The shapes of some mountain peaks in the Canadian Rockies

Tags: Cruden, Hu, Geological Survey of Canada, Ottawa, bedding, the Canadian Rockies, Canadian Geotechnical Journal, friction angle, Alberta, British Columbia, Canada, Rocky Mountains, rock masses, slope angles, Banff, Alberta, rock structure, sedimentary sequences, sedimentary rocks, 60 degrees, dihedral angles, escarpments, shapes, Canadian Rockies, vertical distances, Canadian Rockies Cruden, Baird, dip joints, Rocky Mountain, mountain peaks, Selby, Dogtooth mountains, mountain peak, bedding planes, Canadian Rocky Mountains, slope processes, mountain slopes, dip, Structural control, bedding plane, mountain slope, Canadian Geotechnical Conference, Alberta Rocky Mountains, dihedral angle, discontinuities, rock slopes, steep mountain slopes, Canadian Government Publishing Centre, sliding, unstable slopes, rock surfaces
Content: 1 The Shapes of Some Mountain Peaks in the Canadian Rockies Cruden, D.M. Department of Civil and Environmental Engineering University of Alberta Edmonton, Alberta, Canada T6G 2G7 Phone: 780-492-5923 Fax: 780-492-8198 E-mail: [email protected] Hu, Xian-Qin Department of Earth and Atmospheric Sciences University of Alberta Edmonton, Alberta, Canada T6G 2E3 February, 1999
2 Abstract Different mountain shapes in sedimentary sequences in the Canadian Rockies were enhanced by glacial erosion and have been modified post-glacially by gravity-driven slope processes. Slope modification by both glacial erosion and post-glaciation landslides is related to rock structure, particularly bedding dip, rock mass strength and slope geometry. Five mountain peak shapes in monoclinal sequences each fall into different ranges of bedding dips. (1) Castellate and (2) matterhorn mountains occur in sub-horizontal beds and their slopes on all sides follow combinations of bedding planes and joints. The overall slopes are generally 35 to 65 degrees and oblique to both bedding and joints. Slopes in subhorizontal beds may be controlled by their rock mass strength. (3) Cuestas develop in gently to moderately dipping beds. Dip slopes and steeper, normal escarpments form their cataclinal and anaclinal sides respectively, with the dihedral angle between them about 90 degrees. (4) Hogbacks in moderately to steeply-dipping beds have similar slope angles on both cataclinal and anaclinal slopes. Cataclinal slopes are either dip slopes or underdip slopes but anaclinal slopes are often steepened escarpments, the dihedral angle between the slopes is usually less than 90 degrees. (5) Dogtooth mountains occur in steeply dipping to sub-vertical beds and the dihedral angle can be as low as 60 degrees. Slope gradients in inclined beds are closely related to landslides, whose modes are controlled by bedding dips. Keywords: Mountain, Canadian Rockies, Castellate, Cuesta, Dogtooth, Hogback, Landslide, Matterhorn
3 Introduction Geomorphic classifications of mountain types "generally...employ a nomenclature which recognizes the dynamic process that conditions the gross geometry of the relief, rather than using the geometry itself" (Fairbridge, 1970, p. 751). In such "a simple genetic system of mountain types", the Canadian Rockies would be described as "Fold and Nappe Mountains: of linear, often with more or less bilateral, symmetry" (Fairbridge, 1970, p. 752). They are "fold mountains, typical of younger orogenic belts", p. 753. We are going to discuss some of their shapes. The relationship between the shape of mountains in the Canadian Rockies and their rock structure was first noted in Hector's reconnaissance (Palliser, 1863). Baird (1962, 1963, 1968) described nine different mountain shapes: castellate mountains, matterhorn mountains, mountains in dipping sediments, dogtooth mountains, sawtooth mountains, synclinal mountains, anticlinal mountains, mountains of complex structures, and irregular mountains (Baird, 1963, p. 43). Bird (1980, p. 222), Gerrard (1990, p. 20) and Pole (1992, p. 16) all reproduced Baird's (1963) shapes of the Canadian Rockies in their books. In this paper, we first describe the physical environment of the Rocky Mountain peaks. We then classify the slopes developed in these sedimentary rocks by the angle between the slope and the dip of bedding. This allows us to suggest typical landslide modes on these slopes. We then compare these predictions with the shapes of the small sample of peaks described by Baird and with a larger sample selected from the extensive descriptive literature on the Rockies. Baird's (1962, 1963, 1968) catalogue of mountain shapes made no explicit reference to earlier descriptions of mountain shape from Europe. However, his reliance on rock structure in the catalogue echoes structural geomorphologists (Tricart, 1974) and there is abundant evidence (Cruden and Hu, 1996, Sauchyn et al.,1998, Selby, 1993, Chapter 15) that rock structure strongly
