ENVIRSC 1G03 Lecture Notes - Lecture 24: Mass Wasting, Particle Size, Surface Tension
7 Dec 2016
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Document Summary
Downhill movement of earth materials due to gravity. Movement caused by (cid:710)over-steepening(cid:711) of slopes due to erosion by streams, glaciers, waves, etc. Unconsolidated material at gravitational equilibrium: angle depends on: Wet/dry: varies from 35 to 45 . 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. Flows mudflows, debris flows, earthflows: unconsolidated and sometimes water-saturated materials, catastrophic mud flows due to hurricane mitch in honduras and other. Central american countries: often associated with volcanic complexes (lahars* - observed at mt. * ash mixed with water: creep is the slowest form of mass wasting. Unconsolidated material slowly drifts downhill: rock falls frost wedging contributes to weakening joints.
