Weathering GEO 124

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WeatheringGEO 124

• Introduction
• Geography, Landforms and Systems
• Mineralogy
• Rocks (Igneous, Sedimentary, Metamorphic)
• Earths Interior
• Plate Tectonics
• Oceans and Mountains
• Tectonic Structural Landforms
• Earthquakes
• Volcanism
• Weathering ?
• Mass Wasting
• Groundwater
• Surface Water Rivers
• Glacial Processes
• Coastal Processes

• Introduction to Surface Processes
• Introduction to Weathering
• Mechanical
• Chemical
• Controls
• Products and Landforms

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Form and Process

• Internal Forces (tectonism, volcanism)
• Uplift
• Subsidence
• External Forces (weathering, water, gravity,
  wind, ice)
• Erosion
• Deposition
• History
• Sequence of shapes and forces over time

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Test Wall (1948)
What happened to the wall?
The NIST Test Wall
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Weathering

• All In situ alteration and breakdown of rock and
  soil at or near the earths surface by physical,
  chemical or biotic processes
• Mechanical Increases surface area of material by
  physical disintegration of larger particles into
  smaller particles
• Chemical Breakdown of exposed minerals by
  chemical reaction with water, dissolved chemicals
  and air until they reach equilibrium with surface
  processes.

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Mechanical Processes

• Stress (Pressure) Release
• Frost Wedging
• Salt Weathering
• Thermal Expansion
• Wetting and Drying
• Organic Activity
• (Abrasion - erosion)

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Mechanical Weathering
What is happening to surface area?
Tasa Graphics, Inc.
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Results of Stress Release in Sierra Nevada, CA
What causes jointing?
Plummer, McGeary, Carlson. 2002. Physical Geology
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Stress (pressure) Release Diagram 1
Plummer, McGeary, Carlson. 2001. Physical Geology.
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Stress (pressure) Release Diagram 2
Plummer, McGeary, Carlson. 2001. Physical Geology.
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Enchanted Rock, Texas
http//home.att.net/SAScenics/EnchantedRock1.htm
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Effect of Frost shattering
National Geographic Society
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Frost Shattering 1
Water
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Frost Shattering 2
Ice
Water
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Frost Shattering 3
Ice
Water
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Talus Slope
Plummer, McGeary, Carlson. 2003. Physical Geology
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Weathering by Salt Crystallization in Mojave
Desert, CA
Plummer, McGeary, Carlson. Physical Geology
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Salt Weathering of Granite
http//itc.gsw.edu/faculty/bcarter/physgeol/weathe
r/mechwth4.htm
http//home.tiscali.nl/wr2777/Salt-weathering.htm
l
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Shattered Sandstone after fire
http//w3.salemstate.edu/lhanson/gls210/gls210_we
ath1.htm
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Thermal Expansion
Bland and Rolls. 1998. Weathering.
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Effects of Slaking on Eagle Ford Shale, TX
http//courses.unt.edu/hwilliams/GEOL_1610/fieldtr
ipsites/eagle_ford_shale.htm
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Root Wedging
Plummer, McGeary, Carlson. Physical Geology
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Weathering

• All In situ alteration and breakdown of rock and
  soil at or near the earths surface by physical,
  chemical or biotic processes
• Mechanical Increases surface area of material by
  physical disintegration of larger particles into
  smaller particles
• Chemical Breakdown of exposed minerals by
  chemical reaction with water, dissolved chemicals
  and air until they reach equilibrium with surface
  processes.

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Opportunity for chemical weathering?
Tasa Graphics, Inc.
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Selected Chemical Weathering Processes

• Solution
• Hydrolysis
• Oxidation

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Effects of Solution
Strahler and Strahler. 2000. Physical Geography.
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Solution 1
Tasa Graphics, Inc.
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Solution 2
Water Molecule removes elements
Tasa Graphics, Inc.
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Hydrolysis and Spheroidal Weathering
Plummer, McGeary, Carlson. 2002. Physical Geology
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Chemical Weathering of Potassium Feldspar by
Hydrolysis
Reaction between mineral elements and hydrogen
ions from disassociated water H replaces
elements
Plummer, McGeary, Carlson. Physical Geology
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Weathering rind in Granite mainly oxidation
http//marlimillerphoto.com/images/WE-29.jpg
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Oxidation Reaction
Oxidant Oxygen takes an electron as it combines
with the mineral Reductant loses electron
http//vishnu.glg.nau.edu/people/jhw/GLG101/Weathe
ring.html
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Weathering ControlsGLG 100

• Intrinsic (internal)
• Mineralogy
• Porosity
• Structure
• Extrinsic (external)
• Climate
• Water Table
• Vegetation
• Topography
• Humans

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Mineral Stability 1
mafic
felsic
Karen Lemke. UWSP
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Mineral Stability 2
mafic
felsic
Karen Lemke. UWSP
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Porosity
Sandstone
Granite
Which has more surface area?
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Texture Coarse and Fine
Which has more surface area (around particles)?
School of Ocean and Earth Science University of
Southampton. Southampton Oceanography Centre.
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Structural Effects
RW Christopherson. Geosystems 4ed.
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Cleopatras Needle
3500 years In Egypt
120 years in New York
http//www.bedford.k12.ny.us/flhs/science/images/d
efault.html
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Climate and Weathering
Geology Today. John Wiley and Sons.
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Water Table Position
Above water table
Below water table
Plummer, McGeary, Carlson. 2000. Physical Geology
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Biochemical Weathering in Norway
http//academic.brooklyn.cuny.edu/geology/leveson/
core/topics/weathering/picture_gallery/display/nor
way_68.html
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Slope Effects on Temperature in Northern
Hemisphere
N
S
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Aspect, Temperature and Moisture
Ahrens. 2002. Meteorology
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Acid Mine Drainage
Plummer, McGeary, Carlson. 2002. Physical Geology
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Rock Debris and Soil
Rock
Weathering
Erosion
Sediment
Transportation
Regolith
Deposition
Lithification
Soil Formation
Soil Formation
Rock
Residual Soils
Transported Soils
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Landform effects

• Duricrusts
• Laterite
• Caliche

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Laterite
Strahler and Strahler. 2000. Physical Geography.
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Laterite Formation
RW Christopherson. Geosystems 4ed.
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Caliche
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Petrocalcic Layer (Caliche)
Plummer, McGeary, Carlson. 2002. Physical Geology
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Caprock in Palo Duro Canyon, TX
http//www.texaswallpaper.com/0004-800.jpg
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Review

• What are the internal earth processes that build
  the surface?
• What are the external earth processes that wear
  the surface away?
• Where does weathering occur?
• What is mechanical (physical) weathering and how
  does it change rock?
• What is chemical weathering and how does it
  change rock?
• How and why do the following types of mechanical
  (physical) weathering affect rock and sediment
  stress release, frost action/hydro-fracturing,
  salt weathering, thermal expansion, hydration
  (slaking) and organic action?
• How and why does physical weathering alter a rock
  to make it more susceptible to chemical
  weathering?
• How and why do the following types of chemical
  weathering affect rock and sediment solution,
  hydrolysis, and oxidation?
• Which rocks are most susceptible to chemical
  weathering?
• How do chemical and mechanical (physical)
  weathering interact?
• How and why do intrinsic factors such as mineral
  composition, porosity, texture and structure
  affect the rate of weathering?
• How and why do extrinsic factors such as climate,
  water table position, topography (slope angle and
  aspect), and humans affect the rate of
  weathering?
• What are regolith and soil?
• What are duricrusts such as caliche and
  laterites, how are they created and how do they
  influence landforms?