The distribution of (a) ancient and (b) youthful landslides in Great Britain recorded as a result of the survey of landslides in Great Britain commissioned by the former Department of the Environment (DoE), and completed by Geomorphological Services Ltd (GSL) between 1984 and 1987. After Jones and Lee (1994).

Indicative periods of major landslide activity in Europe derived from EPOCH data (c = radiocarbon (C14) dates; D = important individual dates from the historical record). After Brunsden and Ibsen (1997).

(a) Hutchinson’s classification of mass movements on slopes (1968a); (b) Hutchinson’s (1988) classification (first two levels only).

Terminology of landslides used in The Multilingual Landslide Glossary; profile and plan views. See text for explanation of numbers. After WP/WLI (1993).

Landslide dimensions recommended in The Multilingual Landslide Glossary. See text for explanation of numbers. Based on WP/WLI (1993) and Cruden et al. (1994).

Types of landslides: (1) a fall; (2) a topple; (3) a slide; (4) a spread; (5) a flow. See text for explanation of types. After WP/WLI (1993).

Classification of the states of activity of landslides used in the Multilingual Landslide Glossary: (1) active; (2) suspended; (3) re-activated; (5) dormant; (6) abandoned; (7) stabilized; (8) relict. State (4) inactive is divided into states (5)–(8). See text for explanation of states. After WP/WLI (1993).

Distribution of the activity of landslides: (1) advancing; (2) retrogressive; (3) enlarging; (4) diminishing; (5) confined; (6) moving; (7) widening. See text for explanation of terms. After WP/WLI (1993).

Styles of landslide activity: (1) complex; (2) composite; (3) successive; (4) single; (5) multiple. See text for explanation of terms. After WP/WLI (1993).

The candidate mass-movement GCR sites suggested by the panel of experts consulted in the 1980s.

The final list of selected mass-movement sites as drawn up in the early 1980s.* Glen Pean and Spot Lane Quarry have now been deleted from the Mass-Movements GCR ‘Block’ (selection category) – see text.

The supplementary sites added to the GCR following recent research in Scotland.

The mass-movement GCR sites cdescribed in the present volume; style and type are according to the World Landslide Inventory (WP/WLI 1993), classifications are according to Hutchinson (1968a) and (1988) – described in Table 1.1a,b.

The sites described in the present volume classified by geological age and by WLI mass-movement type: (PC = Precambrian–Cambrian; Si = Silurian; De = Devonian; Ca = Carboniferous; Ju = Jurassic; Cr = Cretaceous; Eo = London Clay; Pl = Pleistocene; fa = fall; to = Topple; sl = slide; sp = spread; fl = flow; * = sites which display cambering and valley-bulging).

Simplified geological map of Great Britain, with the general locations of the mass-movement GCR sites numbered: (1 – Ben Hee: 2 – Trotternish Escarpment: 3 – Hallaig; Beinn Alligin: 4 – Beinn Fhada; Sgurr na Ciste Duibhe; Druim Shionnach: 5 – Coire Gabhail: 6 – Carn Dubh: 7 – The Cobbler; Benvane; Glen Ample: 8 – Cwm-du: 9 – Llyn-y-Fan Fâch: 10 – Hob’s House; Alport Castles; Canyards Hills; Lud’s Church; Mam Tor; Rowlee Bridge: 11 – Eglwyseg Scarp: 12 – Peak Scar; Buckland’s Windypit: 13 – Postlip Warren; Entrance Cutting at Bath University: 14 – Axmouth–Lyme Regis; Black Ven; Blacknor Cliffs: 15 – Folkestone Warren; Stutfall Castle: 16 – High Halstow: Warden Point: 17 – Trimingham Cliffs).

The example model of undrained loading suggested by Hutchinson and Bhandari (1971).

Illustration of a ‘circular’ failure in which the slump block rotates uphill and the graben rotates downhill (after Taylor, 1948). In more recent literature the ‘graben’ morphology is generally interpreted as being diagnostic of planar failure surfaces (non-circular) often related to the dip of the bedding.

The shape of a landslide shear surface in stratified soil with horizontal bedding compared with a hypothetical circular arc surface. After Taylor (1948).

The main characteristics of compound landslides with flat-lying bedding. After Barton (1984).

General location map of the older mountain ranges in Britain. Locations of GCR sites in this chapter are shown in Figure 2.13. Other sites within the older mountain areas are Cwm-du (see GCR site report, Chapter 3) and Coire Gabhail (see GCR site report, Chapter 4).

Beinn Bhuidhe rock slope failure, Arnisdale, Loch Hourn, Western Highlands (NG 860 113). A typical armchair slide with slope toe exceptionally undercut by deep fluvial (rather than glacial) incision, and thus not directly a paraglacial rock slope failure. (Photo: D. Jarman.)

Kirk Fell rock slope failure, Wasdale, Lake District. A classic virtually in-situ slope deformation, with an antiscarp 600 m long crossing the summit plateau and others on the south-west flanks. (Photo: P. Wilson.)

A typical small crag in Moine psammites displays four distinct discontinuities (the foliation or schistosity surface and three joint-sets), which have released a miniature wedge failure. (Photo: D. Jarman.)

Characteristic types of large rock slope failures (RSFs) in the Scottish Highlands and Lake District. Adapted from Jarman (2006) and Wilson et al. (2004). See Figure 2.5 for explanation of terms.

Characteristic types of larger-scale rock slope failure identified in the Scottish Highlands. The plateau rim location is typical of less intensely dissected terrain. In more acute relief, headscarps may daylight below or behind the crest, or split the ridge. After Jarman (2006).