4 influences slope movement processes. The control that rock structure exerts over modes of landsliding is our explanation for the relationship between mountain shape and rock structure in four of Baird's shapes, castellate, matterhorn, dogtooth and mountains of dipping sedimentary rocks. Understanding the relationship between mountain shape, rock structure and landslides is of practical significance in avoiding potentially hazardous slope movements, siting structures and occupying and using space in mountain areas safely. The study of the development of different mountain shapes and the geological controls upon them also has important implications for mountain and relief development, slope morphology and rock mass transfer in the Canadian Rockies. Physical Environment The Canadian Rocky Mountains, 100 km wide, extend 1400 km northwestwards from the U.S.-Canada border 49°N, at 114°W (Mathews, 1986). They are formed by Proterozoic clastics and carbonates, Paleozoic carbonates and clastics, and Mesozoic clastics (Gabrielse and Yorath, 1992). Late Mesozoic and early Cenozoic thrust faults and folds strike NW-SE in the region. The dominant penetrative discontinuities are bedding planes. "Discontinuities are here termed penetrative because they are repeated at distances so small compared with the scale of the whole....that they can be considered to pervade it uniformly and be present at every point" (Turner and Weiss, 1963, p. 21). There are two common joint sets, both perpendicular to bedding; strike joints parallel to the strike of bedding, dip joints are perpendicular to it. Conjugate joint sets which are perpendicular to bedding also develop at some locations but are less common than strike joints and dip joints (Muecke and Charlesworth, 1964; Hu and Cruden,
5 1992a). The strike joints and the conjugate joint sets are kathetal joints, joints "normal to a bedding surface where the orientation of the joint is a function of the orientation of the bedding" (Hancock, 1964, p. 175). The Canadian Rockies show "fabric-relief", in which elements of the topographic relief are correlated with the rock fabric (Sander, 1970, pp. 210-212). Most major valleys and mountain ranges follow the strike of the regional geological structures, which are clearly shown in LANDSAT images (Taylor, 1981). The Canadian Rocky Mountains have experienced several glacial advances over the last two million years; the last glaciation retreated from most of the Rockies as the Holocene began (Clague, 1989) and has left many steep slopes and mountain peaks. Glacially trimmed valleys throughout the Canadian Rockies have slopes up to 70 degrees towards the mountain peaks. Based on the studies of the cross-profile morphology of glaciated valleys by Hirano and Antya, (1988), particularly their model for the Canadian Rockies, it is reasonable to assume that the crests of valley slopes along most glacially-eroded valleys can be steeper than 60 degrees where the rock masses involved are strong enough to maintain such steep slopes. All the mountain peaks and bedrock slopes discussed in this paper are above the tree line with the base of the bedrock slopes all above 2000 metres. Harris (1986) has demonstrated that the lower limit of continuous permafrost is at or above 2400 m (8000 ft) in the Canadian Rockies south of 55°N latitude, i.e. at or above treeline, placing the mountain peaks in the Alpine ecoregion (or zone) (Strong and Leggat, 1992) and the periglacial and glacial morphoclimatic zones of Budel (1982). Slope classification based on rock structure
6 Slope stability and slope movements in stratified rocks are mainly determined by the orientations of discontinuities within these rock masses and the mechanical properties, particularly frictional properties, of the discontinuities (Selby, 1993, Chapter 15). Slopes in the sedimentary sequences in the Canadian Rockies have been classified into cataclinal slopes and anaclinal slopes where bedding strikes are subparallel to the strikes of the slopes (Cruden and Eaton, 1987, Figure 6), using the terms originally introduced by Powell (1875). In cataclinal slopes, the penetrative discontinuity dips in the same direction as the slope. In anaclinal slopes, the penetrative discontinuity dips in the direction opposite to the slope. Conventionally, these descriptive terms can be limited to slopes whose azimuths are within 20 degrees of that of the penetrative discontinuity. Cataclinal slopes may be further divided into overdip slopes which are steeper than the dip of the discontinuity, underdip slopes which are less steep than the dip of the discontinuity and dip slopes which follow the discontinuity (Figure 1). Anaclinal slopes which are perpendicular to the dip of the discontinuity are called normal escarpments, slopes steeper than normal are steepened escarpments and slopes less steep than normal are subdued escarpments (Figure 1). Studies in Kananaskis Country in the southern Rockies, (Cruden and Eaton, 1987, Figure 8) found that cataclinal and anaclinal slopes cover 58% of the total slope surface although their slope directions are limited to 80° out of 360°. This evidence of "fabric-relief" suggests rock fabric controls on slope development. The landslide modes on cataclinal slopes and on anaclinal slopes are shown on a process diagram (Figure 2). Rapid movements and slow movements (Figure 2) are differentiated to indicate the velocities of the slope processes that modify the mountains. This information is necessary for estimates of how far the displaced material in the landslides will travel.
