Monday 31 December 2012

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.

Friday 28 December 2012

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.

 

Thursday 27 December 2012

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....

Monday 24 December 2012

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

Sunday 23 December 2012

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



Monday 17 December 2012

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



The Living Landscape

Patrick Whitefield (2009) Permanent Publications

Reading the landscape is at the heart of this blog, not just in the Peak District but everywhere. This book is the book I have been looking for for ages, it brings together all I have learned and more into one volume. As a reminder for myself I made notes as I read it.

The landscape and how to read it

Four landscape forming factors: rocks, soil, climate and living things.

Or two: the natural and the human.

The four factors are constantly interacting. Rocks affect landforms. Landforms affect climate. Rocks and climate affect the soil. Soil and climate affect vegetation. Vegetation affects soil and climate.

Three important themes. Everything changes. Everything’s connected. Everything has multiple causes.

Different timescales: annual, succession, rotational (human controlled).

Rocks: the bones of the landscape

Most fundamental difference is basic v acidic. Basic - alkaline soils rich in plant nutrients, acidic - acid, nutrient poor soils.

Igneous rock: granite, acidic; basalt, basic.

Sedimentary rocks. Sandstone - acidic, nutrient poor soils. Sandy heaths were often common land as they are nutrient poor and often remain as common land now eg Hampstead Heath. Clay - alkaline, nutrient rich soils. Often used as agricultural land. Limestone (including chalk) almost always makes hills as it is so permeable that no erosive surface water remains. Limestone soils are very alkaline but not necessarily rich in other nutrients so not necessarily fertile. Coal measures are the major determinant in urban v rural landscapes.

Hills and valleys

Upfolds don't always form hills (although they can!). Downfolded rocks are compressed and hardened; upfolds are stretched and weakened. These erode away more quickly than the strengthened rocks of the downfold.

Young rivers form V-shaped valleys which twist and turn. Cultivation is on the hills above the valleys. Glaciers form U-shaped straight valleys where the cultivation is in the valley as the hills above are too exposed for cultivation.

The soil and what plants can tell us about it

Fundamental difference is between the well drained, nutrient poor sandy soils and the alkaline, plastic (and as a consequence not well drained) clay. Clay loams are nutrient rich but plastic (heavy) and was often used for wheat and beans. Easily worked sandy loams were used for vegetables (rabbits and bracken clues to sandy soil).

Soil types. Podsol - acid. Excessive drainage washes nutrients from surface to hard pan below. Often forms on granite and sandstone. Characteristic of heaths and moors. Too acid for worms! Brown earth - not too wet, not too dry. Very good for agriculture. Also found in forests and grasslands. Gley - heavy clay soil with high water table which forms a blue/grey layer. Too wet to cultivate so used for meadow or pasture. Too wet for worms! Peat - extreme waterlogging prevents decomposition leading to peat. Peat can often form when heather forms a hard pan on a podsol leading to poor drainage. Rendzina - thin, alkaline soil on limestone.

Plant indicator species. Strong indicators eg reeds always indicate wet soil v communities. Indicators can tell us about water content, acidity, levels of plant nutrients and light/heaviness. Water content: buttercups - moist not wet; rushes - wet most of year; reeds standing water at least part of year; compacted soil has poor drainage and is often wet - plantain can grow on compacted but not wet soil. Acidity: easy at extremes (heather, acid, old man’s beard, alkaline) but look out for exceptions.

Climate and microclimate

Aspect has an effect but not as much as in other countries or as much as the changes in rock/soil type. Altitude has a much greater effect. It is colder (1C per 100m), windier, wetter and cloudier. Frost pockets form in valleys where the cold air flows down from higher ground. Snow can be used to pick out the wind patterns by studying the drifts. Melting snow picks out the warmer and cooler parts of the landscape. Wind flagged trees show prevailing wind (south west) or effects of local landforms.

