weathering, erosion & soil formation
DESCRIPTION
WEATHERING, EROSION & SOIL FORMATION. WEATHERING, EROSION, TRANSPORTATION. Weathering - Physical disintegration and chemical decomposition of rocks Erosion - Physical removal Transportation - Movement of eroded particles Chemical vs. Physical Weathering Effects of weathering - PowerPoint PPT PresentationTRANSCRIPT
WEATHERING, EROSION & SOIL
FORMATION
WEATHERING, EROSION, TRANSPORTATION
• Weathering- Physical disintegration and chemical decomposition of rocks
• Erosion- Physical removal• Transportation- Movement of eroded particles• Chemical vs. Physical Weathering• Effects of weathering
– Surface alteration of outcrops– Spheroidal weathering– Differential weathering
Physical Weathering
Transport
Abrasion
WEATHERING, EROSION, TRANSPORTATION
• Weathering- Physical disintegration and chemical decomposition of rocks
• Erosion- Physical removal• Transportation- Movement of eroded
particles• Chemical vs. Physical Weathering• Effects of weathering
– Surface alteration of outcrops– Spheroidal weathering– Differential weathering
Differential Weathering
MECHANICAL WEATHERING
• Disintegration of rocks• Frost Action
– Frost wedging - rock pried apart along joints
• water expands upon freezing (ice wedge)– Frost heaving
Frost Action
MECHANICAL WEATHERING
• Pressure Release– sheet joint– exfoliation
• exfoliation domes
• Other– Plant growth; Burrowing animals– Pressure of salt crystals– Extreme temperature changes
• Mechanical weathering increases surface area facilitating chemical weathering
Exfoliation
Organic Action
Mechanical Weathering
Growth of salt crystal in arid/semi-arid regions can split rocksHeat and cold extremes can also cause rock breakage
CHEMICAL WEATHERING
• Decomposition of rock to form new substances– Equilibrium
• Role of Oxygen– Fe in ferromagnesian minerals becomes
oxidized • Hematite• Limonite
Chemical Weathering
• Role of Acid– Hydrogen ions in water– pH=-Log[H+] Acid/Base
• Carbonic Acid H2CO3– CO2 + H2O -> H2CO3
– H2CO3 -> H+ + HCO3- (in water)
– Solution weathering- Karstic Features• Calcite (in limestone) dissolves in acidic water• fluted (channeled) rock surface• caves
Chemical Weathering• Role of Acid
– Hydrogen ions in water– pH=-Log[H+] Acid/Base
• Carbonic Acid H2CO3– CO2 + H2O -> H2CO3
– H2CO3 -> H+ + HCO3- (in water)
– Solution weathering- Karstic Features• Calcite (in limestone) dissolves in acidic water• fluted (channeled) rock surface• caves
KARST
Chemical Weathering
• Chemical weathering of feldspar– H+ + feldspar -> clay mineral
• Chemical weathering of other minerals• Weathering and climate• Weathering Products
Chemical Weathering
• Chemical weathering of feldspar– H+ + feldspar -> clay mineral
• Chemical weathering of other minerals• Weathering and climate• Weathering Products