Transcript File - Earth Science with Mrs. Cox

WEATHERING AND SOIL
Chapter 5
Weathering
- breaking down of rocks
Types
1) Mechanical Weathering
- physical forces that break rock
Occurs 3 Ways:
1) Frost Wedging- water inside rocks freezes
2) Unloading- uplifting of rock, causing pieces
to break off
3) Biological- organism activity breaks rocks
Frost Wedging
Unloading
Biological Activity
2) Chemical Weathering
- transformation of rock into new compounds
* water is the main chemical agent
- carries O2, CO2, SO2
Factors Affecting Weathering
1) Rock Characteristics
- hardness of minerals
- softer minerals weather faster
2) Climate
- temperature & moisture
- most important factor
- hot, wet climates weather rocks faster
Soil Composition
- minerals, air, water, organic matter
Factors Affecting Soil Formation
1) Type of Parent Material (mineral source)
2) Time (thicker soils take time)
3) Climate (temperature/moisture)
4) Organisms (plants, burrowing animals)
5) Slope of the land (steep slopes lose soil)
Soil Profile
- divided into soil horizons (layers)
3 Horizons
1) A Horizon- upper layer (topsoil), soft, loose soil
2) B Horizon- middle layer (subsoil), mostly clay
3) C Horizon- bottom layer, very rocky, less soil
SOIL PROFILE
Soil Types
1) Pedalfer- found in warm, forested areas
2) Pedocal- found in dry areas
3) Laterite- found in hot, wet, tropical areas
Soil Erosion
- carrying away of topsoil by water
- can be slowed down by vegetation
Mass Movement
- movement of rock & soil down a slope due
to gravity.
Causes
1) Water- example: heavy rainfall
2) Steep slopes
3) Removing vegetation- plant roots hold soil
4) Earthquakes
Types of Mass Movements
1) Rockfalls
- rocks breaking from steep slopes
2) Slides
- rocks sliding due to rain/snow
- fast moving
3) Slumps
- small areas of soil sink down slope
4) Flows
- movement of soil that is saturated
with water.
5) Creep
- very slow movement of soil down slope
- caused by freezing & melting of water
inside the soil.