Mam Tor

Image:Mam-tor-from-castleton.jpg]]

Mam Tor is on the southern edge of the Dark Peak (sandstones) and overlooks the White Peak (limestones), including the 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.{{cite book |last1=Waters |first1=C. N. |last2=Davies |first2=S. J. |date=2006 |chapter=Carboniferous: extensional basins, advancing deltas and coal swamps |editor-last1=Brenchley |editor-first1=P. J. |editor-last2=Rawson |editor-first2=P. F. |title=The Geology of England and Wales |edition=2nd |location=London |publisher=The Geological Society |isbn=1-86239-200-5}}

File:SubsidedRoad.jpg

A 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. Indeed, three larger landslides occur on the north side of Mam Tor, one of them cutting the main ridge at Mam Nick which allows a minor road over into Edale; another creates the striking crag of Back Tor well seen from Mam Tor.{{cite book |last1=Cooper |first1=R. |last2=Jarman |first2=D. |date=2007 |chapter=Mam Tor, Derbyshire |title=Mass Movements in Great Britain (Geological Conservation Review Series No. 33) |publisher=JNCC |pages=167–183 |url=https://data.jncc.gov.uk/data/c9bdfe0b-ca6f-4a90-87a6-d03f64e8124c/gcr-v33-mass-movements-c5.pdf |isbn=978-1-86107-481-2 |location=Peterborough |access-date=20 November 2024}}

Evidence for the continued movement of the slide mass is demonstrated graphically by the severe damage to the old Mam Tor road that traversed this flow. The road was built at the beginning of the 1800s and was subsequently relaid until local authorities closed it in 1979. Layers of tarmac and gravel are up to {{convert|2|m}} thick in places, demonstrating the numerous efforts to keep the road open. A short tunnel could readily have been made avoiding the landslip zone, but the opportunity to exclude heavy business and lorry traffic from the middle of the National Park was preferred. A local diversion for light vehicles follows the limestone gorge of Winnats Pass. This is one of the most extreme cases of geological problems affecting main transport systems in Britain, comparable with the railway at Dawlish.

Current mean annual movement 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".{{cite journal |last1=Waltham |first1=A. C. |last2=Dixon |first2=N. |date=2000 |title=Movement of the Mam Tor landslide, Derbyshire, UK |journal= Quarterly Journal of Engineering Geology and Hydrogeology|volume=33 |issue=2 |pages=105–123 |doi=10.1144/qjegh.33.2.105|bibcode=2000QJEGH..33..105W }} The debris flow poses no threat to any inhabited buildings; however, small farm buildings lying in the flow's path may soon be overwhelmed 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.

The summit of Mam Tor is encircled by a late Bronze Age and early Iron Age univallate hill fort. Radiocarbon analysis suggests occupation from around 1200 BC. The earliest remaining features are two Bronze Age burial mounds, one just below the summit and the other on the summit itself, though now buried under the paving. At a later stage over a hundred small platforms were levelled into the hill near the summit, allowing inhabited timber huts to be constructed. The hill fort and burial mounds are a Scheduled Ancient Monument.

File:Castleton from Mam Tor.jpg|View of the village of Castleton from Mam Tor with Hope cement works in the background

File:Mam Tor, trail towards Hollins Cross, overlooking Hope Valley.jpg|Panoramic view overlooking Hope Valley from a trail heading towards Hollins Cross

File:Hope Valley, Derbyshire.jpg|View of the Hope Valley

File:Mam Tor, overlooking the Hope Valley and Castleton.jpg|Panoramic view of the Hope Valley and Castleton

File:Mamtor-paragliding.jpg|Paragliding from Mam Tor

File:Mamtor-valley.jpg|View from Mam Tor looking north towards the Vale of Edale

File:Mam tor path.JPG|Path leading to Mam Tor from Lose Hill

File:Mam tor top.JPG|View of the summit from halfway

File:Mamtorsign.JPG|National Trust Sign

• Breast-shaped hill
• List of hill forts in England
• Shining Tor

{{Reflist}}

• {{cite journal |last1=Coombs |first1=D. G. |last2=Thompson |first2=F.H. |year=1979 |title=Excavation of the hillfort of Mam Tor, Derbyshire |journal=Derbyshire Archaeological Journal |volume=99 |pages=7–51 |ref=none |doi=10.5284/1066415}}

{{Commons category|Mam Tor}}

• [http://www.bgs.ac.uk/science/landUseAndDevelopment/landslides/MamTor.html Mam Tor Landslide] British Geological Survey
• [https://www.mudandroutes.com/routes/walking-route-mam-tor-castleton/ Walk up Mam Tor] Description of the walk up from Castleton

{{Derbyshire Places of interest}}

{{Peaks of the Peak District}}

{{Iron Age hillforts in England}}

Category:Castleton, Derbyshire

Category:Hill forts in Derbyshire

Category:Mountains and hills of Derbyshire

Category:Mountains and hills of the Peak District

Category:Archaeological sites in Derbyshire

Category:Landslides in the United Kingdom

Category:Scheduled monuments in Derbyshire

Category:Bronze Age sites in Derbyshire