Rock slope failure (RSF) incidence, character, landshaping effect, and association with breaching in the Southern Highlands and Kintail area (including clusters 1, 5 and 7 in Figure 2.13). Updated from Jarman (2003a,b). Note: sites may be in more than one character or landshaping category. See Figures 2.15 and 2.18.

Beinn Tulaichean, Balquhidder, Southern Highlands (NN 420 196). A classic short-travel arrested translational slide from a splayed armchair source which splits the summit ridge. Despite the blocky veneer and spray fan, the failed mass is substantially intact, with double-decker-bus-sized fissures in the upper area. (Photo: D. Jarman.)

Tullich Hill rock slope failures, Luss Hills, South-west Highlands (NS 292 998). A translational slide complex from a multiple wedge source; the inner cavity in the west (left) rock slope failure is 30 m deep. (Photo: D. Jarman.)

Mullach Fraoch-choire, Glen Affric (NH 102 187). A sub-cataclasmic debris-lobe 20 m thick with fine levées almost reaches the stream. It emanates from a narrow source pocket, and descends 380 m in 800 m. (Photo: D. Jarman.)

Beinn an Lochain North rock slope failure, Arrochar Alps (NN 217 083). A sub-cataclasmic rockslide, partly fallen from the cliffs (behind which deep fissures indicate incipient increments), but with a sliding component that has sharpened the summit ridge (top left) to an arête. (Photo: D. Jarman.)

Fairfield rock slope failure, Lake District (NY 355 120). An extensive translational slide, with long-travel masses arrested above the floor of Grisedale, which breaches through to Grasmere and Dunmail Raise just to the west (right). The headscarp encroaches into the north-east ridge (left) to shape the arête of Cofa Pike. (Photo: D. Jarman.)

Na Gruagaichean rock slope failure complex, Mamores, Lochaber (NN 195 650). The twin summits (centre and right) are divided by a 140 m-deep gash, the source of a very large wedge slide that has been substantially evacuated leaving a SW-facing bowl that is not a corrie in origin or by adaptation, the floor of which is extensively ruptured with antiscarps up to 3 m high. Another large rock slope failure encroaches onto the south ridge (right), and a third slide lobe sharpens the north-west ridge (left-centre). (Photo: J. Digney.)

Aonach Sgoilte rock slope failure, Knoydart (NG 836 020). The ridge is split over 1.5 km by a source fracture daylighting behind the crest, often 30 m downslope on the north (right). The summit mass seen here has slipped south by 10–15 m. The gentler slope below is extensively antiscarped, one being 500 m long and reaching 7.5 m in height. A wedge slip has left the shadowed notch. The rounded headscarp crest (contrasting with Sgurr na Ciste Duibhe) could indicate relatively ancient inception. (Photo: D. Jarman.)

Spatial distribution and size of 140 larger rock slope failures (RSFs) (> 0.25 km2) in the mainland Scottish Highlands (distribution of all rock slope failures is similar). Rock slope failure is clustered on main watersheds that have been breached and displaced during Pleistocene times. It is scarce in ranges away from the watersheds, in the far north where ice cover was thinner, and in the eastern Grampians where glacial dissection is less intense. Sites reported in this chapter are shown. After Jarman (2006).

The Central Grampian Highlands, including the Loch Ericht–Gaick cluster (cluster 6 in Figure 2.13). All rock slope failures shown true to scale. Failure only occurs in or downvalley from breaches, and is entirely absent from other valley-sides and plateau rims. Failure concentrations in the Loch Ericht and Gaick Pass breaches may point to their recent origin or enlargement; rock slope failure absence from Drumochter Pass (main road/rail corridor) may indicate its earlier development. Adapted and revised from Hall and Jarman (2004).

The Southern Highlands, an area of intense rock slope failure (RSF) activity, including the Arrochar–Cowal–Luss and Trossachs–Lochearnhead clusters (clusters 5 and 7 in Figure 2.13). Failure is scarce or absent in main pre-glacial valleys and some breaches of the main watershed, despite their slopes and geology being susceptible to it. Its paucity along the deep breach trench of Loch Lomond is surprising. Note mini-clusters top-centre and top-right, where locally intense breaching occurs across main and secondary watersheds. The locations of three sites (Glen Ample, The Cobbler, Benvane) are shown. Adapted and revised from Jarman (2003a).

(a) The inferred association of rock slope failure (RSF) with breach incision and enlargement over repeated glacial/paraglacial cycles. (b) Typical locations for rock slope failure responding to exceptional deglaciation stresses directly and indirectly associated with glacial breaching. After Jarman (2006).

The nature of the association between paraglacial rock slope failure and glacial breaching. This suggests why many breaches may lack rock slope failure, and acknowledges that not all failures can be attributed to breaching. After Jarman (2006).

Part of the Affric–Kintail–Glen Shiel rock slope failure cluster (cluster 1 in Figure 2.13). Rock slope failures tend to be located near breaches of the inferred pre-glacial watershed, and in side troughs rejuvenated by breaching. Note the locations of three GCR sites –Beinn Fhada, Druim Shionnach and Sgurr na Ciste Duibhe. Adapted from Jarman (2003b).

