Soil

• Soil


  A mixture of mineral grains, organic material, water, and gas
• Mineral grains


  Clay, silt, sand, and rock fragment
• Soil formation


  Rocks and/or minerals undergo weathering
• Weathering


  The process where rocks break down from either physical or chemical means
• Soil types


  • Clay
  • Sand
  • Silt
• Clay


  • Smallest soil particle [< 0.002 mm], lowest porosity, highest water retention
• Sand


  • Largest soil particle [0.005− 2 mm], highest porosity, poor water retention
• Silt


  • Particle size between sand and clay, porosity and water retention between the two
• Loam soil


  Combination of the three soil types, ideal for agriculture due to high porosity, high water and nutrient retention, and easy aeration
• Soil texture triangle


  Demonstrates any combination from the soil types
• Humus


  An essential component of most fertile soils, made from living and decaying organic matter
• Soil profile layers


  • Organic Layer
  • Topsoil
  • Subsoil
  • Parent Material
  • Bedrock
• Organic Layer (O-Horizon)


  Dark colour due to humus, most easily eroded
• Topsoil (A Horizon)


  Dark appearance due to humus, soft, porous, retains more water
• Subsoil (B Horizon)


  Contains clay and mineral deposits, less organic material, harder, more compact, lighter in colour
• Parent Material (C-Horizon)


  Lumps of rocks with cracks and crevices, also known as regolith
• Bedrock (R-Horizon)


  Extremely hard, rocky composition, not considered a soil layer
• Soil quality


  How well soil does what we want it to do, sustain plant and animal life, maintain/enhance water and air quality, support human health and habitation
• Imperative qualities for soil


  • Arable for agriculture
  • Regulation of water and filtering of potential pollutants
  • Nutrient cycling
  • Foundation and support
  • Mineral deposits
• Afforestation


  Planting or adding of trees in an area where there was never a forest or plantation, to create a new forest
• Reforestation


  Replanting of trees in an area where there was once a forest which was destroyed or damaged
• Exogenic processes


  Geological phenomena and processes originating externally to the Earth's surface, driven by solar energy and other external influences, shaping landforms created from endogenic processes
• Exogenic processes


  • Weathering
  • Erosion
  • Deposition
• Endogenic processes


  Geological phenomena and processes originating within the Earth's surface, responsible for tectonic changes on the surface by releasing energy from within
• Endogenic processes


  • Generation of Magma
  • Volcanism
  • Metamorphism
  • Earthquake
  • Deformation