Weathering and Soil Weathering and Soil FormationFormation

SWBAT identify processes that break SWBAT identify processes that break rock apart; describe processes that rock apart; describe processes that

chemically change rock; explain how chemically change rock; explain how soil evolves.soil evolves.

WeatheringWeathering

• Weathering – a mechanical or chemical surface process

that breaks rocks into smaller pieces.

• Quick Review:– What is the difference between a physical or

mechanical change and a chemical change?

Mechanical WeatheringMechanical Weathering

• Mechanical weathering – does NOT change them chemically.

• What are two causes of mechanical weathering?– Ice wedging

• Water seeps into cracks then freezes creating larger cracks.

– Plants and animals• Animals burrow into ground• Plant roots break up the ground

Chemical WeatheringChemical Weathering

• Chemical weathering – when the chemical composition of rock

changes.

• What type of climate is causes chemical weathering to happen the quickest?– Tropical regions where it is moist and warm

Chemical WeatheringChemical Weathering

• What are 3 things that can cause chemical weathering?– Natural acids

• Formed when water mixes with natural elements such as carbon dioxide

– Plant acids• Plants produce tannin which can form into an acid

that can dissolve minerals

– Oxygen• Can cause chemical changes through oxidation

SoilSoil

• Soil – a mixture of weathered rock, organic matter,

water, and air that supports plant life.

• What 5 factors affect soil formation?– Parent rock– Slope of land– Climate – Time– Organisms

SoilSoil

• Topography– surface features

• For Tomorrow: – bring in a sample of soil from around your

house, for an in class activity.

Homework:Homework:

• On a separate sheet of paper answer self check questions 1-5 on page 321.

• Be sure to use complete sentences.

• You may work with a partner.