mass movement (15) Flashcards
Mass Movement
The downslope movement of rock, regolith, and soil under the direct influence of gravity
What sort of landscapes are rapid mass movements most likely to occur?
Rugged landscapes
How does mass movement combine with stream erosion to expand valleys?
Streams cut down while mass movement widens
Trigger
A factor or event, such as soil saturation, oversteepened slopes, removal of vegetation or ground shaking, that initiates downslope movement of rock material
Angle of Repose
The steepest angle at which loose material remains stationary without sliding downslope
Liquefaction
The transformation of a stable soil into a fluid that is often unable to support buildings or other structures
Fall
A type of movement that is common to mass-wasting processes that refers to the free falling of detached individual pieces of any size
Talus Slope
The characteristic “apron” of angular rock debris that accumulates below mountain cliffs
Slides
A movement common to mass-wasting processes in which the material moving downslope remains fairly coherent and moves along a well-defined surface
Flow
A type of movement common to mass-wasting processes in which water-saturated material moves downslope as a viscous fluid
Rock Avalanche
Very rapid downslope movement of rock and debris. Theses rapid movements may be aided by a layer of air trapped beneath the debris, and they have been known to reach speeds of over 200 km/hr
How can material move during a mass movement?
Fall
Flow
Slide
Slump
The downward slipping of a mass of rock or unconsolidated material moving as a unit along a curved surface
Rockslide
The rapid slide of a mass of rock downslope, along planes of weakness
Debris Slide
A type of rockslide consisting of largely unconsolidated rock debris
Debris Avalanche
One of the fastest and most destructive types of rockslides consisting of unconsolidated rock fragments
Debris Flow/Mudflow
A flow of soil and regolith that contains large amounts of water. Most common in semiarid mountainous regions and on the slopes of some volcanoes
Lahar
A debris flow on the slopes of a volcano that results when unstable layers of ash and debris become saturated and flow downslope, usually following stream channels
Earthflow
The downslope movement of water-saturated clay-rich sediment (humid regions)
Creep
The slow downhill movement of soil and regolith
Solifluction
The slow, downslope flow of water-saturated materials common to permafrost areas
Permafrost
Any permanently frozen subsoil. Usually found in the subarctic and arctic regions
During what season does solifluction in the Arctic occur?
Summer
How might disturbing permafrost lead to unstable ground?
Permafrost when melted is turned into water which is less volume than ice, it sinks
2 indicators that a slope might be failing:
Cracks
Tilted Trees
Deformation of buildings
What are some monitoring methods used for landslides?
Measure size of cracks
Measure changes in soil moisture
Detect noises
Satellites measure position
What are two techniques to strengthen failing slopes?
Drainage channels
Bind sliding surfaces or support them