Large rock slope failures (RSFs) in the Scottish Highlands for which data are available. After Jarman (2006). Sites are listed from the north, with the Great Glen separating the North-west Highlands from the Grampians. Note the disproportionate number of large RSFs studied north-west of the Great Glen, where foliation (F) is rarely as conducive to sliding as in the Southern Highlands. Most studies are of (sub-)cataclasmic RSFs or slope deformations, rather than conventional arrested slides. ‘Ref.’: reference sources are (1) Ballantyne, 2003; (2) Fenton, 1991; (3) Holmes, 1984; (4) Jarman, 2003c,d,e, 2004a, and present volume; (5) Jarman, 2003b; (6) Watters, 1972. ‘Mode’: cata = cataclasmic; sub-cata = sub-cataclasmic; ext def = extensional deformation (sag, creep); comp def = compressional deformation (rebound). ‘Area’: RSF size is here taken as the gross area including source cavity, since most cases are incompletely evacuated. British Geological Survey mapping of RSF is variable and incomplete, but recent sheets only map as ‘landslips’ disturbed ground, thus excluding both source areas and semi-intact slope deformations. The gross area best indicates the geomorphological impact of the RSF, but clearly requires adjustment when volumetric calculations are made. ‘Vol.’(-ume) and maximum ‘Depth’ should be seen as broad estimates, especially sites marked ‘?’ where the depth cannot readily be assessed. #1 depth figures are for cavity (ref. 2) and debris tongue (ref. 1); #2 volume (ref. 3) assumes there is a failed mass with a boundary at ~100 m, no volume can be calculated if the failure partly dissipates at depth; #3 volume and depth are for main cavity within larger deformation. ‘H/S’ = headscarp (rear scarp, source scarp) maximum height. ‘A/S’ = antiscarp (obsequent scarp, counterscarp, uphill-facing scarp) maximum height – figures in brackets are graben trenches or uphill faces of large slipped masses. ‘Slide plane’: F = foliation or schistosity surface; J = joint-sets (in order of significance); RFA = residual friction angle.

The Beinn Fhada rock slope failure seen from the west across Gleann Lichd. Unbroken antiscarps extend up to 800 m across the 30°–35° glacial trough side. Deformation extends for 3 km along the valley and onto the pre-glacial upland surface, reaching the south top (1000 m) in the background, and affecting 3.0 km2. (Photo: D. Jarman.)

Vertical aerial photograph of the Beinn Fhada rock slope deformation. The three major slope convexities are highlighted by antiscarp arrays, as is the extent of the pre-glacial land surface with its structural lineaments. (Photo: Crown Copyright: RCAHMS (All Scotland Survey Collection).)

Geomorphological map of the Beinn Fhada rock slope deformation, showing the location of prominent antiscarps, lineaments, areas of localized sliding failure and the three slope convexities or bulges (labelled ‘West’, ‘Central’ and ‘East’). The map is based on the aerial photograph in Figure 2.20, with an average scale of 1:22 500. After Jarman and Ballantyne (2002).

Antiscarps near the top of the western slope bulge. The farthest of the three antiscarps rises 6–8 m (locally 10 m) out of the slope. (Photo: C.K. Ballantyne.)

Geomorphological map of the Sgurr na Ciste Duibhe rock slope failure. After Jarman (2003b).

Failed slope rising 950 m above Glen Shiel breach, viewed from the south, showing the Glen Shiel Fault (diagonal pecked line), skyline dislocation, lowered summit and some of the failure zones marked on Figure 2.23 (Zone C is shown on Figure 2.26). (Photo: D. Jarman.)

Five Sisters summit ridge dislocated by subsidence along the Glen Shiel Fault. View looking south-eastwards from Point 985. Ridge breaks are 10–15 m high; note the dry hollows, lower-right (Zone C). (Photo: D. Jarman.)

Antiscarps and graben wall below the summit (Zone D). The bulging toe (hiding the road) creates a local gorge. The slide cavity with fissured debris-mass can be seen in the foreground. The long parapet/ antiscarp and uphill-facing crag are marked on Figure 2.24. (Photo: D. Jarman.)

Map and long-section of the Glen Shiel breach with reconstructed pre-glacial watershed and associated rock slope failures on the north side of the main valley and in the trough corries of the south Cluanie ridge (e.g. Druim Shionnach). After Jarman (2003b).

Geomorphological interpretation of the Druim Shionnach rock slope failure based on OS 1:25 000 mapping. After Jarman (2003b).

Section X–X on Figure 2.29, showing over-steepened bulge and graben progressively tilting failed slices away from source. After Jarman (2003b).

The Druim Shionnach rock slope failure is on the flank of a side trough off the main Cluanie pre-glacial valley. The smooth and bulging failed slope is wider than the apparent source scarp and notably lacks surface drainage and a clear lateral margin. (Photo: D. Jarman.)

The Druim Shionnach rock slope failure top surface, seen in close-up from the summit ridge to the south-west. The prominent peak is the 14 m-high antiscarp facing the source scarp across a half-graben. Note the block-flexural toppling in the near-vertical metasediments, revealed in section in the foreground (see inset, Figure 2.29). (Photo: D. Jarman.)

Vertical aerial photograph (1989) of Benvane, with sun from the east accentuating the array of antiscarps, scarplets and benches. (Photo: Crown Copyright: RCAHMS (All Scotland Survey Collection).)

Geomorphological interpretation of the Benvane rock slope failure complex. Based on unrectified aerial photograph with field verification.

Sections X–X through the deformation zone and Y–Y through the translational slide. For locations see Figure 2.34.

Benvane slide bowl and lobe, viewed from the west from Meall Cala, with lattice slope deformation upper-left; extensive springs can be seen above the lowest antiscarp centre-left. (Photo: D. Jarman.)