Heaths and moors

Heaths are usually sandy lowland areas with poor nutrients. Since the advent of fertilisation many of them were turned into agricultural land and they are now uncommon. Moors form on higher ground, usually acidic in nature. Many are semi natural, formed from woodland by grazing. They often follow the pattern of bracken on the slopes and heather or grass moor on the tops (if the slope is too steep heather will take over as the soil is too thin for bracken). Bracken is a very competitive plant but needs more in the way of bases, drainage and deeper soil than other moorland plants. It hates shallow soil, it hates wet feet: where there is shallow soil heather can grow, where it is wet grass and rushes grow. Alternatively gorse may grow on the slope and bracken a the bottom:

There's gold under bracken,

Silver under gorse,

And famine under heather

Moors are usually managed by burning for either grouse or sheep. Trees are more demanding than most heathland plants and often grow by streams where active erosion releases bases allowing them to grow quicker. Blanket bogs form peat where the rainfall is very high and drainage poor resulting in saturated soil. They are natural as they overwhelm the trees whic can't grow in these wet conditions. In the Pennines they often form on the western side at higher altitude, while heather moors form on the eastern side and lower down.

VEGETATION SUMMARY

The Heather Family

Heather or ling. Poor, acid soil, moist to dry, usually a podsol; tolerates thin soil.

Bell heather. Mixed with heather on drier soils, dominant on very dry ones.

Cross-leaved heath. Mixed with heather on wetter soils, dominant where it's too wet for heather.

Bilberry. Often on drier soil or boulders; shade tolerant and often grows in woods.

Plants of More Fertile Soils

Bracken. Deep, well-drained soil, richer and less acid than typical heather soil, usually a brown earth, usually on a slope; can out-compete other plants on a

favourable soil but is sensitive to trampling; altitude limited by cold.

Sweet grasses (bents and fescues). A mix of fine-leaved grasses, usually grazed down short because the animals like them; they grow on similar soils to bracken.

Gorse, common. Slightly poorer soils than bracken but sometimes more alkaline; not cold-tolerant.

Gorse, dwarf and western. Much smaller plants than common gone with similar soil preferences to heather.

Plants of Wet Soils

Matgrass. Similar soil to heather but often a bit wetter; both it and purple moorgrass may take over where heather is overgrazed.

Purple moorgrass. Similar soil to matgrass but usually a bit wetter still; often grows in big tussocks, especially when in a pure stand - very hard going for

walkers.

Bog myrtle. Wet to very wet soil, often with purple moorgrass; like the alder tree, it's a nitrogen-fixer.

Deergrass. Deep peat and bogs, very wet and acid.

Cottongrass. Bogs, even wetter than deergrass and including open water.

Bog moss. The ultimate peat-forming bog plant, only found in extremely wet conditions.

Water in the landscape

Springs form at the junction of permeable and impermeable rock such as limestone and clay. This is often at the boundary of hill and dale. Villages often built near a spring on this boundary with access to grazing and arable land.

Bogs can also form in valleys.

TYPES OF BOG

Blanket. Forms in regions of extremely high rainfall; covers all flat and gently sloping land in a layer of peat. Always acidic.

Valley. Forms in a low place where drainage is impeded, fed by drainage water. Can be acid (bog or moss) or alkaline (fen).

Raised. Forms on top of a valley bog, fed by rainfall. Always acidic.

The rest of the chapters in the book are less relevant to the Peak District or to my particular interests so I have only outlined them here.

The history of the landscape. Very interesting chapter about the farmed history of the landscape including the enclosures.

The three chapters wild animals and how to recognise their signs, niches or how plants and animals make their livings and succession how landscapes change through time are more about ecology than geology.

Woods play a large role in the landscape and there are three chapters are all about them - trees as individuals, the different kinds of woodland and how woods work. Lowland grassland, hedges & other field boundaries, and roads & paths complete the book contents.

Sunday 16 December 2012

Rocks and Fossils: The Peak District



I.M. Simpson (1982) Unwin Paperbacks

1 Edale and Kinder Scout

2 Castleton Area: Treak Cliff and Mam Tor

3 Castleton Area: Cave Dale and Dirtlow Rake

4 Eyam, High Rake and Coombs Dale

5 Tideswell Dale and Miller's Dale

6 Ashford and Monsal Dale

7 Lathkilldale

8 Youlgreave and Alport

9 Black Rock and Steeple Grange

10 Thorpe Cloud and Lower Dovedale

11 Hartington, Wolfscote Dale and the Tissington Trail

12 Ecton and the Manifold Valley

13 Hen Cloud, The Roaches and The Ramshaw Rocks

14 Parsley Hay, the High Peak and Tissington Trails

15 Goyt's Moss



Great Double Dyke – English Heritage Scheduled Monument 31229

Two parallel ditches have marked the boundary between Ashford and Hope land since local families bought it from the Danes in AD926 (SK218736).



