Geography of Dorset is the Blackmore Vale, a relatively low-lying area of clays and limestones of Jurassic age. The south-east of the county forms part of the Hampshire Basin, an asymmetric syncline covered in sands and gravels of Paleogene age. The main rivers in the county are the Stour, Frome and Piddle. The Stour is the county's largest river, although its source is in the neighbouring county of Wiltshire. The Frome and Piddle both lie wholly within the county. The whole of Dorset's coastline is designated part of the Jurassic Coast World Heritage Site, and contains examples of many different coastal landforms, reflecting
Coastline of the United Kingdom has a fractal dimension of 1.13, and that of South Africa is 1.02. As a result of this shape and the number of islands, the coastline of the UK is longer than that of similar sized countries. For example, the coastline of Italy is around 9,226 km in length, France 7,330 km and Spain 7,268 km. Greece, which has a large number of islands similar to the UK, has a coastline of around 15,147 km. This means the UK has a relatively high coast/area ratio. Nowhere in the UK is more than from the coast. It is estimated that around