View north across the degraded headscarp of the slide bowl (Coire Dubh) to the fresher crags of the transitional zone. The extent of incipient encroachment into the broad ridge is indicated with a broken line. (Photo: D. Jarman.)

(a) View south down the spreading ridge to the slide bowl. The 6 m-high source scarp to the subsidence graben is not the limit of encroachment in to the ridge, the true headscarp being just visible on the left edge. (b) A close-up view across the slide bowl of the transitional zone extending into the spreading ridge. (Photos: D. Jarman.)

Benvane and surrounding rock slope failures (RSFs) in their topographical context. This sub-cluster may be associated with glacial transfluence south-east across local watersheds, the breaches being at varying stages of development. Unlike the Glen Ample sub-cluster immediately to the north-east, there is no specific association with main faults.

The Glen Ample rock slope failure (RSF) cluster in relation to the Loch Tay Fault and immature glacial breaches.

Vertical aerial photograph (1989) of the Ben Our rock slope failure. (Photo: Crown Copyright: RCAHMS (All Scotland Survey Collection).)

Geomorphological interpretation of the Ben Our rock slope failure, based on the unrectified aerial photograph with field verification.

Section X–X across Figure 2.42 with inferred failure behaviour on a very low angle creep surface.

Geomorphological interpretation of the Beinn Each rock slope failure. Features A, B, C, D and E are described in the text.

Close-up of the Beinn Each rock slope failure nexus, suggesting extrusion of a component of the failed mass with fracturing along two joint-sets. (Photo: D. Jarman.)

The distinctive profile of The Cobbler from the ESE, with the main rock slope failure on its left flank and a small rockslide into the breach col on the right. Both North Peak and South Peak may be the remnants of former corrie arms truncated by rock slope failure. The wide skyline nick may also result from a headwall collapse, but only small debris-lobes remain in the corrie. (Photo: D. Jarman.)

The Cobbler and adjacent peaks, isolated by glacial breaching and incision, and with rock slope failure (RSF) encroaching into the pre-glacial land surface.

Vertical aerial photograph of the The Cobbler, showing contrasting land surface types and modes of erosion on its flanks. (Photo: Crown Copyright: RCAHMS (All Scotland Survey Collection).)

Geomorphological map of The Cobbler, based on Figure 2.48.

The main rock slope failure complex seen from the south-west across Glen Croe, showing the panels mapped in Figure 2.49. Panel 2 (on the right) has travelled further than Panel 1 to expose the arête culminating in the South Peak (Point 858). The level pre-glacial summit surface of Beinn Narnain (Point 926, right background) suggests the character of The Cobbler before it underwent more intense paraglacial rock slope failure. The summit tor (Point 884) stands out from the vestigial pre-glacial skyline. (Photo: D. Jarman.)

The Ben Hee rock slope failure (RSF) cluster, with glacial breaches and related ice movements.

Geomorphology of the Ben Hee rock slope failure (RSF) in An Gorm-choire. The encroachment into the undulating pre-glacial surface is considerably greater than the extent of the ‘slipped segments’.

View across Tiers 1 and 2 of the main failed mass, and both flanking increments, from the north rim to the summit of Ben Hee. The reconstructed pre-deglaciation crest follows the axis of the picture, whereas the pre-Quaternary crest probably curved more to the left between gentle domes. (Photo: D. Jarman.)

View up An Gorm-choire from the smooth sediment bank, with sub-glacial flute ridges emanating from beneath the rock slope failure toe. Above them, Tier 3 has lateral lineations which contrast with the amorphous slumping mass of Tier 2. The pecked line denotes the pre-failure skyline, reconstructed in Figure 2.56, and inferred to have been lowered by up to 35 m. Pre-glacial surface remnants survive at top-left and top-right. (Photo: D. Jarman.)

The source fracture for the main failed mass and north flank component, mis-interpreted by Godard (1965) as a glacial moraine. The slipped segment retains much of its pre-glacial character. (Photo: D. Jarman.)

The reconstructed pre-failure topography of An Gorm-choire, with the long-section of the main rock slope failure showing reduction of the summit ridge by up to 35 m and the scale of mass displacement.

Map of the Carn Dubh rockslide scar and debris tongues, Ben Gulabin.

The Carn Dubh rockslide scar and debris tongues on Ben Gulabin. The southern debris tongue (left) peters out in low ridges and levées of vegetation-covered debris, whereas the northern tongue terminates in a bold bluff 5 m high. The inner levées of both lobes terminate upslope at the conspicuous bulbous protrusion that diverted flow of rockslide debris into two tongues. (Photo: C.K. Ballantyne.)

The Carn Dubh rockslide, Ben Gulabin, from above. (Photo: D. Jarman.)

The Beinn Alligin rock-avalanche failure scar and runout deposit; map based on 1:25 000 aerial photographs and field mapping from adjacent summits.

The Beinn Alligin rock-avalanche failure scar and runout deposit photographed from the western end of the neighbouring mountain, Liathach. (Photo: C.K. Ballantyne.)

Rock-avalanche runout deposit with the failure scar in the background, showing the coarseness of the runout debris and the converging fault scarps that bound the scar. The vertical height of the fault scarp to the right of the failure scar increases upslope to nearly 60 m immediately below the summit of the mountain. (Photo: C.K. Ballantyne.)

