slopes Flashcards
What are the different types of landslides?
Slumps, slides, falls, flows
What are slumps?
Landslides where there are large blocks of mass along the curved slip plane
Not much deformation within individual blocks
What are the factors that influence slumps?
Materials are rocks, soil, or a combination
Metamorphic foliation, bedding planes, and fault planes provide slip plane
What are the factors that influence slides?
Bedding planes & fractures act as slip planes
Rocks and/or soil
What are slides?
Landslides where there are large blocks of mass along a straight slip plane
Not much deformation along individual blocks
What are falls?
Landslides where there is a direct, free fall down steep slopes
Leads to the formation of talus slopes
What are the factors that influence falls?
- Water
- Earthquakes
- Human activity
What are flows?
Slow flow/soil creep = Fluid-like motion of soil not seen on the surface, evidenced only by infrastructure buckling, relatively slow deformation
Very rapid flow = Debris flow, mud flow, debris avalanche
What are the factors that influence flows?
Material in debris flow and mudflow consist of rock, soil organic matter, air, water
Less than 50% of ‘fines’ (sand, silt, clay) in debris flow, more than 50% in mudflow
What are the factors affecting slope stability?
Type of earth material = Slope shape, particle size
Slope & topography = Sliding vs. resisting force
Climate = Weather patterns over decades & water infiltration (precipitation)
Vegetation= Deep roots add stability, may add weight to slope
Water = Saturation leads to slips, erodes slope bases, quick clay formation
Time = Weathering impacts rock strength & resisting force
What is subsidence and what causes it?
Ground failure characterized by near vertical deformation/downward sinking of earth materials
Caused by withdrawal of fluids from reservoirs or collapse of surface soil & rocks over voids
What are sinkholes and what causes them?
Circular areas of subsidence
Caused by collapse of near-surface subterranean voids/cavern rooms, removal of subterranean earth materials by natural processes (chemical weathering)
What types of rock faces produce falls and slumps?
- Falls are a result of steep slopes
- Slumps are produced by curved slip planes
How does the strength of rock influence the types of landslides?
- Stronger rocks –> primarily rock landslides –> less damage
- Weaker rocks –> higher tendency to rupture –> more damage
What is the relationship between water, climate, and landslides?
A wetter climate with more frequent rainfall will lead to more water infiltrating the land, the water will saturate the soil and will result in shallow soil slips, or slumps/slides
