Weathering Processes Quiz

Weathering

• Weathering is the breakdown of rock on the Earth's surface.
• Two main types: mechanical and chemical weathering.
• Mechanical weathering breaks rocks into smaller pieces physically.
  • Thermal expansion: Temperature changes cause rocks to expand and contract.
  • Frost weathering (ice wedging): Water in cracks freezes and expands, widening cracks.
  • Exfoliation: Outer rock layers peel away as pressure above decreases.
  • Abrasion: Rocks hitting, scraping, and chipping against each other.
  • Salt crystal growth: Water evaporates, leaving crystals pushing into cracks.
• Biological weathering: Living organisms mechanically or chemically weather rock.
• Mechanical, chemical, and biological weathering can occur simultaneously.

Chemical Weathering

• Chemical weathering involves chemical processes.
• Processes like acidification, carbonation, hydrolysis, oxidation, and action of living organisms.
• Relatively slow process, varying with chemical processes.
• Two parts: decomposition of original materials and formation of new materials.
• Factors such as climate (warm/cold) and material characteristics influence speed.
• Enhanced by geological agents (water, oxygen) and biological agents (roots, microbes).

Factors Affecting Weathering Rate

• Exposure to the atmosphere: Exposed rocks weather faster than buried rocks.
• Rock composition:
  • Reactive minerals weather faster (e.g., minerals with iron).
  • Softer and more porous rocks weather faster (e.g., calcite).
• Climate: Warm, humid climates have higher weathering rates than cold, dry climates.

Soil Formation

• Soil is a mixture of sediment, minerals, organic matter, gases, liquids, and organisms.
• Important for plant life (and thus most life).
• Takes a long time to form in barren areas.
  • Develops through weathering, erosion, and deposition.
  • Pioneer species introduce organic matter.
• Soil components: sand, silt, clay, loam (varying proportions).
• Soil structures: granular, platy, columnar (granular preferred for growing).
• Soil profile: layers (horizons) with varying sediment types.
  • Topsoil (most organic matter)
  • Underneath layers are increasing amounts of clay and silt.
  • Bedrock at the bottom.

Soil Erosion

• Soil erosion is the movement of soil by wind, water, or gravity.
• Exposed soil erodes more easily.
• Topsoil erosion reduces soil quality and yields, causing issues for agricultural productivity.
• Runoff carries fertilizers and pesticides, polluting water and ecosystems.
• Preventing soil erosion is aided by:
  • Shelterbelts
  • Prevention of overgrazing
  • No-till farming
  • Cover crops
  • Mulch/soil matting
  • Strip cropping
  • Terracing
  • Contour farming
  • Crop rotation

Mass Wasting

• Mass wasting is the downhill movement of rock, soil, and debris due to gravity.

• Four main types:

  • Slumps: Downward movement of semi-consolidated material along curved surfaces (slow, short distance).
  • Rockslides: Very destructive, rapid movement of rocks along a plane.
  • Debris flow: Water-laden mass of various sizes of rocks and soil moving down a slope (high water content).
  • Earthflow: Flow of fine-grained material, often developing at the lower ends of slopes (slow, oozing).

• Prevention efforts: water drainage, slope stabilization, vegetation (roots anchor soil).

Rock Deformation

• Rocks experience stress (tensional, compressional, shear).
• Three phases of deformation
  • Elastic deformation: Reversible change in shape.
  • Ductile deformation: Permanent change in shape without breaking.
  • Fracture: Rock breaks under stress.
• Factors affecting rock response to stress include:
  • Material properties (brittle vs. ductile)
  • Temperature (higher temp. = more elasticity).
  • Water content (higher water content = more flexibility).