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Abstract
It is known that slopes may retreat, decline, or be replaced by forms with gentler gradients, depending upon structural and environmental conditions. Rock mass strength (RMS) theory allows some of these conditions to be quantified. Slopes on essentially homogeneous strata which are sufficiently strong to support cliffs (RMS ratings of 57 and greater) develop by slope replacement, but slopes on rocks with RMS ratings of 50 and lower develop by decline. A resistant caprock overlying less resistant strata promotes parallel slope retreat where differences in strength between adjacent strata are ofthe order of 10 points on the RMS scale for caprocks of approximately 16 m in thickness, with greater differences in RMS being required for thinner resistant cappings to induce retreat.