EARTHSC 1G03 Lecture 9: Enviro 1G03_ Mass Movement I
5 Apr 2017
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Document Summary
Downhill movement of earth materials due to gravity. Movement caused by over-steepening of slopes due to erosion by streams, glaciers, waves, etc. Angle of repose (angle at which sediments lie when dumped down) Seems to increase with more coarse and heavier sediments. Example: fine sand has a angle of repose of 35 degrees (shallower) where angular pebbles have a angle of repose of 45% (steeper) Surface tension of water causes cohesion of grains if only a film is present. Failure of a slope occurs when the external forces (driving forces) exceed the shear strength. Small amounts of water increase shear strength. Large amounts of water decrease shear strength. If water content is high enough to fill pores, grains will float . Any increase in water pressure will actually push grains apart, leading to flow of unconsolidated materials. Flows- mudflows, debris flows and earth flows. Catastrophic mudflows due to hurricane mitch and other central american countries.
