1. Weathering and Soil Formation

2. The Effects of Weathering
Weathering is the process that breaks down rock and other substances on Earth's surface.
What contributes to weathering?
Heat
Cold
Water
Ice

3. The Effects of Weathering
Forces of weathering break rock into smaller pieces.
Erosion carries the pieces away.
Erosion is the movement of rock particles by wind, water, ice, or gravity
There are two kinds of weathering:
Mechanical weathering
Chemical weathering

4. Mechanical Weathering
Weathering where rock is physically broken into smaller pieces is called mechanical weathering.
smaller pieces have the same composition as the original rock
Mechanical weathering breaks rock by
Freezing and thawing (Ice wedging)
Pressure
Growth of plants
Actions of animals
Abrasion
Abrasion is the grinding away of rock, by rock particles carried by water, ice, wind, or gravity.

5. Mechanical Weathering

7. Chemical Weathering
Chemical weathering is the process that breaks down rock through chemical changes.
The agents of chemical weathering include:
Water
Oxygen
Carbon dioxide
Living organisms
Acid precipitation (acid rain)
Chemical weathering produces rock particles that have a different mineral makeup from the rock they came from.

8. Chemical Weathering

9. Chemical and Mechanical Weathering
Chemical and mechanical weathering often work together.
11. As mechanical weathering breaks rock into pieces, more surface area becomes exposed to chemical weathering.

10. Water and weathering How does water contribute to weathering?
12. Water is the most important agent of chemical weathering.
Water weathers rock by dissolving it.
Over time, many rocks will dissolve in water.

11. Water and weathering
13. Water can also freeze, expand in rock and break it apart. (Ice wedging)

12. Oxygen How does oxygen contribute to weathering?
The oxygen in the air is an important cause of chemical weathering.
Think of a Bicycle or metal tool left outside in the rain
Iron combines with oxygen in the presence of water in a process called oxidation.
The product of oxidation is rust.
Rust makes rock and metal soft and crumbly

13. Oxygen

14. Living Organisms How do living organisms contribute to weathering?
Weak acids around the roots slowly dissolve rock chemically.

15. Acid Rain How does acid rain contribute to weathering?
Over the past 150 years, people have been burning large amounts of fossil fuels (coal, oil, and gas) for energy.
Burning these fuels can pollute the air.
These fuels react chemically with the water vapor in clouds, forming acids.
These acids mix with raindrops and fall as acid rain.
Acid rain causes very rapid chemical weathering like the picture seen before…..

16. Chemical Weathering

17. Rate of Weathering
The most important factors that determine the rate at which weathering occurs are
Type of rock
Sedimentary, Igneous, Metamorphic
Climate

18. Permeable Rocks Some rock weathers easily because it is permeable.
Permeable means that a material is full of tiny, connected air spaces that allow water to seep through it.
Permeable rock weathers chemically at a fast rate

19. Climate How does climate contribute to weathering?
Climate refers to the average weather conditions in an area.
It’s not the same thing as weather.
Both chemical and mechanical weathering occur faster in wet climates.
Chemical reactions occur faster at higher temperatures.

20. Climate and Weathering