SAJC Cluster 2.2 Lecture 12 Notes (Geomorphic Processes Pt.3: Movement of materials on slopes)

St Andrew’s Junior College H2 Cluster 2: Tropical Environments H2 Cluster2_Lecture 12_2025/pg1 Lecture 12 Geomorphic Processes (III): Movement of Materials on Slopes KEY QUESTION: ✓ What influences the movement of materials on slope? With the completion of this lecture, attached readings and tutorial, you should be able to discuss: • how materials move on slopes through mass movement and water erosion • the different forms of mass movements (fall, slide, flow, creep) and water erosion (splash erosion, rainwash and rillwash) • the human and natural factors influencing movement of materials on slopes Lecture Outline 12.1 Introduction: Movement of Materials on Slopes 12.2 Slope Stability 12.3 Classification of Mass Movements 12.4 Fall 12.5 Slide 12.6 Flow 12.7 Creep 12.8 Factors Affecting Shear Stress and Shear Strength 12.8.1 Natural Factors 12.8.1.1 Gravity 12.8.1.2 Climate – The Availability of Water 12.8.1.3 Vegetation 12.8.1.4 Slope Characteristics (a) Steepness of Slope (b) Geology (c) Underlying Rock Type (d) Character of Regolith Box 1: Factors Affecting Mass Movements in Singapore 12.8.1.5 Tectonic Forces – Seismic and Volcanic Activities 12.8.2 Human Factors Box 2: Recovery, construction efforts after Clementi landslide 'may take a few months': Desmond Lee 12.9 Water Erosion 12.9.1 Splash Erosion 12.9.2 Rainwash 12.9.3 Rillwash 12.10 Factors Affecting Water Erosion 12.10.1 Natural Factors 12.10.2 Human Factors 12.11 Conclusion

St Andrew’s Junior College H2 Cluster 2: Tropical Environments H2 Cluster2_Lecture 12_2025/pg2 12.1 Introduction: Movement of Materials on Slopes • As we learnt in Lect. 11, different weathering processes break down rocks into regolith and soil. All these broken materials lie on slopes of the earth’s surface. Since these broken materials are weak and loose, these are susceptible to the pull of gravity, running water, wind, and the movement of glaciers to move them downslope from one place to another. In this lecture, we will focus on the processes involved in the movement of materials down the slope due to the pull of gravity (mass movement) and due to water (water erosion). • Mass movements and water erosion are considered geomorphological processes as their actions alter slope surfaces. • In geography, a ‘slope’ refers to a small strip or patch of the land surface that is inclined from the horizontal. Most slopes are covered by a layer of regolith, which transitions downward into solid, unaltered rock, known simply as bedrock (see Fig. 1). Fig. 1 Profile of a Slope 12.2 Slope Stability • We use the term mass movement to r