7 Cruden and Hu (1996) showed that the modes of the processes depend on the relationships among the orientations of discontinuities, slopes and friction angles of discontinuities. We use the basic friction angles of the discontinuities as estimates of the friction angles. Basic friction angles are measured on planar, sanded rock surfaces (Selby, 1993, Table 6:2). The friction angles on these surfaces with no significant roughness are the lower bounds of rapid, unassisted rocksliding in the Canadian Rockies (Cruden, 1985). The basic friction angles of carbonates and clastics range between 21° and 41° (Cruden and Hu, 1988, Hu and Cruden, 1992b), so 30° is a first approximation and is used as the estimate of basic friction angle in Figure 2. Cohesion along bedding in the slopes in the sedimentary sequences in the Canadian Rockies can be ignored in most cases (Cruden and Hu, 1993). Whether, after glacial retreat, rock masses on steep mountain slopes have moved depends on the stability of these slopes in different modes of movement. The volumes of subsequent landslides can be evaluated from the displaced material of rock slides or rock falls. Most large landslides have occurred on cataclinal overdip and dip slopes; the prehistoric ones documented by Cruden (1976) and Evans et al. (1997), the 1903 Frank slide (Cruden and Krahn, 1973) and the Brazeau Lake slide of 1933 (Cruden, 1982) are examples. Fragmental rock falls from cliffs have produced talus cones and aprons which are much smaller than rock slide deposits in volume. Other processes including fluvial erosion and dissolution of carbonates are all less significant than landslides in modifying rock slopes (Luckman, 1981; Luckman and Fiske, 1997). So rock slopes in the Canadian Rockies have generally remained almost unchanged in the Holocene except where landslides have occurred.
8 Characteristics of different mountain shapes Tables 1 and 2 list 34 mountains in monoclinal sequences, including their bedding dips and slope gradients. The tables detail 9 mountains that Baird (1962, 1963, 1968) used as examples and list 25 further mountains that have been much photographed; we have obtained structural data from published geological maps, or estimated them from photographs if no geology maps are available. The slopes are obtained from 1:50,000 topographic maps; horizontal distances are directly measured and vertical distances read from the contour lines. The vertical differences are always the first 150 metres to 200 metres down from the peaks. The dihedral angle between the anaclinal and cataclinal slopes on a mountain is estimated by the supplement of the sum of the slope angles. The locations of the mountains are listed in gazetteers (Energy, Mines and Resources, 1974, 1985) and in the references given in the Tables. Baird's (1963) mountain shape classification puts these mountains into the following groups. Castellate Mountains "Mountains that are cut into more or less flat-lying sedimentary rocks have profiles in which vertical steps alternate with flat or sloping terraces. Some such mountains look very much like ancient castles and are thus said to be 'castellate' or 'castle' mountains" (Baird (1963, pp. 43-44). The mountains occur in sub-horizontal beds. An upper bound of bedding dips at 15 degrees, or about half of the basic friction angle, is the lower limit for sliding of blocks along bedding with water pressures at the ground surface (Selby, 1993, p. 362). The movement mode of the rock masses, toppling from kathetal joints (Figure 3), may need some assistance on anaclinal slopes. Masses toppling and sliding are generally limited in our field observations to
9 individual blocks separated by bedding and joints. Blocks can move only short distances before pore pressures drain. So slope processes are relatively ineffective and postglacial modifications of mountain slopes are not significant. Rock faces or rock walls follow combinations of bedding and joint surfaces, creating overall slopes which are less steep than the nearly vertical joints. If a set of closely-spaced joints extends a considerable distance, a rock face several kilometres long can develop along the joint set as at Castle Mountain (Figure 4). Because the overall slopes are oblique to both joints and bedding (Table 2), slope angles may be predicted by rock mass strength ratings (Selby, 1993, Figure 6.13) as structural control is not an overriding factor. Slope angles range from 42 to 64 degrees and dihedral angles from 56 to 89 degrees. Such a wide range of slopes suggests that the considerable range in rock