Weather and Weathering

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Weather and Weathering
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(No Transcript)
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Plate Tectonic Wrap-up

• Locations of
• Basalt/Andesite/Rhyolite

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Hot spots

• Long-lived volcanic centers
• Many on mid-ocean ridges why?
• Stationary vs. apparent motion

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Hawaiian hot spot
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Yellowstone Hot Spot

• Eruptive pattern
• Bimodal volcanism

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Volcanoes and Climate

• Dust veil index
• Hemispheric cooling
• Case study Toba

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Volcanoes and Climate

• Dust veil index
• Hemispheric cooling
• Case study Toba

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Weathering weather climate

• Climate
• Water availability
• Temperature

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Weathering weather climate

• Climate
• Water availability

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Weathering weather climate

• Climate
• Water availability
• Temperature

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Weathering (Dis)Equilibrium

• Rock Environment
• Pressure high
• Temperature constant
• Water constant?
• Earth Surface Environment
• Pressure low
• Temperature variable
• Water variable

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Types of Weathering

• Chemical decomposition
• Interactions at the molecular level
• E.g., hydration
• Mechanical (Physical) disintegration
• Interactions at higher levels
• E.g., ice wedging
• Salt?

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Surface area
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Types of Chemical Weathering I

• Hydration
• Addition of water to the structure
• Swelling clays
• Hydration of biotite
• Grussification

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Types of Chemical Weathering II

• Hydrolysis
• Replacement of cations ( charge) with hydrogen
  ions
• Feldspars ? clay minerals

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Types of Chemical Weathering III

• Oxidation
• Oxygen accepts loose electrons (anion)
• Creates stronger cations
• Allows bonding to weak ions (e.g., OH-)
• E.g., Iron oxide (rust hematite/limonite) and
  aluminum oxide

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Types of Chemical Weathering III
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Types of Chemical Weathering IV

• Chelation
• Biotic facilitation of weathering
• Physical chemistry models lie!

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Types of Chemical Weathering V

• Solution
• Polar water molecules bond more strongly to ions
  than ions do to mineral structures
• E.g., salts NaCl, CaCO3

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Relative Weatherability

• Goldich Stability Series

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Relative Weatherability
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Relative Weatherability

• Goldich Stability Series
• But

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Weathering vs. Erosion
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Rates of Chemical Weathering

• Rates f(disequilibrium)
• Decrease at a decreasing rate
• With time, depth, temperature

http//www.usyd.edu.au/su/agric/ACSS/sphysic/pedog
enesis/pedogenesis.html
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Outside-in weathering corestones

• Because weathering f(depth)

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Weathering with Climate

• Dominant controls?

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Results of Chemical Weathering

• Removal of unstable materials
• E.g., CaCO3
• Retention of stable materials
• E.g., quartz
• Creation of new stable material
• E.g., clay minerals

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Soil Formation

• Hans Jennys 5 soil-forming variables
• Parent mat.
• Topography
• Organisms
• Climate
• Time

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Soil Formation, Classification, Distribution and
Application
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Soil Horizons

• Building blocks
• O organic
• A OM-rich, leached
• B accum.
• C little altered
• Subdivisions

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USDA Soil Classification

• Descriptive language for communication
• Soil orders (n12)
• Based on one criterion
• Suborders (nhundreds)
• Secondary criteria
• http//soils.usda.gov/technical/classification/tax
  _keys/index.html
• Gradations
• Intergrades