Weathering

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Weathering
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• Weathering is the physical and chemical breaking
  down of rock material into smaller fragments due
  to exposure to processes that occur at Earths
  surface
• Weathering occurs when rocks in the lithosphere
  are UPLIFTED and is exposed to the atmosphere,
  hydrosphere, and biosphere

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Weathering

• The most important agent involved in the
  weathering of material is WATER

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Two Types OF Weathering

• 1) Physical weathering is breaking rock by force
  into smaller pieces of the SAME material
• ex hitting, scratching, cracking

• 2) Chemical weathering is the chemical reaction
  of water and water vapor breaking down rock by
  changing its chemical composition
• The minerals that make up the rocks are changed
  into another substance

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4 Types of Physical Weathering

• 1) Frost action
• (ice wedging)-
• Water seeps into small cracks in rocks.
• When the water freezes it expands creating great
  pressure.
• The crack widens and allows water to seep deeper
  into the rock.
• Alternating Freezing and Thawing

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Examples of Frost Wedging Potholes
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• 2) Plant action-
• Tiny root hairs seek out small cracks and pits in
  rock.
• Once the root hairs find a place they grow and
  expand.
• The expansion causes great pressure and cracks
  the rock.

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• 3) Exfoliation
• Rocks formed deep in the Earth are made under
  high pressure.
• When the pressure is released the rocks expand
  crack.
• May also be caused by alternate heating and
  cooling of rocks by weather conditions.
• This is basically the peeling away of rock

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Water

• 4) Abrasion- rubbing by other rocks
• Scraping, grinding, and wearing away other rocks
  during erosion

WIND
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Types of Chemical Weathering

• Oxidation
• Hydrolysis (water)
• Carbonation (acid rain)

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• Oxidation-
• Oxygen in the atmosphere chemically reacts with
  minerals.
• ex. rusting

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• Water (hydrolysis)
• Minerals are dissolved in water.
• ex. Halite, calcite
• Much of the time these minerals will end up as
  clay

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• Acid- Carbonic acid
• C02 dissolves in rain water forming a weak acid.
• This acid dissolves the calcium carbonate
  (calcite) in limestones and marbles

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• Acid Rain Sulfur Dioxide in the atmosphere
  dissolves in rain water forming a strong acid
  (sulfuric acid).

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Carbonation Stalagtites and Stalagmites (karst
topography)
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Carbonation Karst Topography

• Karst Topography is the name given to a region
  where the bedrock is easily chemically weathered
• This leads to the rock weathering away and
  forming sinkholes, caverns, disappearing streams

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Karst Topography
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Differential Weathering

• Masses of rock do not weather uniformly due to
  regional and local factors
• Results in many unusual rock formations
• Example Bryce Canyon

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Bryce Canyon National Park
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Rates of weathering will be influenced by

• Surface area exposed - weathering occurs on the
  surface. More surface exposed, the faster the
  weathering will occur.

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A smashed piece has greatest surface area
exposed. The interior can now be attacked.
A full, solid block has the least surface area.
The interior is safe from exposure.
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Rates of Weathering will depend on

• Mineral composition- some minerals are more
  resistant than others.
• ex.Quartz is resistant to chemical and physical
  weathering.

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Where is the rock more resistant to weathering?
F
A
C
E
B
D
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Where is the rock least resistant to weathering?
F
A
C
E
B
D
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You might also see it like this
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You might also see it like this
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Rates of Weathering will depend on

• Climatic Conditions
• Cold and/or dry climates favor physical
  weathering.
• Warm and wet climates favor chemical weathering.
• Frost action works best in areas where the
  temperature fluctuates wildly.

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Soil - The product of weathering

• Soil- rocks, minerals (mainly sand and clay), and
  organic material (regolith and organic matter)
• Soil forms layers of different characteristics
  called horizons.

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Soil Horizons