Long profile of the failure scar and runout tongue, projected along intersecting lines drawn down the axis of the scar and up the axis of the tongue (Figure 2.60). Excess runout is the difference between actual runout and the runout that is expected under frictional sliding alone. Under the latter condition H/L = 0.6 and tan–1(H/L) = 32°. At Beinn Alligin, H/L = 0.38 and tan–1(H/L) = 21°. Excess runout (Le) = (L – Htan 32°) = (1763 – 1080) m = 683 m, implying that the runout debris extended 683 m farther than would be expected under conditions of frictional sliding alone.

Areas of Silurian strata (shaded), and the location of the Cwm-du GCR site, described in the present chapter.

The location of Cwm-du in the Upper Ystwyth valley. Contours are in metres. After Watson (1966).

View across the Upper Ystwyth valley looking southwards into Cwm-du, up the extensive ‘drift’ or landslip debris incised by an 18 m-deep gully. (Photo: S. Campbell.)

(a) Field survey of Cwm-du and its associated debris fan. ?(b) Surveyed sections, J–K, M–L, O–N. Scarps discussed in the text are numbered I–III. Scarp IV lies at the mount of the Cwm. Scarp V on the map is a protalus in the south-west corner. The dashed line is the profile of the main valley-side. After Watson (1966).

Profiles (P–Q, R–S) through Cwm-du. Roman numerals, IV, V, correspond to Figure 3.4. The dashed lines reconstruct the floor of the cwm. After Watson (1966).

Exposures of the deposits in the Cwm-du fan. The profile is the west bank of the gully projected onto section J–K. After Watson (1966).

The sequence of head deposits in Nant Cwm-du gully, 120 m south-west of profile J–K. The scale begins at stream level. After Watson (1966).

Block-diagram of a snowpatch during the melt season. Based on Botch (1946) and Watson (1966).

The evolution of Cwm-du. Step IIa is shown as marking a snow limit. If these steps represent climatic pauses, Watson (1966) suggested that research elsewhere in Wales may help to decide its status. After Watson (1966).

Stages in the development of the Cwm-du profile. The continuous line is a composite profile along section J–K. Bedrock is in part hypothetical. ‘A’ represents the initial profile; I–IV represent backwall positions corresponding to steps in the fan; ‘a’ is the profile of the main valley-side.

Areas of Devonian strata (shaded), and the locations of the GCR sites described in the present chapter.

Geomorphological map of the Coire Gabhail rock-avalanches, showing the failure sites, the extent of the talus complex representing landslide runout and the area of alluvium deposited in the upper valley as a result of damming of the valley by runout debris. (1) site of initial rock-avalanche; (2) site of later rock-avalanche.

The complex talus accumulation formed by runout of the Coire Gabhail rock-avalanches, viewed from the south-west. The southern (left) edge of the larger talus cone is partly buried under alluvium. The conspicuous large boulder just beyond the toe of the cone rises about 10 m above the alluvium in which it is embedded. (Photo: C.K. Ballantyne.)

The south-west end of the talus complex, showing the fringe of large boulders. Alluvium deposited due to damming of the valley by the rock avalanche is visible in the foreground. (Photo: C.K. Ballantyne.)

General view of the Llyn-y-Fan Fâch GCR site, showing the scarp face of the Black Mountain (Mynydd Du), and screes and gullies. (Photo: S. Campbell.)

The location of the Llyn-y-Fan Fâch mass-movement site.

Range of sediment grain-size distribution of scree debris at Llyn-y-Fan Fâch. After Statham (1976).

Detail of the gullying and mass-movement deposits at Llyn-y-Fan Fâch. (Photo: S. Campbell.)

Profile of a typical gullied debris-flow cone system at Llyn-y-Fan Fâch. After Statham (1976).

(a) Block-diagram of the Black Mountain scarp. (b) Plane table survey of three debris-flow gullies. After Statham (1976).

Areas of Carboniferous strata (shaded) and the locations of the GCR sites described in the present chapter.

The distribution of recorded landslides in Derbyshire. After Geomorphological Services Ltd (1988); from Doornkamp (1990).

View of Eglwyseg Scarp, surveyed by Tinkler (1966). (Photo: R.G. Cooper.)

Aerial phtograph of the scree-slopes at Eglwyseg Mountain, near Llangollen. (Photo: Cambridge University Collection of Air Photographs, Unit for Landscape Modelling.)

The geology of the Eglwyseg Valley, North Wales. After Tinkler (1966).

The geomorphology of the Eglwyseg Valley, North Wales. After Tinkler (1966).

Slope profiles of (a) World’s End, and (b) Craig Arthur. After Tinkler (1966).

Slope profiles on Eglwyseg Scarp, North Wales, surveyed by Tinkler (1966).

Histogram of all recorded slope angles on the Eglwyseg Valley, North Wales.

The backscar and transported blocks of the Hob’s House landslide. (Photo: S. Graham, English Nature/Natural England.)

Location of Hob’s House GCR site.

Slope profile at Hob’s House.

Sketch plan of Hob’s House (Hobhurst Castle). ‘A’ is the mouth of the fissure in the cliff-top, probably a camber structure or landslide ‘labyrinth’.

Location of the Alport Castles and Rowlee Bridge GCR sites, showing other landslips (stippled) and scars (‘spiked’ lines) in the vicinity.

Aerial photographs of the Alport Castles landslip complex. (Photos: © Crown Copyright/MOD. Reproduced with the permission of the Controller of Her Majesty’s Stationary Office.)

Morphological map of the Alport Castles landslip complex, identifying the main slip units described in the text, and indicative geology. The source scar transgresses the original valley rim above Units B and C, but daylights below it elsewhere. After Johnson and Vaughan (1983).

