Name _________________________________________ Date ____________

Period ____

Mechanical vs. Chemical Weathering

What is weathering? Weathering is the process by which exposed rocks and other materials break down. The surface of the Earth is constantly changing due to the process of weathering. There are 2 types of weathering: mechanical and chemical. Mechanical weathering is the process of breaking rock into smaller pieces by mechanical or physical means. Chemical weathering is weathering that changes the chemical composition of rocks.

Key Things to explore in Chapter 8.1

1. Be able to describe the causes of mechanical weathering
2. Be able to describe the cause of chemical weathering
3. Compare and contrast mechanical and chemical weathering
4. Predict the rates of weathering

Type of Weathering	Mechanical or Chemical	How it works	What is the result
Ice Wedging	Mechanical	Water enters cracks in rocks and freezes	As water melts and freezes over a period of time it will cause the rock to expand and break apart
Plant Weathering	Mechanical	Wind carries seeds into cracks in the rocks	Seeds will grow and the roots will break apart the rocks
Animal Weathering	Mechanical	Animals digging into the ground	Holes in ground allow air and water to get in the ground and will cause weathering to happen faster. As animals dig they will disturb the rock and make it weak
Temperature Change	Mechanical	Sun warms up surface of rock in day- heat causes rock surface to expand At night process is reversed	Day after day as this happens it will eventually cause the surface of rock to crack and flake off
Water Abrasion	Mechanical	Rivers and streams carry particles of rock and sand- particles scrap against each other and other rocks as water moves by	After time this will cause rock to break down and smooth out
Wind Abrasion	Mechanical	Wind carries sand, dust, and small rock particles over a region. Particles scrap against the surface of rocks	After time it can polish and flatten the sides of rocks
Oxidation	Chemical	Rust- iron + oxygen= iron oxide or rust	Causes rocks to eventually fall apart
Water	Chemical	Water dissolves minerals and can also combine with gasses in the air to form acids	Causes rocks to change composition or fall apart
Carbonation	Chemical	Carbonic acid	Causes holes and small pits in rocks which will cause them to fall apart
Sulfuric Acid	Chemical	Burning of fossil fuels release sulfur dioxide in the air. Water vapor + sulfur dioxide forms sulfuric acid	Sulfuric acid rain will cause materials to fall apart and will also cause harm to plants and fist
Plant and Fungal Acids	Chemical	Some plants/fungi make acids	Acids will come from root tips and dissolve rocks and minerals

What are the factors that affect weathering?

a. Type of rock

a. Weaker= weathers faster

b. Cracked/holes= weathers faster

b. Climate

a. Climate= precipitation, location, and temperature

b. Warm, moist climates will cause weathering to occur faster