Soil - The product of weathering

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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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Weathering
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• Weathering is the process that produces change in
  the surface of rocks exposed to the atmosphere
  and/or hydrosphere.
• The breakdown of the materials of the Earths
  crust into smaller pieces

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Two Types OF Weathering

• Physical weathering is breaking rock by force.
• ex hitting, scratching, cracking

• Chemical weathering is where the rock material is
  changed into another substance by reacting with a
  chemical.

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• 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.

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Frost Wedging
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• 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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Plant Roots
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• 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.

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• Abrasion- rubbing by other rocks.

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Friction and Repeated Impact
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• Oxidation-
• Oxygen in the atmosphere chemically reacts with
  minerals.
• ex. rusting of a nail

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• Water (hydrolysis)
• Minerals are dissolved in water.
• ex. Halite, calcite

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• Acid- Carbonic acid
• C02 dissolves in rain water forming a weak acid.

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• Acid Rain Sulfur Dioxide in the atmosphere
  dissolves in rain water forming a strong acid
  (sulfuric acid).
• Wanna hear how acid rain was discovered?

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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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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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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

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Karst Topography

• A type of landscape in rainy regions where there
  is limestone near the surface, characterized by
  caves, sinkholes, and disappearing streams.
• Created by chemical weathering of limestone

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Features of Karst Sinkholes
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Features of Karst Caves
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Features of Karst Disappearing Streams
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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

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