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  • 1. Weathering by David Edwards
  • 2. There are two main types of weathering which are called: Chemical Weathering & Freeze-Thaw Weathering
  • 3. Chemical Weathering
  • 4. Chemical weathering is when rain water (carbonic acid) reacts with limestone and dissolves or removes the limestone slowly.
  • 5. The rain water flows down the joints and into the bedding planes, and over time the joints widen to create grykes.
  • 6. This happens because the rock is PERVIOUS
  • 7. Pervious rock allows water to flow through the joints and bedding planes, but not sink through the rock itself.
  • 8. The equation for chemical weathering is: Limes tone + Carbonic Acid (rain water) = Calcium Bicarbonate (soluble lim estone) Or CaCO ³ + H ² CO ³ = Ca(HCO ³ ) ²
  • 9. Freeze-thaw Weathering
  • 10. Water collects in the cracks and joints in the rock . This is how freeze-thaw weathering works:
  • 11. The temperature cools and the water freezes, expanding by 9% in the cracks., and the increased pressure leads to cracks widening.
  • 12. Repeated freeze-thaw action increases the size of the crack until a block of the rock breaks off. These loose bits of rock are called scree.
  • 13. Freeze-thaw weathering can lead to the forming of tors such as "Bowermans' Nose".
  • 14. Key Words
    • Bedding Planes – Horizontal gaps in rock
    • Joints – Vertical gaps in rock
    • Grykes – Widened joints due to weathering
    • Pervious Rock – Rock that allows water top go through its joints and bedding planes but not to sink through the rock
    • Scree – Small pieces of rock that fall as a result of freeze-thaw weathering
    • Tor – A granite structure formed after lave cools