandstone and mudstone already deposited in the Karoo 240 million years ago. Such horizontal intrusions are called sill's. These now form part of the Park's skyline because all the deposits on top of it (about 2km thick) have been eroded away.
Magma intrusions never reached the surface and cooled down within the sediments to form dolerite. These dolerite stacks are the result of selective erosion, vertical joints and spheroidal weathering. Cubic blocks develop abraded corners and eventually acquire a ‘wool sack’ appearance. These blocks will eventually weather away completely and will form an important part of the fertile Karoo topsoil.
Like a wedding cake in the Karoo, there are perfectly horizontal layers of sandstone and mudstone deposited by rivers long ago. In the absence of tectonic movement these layers remained unfolded. Fossils of mammal–like reptiles were recovered from the purple mudstone. It was in this environment that the animals were trapped in the mud of the riverbanks when rivers broke their banks during flash floods that occurred seasonally.
A dolerite sill is clearly visible from the Klipspringer Pass as it winds its way up to the Rooivalle view site, giving it its sharp upper edges. The geology of the Karoo is fascinating and no better portrayed than in the Karoo National Park.