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
Geology of Dorset Geology of Dorset Dorset (or archaically, Dorsetshire) is a county in South West England on the English Channel coast. Covering an area of ; it borders Devon to the west, Somerset to the north-west, Wiltshire to the north-east, and Hampshire to the east. The great variation in its landscape owes much to the underlying geology which includes an almost unbroken sequence of rocks from 200 Ma to 40 Ma and superficial deposits from 2 Ma to the present. In general the oldest rocks (Early Jurassic) appear in the far west of the county, with the most recent (Eocene) in the