Mam Tor landslide - BGS

It's new year's eve and in a idle moment (acually all day at work today is an idle moment!) I was surfing the BGS website and found an interesting link to the landslide:

The landslide

The landslide itself is over 4000 years old and is a rotational landslide which has developed into a large debris flow at its toe (Waltham and Dixon, 2000). It is over 1000 m from backscarp to toe, has a maximum thickness of 30-40 m and the backscarp is over 70 m high. 
Waltham and Dixon (2000) have divided the landslide into three distinct zones (backscarp area, transition zone and debris flow) according to their structure as follows:

1. The upper part of the slide material is a series of rock slices or blocks that were produced by the non-circular rotational failure of the original slope; most of these slices above the upper road show little sign of current movement
2. The central part of the slide is a transition zone, forming most of the ground between the two segments of road; it lies between the upper landslide blocks and the lower debris flow. It is composed of an unstable complex of blocks and slices, some of which can be identified by ground breaks along their margins; they overlie the steepest part of the landslide's basal shear, which was the hillside immediately downslope of the initial failure. The upper road lies along the highest section of the transition zone, which is currently the most active part of the whole slide.
3. Disintegration of the lower part of the slipped material has created a debris flow that now forms half the total length of the slide. This is described as a flow because it moves as a plastic deformable mass, but it may also be regarded as a debris flow slide because it has a well-defined basal shear surface.

The literature listed below give good accounts of this landslide in more detail.

The geology

Underlying the landslide are Dinantian limestones which are not included with the landslide (Waltham and Dixon, 2000). Overlying the limestone is the Bowland Shale Formation which consist of dark grey mudstone. The top of the landslide exposes the Mam Tor Beds. These are a sequence of turbidites of mudstones siltstones and sandstones.

Further reading

Aitkenhead, N., Barclay, W.J., Brandon, A., Chadwick, R.A., Chisolm, J.I., Cooper, A.H. & Johnson, E.W. (2002). British regional geology: the Pennines and adjacent areas. 4th ed British Geological Survey, Keyworth, Nottingham.
Arkwright, J.C., Rutter, E.H. & Holloway, R.F. (2003). The Mam Tor landslip: still moving after all these years. Geology Today, v.19, pp.59-64.
Cripps, J. C. and Hird, C. C. (1992) A guide to the landslide at Mam Tor, Geoscientist v.2 (3), pp. 22-27.
Dixon, N. and Brook, E. (2007) Impact of predicted climate change on landslide reactivation : case study of Mam Tor, UK in Landslides : Journal of the International Consortium on Landslides, v. 4 (2) pp. 137-147.
Donnelly, L.J., (2006). The Mam Tor Landslide, Geology & Mining Legacy around Castleton, Peak District National Park, Derbyshire, UK, in Culshaw, M.G., Reeves, H., Jefferson, I. & Spink, T. (eds) Engineering Geology for Tomorrow's Cities, Proceedings of the 10th Congress of The International Association for Engineering Geology and The Environment, Nottingham, UK, 6-10 September 2006. Geological SocietyLondon(CD-ROM).
Doornkamp, J.C., (1990) Landslides in Derbyshire. East Midlands Geographer, v. 13 pp.33-62.
National Trust: About Mam Tor, The Shivering Mountain (2009)
Rutter, E. H., Arkwright, J. C., Holloway, R. F. and Waghorn, D. (2003) Strains and displacements in the Mam Tor landslip, Derbyshire, England, Journal of the Geological Society of London v.160 (5) pp. 735-744.
Skempton, A. W., Leadbeaater, A. D. and Chandler, R. J. (1989) The Mam Tor landslide, north Derbyshire, Philosophical Transactions of the Royal Society of London, v. 329, No 1607, pp 503-547.
Walstra, J., Dixon, N. and Chandler, J. H. (2007) Historical aerial photographs for landslide assessment: two case histories. Quarterly Journal of Engineering Geology and Hydrogeology. V.40, Part 4, November, p315-332.
Waltham, T. and Dixon, N. (2000) Movement of the Mam Tor landslide, Derbyshire, UK, Quarterly Journal of Engineering Geology & Hydrogeology v.33 (2)pp.105-123.

Stratification and lichen

The cross stratification on this sandstone block on Froggatt Edge forms a sheltered micro-climate for lichen.

Visean and Dinantian

According to an earlier blog on the Carboniferous the Dinantian is a series and the Visean a stage. According to the BGS book The Pennines and adjacent areas (p16) the Dinantian is a subsystem and the Visean a series which is divided into stages:

I am more inclined to believe the BGS over Wikipedia!

Whichever is true the geology of the Peak District is often described as Dinantian, Namurian and Westphalian which is a mixture of subsystem and series (on the BGS criteria) with the occasional mention of the Visean. Geologists always seem out to confuse.

 

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System v Period

There seems to be a confusing mixing of chronologies with Carboniferous being both a Period and System. According to Wikipedia the TIME (geochronology) divisions are as follows:

Eon, era, period, epoch, age

The ROCK (chronostratigraphy) divisions which correspond to them are:

Eonthem, erathem, system, series, stage

Confusing....

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Counties

Here is a list of the five (or six if you split Yorkshire into South and West!) in which the Peak District lies, so beloved of local pub quizzes.

Cheshire
Derbyshire
Greater Manchester
Staffordshire
Yorkshire

When is a millstone not a millstone?

This is a good site on millstones and when a circular stone (like the ones above under Stanage Edge which ARE millstones!) is not a millstone.

Millstones - used in pairs to shear grains fed into a narrow gap between their faces; used in grist mills

Quern-stone - manual version of millstones

Grindstones - used to sharpen metal cutting tools etc. pushed against their edges

Pulp stones - a special type of grindstone that was quarried in large numbers in the late 19th and early 20th centuries: exported to Canada and Scandinavia to be mounted in machines used to pulp timber for paper making

Edge runners - cylindrical stones mounted on an axle and used to crush a variety of materials and even foodstuffs as they rolled around a pivot

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Geological excursions in the Sheffield region

Various (1967) University of Sheffield

1. The Wye Valley

2. Earl Sterndale Area

3. The Castleton Reef Belt and adjoining areas

4. The Carboniferous Limestone of the Stony Middleton Area

5. The Visean Rocks of the Matlock—Wirksworth—Monyash Area

6. The Ashover Area

7. The Crich Inlier

8. Volcanic Rocks in the Peak District

9. Some Mineral deposits of the Carboniferous Limestone of Derbyshire

10. Fossiliferous localities in the Namurian Rocks of Edale

11. Namurian Sedimentation in the High Peak

12. The Bradfield—Ewden Area

13. The Ashover and Chatsworth Grits in North-East Derbyshire

14. The Namurian and Basal Westphalian Rocks of the Beeley—Holymoorside Area

15. The Namurian and lowermost Westphalian Rocks in the southern part of the Goyt Syncline

16. Westphalian A Palaeontology and Stratigraphy of the Langsett—Penistone Area

17. The City of Sheffield

18. The litho-facies of a Lower Coal Measure Sandstone Unit between Sheffield and Brighouse

19. The Middle and Upper Coal Measures (Westphalian B and C) north-east of Sheffield

20. Conisborough

21. The Permo-Triassic Rocks of the Worksop Area

22. Scunthorpe

23. Kirton, Lincolnshire

24. Nettleton, Lincolnshire

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