ERTH 2415 Chapter 9: Chapter 9 Summary.docx
14 Mar 2012
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Chapter 9 summary mass movements and snow avalanches. Gravity tugs incessantly at all landforms on earth, commonly causing failures called mass movements. Slopes approach failure due to external factors, such as steepening of the slope, adding mass upslope, or removing mass low on a slope. Movement is usually initiated by a triggering event, such as heavy rains, an earthquake, or human activities. In canada, most mass movements occur in the spring and fall in conjunction with meteorological events. Mass movements range from the barely perceptible surface creep of hill slopes and gelifluction of periglacial soils to events involving material moving in excess of 325 km/h. Major types of mass movement are downward, as in falling or subsiding, or downward and outward, as in sliding and flowing. Falls are rock masses dislodged from elevated slopes. Slides are mass movements on top of failure surfaces. Flows are mass movements that behave like fluids, even when they are dry.
