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• slope breaks are minor features which will have little influence on rockfall trajectories, but may help to delineate sunlcial or solid geological boundaries. The general distribution of the surficial materials appears to be related to the slope breaks, however they were mapped only in sufficient detail to enable appropriate rebound parameters to be assigned for use in the CRSP models. These materials consist predominantly of talus and colluvium. Talus appears to be restricted to the upper part of the slope, and may include some buried or partially buried material. The colluvium is a widespread deposit consisting mainly of fine sand or silty fine sand with a variable content of sandstone pebbles, cobbles and boulders. In areas where the marine shale horizon is close to the surface, the colluvial matrix contains a higher proportion of silt and some clay sized material. In the course of morphological mapping a number of tension cracks associated with Panel No. 6 were encountered. Several of these were staked and subsequently • surveyed by Twentymile Coal Company personnel. 2.2 Boulder Catalog The boulder catalog is presented in Table 2-1 and locations of the blocks are shown on Drawing 1. The X, Y and Z dimensions are measured respectively in the direction of the slope, normal to the slope, and across the slope. The term 'rim' refers to the upper part of the cliff face, where the bedding plane jointing is more frequent, due either to primary sedimentary structures or stress relief. This area of the face has numerous rather rounded exfoliated blocks, many of which are detached or partially detached from the substrate, and is the probable source of many of the smaller blocks found on the slopes below. The source area elevations are estimated from the 1" to 200' topographic maps. West Fall and East Fall refer to the areas which failed recently in response to undermining by Panel No. 6.