Rocks and minerals break down through physical and processes. splits rocks without changing their chemistry, while chemical weathering alters their composition. These processes work together to shape Earth's surface and create soils.
Chemical weathering involves reactions like , , and . These reactions produce clay minerals, , and crucial for and . Understanding these mechanisms is key to grasping Earth's geochemical cycles.
Physical Weathering Mechanisms
Physical vs chemical weathering
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5.4 Weathering and the Formation of Soil – Physical Geology View original
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Rock Weathering CO2 Cycle (with annotations) View original
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Top images from around the web for Physical vs chemical weathering
5.4 Weathering and the Formation of Soil – Physical Geology View original
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Putting It Together: Rocks and the Rock Cycle | Geology View original
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Rock Weathering CO2 Cycle (with annotations) View original
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5.4 Weathering and the Formation of Soil – Physical Geology View original
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Putting It Together: Rocks and the Rock Cycle | Geology View original
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Physical weathering mechanically breaks down rocks and minerals without altering chemical composition resulting in smaller fragments and increased for chemical weathering
Chemical weathering alters rock and mineral composition through reactions with , air, or producing new minerals or dissolved substances transforming original material
Mechanisms of physical weathering
occurs when water enters rock cracks, freezes, and expands exerting pressure causing fragmentation through repeated freeze-thaw cycles
stresses rocks as different minerals expand and contract at varying rates during daily fluctuations leading to fracturing over time
exerts pressure on rock structures when salt-laden water enters pores, evaporates, and leaves growing crystals (common in coastal and arid environments)
Chemical Weathering Mechanisms
Chemical weathering reactions
Hydrolysis replaces mineral cations with H+ and OH- ions from water ( to clay minerals)
KAlSi3O8+H2O→HAlSi3O8+K++OH−
Oxidation occurs between minerals and oxygen, common in iron-bearing minerals (pyrite oxidation)
4FeS2+15O2+14H2O→4Fe(OH)3+8H2SO4
Carbonation dissolves minerals using carbonic acid formed by dissolved CO2 in water (limestone dissolution)
CaCO3+H2CO3→Ca2++2HCO3−
Products of chemical weathering
Clay minerals result from silicate weathering, have high , retain nutrients and water in soil
Metal oxides and hydroxides form from oxidation reactions, contribute to soil color and structure (iron oxides in red soils)
Dissolved ions released during mineral dissolution provide essential nutrients for plant growth (Ca, Mg, K, phosphate)
Carbonates and bicarbonates buffer soil pH and influence water hardness in aquatic systems
Organic acids produced by plant roots and soil microorganisms enhance mineral weathering rates and nutrient availability