ROCK-SLOPE DEFORMATION AT AFFLICTION CREEK, SOUTHERN COAST MOUNTAINS, BRITISH-COLUMBIA

A 7 year record of rock-slope deformation is reported from Affliction Creek, in the southern Coast Mountains of British Columbia. An estimated 3 × 107 m3 of monzonite basement and overlying Garibaldi-aged volcanic material is involved in a slow gravitational movement. Ground-motion vectors suggest that movement has occurred along a deep-seated shear zone and was accompanied by a downslope extension of the moving mass. Near-surface flexural toppling, producing antislope scarps, has taken place where tension cracks crop out on steep slopes or wherever rock faces with strong planar jointing are glacially undercut. Structural data indicate the feasibility of both sliding and toppling at this site. The stratigraphic evidence indicates that most of the tension cracks, grabens, and antislope scarps constituting the slope-movement complex are less than 4300 years old and that many of these landforms may have developed quite recently, as a result of rock-slope debuttressing during the retreat of Affliction Glacier from its late-Neoglacial maximum. -from Author