Chapter 5 Weathering, Soils, & Mass Movements

What do you know? What process breaks down rock into smaller pieces? A.) cementation B.) compaction C.) weathering D.) deposition Answer – C.) weathering

What do you know? Which of the following are types of weathering? Mechanical? Chemical? Answer: Both are forms of weathering

Mechanical Weathering physical forces break rock into smaller without changing rock’s mineral composition Each piece has the same characteristics as the original rock

Mechanical Weathering Mechanical Weathering Animation Mechanical Weathering How does surface area affect weathering? increases as breakup a rock

Mechanical Weathering of Rocks 3 types 1 2 Unloading Frost wedging 3 Root wedging

1. Unloading What is it? Large masses of igneous rock exposed through uplifting and erosion of overlying rocks

2. Frost Wedging 1. Mechanical breakup of rock caused by expansion of freezing water in cracks and crevices 2. Sections of rock that are wedged loose and fall apart Frost Wedging Animation Can of coke explodes when it is frozen!

Frost Wedging

3. Biological Activity What is it? 1. Plant roots can grow into cracks in rock and wedge rock apart as they grow 2. Burrowing animals move rocks to surface, where weathering is more rapid

Chemical Weathering What is it? Chemical weathering - transformation of rock into one or more new compounds If I gave you a piece of paper, how would you show me mechanical weathering? How would you then show me chemical weathering?

Chemical Weathering Agents of Chemical Weathering 1. Water (rain) 2. Carbon Dioxide (CO2)

How does carbonic acid cause chemical weathering? Rain mixes with CO2 (gas) in atmosphere Rain + CO2 = carbonic acid Carbonic acid dissolves and breaks down rocks

Chemical Weathering Examples (1) Rust Iron on barrels coverts to rust Iron + oxygen (from air) coverts to iron oxide (rust)

Chemical Weathering Examples (2) Acid Rain Rain + sulfur + nitrogen = acid rain Where does sulfur and nitrogen come from? burning fossil fuels- like coal & gasoline

Chemical Weathering “Acid Rain” Acid rain accelerates the chemical weathering of stone monuments and structures

Chemical Weathering Exposure to moisture and oxygen turns the copper into copper sulfate which is green in color.

Chemical Weathering Examples (3) Cave formation Rain + CO2 = carbonic acid Carbonic acid enters soil Areas where soil contains limestone can form caves

Chemical Weathering Examples (4)- Sinkholes Rain + CO2 = carbonic acid Carbonic acid weathers holes in limestone rock