mass strength in these sedimentary sequences may be a determining factor in the slope angles observed (Selby, 1993, Chp. 16). Matterhorn Mountains Matterhorns are "sharp, semi-pyramidal towers" (Baird, 1963, p. 48). The slope processes that create matterhorn mountains are the same as those that form castellate mountains (Figure 2). Erosion develops on all slopes of the matterhorn without a preferred orientation; a distinctive example is Mount Assiniboine (Figure 4), which ascends 750 metres at 50 degrees from its shoulders to the peak. We attribute the symmetry of the Matterhorn (Collet, 1927, Plate 8) and Mt. Assinboine to the horizontal penetrative discontinuities, foliation and bedding respectively, that pervade these mountains.The slopes of matterhorns are generally oblique to joints, possibly varying with rock mass strength rating (Selby, 1993, Figure 6.13). Like
10 castellate mountains, matterhorns have experienced little modification after the retreat of the last glaciation because large landslides are not kinematically possible. Again like castellate mountains, the ranges of slope and dihedral angles are large, 37 to 65 degrees and 57 to 89 degrees (Tables 1, 2; Figure 9). Mountains in dipping sedimentary rocks: Cuestas and Hogbacks "Mountains cut in dipping layered sedimentary rocks which dip from nearly horizontal to 60 degrees....have one smooth slope which follows the dip of a particular rock layer from its peak almost to its base, and on the other side, a less-regular slope which breaks across the upturned edges of the layered rock units" Baird (1963, pp. 44-45). The cataclinal slope of a dipping mountain may follow an individual rock layer from the base to the peak of the mountain (Figure 5). Sliding along bedding can occur either by gravity only or assisted by cleft water pressure, pressure from rocks fallen into joints behind the moving block or ice pressure when bedding dip is less than the friction angle along bedding (Simmons and Cruden, 1980). On the anaclinal slope, sliding along kathetal joints can occur if the slope is steeper than kathetal joints (Hu and Cruden, 1992a). This process produces normal escarpments on anaclinal slopes. Sliding on anaclinal slopes is generally limited to individual joint-bounded blocks because of the non-penetrative nature of joints, displaced volumes are usually small in single events (Hu and Cruden, 1992a). If the anaclinal slope is less steep than bedding dip, small topples prevail and the slope profile experiences little change. When a single peak forms, one slope follows bedding from the top to the base (Baird, 1963, p. 44) and the other slopes follow combinations of joints and bedding to form steep scarp
11 slopes. When a long range forms, one side is a dip slope and the other side is usually a normal escarpment. We can divide these mountains into cuestas whose bedding is less steep than the friction angle and hogbacks which have bedding steeper than the friction angle. The cataclinal slopes on hogbacks are either dip slopes or underdip slopes and the anaclinal slopes are steepened escarpments (Figure 6). The post-glaciation processes on cataclinal slopes include sliding along bedding (Figure 2) to create locally steep dip slopes. Rupture surfaces form along bedding and their toes follow joints or faults (Evans et al., 1997). Toppling is a slow process and slopes steepened by glaciation remain little changed (Cruden, Hu, 1994). Both processes maintain steep cataclinal slopes in the main scarps of the movements. On the anaclinal slopes of hogbacks, there are also two processes: toppling from bedding and sliding along joints. Toppling from bedding can create rapid topple-slides (Figures 2, 6) that reduce slope gradients. Field examples show that these slopes, after toppling and sliding, are still steeper than 45 degrees; a typical example is Elk Ridge, Alberta (Hu and Cruden, 1992a, Figure 6). Sliding along kathetal joints creates small rock slides (Hu and Cruden, 1992a) when dips of kathetal joints are steeper than 40 degrees, close to the upper bound of the basic friction angles of carbonates and clastics, because joints are not penetrative and joint surfaces can be rough. So both processes can maintain anaclinal slopes at over 45 degrees. "Dogtooth Mountains Sharp jagged mountains sometimes result from the erosion of masses of vertical or nearly vertical beds of rock. The peaks may be centered on a particularly resistant bed, in which case a tall spine or rock wall may result," Baird (1963, p. 45). A typical example is Mt. Louis in Banff National Park (Figure 7).
