Weathering

• Weathering


  • Physical weathering
  • Chemical weathering
  • Biological weathering
• Weathering


  A group of processes that breaks down rocks, soils and minerals into smaller pieces through contact with the Earth's atmosphere, biota and waters
• Weathering processes are usually very slow
• Weathering processes can take thousands of years
• Weathering is responsible for the creation of soil and many unique features on Earth
• Examples of unique features created by weathering

  • Fish River Canyon
• Erosion


  The process by which rock particles already broken down by weathering are carried away
• Types of physical weathering

  • Granular disintegration
  • Exfoliation
  • Block separation
• Granular disintegration


  Occurs when rocks break up into small grains or pieces to form sand or very small pieces of gravel
• Exfoliation


  The process where rocks weather by peeling off in sheets
• Block separation


  Occurs when rocks break up into large fragments related to rock joints
• The main cause of block separation is frost shattering
• Physical weathering occurs as a result of extreme temperature changes
• Experiment with physical weathering

  1. Pour water into bottles

  2. Place bottles in freezer

  3. Check bottles after two or three hours

  4. Make observations and discuss findings

  5. Explain how experiment links to physical weathering
• Chemical weathering


  The breakdown of rocks into particles with a different mineral composition from the original rock
• Agents of chemical weathering

  • Water
  • Oxygen
  • Carbon dioxide
• Solution weathering


  Minerals or soluble chemicals in the rock dissolve directly in water
• Hydrolysis


  A chemical reaction between the minerals in the rock and hydrogen in rainwater
• Hydration


  Minerals in rocks absorb water and expand, causing the rock to break up
• Oxidation


  Rock minerals react with dissolved oxygen to produce oxides or hydroxides
• Carbonation


  Occurs when carbon dioxide dissolves in water to form carbonic acid
• Biological weathering


  Involves living things breaking down rocks through physical actions or chemical actions
• Biological weathering can involve plant root growth or animal burrows
• Some organisms produce or secrete acids that can chemically weather rocks and minerals
• A large release of carbon dioxide can cause acid rain
• Human activities can increase the rate of weathering on rocks or buildings
• Human activities that can cause weathering

  • Burning of fossil fuels
  • Constructing roads with dynamite
  • Mining operations
  • Quarrying
• Deposition


  Occurs when eroded material is deposited in a new location
• Agents of erosion and deposition

  Gravity<|>Water (rivers)<|>Glaciers (moving ice)<|>Sea waves<|>Wind
• The main difference between weathering, erosion, and deposition is that weathering does not involve movement of material
• Erosion is the process by which soil and rock are moved from one area of the Earth's surface
• Deposition is the end of the process that started with weathering
• Stages of a river


  • Youth
  • Maturity
  • Old age
• Youth stage of a river

  The beginning of a river characterized by rapid vertical erosion and steep slopes
• Characteristics of the youth stage of a river

  • Waterfalls
  • Narrow channel
  • V-shaped valleys
  • Rapids
• Stages of a river course


  • Youth
  • Maturity
  • Old age
• River source


  Where a river starts flowing
• Youth stage of a river

  • Flows quickly
  • Has waterfalls
  • Cuts a narrow channel
  • Characterised by rapid vertical erosion
  • Has steep slopes
  • Forms V-shaped valleys
  • Includes waterfalls and rapids
• Mature stage of a river

  • Valley with a wide floor
  • More lateral erosion
  • U-shaped valley
  • Gentle slopes
  • Narrow flood plain
  • Meanders
• Old age stage of a river

  • Very flat relief
  • Slow river flow
  • Dominant meandering courses
  • Characterised by deposition
  • Oxbow lake development