The main source scar at its greatest above The Tower (Unit B). The sandstone cliff has a degraded upper slope to the plateau rim and a long talus slope with abundant coarse debris in the trench. The rounded and split slip of Birchin Hat (Unit A) beyond contrasts with the ruggedness of The Tower (Unit B). Far below Unit A, the lower parts of the failure bulge into the broad trough of Alport Dale, where it widens out from a narrow, V-shaped valley. (Photo: R.G. Cooper.)

Profiles showing the varying arrangements of slump units at Alport Castles (letters refer to slump units in Figure 5.16). Note that the depth and nature of a failure surface or zone are not surmised. After Johnson and Vaughan (1983).

Location of Canyards Hills, showing linear features below the rockface and the upper slope.

Geological map of the setting of the Canyard Hills landslide complex south of the Broomhead Reservoir.

General view of the Canyards Hills landslide complex from the south-west, showing the elongate ridges and troughs of the upper slope and the lateral extension of the slope. (Photo: R.G. Cooper.)

Canyards Hills landslide complex viewed from ENE – the uppermost failure blocks and arcuate scar. (Photo: R.G. Cooper.)

The location and general morphology of Lud’s Church, Staffordshire.

View along the ‘labyrinth’ of the Lud’s Church fissure. (Photo: R.G. Cooper.)

Location of the Mam Tor landslide, showing other major landslides also encroaching into Mam Tor hillfort and Rushup–Lose Hill ridge, and the former trunk road severed by it.

The Mam Tor landslide scar from the top of the upper slump sector. (Photo: M. Murphy, English Nature/Natural England.)

Oblique aerial photograph of the Mam Tor area, showing the old road which was closed in 1979 owing to repeated slippage. The scar of the landslip is clearly visible, as well as a slumped mass. (Photo: © National Trust/High Peak.)

Schematic plan of the Mam Tor landslide, showing sectors, geology, borehole locations, and the former trunk road. The line running almost west–east is the line-of-section shown in Figure 5.29. After Skempton et al. (1989).

Longitudinal section and location of boreholes through the Mam Tor landslide. After Skempton et al. (1989). The section line is shown in Figure 5.28.

Stratigraphical section at Mam Tor. After Skempton et al. (1989).

Geological and morphological details of the scar and the upper slump sector of the Mam Tor landslide, showing the locations of boreholes 4 and 8 (BH 4 and BH 8). After Skempton et al. (1989).

Transverse section of the middle transition sector of the Mam Tor landslide (Ordnance Survey, gridline 133). The shaded area is the landslide; borehole (BH) positions are marked. After Skempton et al. (1989).

Records of movement and rainfall at Mam Tor, 1915–1977. After Skempton et al. (1989).

The relationship between rainfall and landslide movements, winter 1956–1966. Recorded by Brown (1966), updated by Skempton et al. (1989).

The relationship between average monthly rainfall and the incidence of heavy rain (1915–1980) and the return periods of monthly rainfall on an annual and winter basis. After Skempton et al. (1989).

Piezometric levels recorded at Mam Tor during 1977 and 1978. After Skempton et al. (1989).

Displacements at Mam Tor caused by winter rainstorms. Note: movement begins at a piezometric level that is lower than the level at which movement ceases. This may imply that there has been a strength gain that may be of chemical origin in which movement releases cations. After Skempton et al. (1989).

The stability analysis used by Skempton et al. (1989) at Mam Tor. Case 1: j–e–g; Case 2: j–e–f–k; Case 3: h–d; Case 4: b–c. The uppermost part of the failed mass is shaded.

Method of determining age of Mam Tor landslide by projecting back from current configuration and rate of movement (points B–D as Figure 5.39). T = 0 corresponds to 1950 AD After Skempton et al. (1989).

Inferred evolution of the Mam Tor landslide (ß = slope angle at toe): (a) initial failed mass; (b) arrested slide immediately after initial landslide event; (c) early stage in progressive advance of toe; (d) present profile. After Skempton et al. (1989).

Landslide profiles at Mam Nick, where ß = 10°. After Skempton et al. (1989).

Mam Nick landslide source cavity and upper slump zone, from Rushup Edge looking east. Note the far flank scar interrupting Mam Tor hillfort rampart, and the headscarp narrowing the former plateau ridge to a crest. Edale road passes through Mam Nick and descends across the slump, which has grassy slip-masses presenting uphill-facing scarps. (Photo: D. Jarman.)Figure 5.42 Back Tor landside from the east. The 60 m main crag is a source scar comparable to Mam Tor. The intervening ridge has been lowered by some 50 m by virtue of the slide surface here exposed behind the crest. (Photo: D. Jarman.)

Valley-bulge structures exposed in the Rowlee Bridge section, in the Ashop Valley, Derbyshire. The sharp, symmetrical folds are one of the most remarkable examples of compressional folding ever recorded. The folds are due to the extrusion of clays and ductile flow in bedded strata, often called valley-bulging. (Photo: R.G. Cooper.)

Section through valley-floor crumple (according to Thompson (1949)), at Ladybower Reservoir. After Hill (1949).

Areas of Jurassic strata (shaded) and the locations of the GCR sites described in the present chapter. The Storr and Quiraing lie within the larger Trotternish Escarpment GCR site.

Location of the Postlip Warren GCR site.

View across Cleeve Common showing the deep dissection of the escarpment and the setting of Postlip Warren. (Photo: Gloucestershire Geology Trust.)

Representative slope profiles at Postlip Warren to show distribution of maximum angles. After Goudie and Hart (1976).

Representative profile at Postlip Warren to show broad and flat valley floors.

