Question: what is the largest biome in south africa

title: Vredefort crater
text: The impact distorted the Witwatersrand Basin which was laid down over a period of 250 million years between 950 and 700 million years before the Vredefort impact . The overlying Ventersdorp lavas and the Transvaal Supergroup which were laid down between 700 and 80 million years before the meteorite strike , were similarly distorted by the formation of the 300 km wide crater . These rocks form partial concentric rings round the crater center today , with the oldest , the Witwatersrand rocks , forming a semicircle 25 km from the center . Since the Witwatersrand rocks consist of several layers of very hard , erosion resistant sediments ( e.g. quartzites and banded ironstones ) , they form the prominent arc of hills that can be seen to the NW of the crater center in the satellite picture above . The Witwatersrand rocks are followed , in succession , by the Ventersdorp lavas at a distance of about 35 km from the center , and the Transvaal Supergroup , consisting of a narrow band of the Ghaap Dolomite rocks and the Pretoria Subgroup of rocks , which together form a 25 -- 30 km wide band beyond that . From about halfway through the Pretoria Subgroup of rocks around the crater center , the order of the rocks is reversed . Moving outwards towards where the crater rim used to be , the Ghaap Dolomite group resurfaces at 60 km from the center , followed by an arc of Ventersdorp lavas , beyond which , at between 80 and 120 km from the center , the Witwatersrand rocks re-emerge to form an interrupted arc of outcrops today , of which the Johannesburg group is the most famous , because it was here that gold was discovered in 1886 . It is thus possible that if it had not been for the Vredefort impact this gold would never have been discovered .