1. Weathering
Pg. 69

2. Weathering
The process by which rocks on or near Earth’s surface break down and change
The removal and transport to other locations is erosion

3. Types of Weathering Mechanical – by physical processes Chemical –
Only changes the shape and size
Chemical –
Changes the chemical composition of the rock

4. Mechanical Weathering
Mechanical weathering is affected by:
Temperature-
Water freezes in rocks and causes them to expand and then contract eventually causing cracks (Frost Wedging)
Causes potholes
Pressure-
overlying rock is carried away, lower rock layers expand and create cracks known as joints
when outer rock layers are stripped away it is called exfoliation

5. Chemical Weathering Agents of chemical weathering: Water Oxygen
Can dissolve many rocks and minerals
Reaction of water with other substances called hydrolysis
Oxygen
Chemical reaction of oxygen w/ other substances called oxidation
Carbon dioxide
When combined w/ water, produces carbonic acid
Acids
Acid rain can degrade rocks (caused by sulfur dioxide and nitrogen oxides we put into the air)
Use pH to determine the acidity (the lower the more acidic)
5.6 is the pH of normal rainfall

6. Rate of weathering
Weathering occurs very slowly (2000 yrs to weather 1 cm of limestone)
Climate can influence the rate of erosion
Amount of rainfall, temperature, and evaporation
Chemical weathering occurs more in warmer wet climates (lots of organic material in soil that eventually produces carbonic acid)
Mechanical weathering occurs more in cooler dry climates
Rock Type
Sedimentary rocks more easily broken down
Surface area
The smaller the pieces, the more surface area, the more chemical weathering
Topography
Materials on slope undergo weathering more readily

7. Questions Pg. 70 Answer numbers 1-4 on page 161
Write both the question and answer

8. Questions 1. Distinguish between weathering and erosion.
2. List several variables that affect the rate of weathering.
3. What two climatic factors are most important in the weathering process?
4. Describe how one variable may affect another variable in the weathering process (i.e. how mechanical weathering can affect chemical weathering).
5. make a graph that would represent the relationship between the rate of weathering and the surface area of material.