The balance between the weight of a mountain range and the buoyancy provided by the underlying mantle is termed

The answer is; Isostasy

Just like a boat displaces water in which it floats, so does the solid lithosphere on the fluid asthenosphere. The heavier regions of the lithosphere, such as those with high mountains above them penetrate deeper into the asthenosphere and displace a huge portion. Isostasy occurs when each block settles into equilibrium with the underlying mantle (buoyed with a force equal to the weight of the displaced fluid).

since there isn't any suggested answers i will give you the reason and hopefully you can figure it

south africa, or rather all of africa, has not been in the location in which it is nowadays throughout the geological past. after the super-continent pangaea started to break apart, gondwanaland, in which was africa, moved further south, and parts of it came to be very close to the south pole. because the climate in this part of the world is very cold due to the very dispersed sun rays in there, what is now south africa, started to freeze, and the conditions were right for the formation of glaciers. the glaciers existed up until the period when gondwanaland started to break apart and what is now africa started to move towards north, sp it warmed up and the glaciers melted.