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Mass Movement

Down slope movement of earth under the influence of gravity

Mass wasting

a comprehensive term for any type of downslope movement of rock or soil as a coherent mass.


a type of ground failure characterized by nearly vertical deformation/Very slow to rapidly sinking or settling of Earth materials.
-Withdrawal of Fluids
-Salt deposits
-Coal mining


This term is inclusive of Mudflows, Rockfalls, and Snow or Debris (course material) Avalanches


Snow avalanches travel in these channels

Vertical deformation

Downward sinking of Earth materials

Soil Creep

Slowest type of Mass Movement, occurs due to freeze and thaw cycle


A sheet of material that slips over a failure plane which Creates concave scarps


Backward rotation as material moves along a curved slope which Results in "step-like" formations


This Type of Mass Movement happens over permanently frozen ground. It Occurs in summer when uppers layers thaw and lower layers stay frozen


These are Movement on gentle slopes that are Triggered by earthquakes that liquefy the underlying material


This Most sudden form of mass movement Involves gravity. Blocks fall from cliffs, debris pile


Movement of soil, weak shale, or clay that is saturated with water which is Usually triggered by heavy or seasonal rainfall. Occurs where farming has stripped vegetation or locations of previous landslides. Involves unconsolidated material


Slow moving, accompanied by slump that is Not confined to a channel, more common in humid areas


Rapid moving flow of Unconsolidated surface material, steep slopes with intermittent rain, and sparse vegetation.
Happens in dry areas with heavy rainstorms, occupy stream channels

Driving Forces

This force moves Earth materials down a slope.

Resisting Forces

oppose driving forces

Safety Factor

Ratio of the resisting force to the driving force. Evaluates slope stability

Slip planes

geologic surfaces of weakness in slope material. It has Foliation planes in schist, Bedding planes of sedimentary rock, and Fractures

Affects of Water on Slope Stability

Saturating slopes (shallow soil slips), Years of water infiltration into slope (slumps), and Eroding base or toe of slope.


This factor adds weight to the slope, the root system adds cohesion to slope materials, and it provides cover to lessen the impact of rain.
-Soil type
-Fire History


Characteristic weather at a particular place or region over seasons, years, or decades.


Lack of rain over prolonged time


Great Plains of the US drought. "Dust Bowl" comes from loss of top soil.


Drought in Africa, several countries lost their financial infrastructure


Drought in Britain. 15 months without rain. Extreme rationing.


Australian Drought. Lack of rain for a full year. Sixty percent of sheep and cattle died.

Vaiont Dam

October 9, 1963, 2600 lives lost. No structural damage. Entire event (slide and flood) was over in 7 minutes.

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