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Weathering, Erosion & Soils

Weathering, Erosion & Soils. Weathering is the the breakdown of solid rock at or near the Earth's surface. Weathering may be mechanical or chemical. Mechanical weathering is the physical abrasion due to the action of: Water (Streams, Rivers and Surf) Ice (Frost, Snow, Glaciers) Wind

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Weathering, Erosion & Soils

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  1. Weathering, Erosion & Soils Weathering is the the breakdown of solid rock at or near the Earth's surface.

  2. Weathering may be mechanical or chemical • Mechanical weathering is the physical abrasion due to the action of: • Water (Streams, Rivers and Surf) • Ice (Frost, Snow, Glaciers) • Wind • Chemical weathering is the chemical reaction of minerals with the water and oxygen of our atmosphere.

  3. Mechanical Weathering • Mechanical Action of Streams and Rivers

  4. Mechanical Weathering • By the Action of Ice

  5. Mechanical Weathering • By the action of Wind

  6. Chemical weathering • By oxidation, hydration, or biological activity

  7. Chemical Weathering:Exfoliation

  8. Chemical Weathering • Increases with Temperature • Increases with Moisture (Rainfall) • Increases with Acidity • Decreases with Silica Polymerization (Bowen’s Reaction Series)

  9. Chemical Weathering of Igneous Rock Minerals • Oxides > Hydroxides • Ferromags > Mg-Fe Clay • Feldspar > Al-Clay + Na+ + K+ + Ca++ • Mica > Al-Fe Clay + Na+ + K+ + Ca++ • Quartz > Quartz Sand

  10. Erosion and Transport • Erosion is the reduction of exposed landforms. • Transport is the movement of eroded material down slope. • Transport by water sorts the particles by size. • Because different minerals dominate different size fractions, the deposited material differs from the parent rock in mineralogy and chemistry.

  11. Weathering Products Are Sorted by Size • Coarse particles require moving water or wind • Rock grains: Pebbles, Cobbles, Boulders • Quartz: Pebbles and Sand • Fine particles require standing water. • Clays Very fine (<10 mm) • Dissolved ions require evaporation • Na+ + K+ + Ca++ Dissolved

  12. Depositional Environments

  13. Soils • Aregolithis any accumulation of fine rock material on a planetary surface. • A soil is the accumulation of weathered rock material together with organic matter. • A pedocalis a dry-climate soil containing soluble calcium minerals (calcite). • A pedalfer is a humid-climate soil rich in Al and Fe. • A laterite is an extreme pedalfer in tropical climates.

  14. Soil Types

  15. Laterites are Tropical Soils

  16. Soil Changes in US

  17. Acid Rain • Results from burning of sulfur-rich fossil fuels (mainly coal). • Is mainly a problem in humid temperate climates (NE US, Europe).

  18. Acid Mine Drainage • Results from oxidation of sulfide minerals (pyrite) in unsaturated rock. • 2FeS2 +7H2O + 2O2 > 2Fe(OH)3 + 4H2SO4 • Pyrite + water + oxygen > limonite + sulfuric acid • Big Problem in CO

  19. Acid Mine Drainage

  20. Chemical weathering Mechanical weathering Spheroidal weathering Pedocal Pedalfer Laterite Bauxite Hydration Oxidation Exfoliation Erosion Soil Regolith Humus Acid mine drainage Weathering Terms

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