Some forms of mountain peaks in the Canadian Rockies controlled by their rock structure

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 slope geometry and rock structure, particularly bedding dip. 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 are generally 35–65° and oblique to both bedding and joints. (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°. (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 <90°. (5) Dogtooth mountains occur in steeply dipping to sub-vertical beds and the dihedral angle can be as low as 60°. Slope gradients on a sample of 34 peaks are closely related to landslides, particularly rock slides and rock topples. These landslide modes are controlled by bedding dips.