WEATHERING AND SOIL Chapter 5 Weathering breaking down

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 O 2, CO 2, SO 2

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.