12 Sliding along bedding rarely develops on subvertical cataclinal slopes. Bedding is steep and cohesion is insufficient for rock masses to remain above a bedding plane after the toe support from glacier ice is removed. Erosion of subvertical beds generally produces underdip cataclinal slopes and steepened escarpments. Rock blocks on underdip cataclinal slopes can topple from bedding, a slow process (Figure 2), with assistance from frost heave (McAffee, Cruden, 1996) or pressure from rock debris falling behind the toppled block (Cruden, Hu and Lu, 1993). Buckling is also possible (Hu and Cruden, 1993) where slopes are only a few degrees less than bedding dips. Although complex or composite topple-slides are kinematically possible on anaclinal slopes as indicated in Figure 2, none have been reported. Discussion Structural controls on mountain slope angles can be observed from the relationship of the dihedral angle between the cataclinal and anaclinal slopes and bedding dip (Figure 8). The data are from the mountains listed in Tables 1, 2. When bedding dips are greater than 15 degrees, Figure 8 shows that the dihedral angle decreases as bedding dip increases. The trend can be explained by Figure 2 which indicates that dip slopes and normal escarpments are characteristic landforms, the results of sliding along bedding and kathetal joints where kinematically possible. When beds are gently to moderately dipping, between 15 degrees and 60 degrees in Figure 8, the glacially-steepened slopes may slide along bedding surfaces and kathetal to form dip slopes and normal escarpments. If bedding dips are steeper than 60 degrees, glacially-steepened dip slopes, underdip slopes and steepened escarpments have been limited to slopes about 60 degrees. Buckles (Hu and Cruden, 1993) and topples (Cruden and Hu, 1994) limit cataclinal slopes. Topple-slides have occurred on anaclinal slopes such as the Elk Ridge
13 landslide (Hu and Cruden, 1992a, Figure 6). Consequently, the dihedral angles of mountain peaks in steeply dipping beds can be as low as 60° less than those in moderately dipping beds. So, dogtooth mountains are more slender than cuestas. Structural control by bedding on slopes can also be shown on an overlay (Figure 9) which places all the mountain slopes on the process diagram (Figure 2). When bedding is less than 15 degrees, the dihedral angle (Figure 8) ranges from 55 degrees to 90 degrees, or the slope angle on each side varies from 45 degrees to 62 degrees if the two sides have similar gradients. The slope gradients are not controlled by discontinuity dips. These slopes may be strength-equilibrium slopes (Selby, 1993, Figure 6.13). Overdip slopes occur only where bedding dips are less than 15° in our sample, then the rock masses above bedding surfaces may not slide and evolve into dip slopes. When bedding is between 30° and 60°, the characteristic cataclinal slopes are dip slopes which formed as the result of rock sliding from overdip slopes. When bedding is steeper than 60°, underdip slopes develop. On anaclinal slopes, normal escarpments, the complements of dip slopes, are not as common as dip slopes due to the non-penetrative nature of kathetal joints. Comparing the examples of the cataclinal slopes and anaclinal slopes in Figure 9, it is clear that the structural control is more pronounced on cataclinal slopes than on anaclinal slopes. When bedding dip is over 30°, above the basic friction angles of rocks in the Canadian Rockies (Cruden and Hu, 1988, Hu and Cruden, 19992b), most of the glacially steepened overdip slopes have become dip slopes by sliding (Cruden and Hu, 1993). A consistent model suggests the frequency of rock sliding on overdip slopes was once considerably greater than at present and has decreased over time since the retreat of the last glaciation (Cruden and Hu, 1993). The dip
