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

• 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