General Factors Affecting Type + Rate of Weathering

Question 1

What are the general factors affecting the type + rate of weathering?

Answer 1

• climate
• rock type + structure
• vegetation
• relief

Question 2

How does climate affect the type + rate of weathering?

Answer 2

• some climates can accelerate + prevent certain types of weathering
• e.g. salt crystallisation requires dry climates so water can evaporate to leave crystals

Question 3

How does rock type affect the rate + type of weathering?

Answer 3

• affected due to:
  
  • chemical composition
  • nature of cements in sedimentary rocks (Fe2O3 based = prone to oxidation, quartz = v. resistant)
  • joints + bedding planes
• water soluble rocks = more vulnerable to chemical erosion so weathered quicker
• limestone consists of CaCO3 so is prone to carbonation solution

Question 4

How does rock structure affect the rate + type of weathering?

Answer 4

• mineral type in rocks:
  
  • resistant materials (quartz, feldspar in granite) resist weathering
  • weaker minerals weather rapidly
• grain size influences speed:
  
  • coarse: weather quickly due to large void space + high permeability
  • fine: greater SA for weathering, highly vulnerable
• permeable rocks = pores leaving it vulnerable to many type of weathering
• impermeable rocks = lower rates of weathering bc more energy require to break rocks

Question 5

How does vegetation affect the rate + type of weathering?

Answer 5

• rate influenced by moisture content, root depth + acidity of humus
• type influenced as weathers rock in 2 ways:
  
  • secretion of organic acids (chemically)
  • growth of roots (physically)
• depth of soil
  
  • soils may protect rocks from further breakdown
  • may inc. rate bc supports more veg.
• more weathering in forests as more root action

Question 6

How does relief affects the rate + type of weathering?

Answer 6

• gentle slopes: prone to standing water which infiltrates into ground (encourages C weathering)
• steep slopes: inc. some form of P weathering, but slows C weathering: requires water but prone to fast overland flow
• direction slope faces, affects sunshine recieved: more = more veg. so inc. root action + C weathering, less = colder + less veg. so more prone to freeze-thaw