The character of this unique landscape of the North Pennines AONB Global Geopark has its foundation in the underlying rocks and has been 500 million years in the making. Layers of carboniferous lime stone, shale and sandstone form terraced hillsides, and have provided stone for the area's distinctive dry stone walls and villages. The famous Whin Sill, a 295 million year old igneous intrusion, forms dramatic cliffs and spectacular waterfalls. Cutting through the rocks are veins of lead ore and other minerals and the North Pennines is perhaps most famous for the North Pennine Orefield and its worldclass mineral riches. Centuries of mining have left a rich heritage of ruins and spoil heaps, now colonised by unusual plants. During the last glaciation a thick ice sheet smoothed the landscape, creating glacial landforms and deposits. A thick blanket of peat, which formed on the uplands after the ice melted, is a special habitat and represents England's most important peatland resource.