SEDIMENTARY ROCKS - SLG 8.2.2

Cards (11)

  • Sedimentary Rocks - formed from pre-existing rocks and other materials such as minerals and remains of living things. These bits and pieces are called sediments.
  • The word sediment came from the Latin word sedimentum which means deposit or settling. This explains the nature of the rock as these sediments settle to a location, will be compacted, and then cemented.
  • There are 4 types of sedimentary rocks, namely;
    1. Detrital Sedimentary Rocks
    2. Chemical Sedimentary Rocks
    3. Biochemical Sedimentary Rocks
    4. Organic Sedimentary rocks
  • Detrital sedimentary Rocks - Rocks formed from the accumulation of dead organic matter or detritus. It is mostly made up of clay minerals and quartz.
  • Types of Detrital Sedimentary Rocks based on Particle Size
    1. Coarse - <2mm
    2. Medium - 1/16-2mm
    3. Fine - 1/16-1/256
    4. Very Fine - >1/256mm
  • Chemical Sedimentary Rocks - formed from the materials that are carried to bodies of water like lakes & seas. The dissolved materials precipitate through physical processes to form chemical sediments.
  • Biochemical Sedimentary Rocks - are formed from the remains of water-dwelling animals
  • Types of Chemical and Biochemical Sedimentary Rocks
    1. Calcite, Calcium Carbonate, (CaCO3)
    2. Quartz, (Silica - SiO2)
    3. Gypsum (Calcium sulphate dihydrate CaSO4 . 2H2O)
    4. Halite(Salt–NaCl)
  • Organic Sedimentary Rocks - Formed from the accumulation of organic matter and other materials in sedimentary environments. An example of this is coal.
  • How are coals made? They are made for millions of years by the slow process of decay of plants and animals. The heat and pressure turned dead plants into coal.
  • Distinct Features of Sedimentary Rocks
    1. Strata or beds - Layers of rocks on the Earth's surface tell stories about the past environment during the time.
    2. Fossils - these help geologists understand the environment during the time of the formation of the sedimentary rock.