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28 terms

Kolb Chapter 9

STUDY
PLAY
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.