In the reserve are several granite koppies or “tors” (an Anglo Saxon word for small rocky hills) which show a characteristic feature of granite boulders – leaving large round boulders on top of one another. The granite of the Norscot tors was formed in the earth’s crust over three thousand million years ago. Localized masses resisted weathering more than the surrounding rock, which decomposed to form soil. Erosion removed the soil, leaving the denser boulders in the form of tors.
The altitude of the koppies varies from 1440m to 1463m. The annual rainfall is 400-600mm p/a.
Human habitation of this region dates back many thousands of years. Stone-age peoples visited the koppies at various times from 50 000 BC onwards. During the last four or five centuries, Iron-Age people came to the district where they smelted iron, made pottery and hunted.
While not the oldest rocks in the Transvaal, the older granites of the Halfway House Dome formed 3 100 million years ago and are among the oldest of the rock outcroppings of the earth’s crust. Various land movements and cycles of erosion have sculpted the present land surface. At present, this surface is in a continuing phase of erosion, which began some 65 million years ago. These granite tors host a variety of trees and shrubs, which have taken a great deal of time to develop. The quarries on Norscot Nature Reserve show that man can destroy these fascinating rock formations in just a few years.