A road built across it nearly 200 years ago, and now closed, provides graphic evidence of continued movement of the slide mass this has now been monitored for eight years. The initial slope failure occurred over 4000 years ago as a rotational landslide that developed into a large debris flow at its toe.
^ Waltham & Dixon (2000), Movement of the Mam Tor landslide, Derbyshire, UK, The Quarterly Journal of Engineering Geology and Hydrogeology, Volume 33, Number 2, May 2000, pp.The Mam Tor landslide is a kilometre‐long feature in shales and sandstones. (editors) (2006) The Geology of England and Wales, 2nd edition, London, The Geological Society (2006) Carboniferous: extensional basins, advancing deltas and coal swamps - Chapter 9 of Brenchley, P. ^ Natural Curiosities of Derbyshire, in: The Every-day Book and Table Book or, Everlasting Calendar of Popular Amusements, Sports, Pastimes, Ceremonies, Manners, Customs, and Events, Each of the Three Hundred and Sixty-Five Days, in Past and Present Times Forming a Complete History of the Year, Months, and Seasons, and a Perpetual Key to the Almanac, Including Accounts of the Weather, Rules for Health and Conduct, Remarkable and Important Anecdotes, Facts, and Notices, in Chronology, Antiquities, Topography, Biography, Natural History, Art, Science, and General Literature Derived from the Most Authentic Sources, and Valuable Original Communication, with Poetical Elucidations, for Daily Use and Diversion. The 2000 study suggests that deep drainage may be the most effective means of stabilising the flow, though this may not completely stop movement. The debris flow poses no threat to any inhabited buildings near the peak however, small farm buildings lying in the flow's path may become inundated over the next century assuming a flow rate similar to that of the present. Layers of tarmac and gravel are up to 2 metres (6 ft 7 in) thick in places, demonstrating the numerous efforts to keep the road open.Ĭurrent mean annual movement according to a study made in 2000 is "up to 0.25 m this increases greatly when winter rainfalls exceed thresholds of both 210 mm/month and 750 mm in the preceding six months." The road was originally built at the beginning of the 1800s and was subsequently relaid until local authorities closed the road in 1979. Evidence for the continued movement of the slide mass is demonstrated graphically by the continued severe damage to the old A625 road that traversed this flow. The initial failure exposed bedrock displaying a sequence of shales and sandstones near to the summit. 
One of the distinguishing features of Mam Tor Peak is the active debris flow resulting from a rotational landslide that occurred roughly 4,000 years ago.
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