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
Prawle Point and Start Point Site of Special Scientific Interest East Prawle, West Weare (Portland, Dorset), and Thursley Common (Surrey). Prawle is also an important site for the Cirl bunting, and supports a rich lichen assemblage. Prawle Point and Start Point Site of Special Scientific Interest The Prawle Point and Start Point Site of Special Scientific Interest ( to ) is a 341.2 hectare biological and geological Site of Special Scientific Interest in southern Devon, notified in 1976. It includes the coastal headlands of Prawle Point and Start Point. The soft cliffs between Prawle Point and Start Point are recognised as being one of the most important sites for solitary