Weathering + Erosion

• Weathering


  The combined actions of all processes that cause rock to disintegrate physically or decompose chemically
• Erosion


  Removal of rocks and soil by wind, water, ice and gravity
• Geomorphology


  The science of landforms, their origin, evolution, form, and spatial distribution

  
• Denudation


  Any process that wears away or rearranges landforms
• Crust


  • In a constant state of change
  • Being formed by endogenic (internal) processes
  • Worn down by exogenic (external) processes
• Weathering


  • Disintegrates surface and subsurface rock into mineral particles or dissolves them in water
  • Includes 'physical' weathering and 'chemical' weathering
• Physical Weathering


  • Breaks rocks down into smaller and smaller pieces without changing the basic mineralogy
• Frost action


  Freezing expands water by 9%, causing freeze-thaw action and joint-block separation

  
• Salt crystallization


  Moisture evaporates, leaving salt crystals that exert force on the rock, common in arid climates
• Pressure-release jointing


  As overlying material is removed, layers of rock are exfoliated (sheeted) from the underlying intrusive igneous rocks, producing dome-shaped features
• Other physical weathering


  • Surface heating and cooling
  • Fire fracturing
  • Bioturbation (plant roots, animal burrowing)
• Chemical Weathering


  • Decomposition or chemical change of minerals in rock
  • Dominant form in warm, moist climates
  • Minerals combine with oxygen or carbon dioxide, or dissolve in water
• Hydration


  Mineral is combined with water, often producing a new mineral compound that is larger than the original, leading to rock decay
• Hydrolysis


  Minerals chemically react with water, forming new materials and weakening the rock
• Oxidation


  Oxygen and water react with iron-rich minerals, changing their color and weakening the rock structure
• Solution and Carbonation


  Dissolving of calcium carbonate (limestone) in acidic groundwater, producing bicarbonate
• Agents of Erosion


  • Wind
  • Water
  • Ice
  • Gravity
• Wind Erosion


  Picks up and transports weathered materials, depositing them elsewhere
• Water Erosion


  Transports weathered materials from their source to another location where they are deposited
• Ice Erosion


  Particles are plucked up or incorporated by moving ice, such as glaciers, and transported downhill
• Gravity Erosion


  Facilitates the downslope transportation of loosened, weathered materials without the aid of water, wind, or ice
• Geological Cycle


  Being formed by endogenic (internal) processes.

  Worn down by exogenic (external) processes.