government and Welsh Government representatives, and its main offices are at Penrhyndeudraeth. Unlike national parks in other countries, Snowdonia (and other such parks in Britain) is made up of both public and private lands under a central planning authority. The makeup of land ownership at Snowdonia is as follows: More than 26,000 people live within the park, of whom 58.6% could speak Welsh in 2011. While most of the land is either open or mountainous land, there is a significant amount of agricultural activity within the park. Since the local government re-organisation of 1998, the park lies partly in the county of Gwynedd, and partly in the county borough of Conwy. It is governed by the 18-member Snowdonia National Park Authority; nine members are appointed by Gwynedd, three by Conwy, and the remaining six by the Welsh Government to represent the national interest. Unusually, Snowdonia National Park has a hole in the middle, around the town of Blaenau Ffestiniog, a slate quarrying centre. This was deliberately excluded from the park when it was set up to allow the development of new light industry to replace the reduced slate industry. (There is a similar situation in the Peak District National Park where the boundaries were drawn to exclude large built-up areas and industrial sites from the park with the town of Buxton and the adjacent quarries outside but surrounded on three sides by the park.) The Snowdonia Society is a registered charity formed in 1967; it is a voluntary group of people with an interest in the area and its protection. Amory Lovins led the successful 1970s opposition to stop Rio Tinto digging up the area for a massive mine. Geology The geology of Snowdonia is key to the area's character. Glaciation during a succession of ice ages, has carved from a heavily faulted and folded succession of sedimentary and igneous rocks, a distinctive rocky landscape. The last ice age ended only just over 11,500 years ago, leaving a legacy of features attractive to visitors but which have also played a part in the development of geological science and continue to provide a focus for educational visits. Visiting Cwm Idwal in 1841 Charles Darwin realised that the landscape was the product of glaciation. The bedrock dates largely from the Cambrian and Ordovician periods with intrusions of Ordovician and Silurian age associated with the Caledonian Orogeny. There are smaller areas of Silurian