Weathering and Soil

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Soil Weathering
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Weathering

• The breakdown of materials of Earths crust into
  smaller pieces.

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Mechanical Weathering

• Process by which rocks are broken down into
  smaller pieces by external conditions.
• Types of Physical weathering
• Frost wedging
• Plant roots
• Friction and impact
• Burrowing of animals
• Temperature changes

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Frost Wedging
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Plant Roots
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Friction and Repeated Impact
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Burrowing of Animals
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Temperature Changes
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Questions
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Chemical Weathering

• The process that breaks down rock through
  chemical changes.
• The agents of chemical weathering
• Water
• Oxygen
• Carbon dioxide
• Living organisms
• Acid rain

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Water

• Water weathers rock by dissolving it

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Oxygen

• Iron combines with oxygen in the presence of
  water in a processes called oxidation
• The product of oxidation is rust

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Carbon Dioxide

• CO2 dissolves in rain water and creates carbonic
  acid
• Carbonic acid easily weathers limestone and marble

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Living Organisms

• Lichens that grow on rocks produce weak acids
  that chemically weather rock

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Acid Rain

• Compounds from burning coal, oil and gas react
  chemically with water forming acids.
• Acid rain causes very rapid chemical weathering
• Acid rain has the same ph level as tomato juice

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Soil

• What is soil?
• Loose mixture of weathered rock, organic matter,
  water, and air
• Is chemically and physically different from
  parent material

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Soil Horizon

• Soils have distinct zones that roughly parallel
  land surface

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Horizon Layers

• Typical soil profile
• O horizon -- dark organic matter
• A horizon -- contains some organic matter but
  many minerals are removed from this layer
  Lighter-colored than O
• B horizon -- contains decomposed rock such as
  clay, iron oxides, calcite may be red, yellow,
  or tan
• C horizon -- slightly altered parent material

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Soil Horizons in Archaeology
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Ashland, home of Henry Clay
Soil Horizon ?
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Can you see the layers?
Monticello, VA
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Can you figure out the layers?

• Which is horizon O, A, B, C?

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Erosion

• The process by which water, ice, wind or gravity
  moves fragments of rock and soil.

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Water Erosion

• Rivers, streams, and runoff

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Ice Erosion

• Glaciers

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Wind Erosion
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Mass Movements

• Landslides, mudslides, slump and creep

landslide clip.mpeg
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POP QUIZ TIME!!

• You may use your notes

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POP QUIZ TIME!!

• What is mechanical weathering?

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POP QUIZ TIME!!

1. What are the two types of weathering?

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POP QUIZ TIME!!

1. What are the two types of weathering?
2. Acid rain is which type of weathering?

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POP QUIZ TIME!!

• What are the two types of weathering?
• Acid rain is which type of weathering?
• Iron combines with what 2 things to form rust?

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POP QUIZ TIME!!

• What are the two types of weathering?
• Acid rain is which type of weathering?
• Iron combines with what 2 things to form rust?
• Frost wedging animal burrowing are which type
  of weathering?

34
POP QUIZ TIME!!

• What are the two types of weathering?
• Acid rain is which type of weathering?
• Iron combines with what 2 things to form rust?
• Frost wedging animal burrowing are which type
  of weathering?
• Which horizon has dark, organic matter?

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POP QUIZ TIME!!

• What are the two types of weathering?
• mechanical chemical
• Acid rain is which type of weathering?
• chemical weathering
• Iron combines with what 2 things to form rust?
• oxygen water
• Frost wedging animal burrowing are which type
  of weathering?
• mechanical
• Which horizon has dark, organic matter?
• Horizon O