How lithology affects resistance

• Igneous

  • Erode and weather very slowly because it’s composed of interlocking crystals, forming hard resistant rock
  • They usually have fewer joints
  • Recede at less than 0.1cm/year
• Metamorphic

  • Recrystallisation of sedimentary and igneous rocks through heat and pressure
  • Hard and resistant because it has a crystalline structure
  • Metamorphic coasts often recede slowly at about 0.1-0.3cm/year
• Sedimentary

  • Formed by the compaction and cementation of sediment
  • Sometimes the sediment is a precipitate e.g. limestone
  • Sometimes the sediment is made of dead organic material e.g. coal/chalk
  • Less resistant than metamorphic or igneous rocks due to weak bedding planes, clastic structure, often heavily jointed as a result of compaction and pressure release
• Unconsolidated sediment

  • Sediment that has not yet been cemented to form solid rock (lithification)
  • Drift geology is recently deposited unconsolidated that usually overlies the solid geography of the bedrock
  • Fluvial alluvium, glacial boulder clay, aeolian loess
  • 2-10m/year