Mass MovementMass Movement

OverviewOverviewGeomorphologyGeomorphologySlope ProcessesSlope ProcessesMass Movement (Mass Wasting)Mass Movement (Mass Wasting)

GeomorphologyGeomorphologyThe science of landformsThe science of landforms

OriginOriginProcesses of changeProcesses of changeDistribution on the planetDistribution on the planet

Landforms are the product ofLandforms are the product ofForces that build up the landformsForces that build up the landformsForces that wear it down or modify itForces that wear it down or modify it

DenudationDenudationweatheringweatheringmass movementmass movementerosion, transportation and depositionerosion, transportation and deposition

Gravity and moving air, water, waves, and iceGravity and moving air, water, waves, and ice

Dynamic Equilibrium ModelDynamic Equilibrium ModelEnergy constantly flowing through landscapesEnergy constantly flowing through landscapes

Potential energy: energy of position (gravity): upliftPotential energy: energy of position (gravity): upliftKinetic energy: energy of motion: hydrologic cycleKinetic energy: energy of motion: hydrologic cycleHeat energy: solar energy: sunHeat energy: solar energy: sunChemical energy: from atmosphere and within the crustChemical energy: from atmosphere and within the crust

Landforms are a balance between stabilizing forces Landforms are a balance between stabilizing forces (friction, inertia, cohesion) and destabilizing forces (friction, inertia, cohesion) and destabilizing forces that can set things in motionthat can set things in motionCycleCycle

Equilibrium stabilityEquilibrium stabilityA destabilizing eventA destabilizing eventAdjustmentAdjustmentNew equilibrium stabilityNew equilibrium stability

Slope Slope ProcessesProcesses

Erosion: Erosion: weatheringweatheringTransportation: Transportation: Mass wastingMass wastingDeposition: Deposition: Debris slope, Debris slope, talus conetalus cone

Mass MovementsMass Movements

Also called: Mass WastingAlso called: Mass WastingWeathering prepares material for movementWeathering prepares material for movementGravity sets material in motionGravity sets material in motion

Steepness of slopeSteepness of slopeFriction and cohesive nature of the materialFriction and cohesive nature of the materialAngle of reposeAngle of reposeAmount of moisture availableAmount of moisture available

Characteristics of a particular mass movement Characteristics of a particular mass movement depend on speed of movement and amount of depend on speed of movement and amount of water mixed with the materialwater mixed with the materialFall, slide, flow, creepFall, slide, flow, creep

Angle of ReposeAngle of Repose

The maximum angle at which slope material The maximum angle at which slope material can be inclined without moving can be inclined without moving downslopedownslopeIt is a critical value for stability for a It is a critical value for stability for a particular slopeparticular slope

If the actual slope angle is less than the angle of If the actual slope angle is less than the angle of repose, the slope is stablerepose, the slope is stableIf the actual slope angle is greater than the angle If the actual slope angle is greater than the angle of repose, mass movement can occurof repose, mass movement can occurThe angle of repose changes as slope conditions The angle of repose changes as slope conditions (such as soil moisture) changes(such as soil moisture) changes

The angle of repose can never be exceededThe angle of repose can never be exceededAngle of repose can decrease under severe Angle of repose can decrease under severe motion (earthquakes) or saturationmotion (earthquakes) or saturation

Types of Mass MovementsTypes of Mass MovementsRockfallRockfall

Loose rocks fall through the air, accumulate in a talus coneLoose rocks fall through the air, accumulate in a talus coneHigh angle of reposeHigh angle of repose

Debris avalancheDebris avalancheRocks, debris and soilRocks, debris and soilExtremely high velocityExtremely high velocity

Water and ice often fluidize debrisWater and ice often fluidize debris

LandslideLandslideUnsaturated mass of bedrock and regolith that moves suddenly andUnsaturated mass of bedrock and regolith that moves suddenly andrapidlyrapidly

Rotational slumpingRotational slumpingTranslational slidesTranslational slides

FlowsFlowsearthflowearthflowmudflowmudflow

Creep: a persistent movement of soil down slopeCreep: a persistent movement of soil down slope

RockfallRockfall

Rotational Rotational block slumpblock slump

Debris Debris avalancheavalanche

Debris avalancheDebris avalanche

Soil CreepSoil Creep