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
World Heritage Site its "outstanding universal value", is also evaluated by the advisory bodies before being sent to the Committee. Such proposals can be rejected by either the advisory bodies or the Committee if they judge it to be a significant change instead of a minor one. Proposals to change the site's official name is sent directly to the Committee. A site may be added to the List of World Heritage in Danger if there are conditions that threaten the characteristics for which the landmark or area was inscribed on the World Heritage List. Such problems may involve armed conflict and war, natural