A geological map of Dorset is pretty complex (but then geology is a complex subject in my view!). It illustrates the diversity of rock that forms the basis of Dorset's natural history and the extent to which chalk and limestone (calcareous rocks) form the back-bone of the county. All of the rock in Dorset is sedimentary, there are none of the volcanic rocks found further west and north. The also reveals just how much coastline there is in Dorset and the variable rock types that are exposed at the sea shore and cliffs. [You can see a geological map of Dorset here] These are the important geolocally significant areas which have an effect on the natural history of the county and its rich biodiversity.Limestone:The Purbeck Beds and Portland limestone are extremely important for flora. The Purbeck cliffs and Portland Bill together with the south western ridge are home to many limestone loving flowers, grasses and fungi. Predominantly high cliffs topped with grassland you get superb views of the dramatic Jurassic coast along with some rare plants. Walking can be trying for the less able with some aggressive climbs and descents in places but well worth it if you can manage it. There are places where you can access the limestone grasslands safely, notably Durlston, Portland Bill and the area around the Hardy Monument.Chalk:Much of the centre of Dorset is a chalk ridge running from Cranborne Chase in the north east down to the west of Dorchester and then a thin strip along the Purbeck Ridge westwards from Lulworth to Ballard Down near Swanage. The calcareous soils favour chalk loving plants and they also provide some wonderful views.Poole Basin:Cupped by the high chalk ridges is the Poole Basin; a low lying area of sand, gravel and clays that give rise to the unique landscape and environment of the internationally important Dorset heath which is home to all six species of indigenous reptiles as well some other rare invertebrates and plants, especially in the more boggy areas. In the centre of the basin is Poole Harbour itself. Said to be the second largest natural harbour in the word it is shallow and quickly reveals large areas of mud flats as the tide recedes and this makes it an important refuge for wintering wildfowl and wading birds.Clays:To the west of the chalk ridge is an assortment of clays. This gives heavy, damp pasture and some ideal sites for orchids and other plants that need such conditions. West and north Dorset is truly beautiful and gives a feeling that things have gone on unchanged here for centuries.Chesil and the Fleet:The Fleet is the name given to the stretch of water that lies behind Chesil beach. Chesil Beach is one of the natural wonders of Britain and the water behind it is a magnet for wildfowl in winter and features the famous swannery at Abbotsbury.Lias:To the extreme west of the county is a further area formed of a limestone called lias. This is the area around Lyme Regis and Golden Cap and some of the highest hills in Dorset, Lewesdon and Pilsden Pen. The coast here is famous for its fossils and the views are amazing and it is said that you can see five counties from here including the coast of Wales. Each of these geological areas produces habitats that suit the soil of the region. This diversity of geology in Dorset is why it has such a diverse array of wildlife.