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
East Devon Pebblebed Heaths is mostly Bunter Pebblebeds of Triassic age, though there is some New Red Sandstone and marls of Permian age. Notable breeding bird species that have been recorded on the site include the European nightjar, Eurasian hobby and Dartford warbler. Rare dragonflies include the small red damselfly, the southern damselfly and the downy emerald. Other insects recorded include the bog bush cricket. Annual wildlife surveys are carried with groups such as the Devon Amphibian and Reptile Group (DRAG), the Devon Bat Group, Butterfly Conservation, the Devon Wildlife Trust and the Devon Biodiversity Records Centre helping coordinate the work. East Devon Pebblebed