Mam Tor  Mam Tor is a hill near Castleton in the High Peak of Derbyshire, England. Its name means "mother hill", so called because frequent landslips on its eastern face have resulted in a multitude of "mini-hills" beneath it. These landslips, which are caused by unstable lower layers of shale, also give the hill its alternative name of Shivering Mountain. In 1979, the continual battle to maintain the A625 road (Sheffield to Chapel en le Frith) on the crumbling eastern side of the hill was lost when the road officially closed as a through-route, with the Fox House to Castleton section of the road being re-designated as the A6187. The hill is crowned by a late Bronze Age and early Iron Age univallate hill fort, and two Bronze Age bowl barrows. At the base of the Tor and nearby are four show caves: Blue John Cavern, Speedwell Cavern, Peak Cavern and Treak Cliff Cavern where lead, Blue John, fluorspar and other minerals were once mined. Mam Tor as declared to be one of the Seven Wonders of the Peak by Thomas Hobbes in his 1636 book "De Mirabilibus Pecci." Simon Jenkins rates the panorama from Kinder Scout to Stanage Edge as one of the top ten in England. Mam Tor is on the southern edge of the Dark Peak (sandstones) and overlooks the White Peak (limestones), including the notable dry gorge of Winnats Pass. It is a dominating link between the eastern end of Rushup Edge and the western end of the Great Ridge, which together separate the Hope Valley to the south from Edale to the north, and is a popular ridgewalk. Mam Tor is made of rocks of Carboniferous age, approximately 320 million years old. The base of Mam Tor is composed of black shales of the Bowland Shale Formation of Serpukhovian age overlain by turbiditic sandstone of the Mam Tor Sandstone Formation of Bashkirian age. The most notable feature of Mam Tor is the active landslide which invades its southeast side almost to the summit, and interrupts the ramparts of the hillfort, unless its builders used it as part of the defences. This rotational landslide began roughly 4,000 years ago. The toe is a debris flow. The landslide is due to weak shales underlying sandstones, a common phenomenon all around the Dark Peak, notably at Alport Castles, Longdendale, Glossop and Canyards Hills, Sheffield.