14 slopes which have resulted from sliding represent stable and characteristic slope forms on cataclinal slopes. There are many steepened escarpments in Figure 9 where sliding and toppling are indicated as rapid slope processes. Although some large landslides are recorded (Cruden and Hu, 1992a), landslides on the steepened escarpments have not been as frequent as on cataclinal slopes. The magnitudes of slope processes and mountain slope development have directional preference depending on bedding dips. When bedding is gently to steeply dipping, sliding along bedding and strike joints and toppling from bedding surfaces, all parallel to or opposite to the dip direction of bedding, are the dominant processes. So, mountain ranges generally develop to follow NW-SE trending strikes and cataclinal and anaclinal slopes cover more ground surface than other slopes (Cruden and Eaton, 1987). When bedding is sub-horizontal, slope processes such as toppling from strike and dip joints have no directional preference and isolated peaks or castellate mountains form. Conclusions Mountain shapes in monoclinal sedimentary sequences in the Canadian Rockies are determined by rock structures and slope movement processes on the glacially-steepened slopes. When bedding is steeply dipping to subvertical, the dihedral angles between cataclinal and anaclinal slopes can be as low as 60 degrees on dogtooth mountains. When bedding is gently to moderately dipping, sliding on bedding and on kathetal joints creates hogbacks and cuestas whose dihedral angles are about 90 degrees. When bedding is subhorizontal to gently dipping, the typical mountains are castellate or matterhorns. Half the basic friction angle is the lower
15 limit of the dip of bedding which exerts structural control on slopes. At lower dips, slopes may be in strength equilibrium. Examples show that the critical angles (Figure 2) for landslides on different types of slope are useful in identifying potentially unstable slopes. Acknowledgement Our work in the Canadian Rockies has been supported by Alberta Environment, Alberta Transportation, Geological Survey of Canada and the Natural Sciences and Engineering Research Council. We are grateful to our colleagues at the University of Alberta and the Geological Survey of Canada for valuable discussions. References Baird, D.M., 1962. Yoho National Park, the mountains, the rocks, the scenery. Geological Survey of Canada, Miscellaneous Report, 4, 107 p. Baird, D.M., 1963. Jasper National Park, Behind the Mountains and Glaciers. Geological Survey of Canada, Miscellaneous Report 6, 184 p. Baird, D.M., 1968. Banff National Park, How Nature Carved its Splendour. Geological Survey of Canada, Miscellaneous Report 13, 307 p. Bird, J.B., 1980. The natural landscapes of Canada. Wiley, 260 p. Boles G.W., Kruszyna, R., Putnam, W.L., 1979. The Rocky Mountains of Canada - South. The Alpine Club of Canada, Banff, 473 p. Budel, J., 1982. Climatic geomorphology. Princeton University Press, Princeton, New Jersey, 443 p.
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19 McMechan, M.E., 1993. Geology, Rocky Mountain Foothills and Front Ranges in Kananaskis Country, Alberta. Map 1865A. Geological Survey of Canada, Ottawa. McMechan, M.E. and Thompson, R.I., 1995. Geology and structure cross-sections, Jarvis Lakes, British Columbia, Geological Survey of Canada, Map 1874A. Mountjoy, E.W. and Price, R.A., 1972a. Geology, Banff ­ East Half, Alberta-British Columbia, Map 1294A. Geological Survey of Canada, Ottawa. Mountjoy, E.W. and Price, R.A., 1972b. Geology, Mount Eisenhower ­ West Half, Alberta, Map 1297A. Geological Survey of Canada, Ottawa. Mountjoy, E.W. and Price, R.A., 1988. Geology, Amethyst Lakes, Alberta-British Columbia, Map 1657A. Geological Survey of Canada, Ottawa. Muecke, G.K. and Charlesworth, H.A.K., 1966. Jointing in folded Cardium sandstones along the Bow River, Alberta, Canadian Journal of Earth Sciences, 3:579-596. Palliser, J., 1863. The Journals, Detailed Reports and Observations relative to the exploration by Captain Palliser of that portion of British North America which in Latitude lies between the Boundary Line and the Height of Land or Watershed of the Northern or Frozen Ocean respectively, and in Longitude, between the Western Shore of Lake Superior and the Pacific Ocean during the years 1857, 1858, 1859 and 1860. Her Majesty's Stationery Office, London, 325 p. Pole, G., 1992. Canadian Rockies. Altitude Publishing, Banff, Alberta, Canada, 349 p. Powell, J.W., 1875. Exploration of the Colorado River of the West and its tributaries, Government Printing Office, Washington, U.S.A., 291 p. Price, R.A., 1970. Geology, Canmore ­ West Half, Alberta, Map 1266A. Geological Survey of Canada, Ottawa.
