rocks n weather

• Define the weathering term 'heating and cooling'

  • 'Heating and cooling' is the process where the alternate expansion of the rock by heating, and contraction by cooling (1)
  • leads to rock breakdown (1).
• Define the weathering term vegetation root action

  • Vegetation root action is the break-up of rock by the prising apart of joints (1)
  • by the growth of roots in the crack (1).
• Briefly explain how sheetwash occurs on slopes

  • When there is intense precipitation on inclined terrains,
  • the water can surpass the soils infiltration capacity,
  • resulting in surface run-off.
  • This run-off occurs in unconcentrated sheets,
  • due to the relatively smooth surfaces & homogeneous surface geology, leading to sheet wash.
  • It involves the uncontrolled flow of water over the land in thin layers due to the surplus rainfall.
• Explain the formation of fold mountains.

  
  

  • unfolds down folds
  • pressure squeezing accretionary wedge
  • fold subduction of continental plate under oceanic
• Define the mass movement terms: heaves & falls.

  • Heaves are the upward movements of soil particles at the surface (1)
  • parallel to the slope (1)

  AND

  • Falls are the sudden movement, usually of rock (1)
  • from a vertical or steeply inclined rock face (1).
• Briefly explain how rocks can be weathered by freeze–thaw action:

  • Water enters rock joints and pores, freezes and expands (1)
  • and puts pressure on the rock (1).
  • Repetition of the process might lead to rock failure (1).
• Explain how human activity may increase the stability of slopes:

  boom
• ‘Rock type and rock structure are the most important factors in affecting 15 the type of weathering.’

  pow
• Describe differences between flows and slides:


  • Flows tend to be more fluid with a higher water content
  • Flows tend to move faster
  • Flows tend to move in channels, whereas slides do not
  • Flows tend to move further
• Briefly explain how rills occur on slopes:

  Rills are concentrated thin streams of water on the slope.

  Thus:

  • They need rainfall amounts that exceed the infiltration capacity of the soil/saturated soil/ground
  • They need bare surfaces
  • They need to have soil characteristics that affect infiltration capacity
  • They need to be on relatively steep slopes
  • They become concentrated in thin rivulets by surface irregularities/roughness
• Define the weathering terms: heating and cooling & vegetation root action.


  • Heating and cooling is the process where the alternate expansion of the rock by heating and contraction by cooling (1)
  • leads to rock breakdown (1).

  AND

  • Vegetation root action is the break-up of rock by the prising apart of joints (1)
  • by the growth of roots in the crack (1).
• Briefly explain how sheetwash occurs on slopes


  • Heavy rainfall
  • Sloping surfaces
  • On bare surfaces
  • Exceeding the infiltration capacity of the soil
  • Leading to surface runoff in sheets (unconcentrated) because of relativelysmooth surfaces
  • Homogenous surface geology/texture
• Define the weathering terms hydration and freeze-thaw:


  • Hydration occurs when water enters into the mineral fabric of a rock (1)
  • causing it to expand, putting pressure on the rock (1).

  AND

  • Freeze-thaw is the mechanical process whereby water enters the joints or pores of a rock (1)
  • and expands and contracts on freezing and thawing (1).
• Briefly describe the results of weathering to rocks by heating & cooling:


  • Heating and cooling leads to the expansion and contracting of a rock (1)
  • which leads to stresses (1)
  • causing the rock to disintegrate (1)
  • aka, granular and block weathering
• Describe the nature of conservative plate boundaries:


  • boundaries where two plates are moving side by side
  • either in the same/opposite direction but at different speeds
  • no landforms are created or destroyed
• Explain how ocean ridges are formed:


  • the moving apart of oceanic plates
  • as a result of convection currents in the mantle
  • rising of magma
  • which cools and accumulates to form the ridges
• Describe and explain how vegetation affects the weathering of rocks:


  Direct action of roots/humic acids

  Indirectly by protecting the surface from physical weathering.

  Vegetation leads to:

  • increased chemical weathering through the release of organic acids
  • increased carbonation by release of carbon dioxide from roots anddecaying vegetation
  • increased chelation by growth of lichens on rock surfaces
  • increased biological weathering by pressure caused by root growth incracks and crevices in the rock
  • reduced physical weathering by protection of the surface reducingthermal insulation