Location of the Entrance Cutting at Bath University GCR site. (Photo: English Nature/Natural England.)

Geological sections at the Entrance Cutting at Bath University GCR site. After Hawkins (1977).

The section at the Entrance Cutting at Bath University GCR site showing the dip-and-fault structures. (Photo: R. Wright, English Nature/Natural England.)

Geological and geomorphological map of the Trotternish Escarpment GCR site. The extent of landslide terrain is based partly on British Geological Survey mapping. Modified after Ordnance Survey (1964).

Detached lava blocks at Dùn Dubh (NG 441 666). Since deglaciation, these displaced blocks have foundered and moved laterally away from the scarp face, but without the back-tilting of lava flows characteristic of rotational sliding. (Photo: C.K. Ballantyne.)

Pinnancles of shattered basalt at The Storr landslide. The highest pinnacle is the Old Man of Storr. Note the eastwards (forwards) tilt of the slipped mass, away from the escarpment. (Photo: C.K. Ballantyne.)

A previous interpretation of The Storr landslide, redrawn from Anderson and Dunham (1966; The geology of northern Skye, Memoir of the Geological Survey of Great Britain, p. 191, fig. 23), by permission of the Director, British Geological Survey. Their model depicts slide evolution as a sequence of successive deep rotational slides in the sedimentary rocks and palagonite tuffs underlying the basalt scarp, and involves back-titling of lava blocks. Compare with Figures 6.10 and 6.11.

Relict talus accumulations at the southern end of the Trotternish Escarpment. The talus slopes are now vegetated and deeply dissected by active gullies. The main period of talus accumulation occurred prior to 11.5 cal. ka BP. (Photo: C.K. Ballantyne.)

The geological setting of the Hallaig landslide on the coast of the Isle of Raasay.

Slipped masses of the Hallaig landslips and the offshore features. After Russell (1985).

Cross-sections of the Hallaig landslip. After Russell (1985).

Factors of Safety (F) for the Hallaig landslip. After Russell (1985).

The Hallaig landslide – Beinn na’ Leac ridge. (Photo: R.G. Cooper.)

The Axmouth to Lyme Regis Undercliffs region. This photograph shows the famous Bindon Landslide that took place on Christmas Eve 1839. It is probable that this is the first landslide to be fully described in a scientific memoir. (Photo: courtesy of http://www.ukaerialphotography.co.uk.)

Schematic geological section of the coast between Axmouth and Lyme Regis. (1) River Axe; (2) Haven Cliff; (3) Culverhole Cliffs; (4) Bindon Cliffs; (5) Dowlands; (6) Rousdon Cliff; (7) Charton Bay; (8) Humble Point; (9) Pinhay Bay; (10) Ware Cliffs; (11) Lyme Regis. Geological succession: G3 – Upper Chalk; G2 – Middle Chalk; G1 – Cenomanian limestone; E3 – Phosphatic Upper Greensand; E2 – Cherty Upper Greensand; E1– Foxmould; D – Gault; C2 – Shales-with-Beef; C1 – Blue Lias; B2 – Lilstock Formation; B1 – Westbury Formation; A2 – Blue Anchor Formation; A1 – Red and Variegated Marls of the Mercia Mudstones Group. After Pitts (1979).

The landslides of the Axmouth to Lyme Regis Undercliffs National Nature Reserve. After Pitts and Brunsden (1987).

Ground plan and section of the Bindon Landslip (1839). From Conybeare et al. (1840), reproduced with permission of Lyme Regis Museum.

A view of ‘The Chasm’ looking west. From Conybeare et al. (1840), reproduced with permission of Lyme Regis Museum.

A view of ‘The Chasm’ looking west. From Roberts (1840), reproduced with permission of Lyme Regis Museum.

The reef and lagoon at Culverhole Point looking east. An engraving on stone by G. Hawkins Jr, reproduced with permission of Lyme Regis Museum.

Plan of the landslip near Axmouth, Devon. After Anon (1840), from Pitts (1974).

Geomorphological map of the Bindon Landslide. After Pitts and Brunsden (1987).

Geological section of the Bindon Landslide. The Rhaetavicula contorta Shales are the Westbury Formation and the Keuper Marl is the Mercia Mudstones Group in the modern terminology of Warrington (1980). After Pitts and Brunsden (1987). There are no accurate sub-surface data for this slide.

Diagrammatic reconstruction of the development of the Bindon Landslide. ‘F’ refers to the factor of safety against landsliding. An M-type failure is a multi-rotational slide from the classification of Skempton and Hutchinson (1969). After Pitts and Brunsden (1987).

(a) Model for limiting equilibrium analysis of toppling failure on a stepped base. (b) Forces acting on a toe block liable to failure by basal shearing. After Hoek and Bray (1981).

Cross-sections and evolutionary reconstruction of the Chapel Rock landslide and the surveyed movements at the undercliff water pumping-station. Note the loss of the Foxmould by flow or extrusion. After Grainger et al. (1985).

Comparison of rainfall and ground movement of the lower slopes of the landslide between Humble Point and Pinhay. After Grainger et al. (1985).

Hypothetical section through the Bindon Landslide showing a rotational failure mechanism (after Macfadyen, 1970, from Pitts, 1974). The model is not substantiated by sub-surface information. Note that the model does not explain the toe slips, nor why the strata in Goat Island remain horizontal when subject to rotational movement. The graben is diagnostic of a non-circular failure on the bedding.

The Black Ven landslide. (Photo: R. Edmonds, Dorset County Council.)

