Dominating the north western end of the Hope Valley is Mam Tor, the “Shivering Mountain”. It looks as if it is or has been a large quarry. What you are actually seeing is the result of a massive landslide that happened a long time ago.
Put simply, a great slice of Carboniferous shale and sandstone slipped down the front of Mam Tor. The bare rock face is where it all came from. The debris from the landslide forms the lumpy broken slopes below the face of Mam Tor and is over 1000 metres long. This debris, an estimated 3.2 million cubic metres, is still moving slowly downwards under its own weight, something like 8.5 million tonnes.
The evidence for all this movement can be seen by looking at the destruction of the higher and lower parts of the Mam Tor road where it crosses the landslide. Also look down to the toe of the landslide and see how it is encroaching on the fertile fields of the valley floor and destroying good grazing land. Within the last 60 or so years Blackett Ley Barn, a substantial stone built structure which lay directly in the path of the landslide has been pushed over and totally obliterated.
The Mam Tor road known locally as the “New Road” was opened in 1810 and starts from the end of the road to the Winnats Pass. The New road was built over the landslide debris, crossing it twice. This new road bypassed the very steep road through the Winnats Pass with its 1 in 5 gradient (20%).
Because of the continual downward movement of the landslide debris the road needed constant repair and rebuilding until a larger slip in 1975-1976 caused its destruction. After trials with single file traffic with passing places, then with traffic lights, both proving unsuccessful, the road was finally closed in 1979. Once again the Winnats Pass became the only road out of Castleton to the west.
Current geological research suggests the Mam Tor landslide happened 3500 to 4000 years ago and the mean average downward movement of the landslide is about 25 centimetres per year but this movement increases considerably during a very wet winter following a significantly wet summer.
The natural erosion of the face of Mam Tor by sun, frost, wind and rain is negligible when compared to the landslide.
The Neolithic family buried in Treak Cliff Sepulchre Cave would have seen Mam Tor as a complete mountain. The Celtic Brigantes who came from Northumbria much later (about 1000 years B.C.) would see it much as we do now and they used the steep face of Mam Tor as part of the defences of their encampment.
They raised double earthworks enclosing about 16.5 acres on the top of Mam Tor. Within this enclosure the tribe built their rude dwellings and started some form of community life. Finding enough water on Mam Tor would have been a problem for them.
Information on this page was taken from ‘Castleton historical Society By Peter C. Harrison’