20 Price, R.A., Cook, D.G., Aitken, J.D. and Mountjoy, E.W., 1980a. Geology, Lake Louise, East Half, Alberta and British Columbia, Map 1483A. Geological Survey of Canada. Price, R.A., Cook, D.G., Aitken, J.D. and Mountjoy, E.W., 1980b. Geology, Lake Louise, West Half, British Columbia and Alberta, Map 1483A. Geological Survey of Canada, Ottawa. Price, R.A., Mountjoy, E.W., 1972. Geology, Banff ­ West Half, Alberta ­ British Columbia, Map 1295A. Geological Survey of Canada, Ottawa. Price, R.A., Mountjoy, E.W. and Cook, D.G., 1978. Geology, Mount Goodsir, East Half. British Columbia and Alberta, Map 1476A. Geological Survey of Canada, Ottawa. Putnam W.L., and Boles, G.W., 1973. Climber's Guide to the Rocky Mountains of Canada South. Alpine Club of Canada, Banff, Alberta, 330 p. Sander, B., 1970. An Introduction to the Study of the Fabric of Geological Bodies. Pergammon, Oxford, England, 641 p. Sauchyn, D., Cruden, D.M. and Hu, X.Q., 1998. Structural control of rockwall morphometry, Kananaskis region, Canadian Rocky Mountains, Geomorphology, 22, 313-324. Selby, M.J., 1993. Hillslope materials and processes. Oxford University Press, Oxford, U.K., 451 p. Simmons, J.V. and Cruden, D.M., 1980. A rock labyrinth in the Front Ranges of the Rockies, Alberta, Canadian Journal of Earth Sciences, 17:1300-1309. Strong, W.L. and Leggat, K.R., 1992. Ecoregions of Alberta, Alberta Forestry Lands and Wildlife, Edmonton, Publication T245, 59 p. Taylor, C.G., 1981. Fort St. John. In Slaney, V.R.(Editor), LANDSAT Images of Canada, A Geological Appraisal. Geological Survey of Canada, Ottawa, Canada, Paper 80-15, p. 88. Tricart, J., 1974. Structural Geomorphology, Longman, London, UK., 305 p.
21 Turner, F.J., Weiss, L.E., 1963. Structural Analysis of metamorphic tectonites. McGraw-Hill, New York, 545 p.
22 Table 1. Examples of mountain peak shapes
Mountains Castle Mountain Mt. Babel Mt. Edith Cavell Mt. Geikie Mt. Quadra Mt. Stephen Mt. Temple Pilot Mountain Stanley Peak Mt. Assiniboine Mt. Bowlen Mt. Ida Mt. King George Mt. Little Mt. Sir Douglas Mt. Tuzo Neptuak Mtn. Mt. Bogart Mt. Sparrowhawk Sunwapta Peak Mt. Birdwood Mt. Engadine Mt. Foch The Fortress Mt. Indefatigable Mt. Rundle Mt. Shark Mt. Sarrail NW Elk Range Elpoca Mtn. Mt. Blane Mt. Brock Mt. Edith Mt. Louis
Shape Castellate Castellate Castellate Castellate Castellate Castellate Castellate Castellate Castellate
Geological Map Mountjoy and Price, 1972b Price et al., 1980a Mountjoy and Price, 1988 Mountjoy and Price, 1988 Price et al., 1980a Price et al., 1980b Price et al., 1980a Price and Mountjoy, 1972 Price et al., 1978
Matterhorn Matterhorn Matterhorn Matterhorn Matterhorn Matterhorn Matterhorn Matterhorn
Leech, 1979 Price et al., 1980a McMechan, Thompson, 1995 Leech, 1979 Price et al., 1980a Leech, 1979 Price et al., 1980a Price et al., 1980b
Cuesta Cuesta Cuesta
McMechan, 1993 McMechan, 1993
Hogback Hogback Hogback Hogback Hogback Hogback Hogback Hogback Hogback
Leech, 1979 McMechan, 1993 McMechan, 1993 McMechan, 1993 McMechan, 1993 Price, 1970 Leech, 1979 McMechan, 1993 McMechan, 1993
Dogtooth Dogtooth Dogtooth Dogtooth Dogtooth
McMechan, 1993 McMechan, 1993 McMechan, 1993 Mountjoy and Price, 1972a Mountjoy and Price, 1972a
Illustrated in 3) p.9 9) p.157 2) p.108 2) p.146, 8) p.253 9) p.157 1) p.37 9) p.181, 4) p.275 9) p.143, 4) p.221 3) p.19 9) p.157 8) p.310 9) p.59 9) p.157 9) p.66, 4) p.73 9) p.170 9) p.174 9) p.79, 7) p.61 7) p.88 2) p.94 9) p.79 9) p.79 9) p.46 9) p.79 5) 3) p.11 7) p.89 9) p.46 6) 4) p.148 9) p.88 4) p.148 4) p.144 3) p.12
Illustrations are in: 1) Baird, D.M., 1962; 2) Baird, D.M., 1963; 3) Baird, D.M., 1968; 4) Boles, G.W., et al., 1979; 5) Cruden, D.M. and Eaton,T.M., 1987; 6) Hu, X-Q. and CrudenD.M., 1992a; 7) Kane, A., 1992; 8) Kruszyna, R., and Putnam, W.L., 1985; 9) Putnam, W.L., and Boles, G.W., 1973.
