Joints/Folds/Faults/Dips/Bedding planes/Strata

Cards (6)

  • Strata
    • Layers of different rocks
    • Formed by fresh sediments originally deposited in a basin
    • Weathering, erosion, deposition, compaction, cementation
  • Bedding planes
    • Horizontal layers
    • Caused by natural changes in sedimentary deposition processes e.g. flow rates during water deposition
    • Simplest sedimentary structure
  • Joints
    • Vertical cracks/fractures that are created without displacement
    • Occur in most rocks, often in regular patterns
    • In igneous rocks, cooling joints form when magma contracts as it loses heat
    • In sedimentary rocks, they form when rock is subject to compression or stretching by tectonic forces
    • When overlying rock is removed, underlying strata expand and stretch, crating unloading joints parallel to the surface
    • Increases erosion rates by creating fissures which marine processes can exploit
  • Faults
    • Major fractures in rock created by tectonic forces, with displacement of rocks either side of the fault line
    • Large in scale, extending many km
    • Significantly increases erosion rate, since easily exploited
    • Huge forces either side of the fault
  • Folds
    • Bends in rock. Sedimentary rock layers being squeezed by tectonic forces
    • Two main types: anticline and synclines
    • More heavily jointed and fissured - more easily eroded
    • Increases erosion rates by increasing angle of dip, and by causing joint formation as rock is stretched along anticline crests and compressed in cyclone troughs
  • Dips
    • The angle of inclination of rock strata from the horizontal
    • Tectonic feature
    • Sedimentary rocks deposited horizontally but can be titled by folding
    • Horizontal dip - vertical profile with notches
    • High angle of seaward dip produces sloping, low-angles profile with one rock layer facing the sea
    • Bedding planes easily loosened by weathering
    • Low angle of seaward dip produces steep profile
    • Landward facing dipping - steep profile