Controls of Weathering 3.2

Question 1

Climate

Answer 1

Temperature: Higher temperatures accelerate chemical weathering (e.g., oxidation, hydrolysis), while freeze-thaw cycles in colder climates enhance physical weathering.
Precipitation: More rainfall increases chemical weathering (e.g., solution, carbonation) and promotes mass movement.
Humidity: In humid environments, biological weathering is more active due to plant and microbial activity.

Question 2

Rock Type

Answer 2

• Mineral composition affects susceptibility (e.g., limestone undergoes carbonation, feldspar in granite hydrolyzes).
  
  • Cementing material in sedimentary rocks influences weathering resistance (e.g., iron oxide-based cement is more resistant than quartz cement).
  • Goldich’s weathering system ranks minerals from least to most stable, showing their resistance to weathering.

Question 3

Rock Structure

Answer 3

• Joints, faults, and bedding planes provide weaknesses for weathering to act upon.
  
  • Grain size affects permeability:
  • Coarse-grained rocks (e.g., granite) have larger voids, allowing faster weathering.
  • Fine-grained rocks (e.g., shale) have a greater surface area, making them more vulnerable.
  • Porosity and permeability influence weathering speed (e.g., sandstone has high permeability, allowing more chemical weathering).

Question 4

Vegetation

Answer 4

• Root action breaks down rocks mechanically.
  
  • Organic acids from decomposing plants promote chemical weathering.
  • Soil moisture linked to vegetation affects the type and intensity of weathering.
  • Depth of soil may either protect rocks or increase their breakdown by retaining moisture.

Question 5

Relief

Answer 5

• Steep slopes promote erosion and prevent deep weathering.
  
  • Gentle slopes allow moisture accumulation, enhancing chemical weathering.
  • Aspect affects temperature variations, influencing freeze-thaw weathering in cold climates.