8.2 Factors Influencing Weathering Rates

Climate and rock properties play crucial roles in weathering processes. Temperature, rainfall, and freeze-thaw cycles impact weathering rates, while rock composition and structure determine susceptibility. These factors shape landscapes, from tropical laterites to desert pavements.

Biological activity and time further influence weathering. Lichens, plants, and microorganisms accelerate mineral breakdown, while long-term exposure transforms bedrock into soil. Over geological timescales, these processes create diverse landforms like karst topography and inselbergs.

Climate and Rock Properties

Climate's impact on weathering rates

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Top images from around the web for Climate's impact on weathering rates

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  Frontiers | Use of Mineral Weathering Bacteria to Enhance Nutrient Availability in Crops: A Review View original

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• 

  Frontiers | Soil Moisture but Not Warming Dominates Nitrous Oxide Emissions During Freeze–Thaw ... View original

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• 

  Frontiers | Mineral Weathering and Podzolization Control Acid Neutralization and Streamwater ... View original

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• 

  Frontiers | Use of Mineral Weathering Bacteria to Enhance Nutrient Availability in Crops: A Review View original

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  Frontiers | Soil Moisture but Not Warming Dominates Nitrous Oxide Emissions During Freeze–Thaw ... View original

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• Higher temperatures accelerate chemical reactions increase mineral dissolution rates (calcite in limestone)
• Freeze-thaw cycles in cold climates cause physical weathering expand water in rock cracks
• Increased rainfall promotes chemical weathering dissolves minerals and acids in soil
• Water acts as a solvent for minerals carries dissolved ions away from parent rock
• Facilitates hydrolysis reactions breaks down silicate minerals (feldspar to clay)
• Tropical regions experience faster weathering due to high heat and moisture create laterite soils
• Arid regions have slower weathering rates form desert pavements
• Wet seasons intensify chemical weathering leach nutrients from soil
• Dry seasons may lead to salt crystallization and physical weathering form tafoni in sandstone

Rock properties in weathering susceptibility

• Igneous rocks generally more resistant than sedimentary rocks withstand erosion longer (granite vs sandstone)
• Minerals with higher silica content are more resistant form resistant landscape features (quartz ridges)
• Calcite dissolves more readily than quartz creates limestone caves and sinkholes
• Feldspars are susceptible to chemical weathering break down into clay minerals (kaolinite)
• Fine-grained rocks weather more slowly than coarse-grained rocks resist water penetration (basalt vs granite)
• Presence of fractures and joints increases weathering rates allow water and roots to penetrate
• Larger surface area-to-volume ratio increases weathering rates accelerates breakdown of small particles
• Smaller rock fragments weather faster than larger ones create soil more quickly
• Higher porosity allows greater water penetration increases chemical weathering in sandstone
• Increased permeability facilitates chemical weathering allows faster mineral dissolution in gravel beds

Biological and Temporal Factors

Biological activity in weathering processes

• Lichens produce organic acids dissolve minerals create pits on rock surfaces
• Lichens cause physical weathering through thallus expansion and contraction break apart rock fragments
• Mosses retain moisture on rock surfaces promote chemical weathering of underlying rock
• Mosses enhance chemical weathering maintain humid conditions on rock surfaces
• Plant roots cause mechanical weathering grow into cracks and expand
• Plant roots induce chemical weathering release organic acids that dissolve minerals
• Bacteria and fungi accelerate mineral decomposition produce organic and inorganic acids
• Biofilms on rock surfaces increase chemical weathering trap moisture and produce acids
• Burrowing organisms expose fresh rock surfaces bring unweathered material to surface (earthworms)
• Burrowing increases soil aeration and water infiltration enhance chemical weathering processes

Time factor in landscape weathering

• Weathering intensity increases over geological time scales transform solid bedrock into soil
• Gradual breakdown of resistant minerals form sand grains from quartz (beach sand)
• Formation of soil profiles develop distinct horizons (O, A, B, C horizons)
• Development of karst topography create caves and sinkholes in limestone regions
• Longer exposure leads to more extensive weathering deepen soil profiles over time
• Newly exposed surfaces weather more rapidly initially slow down as resistant minerals remain
• Weathering rates may decrease as easily weathered materials are removed leave behind resistant minerals
• Resistant materials remain as residual features form inselbergs in tropical regions
• Erosion exposes fresh surfaces for weathering maintain active weathering in mountain ranges
• Tectonic uplift renews weathering potential create steep slopes prone to physical weathering