Mass Wasting Flashcards
What are the four factors that help identify different mass movements
- Type of mineral
- Velocity of the movement
- Nature of the mass
- Movement environment
What are the four types of materials in mass movements
- Rock
- Regoloiths (loose sediment at the surface)
- Snow
- Ice
What are the three natures of mass movements and briefly explain each
- Chaotic
- Coherent
- Slurry
What are the two movement environments
- Subaerial
- Submarine
What is a creep and explain how it occurs
A slow downhill movement of regolith caused seasonal expansion and contraction of the soil
What is evidence that creeping has occurred
Tilting of landscape features (eg. Tree, telephone pole, etc.)
What is solifluction and explain how it occurs
Low downhill movement of tundra, caused by melted permafrost flowing over deeper-frozen soil
What is slumping and explain how it occurs
Sliding of regoliths in coherent blocks, these occur on a failure surface and can vary in size and speed
What are the three distinctive features of slumping
- Head scarp (upslope cliff face)
- Toe (material at the base)
-discrete faulted slice
Where are slumps common
seacoast and river cut banks
What is a mudflow and in what environment are they the most common
A slurry of water and fine sediment, and is most common in tropical settings with abundant rainfall
What is a debris flow
A mudflow with many large rocks
What is a lahar
Special volcanic mud or debris flow
What are rock and debris slides and how do they differ
Both are sudden movements downslope, but rock slides consist of only rock. Whereas debris slides are comprised of mostly regolith
What are two factors that affect the speed of mudflows, debris flows, and lahars
- Slope steepness
-Addition of water (more water the faster the movement)
What is an avalanche
Turbulent clouds of debris and air
What are a rockfall and debris fall
A vertical freefall of mass
What are the three types of submarine mass movements and briefly explain each
-Submarine slumps, semicoherent blocks break and slip
-Submarine debris flow, broken material moving in a slurry
-Turbidity currents, sediment moves as a turbulent cloud
Submarine mass movements are often connected to what kind of natural disaster
Tsunami
Mass movements require that earth material is: (2)
-Subjected to topographic (slope) forces
- Be weakened or loosened from attachments
What are the forces acting on a slope (2)
- Downslope force created by gravity
-Resistance force created by the material making up the slope that is resisting gravity
What is the angle of repose
The max slope angle based on sediment size
What factors determine the angle of repose (3)
- Particle size
- Particle shape
-Surface roughness
Common weak subsurfaces failures (4)
- Saturated sand or clay layer
- Joints parallel to the land surface
- Weak sedimentary bedding (shale, evaporites)
- Metamorphic foliation planes
What factors change slope strength (3)
- Weathering
- Vegetation
- Water
Two factors significant to mass movements
- Relief
- Climate
Look at slides 39-45 to see prevention of mass movements
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