According to Alfred Wegener, all the major continents formed one giant supercontinent, called Pangaea. About 200 million years ago, the supercontinent Pangaea began to rift.
Karst topography is a result of the dissolution of soluble rocks like limestone, dolomite and gypsum. Caves are formed due to weathering of rock deep underground. Cave or cavern is a natural void and is a space large enough so that a human can enter. The study of the formation and development of caves is called as Speleogenesis. Most of the formation of caves takes place in limestone rocks by dissolution.
Large units where sheep are reared in Australia are called sheep stations. The term applied to large animal farms inSouth America is estancias. The ranches or sheep stations consist of large areas of natural pasture and also the ranch house and some area devoted to supplementary feed crops.