GEOL 102 1st Edition Lecture 13Outline of Last Lecture I. Groundwater Contamination Outline of Current Lecture I. Mass Movement RelevanceII. Styles of Mass MovementsCurrent LectureI.Mass Movement RelevanceThey play roles asNatural hazardsPart of the rock cycleControls the height of mountainsSocioeconomic impact – the most expensive hazard1925-1975 – 1000 deaths, $75 billion in damage (only $20 billion for all other hazards combined)Biological functions – creating gravel for fishHigh Impact Historical Landslides1920 China – earthquake triggered, 675 landslides, 200,000 deaths1949 Russia – earthquake triggered rockslide, 20,000 deaths1980 Mt. St. HelensII. Styles of Mass MovementThe different types are distinguished byThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Types of materialVelocityEnvironment or settingSlow Mass Movement ProcessesCreepSlow, continuous process of downslope movementOccurs on soil-mantled slopesDriven by: freeze-thaw cycles and biological disturbancesSolifluctionPoorly drainedFrozen at depthThin sheetflows in summerSlumpingDistinct morphologyHeadscarp, fractures at topFolds at toeBench-like depositDiscrete failure surfaceHummocky terrainFast Mass Movement ProcessesFlowsMixture of rock, soil, and waterVelocity varies with. . .SteepnessViscosityMaterialEarthflows: highly viscous and slow moving, deeply weathered soil and rock, deposit on moderate slopesDebris flows: coarse-grained material, low viscosity, deposit on gentle slopesMudflows: fine-grained material, very low viscosity, deposit on gentler slopesLahars: volcanic ash and water, snowmelt-related (eruption or rain), scalding
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