Mam Tor - Mam Tor Landslide

Mam Tor Landslide

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. The initial failure exposed bedrock displaying a sequence of shales and sandstones near to the summit. 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 road was originally built at the beginning of the 1800s and was subsequently relaid until local authorities closed the road in 1979. 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.

Current 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 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. The 2000 study suggests that deep drainage may be the most effective means of stabilising the flow, though this may not completely stop movement.