The mass-movement complex at Black Ven as it appeared in 1974. After Conway (1974).

The Black Ven mudslide complex showing movements between 1958 and 1994. After Chandler and Brunsden (1995).

Geological cross-section of Black Ven showing the lobes of the 1958 mudslide. After Conway (1974).

Section through cliffs to the west of Black Ven showing regional dip and benches under-scoured by landslide debris.

Aerial photograph for the 1946 epoch. (Photo: English Heritage (NMR) RAF Photography.)

Oblique aerial photograph for the 1958 epoch. (Photo: Crown Copyright/MOD. Reproduced with the permission of the Controller of Her Majesty’s Stationery Office.)

Aerial photograph for the 1969 epoch. (Photo: Copyright reserved Cambridge University Collection of Air Photographs.)

Aerial photograph for the 1976 epoch. (Photo: reproduced by permission of Ordnance Survey on behalf of HMSO © Crown Copyright (2006). All rights reserved. Ordnance Survey Licence number 100038718.)

Oblique aerial photograph for the 1988 epoch. (Photo: J. Chandler.)

Contour plot of Black Ven after the 1958 movements produced by interpolation of 11 000 data points established by photogrammetry. After Chandler and Brunsden (1995).

Digital terrain models (DTMs) shown as isometric views for the Black Ven mudslide at five epochs between 1958 and 1995. Note that the 1958–1988 epochs are based on analytical photo-grammetry and an 11 000 point data set. The 1995 model is based on a larger data set aquired by digital photogrammetry. After Chandler and Brunsden (1995).

Contours of surface difference in elevation (i.e. erosion–deposition–no change) for the periods (a) 1958–1946, and (b) 1969–1958. Period (a) shows the location of the 1958 failures. This can be regarded as the formative event. Period (b) shows the diffusion of the wave erosion of the toe and continued input. The ‘no change’ along the main mudslide axis shows input = output and dynamic equilibrium over a decade interval. After Chandler and Brunsden (1995). Contours of surface difference in elevation (i.e. erosion–deposition–no change) for the periods (c) 1976–1969, and (d) 1988–1976. The ‘no change’ along the main mudslide axis shows input = output and dynamic equilibrium over a decade interval. After Chandler and Brunsden (1995). Contours of surface difference in elevation (i.e. erosion–deposition–no change) for the periods (e) 1995–1988, and (f) 1988–1946. The ‘no change’ along the main mudslide axis shows input = output and dynamic equilibrium over a decade interval. After Brunsden and Chandler (1996).

The seasonal behaviour of rainfall movement and porewater pressure at Black Ven. The observation that movement ceased on 5/11/88 suggests that there may have been a considerable strength gain following movement. After Koh (1990).

Cliff recession at Black Ven between 1958–1988. After Chandler and Brunsden (1995).

Linear model of landslide activity at Black Ven. The lowest diagram is a speculative cyclic model. After Chandler and Brunsden (1995).

Slope-angle graphs for (a) the east system and (b) the west system of Black Ven. After Brunsden and Chandler (1996).

Climate and landslide series for the south coast of England. (a) Moisture balance (mm) for Ventnor (Isle of Wight) (1639–1987) plotted as a 9-year moving average. (b) The number of landslide events for the south coast. After Ibsen and Brunsden (1996). (c) The cumulative moisture balance departure from the mean (CDEP), the cumulative number of years with moisture balance greater than the mean (SJAM) and the landslide occurrence at Ventnor (after Ibsen and Brunsden, 1996). (d) The sequence of years of higher rainfall and landslide occurrences for west Dorset (after Brunsden and Chandler, 1996).

A temporal model of episodic landform change at Black Ven. After Brunsden and Chandler (1996).

Geomorphological map of the Black Ven mudslide in 1995. Uncontrolled mosaic based on 1:50 000 scale aerial photographs, NERC 2/95, site no. 94/26, Charmouth, not to scale. After Brunsden and Chandler (1996).

The Peak Scar mass-movement complex. After Cooper (1980).

The distribution of widened joints (‘windypits’) and ridge-and-trough features on the Hambleton Hills between Hawnby and Ampleforth, including the locations of Peak Scar and Buckland’s Windypit (described later in the present chapter). After Cooper (1980).

Peak Scar, showing a tower of rock just beginning to detach from the rockface owing to unloading and opening of the joints. (Photo: R.G. Cooper.)

Terms and definitions used in modelling a hypothetical topple: (A: point of convergence based on extrapolation from joint surveys on the topple and the cliffs; C: cliff crest; T: crest of the topple; DB: elevation at the base of the dolerite sheet; LC: distance a–c; LT: distance a–t; Ic: joint inclination on the cliff; It: joint inclination on the topple; ": tilt angle of the topple (Ic–It); dH: vertical lowering of the topple crest; dX: lateral displacement of the topple crest; f: angle from c–t). After Caine (1982).

Blacknor Cliffs, Isle of Portland. (Photo: R. Edmonds, Dorset County Council.)

Location of the Blacknor Cliffs GCR site.

View of Blacknor Cliffs from the sea showing the build-up of limestone blocks at the base of the debris slopes. (Photo: R. Edmonds, Dorset County Council.)

Detailed surveys of Buckland’s Windypit showing how the lateral spreading of the hillside opens up joint or fissure caves to form a typical labyrinth network. In this case the fissures are beneath the surface suggesting loss of support from below owing to ductile behaviour of the Oxford Clay.

Buckland’s Windypit showing part of Oxtail Chamber with animal bones. (Photo: © M. Roe.)