23
Table 2. Examples of mountain slopes
Mountains Castle Mountain Mt. Babel Mt. Edith Cavell Mt. Geikie Mt. Quadra Mt. Stephen Mt. Temple Pilot Mountain Stanley Peak Mt. Assiniboine Mt. Bowlen Mt. Ida Mt. King George Mt. Little Mt. Sir Douglas Mt. Tuzo Neptuak Mtn. Mt. Bogart Mt. Sparrowhawk Sunwapta Peak Mt. Birdwood Mt. Engadine Mt. Foch The Fortress Mt. Indefatigable Mt. Rundle Mt. Shark Mt. Sarrail NW Elk Range Elpoca Mtn. Mt. Blane Mt. Brock Mt. Edith Mt. Louis
Bedding Dip 0-5 0-10 5-10 0-5 0-10 0-5 0-10 5 0-10 0-5 0-10 0-10 0-10 0-10 0-10 0-10 0-10 15-25 25-30 29 50-60 30-35 30-40 35-40 45-50 30-35 55-65 30-35 65-70 80-90 80-90 80-90 65-70 65-70
Cataclinal Slopes 50 60 53 64 53 46 55 64 42
Anaclinal Slopes 45-55 64 52 45-60 50 45 45 60 58
Dihedral Angle 75 to 85 56 75 56-71 77 89 80 56 80
50
57
73
37
64
79
57
60
63
56
56
68
41
50
89
56
51
63
55
65
60
58
65
57
37
50
93
30
60
90
29
63
88
56
58
66
35
66
79
42
50
92
40
64
76
50
51
79
30
55
85
50
60
70
35
60
85
38
60
82
58
60
62
50
56
74
60
58
62
58
59
63
63
57
60
Height m.a.s.l. 2766 3101 3363 3270 3173 3199 3543 2935 3115 3618 3072 3180 3422 3140 3406 3245 3237 3144 3121 3315 3097 2970 3180 3002 2670 2949 2786 3174 2744 3029 2993 2902 2554 2682
24 Figure 1. Classification of anaclinal and cataclinal slopes. Thin lines represent bedding, the thick lines indicate slopes. The symbols ud, ds, od, se, ne and su are from Cruden and Hu (1996). The 6 slopes diagrammed are plotted on Figure 2.
Figure 2. Process on anaclinal and cataclinal slopes. The bedding dip is and the slope angle . su, ne, se, ud, ds and od are defined in Figure 2; the 6 slopes in Figure 1 are plotted as triangles on Figure 2. Additional symbols, -R, -F, denote rapid and slow movements; superscripts T, S and B indicate toppling, sliding and buckling. Symbols follow Howes and Kenk (1988).
Figure 3. Castle Mountain (from the Collection of the Whyte Museum of the Canadian Rockies, V263/71-4618).
Figure 4.
Mt. Assiniboine (from the Collection of the Whyte Museum of the Canadian Rockies, NA66-573).
Figure 5. Mt. Rundle
Figure 6. Elk Ridge
Figure 7.
Mt. Louis (from the Collection of the Whyte Museum of the Canadian Rockies (V263/71-4477).
Figure 8. Bedding dip and dihedral angle for the peaks in Tables 1-2. Points plotted may be midranges. Coincident points are not distinguished.
Figure 9. Mountain slopes on the process diagram.
25 Figure 1. Classification of anaclinal and cataclinal slopes. Thin lines represent bedding, the thick lines indicate slopes. The symbols ud, ds, od, se, ne and su are from Cruden and Hu (1996). The 6 slopes diagrammed are plotted on Figure 2.
26 Figure 2. Process on anaclinal and cataclinal slopes. The bedding dip is and the slope angle . su, ne, se, ud, ds and od are defined in Figure 1; the 6 slopes in Figure 1 are plotted as triangles on Figure 2. Additional symbols, -R, -F, denote rapid and slow movements; superscripts T, S and B indicate toppling, sliding and buckling. Symbols follow Howes and Kenk (1988).
27 Figure 3. Castle Mountain (from the Collection of the Whyte Museum of the Canadian Rockies, V263/71-4618).
28
Figure 4.
Mt. Assiniboine (from the Collection of the Whyte Museum of the Canadian Rockies, NA66-573).
29 Figure 5. Mt. Rundle
30 Figure 6. Elk Ridge
31
Figure 7.
Mt. Louis (from the Collection of the Whyte Museum of the Canadian Rockies (V263/71-4477).
32 Figure 8. Bedding dip and dihedral angle for the peaks in Tables 1-2. Points plotted may be midranges. Coincident points are not distinguished.
33 Figure 9. Mountain slopes on the process diagram.

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