1. Weathering and Soil Formation
Chapter 8

2. Section 1: Rocks and Weathering
Review:
What are mountains made of?
Rocks
How are rocks made into mountains?
Plate tectonics
What do you think happens to rock once it is exposed to the surface of the Earth?
Weathering and Erosion

3. Weathering
Weathering is the process that breaks down rock and other substances at Earth’s surface.
Heat, cold, water, ice, oxygen, and carbon dioxide are elements of weathering.
What are some examples?

5. Erosion Weathering breaks down rock…
Erosion is the removal of rock particles by wind, water, ice and gravity.
Weathering and erosion work together to break down and carry away rocks at Earth’s surface

6. Uniformitarianism
Uniformitarianism is the principle that states that the process we see today are the same as those in the past.
This is how scientists make hypotheses about things that occurred in the past.

7. 2 kinds of Weathering
Mechanical Weathering is when rock is physically broken into smaller pieces.
Smaller pieces are the same composition as the larger pieces
Takes long periods of time
Can break down mountains!

8. Causes of Mechanical Weathering
Freezing, thawing, release of pressure, plant growth, animals, abrasion

9. Abrasion
Abrasion is the grinding away of rock by particles carried in wind, water, ice, or gravity.

10. Abrasion

11. Ice Wedging
Ice wedging is the process of liquid water settling into cracks in rocks, freezing and cracking the rock as it expands

12. Ice Wedging

13. Chemical Weathering
Chemical weathering is the process that breaks down rock through chemical changes.
Causes include action of water, oxygen, carbon dioxide, living organisms, and acid rain

15. Chemical Weathering
Chemical weathering can change or produce new minerals as it breaks down rock
Example: granite is made of several minerals (feldspar, quartz, & mica)
During chemical weathering, the feldspar minerals are changed to clay minerals.

17. Chemical and Mechanical Weathering Work Together
Chemical weathering creates soft spots or holes in rocks so the rock breaks apart more easily
Chemical and mechanical weathering work together how?
Mechanical weathering creates more surface area to be exposed to chemical weathering

18. Review
Weathering is?
the process that breaks down rock and other substances at Earth’s surface.
Erosion is?
the removal of rock particles by wind, water, ice and gravity.

19. Uniformitarianism is?
the principle that states that the process we see today are the same as those in the past.
Mechanical Weathering is?
when rock is physically broken into smaller pieces.

20. What is this an example of?

21. What is this an example of?

22. Chemical weathering is?
the process that breaks down rock through chemical changes.
Chemical and mechanical weathering work together how?
Mechanical weathering creates more surface area to be exposed to chemical weathering

23. Read about the 5 types of chemical weathering.
On your own
Read about the 5 types of chemical weathering.
In the same notes we have been working on, tell how each of these elements helps to break down rock.

24. Chemical Weathering Water: dissolves rock
Oxygen: when in contact with iron it oxidizes (rusts) makes rock crumbly and brown/red.
Carbon dioxide: dissolves in water and creates weak acid (carbonic acid). Easily weathers rocks

25. Chemical Weathering
Living Organisms: Plant roots can produce weak acids that break down rock
Acid rain: chemicals from burning fossil fuels (sulfur, carbon, nitrogen) combine with water vapor and fall as acid rain. Acid easily breaks down rock.

26. Slate tombstones from the 1700s are less weathered and easier to read than marble tombstones from the 1800s.
Why?

27. Slate vs Marble

28. Rate of Weathering
Factors that affect the rate of weathering are the type of rock and the climate.
1. Type of rock:
type of minerals determine how fast a rock weathers
Permeable rocks (those with air holes) allow water to seep in

29. Rate of Weathering 2. Climate: Average weather in an area
Both chemical and mechanical weathering occur faster in wet climates.
Chemical reactions occur faster at higher temperatures
Hot, wet climate = faster rate of weatehring