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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.

Subsidence

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

Landslides

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

Chutes

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

Slide

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

Slumps

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

Solifluction

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

Spreads

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

Rockfall

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

Flows

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

Earthflow

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

Mudflow

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.

Vegetation

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
-Climate
-Topography
-Fire History

Climate

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

Drought

Lack of rain over prolonged time

1931-1938

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

1972-1974

Drought in Africa, several countries lost their financial infrastructure

1976

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

1982-1983

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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