Chapter 10 – Weathering,
Soil and Erosion
Earth Science and the Environment (4th ed)
Thompson & Turk
10.1 Weathering and erosion
►Weathering – processes that decompose
rocks into sediments
 Mechanical (physical) weathering...
10.2 Mechanical weathering
► Pressure release
fracturing – formerly
buried rocks expand
when uncovered
► Frost wedging – w...
Weathering Con’t
► Organic activity – roots
► Thermal expansion /
contraction
Organic Action
Thermal Expansion
10.3 Chemical weathering
► Dissolution – many
minerals dissolve to
some degree
► Hydrolysis – reaction
with water, new
min...
Destructional -Weathering
Landscapes broken down by
chemical & physical processes & erosion
Physical
► includes temperatur...
Factors affecting the
RATE of weathering
Factors affecting
the RATE of Weathering
► Surface area
 Increases the areas exposed to water,
chemicals and wind.
► Time...
Erosion
►Erosion is the
MOVEMENT of the
particles once they
have been
weathered.
►Erosion is caused by
both wind and
water.
Creation of Rock vs Soil
► Sedimentary Rock
formation follows
weathering and
erosion when the
particles undergo
compaction...
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HPU NCS220 Weathering and erosion

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HPU NCS2200 Earth Science for Elementary Education Majors Summer 2014 online course Weathering and erosion lecture

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HPU NCS220 Weathering and erosion

  1. 1. Chapter 10 – Weathering, Soil and Erosion Earth Science and the Environment (4th ed) Thompson & Turk
  2. 2. 10.1 Weathering and erosion ►Weathering – processes that decompose rocks into sediments  Mechanical (physical) weathering – physical disintegration without chemical change  Chemical weathering – reaction with air/water creates a product different physically and chemically
  3. 3. 10.2 Mechanical weathering ► Pressure release fracturing – formerly buried rocks expand when uncovered ► Frost wedging – water in cracks expands when frozen ► Abrasion – rock particles moving in contact wear each other away
  4. 4. Weathering Con’t ► Organic activity – roots ► Thermal expansion / contraction Organic Action Thermal Expansion
  5. 5. 10.3 Chemical weathering ► Dissolution – many minerals dissolve to some degree ► Hydrolysis – reaction with water, new mineral forms ► Oxidation – reaction with oxygen, new mineral forms
  6. 6. Destructional -Weathering Landscapes broken down by chemical & physical processes & erosion Physical ► includes temperature changes (freezing and thawing, thermal expansion), crystal growth, pressure, plant roots, burrowing animals ► causes disintegration of parent material and facilitates chemical weathering Chemical ► always in water ► includes hydration, hydrolysis, oxidation, reduction, carbonation and exchange ► examples :  oxidation of Fe to form limonite, deposited in joints, inhibits groundwater flow  hydrolysis of feldspars to form clay (kaolin) - forms infill for joints
  7. 7. Factors affecting the RATE of weathering
  8. 8. Factors affecting the RATE of Weathering ► Surface area  Increases the areas exposed to water, chemicals and wind. ► Time  The longer a rock is exposed the more weathering will occur ► Composition  Some minerals are more susceptible to chemical reaction ► Climate  Chemical reactions are sped up with high temperatures and moisture
  9. 9. Erosion ►Erosion is the MOVEMENT of the particles once they have been weathered. ►Erosion is caused by both wind and water.
  10. 10. Creation of Rock vs Soil ► Sedimentary Rock formation follows weathering and erosion when the particles undergo compaction and cementation this usually occurs at the bottom of lakes and oceans but can occur anywhere layers of sediment accumulate and are not disturbed. ►Soil formation occurs when weathered and eroded rock material mixes with humus or organic material and accumulates.

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