Deep rake

At the end of the opencast workings on the OS map in grid square SK2273 (above Calver) the mine at the end of Deep Rake is visible.

 
 

 

Saturday 15 December 2012

Wednesday 12 December 2012

Rocky Rambles in the Peak District

Fred Broadhurst (2001) Sigma Leisure

A short introduction to Peak geology is followed by the walks. Nice overview section of the geology.

The walks:

Walk 1: Castleton - Cave Dale - Pin Dale

Limestones, Lava and Lead

Walk 2: Castleton - Lose Hill - Mam Tor

Ridge, Landslip and a Resurrected Sea Floor

Walk 3: Edale - Kinder Scout

Sandstone Scenery, Wind Sculptures

Walk 4: Monsal Dale

Landslips and Fossils

Walk 5: Millstone Edge - Stanage Edge

Millstones and Concretions

Walk 6: Wirksworth

National Stone Centre and Dolomite

Walk 7: Dovedale

Limestone Scenery

Walk 8: The Roaches, Lud's Church

Geology and Scenery

Walk 9: Earl Sterndale - Parkhouse Hill - Chrome Hill

Limestone 'Reefs'

Walk 10: Lyme Park - Cage Hill - Bowstones

Sandstones, Glacial features

Walk 11: Lyme Park - West Parkgate

Glacial Spillway, Fossil Soils and Fossil Ripple marks

Walk 12: Lathkill Dale

Limestones, Fossils and Lead Mines

Walk 13: Goyt's Moss - Shining Tor

Sandstone Scenery and Coal

Walk 14: Ashford-in-the-Water - Magpie Mine

'Black Marble' and Lead

Walk 15: Tegg's Nose

Sandstone and Sandstone Quarries

Walk 16: Tideswell Dale - Miller's Dale

Limestones and Lavas

Walk 17: Rowarth - Cown Edge

Faults, Folds and Landslips

Walk 18: Rowarth - Lantern Pike

Rocks and Topography



Monday 3 December 2012

Geology Explained in the Peak District



F. Wolverson Cope (1998). Scarthin Books

This was the first Peak geology book I bought and I found it hard going when I first got into geology (before I started on my OU degree!), so we shall see if it makes more sense now!

Oh dear. After a somewhat superfluous set of introductory chapters this book ploughs on with descriptions of specific areas. It is written for someone with a degree in geology and lacks the idea of a specific itinary which is present in the other 3+ geology walk books available. It is also very old fashioned. Give it a miss.

1 Geology In The Field Field equipment - the Countryside Code - the Peak DistrictNational Park

2 Identifying Rocks, Minerals and Fossils Rocks - minerals - fossils

3 The Geological Time-scale

4 Geological Structure of the Peak District

5 The Valley of the River Wye: Buxton to Little Longstone The Carboniferous basement - the sequence east of Woo Dale - the massif fades

6 The Valley of the River Goyt Millstone Grit and Namurian - pre-Namurian denudation - the Goyt Syncline - Namurian cyclic sedimentation - contorted beds

7 Castleton, Edale and Mam Tor Reef limestones - caves of the Castleton district - the Speedwell Vent - fossils of the reef limestones - the use of goniatites - the Namurian of the Edale valley

8 Bradwell Dale and Eyam Bradwell Dale - Eyam - the Eyam and Woo Dale boreholes

9 Monsal Dale and Ashford-in-the-Water The Hobs House Coral Band - igneous rocks in Monsal Dale - the Ashford marble

10 Matlock, the Via Gellia, and Brassington The Grangemill vents - lead mining in the Peak District - dolomitisation of limestones - Tertiary pocket deposits

11 Ashover Dinantian rocks of Ashover - Namurian rocks of Ashover

12 The Valley of the River Dove Reef limestones of Thorpe Cloud and Bunster

13 Chrome Hill and Parkhouse Hill

14 The Valley of the River Manifold

15 The Roaches and Goldsitch Moss The Rough Rock of Quarnford and Goldsitch - Namurian successions in the Peak District

16 Kinder Scout The Mam Tor Beds - the Shale Grit - the Kinder Scout Grit

17 Economic Geology of the Peak District General and water supply - mining - quarrying



Sunday 2 December 2012

Millstones and bedding

When there is good weather at this time of year it really is fantastic. Here are some iPhone shots taken under Stanage Edge.