rocks and weathering

Subdecks (4)

Cards (39)

  • hortonian flow
    • when soils infiltration capacity is exceeded by precipitation rate
  • rain splash
    • rain hits bare, soil surface, leading to detachment and so displacement of soil particles
  • sheet wash
    • form of surface run-off critical in transportation of soil sediments
    • flow has enough force to detach and transport soil particles
  • rills
    • typically narrow and shallow but extensive in length
    • often interconnect forming network over large slope area
    • signifies beginning of erosion
    • often only a few cm deep
  • strategies to modify slopes
    • netting : metal, mesh nets catch rocks from falling onto roads, railways etc.
    • afforestation : more interception, so less run-off and erosion. reduced infiltration = less mass. roots bound soil
    • grading : reducing slope angle and reshaping slope surface to provide a more uniform topography
    • drainage : reduce excess water
    • pinning : increased strength so it can take more stress
  • increased sheer stress
    • removal of lateral support (undercutting / slope steepening)
    • removal of underlying support
    • slope loading
    • lateral pressure
    • transient stresses
  • decreased shear strength
    • weathering effects
    • changes in pore-water pressure
    • changes of structure
    • organic effects
  • volcanic island arcs
    • chains of volcanic islands on the continental side of an ocean trench
    • subducting plate heats up and melts deep
    • magma formed rises to surface and meets overriding plate
    • material is added to crust, building volcanoes
    • if upper plate is oceanic, volcanoes pile up until they poke through surface - forming an island arc
  • slab pull
    • force that the sinking edge of the plate exerts on the rest of the plate
  • ridge push
    • magma intrusion at ocean spreading ridges
    • which propels the two plates apart
  • hot spot movement
    • lava plume through mantel responsible for original crust rifting
    • outward flow fo viscous magma creates drag force on plates causing movement
  • convection theory
    • radioactive decay in earth's core produces heat
    • hot magma rises in convection currents, cools at surface and sinks as denser
  • human activity which decreases slope stability
    • mining
    • tourism e.g. skiing
    • construction : add mass to slope, increase slip likelihood. also cutting into slope creates slope too steep for stability
    • agriculture
    • vegetation : deforestation - no roots - material not bound together - compromised stability
    • water : drainage routes disturbed - excess water - increased mass - will lead to slips
    • traffic vibrations - may trigger mass movements
    • footpath trampling : intensified localised erosion
  • slip plane
    junction between two layers along a bedding line
    or the joint between two rock types