In geological terms, the Pennines, known as the "backbone of England", are the oldest range of mountains in the country, originating from the end of the Paleozoic Era around 300 million years ago. Their geological composition includes, among others, sandstone and limestone, and also coal. There are karst landscapes in calcite areas such as parts of Yorkshire and Derbyshire. The Pennine landscape is high moorland in upland areas, indented by fertile valleys of the region's rivers. They contain two national parks, the Yorkshire Dales and the Peak District. In the West Country, Dartmoor and Exmoor of the Southwest Peninsula include upland moorland supported by granite, and enjoy a mild climate; both are national parks.