1. Section 5.1

2. There are two types of weathering:
Weathering is a basic part of the rock cycle and a key process in the Earth system.
Weathering: The breaking down and changing of rocks at or near Earth’s surface.
There are two types of weathering:
Mechanical Weathering
Chemical Weathering
Even though they are different, they are at work at the same time.

3. Mechanical Weathering
Occurs when physical forces break rock into smaller and smaller pieces without changing the rock’s mineral composition.
Each piece has the same composition.
Breaking a rock into smaller pieces increases the surface area of the rock.
In nature, three physical processes are especially important causes of mechanical weathering:
Frost wedging
Unloading
Biological activity

4. Frost Wedging:
When liquid freezes, it expands by about 9%, exerting a tremendous outward force.
When water freezes in the cracks of rocks, it enlarges the cracks.
This process is known as frost wedging.
It is most common in mountainous regions in the middle latitudes.
Sections of rock that are wedged loose may tumble into large piles called talus, which typically form at the base of steep, rocky cliffs.

6. This is known as unloading.
Large masses of igneous rocks may be exposed through uplift and erosion of overlying rock.
When this happens, the pressure exerted on the igneous rock is reduced.
This is known as unloading.
Unloading causes the outer layers of the rock to expand more than the rock below.
Slabs of outer rock separate like layers of an onion and break loose in a process called exfoliation.
Especially common in granite.
It often produces large, domed shaped rock formations.
Ex: Stone Mountain in Georgia and Liberty Cap in Yosemite National Park.

8. 3. Biological Activity:
The activities of organisms, including plants, burrowing animals, and humans can also cause mechanical weathering.
Examples:
Tree roots.
Burrowing animals move rocks to the surface.
Decaying organisms produce acids which cause chemical weathering.
Humans accelerate weathering through deforestation and blasting.

10. The process that occurs when physical forces break rock into smaller pieces without changing the rock’s chemical composition is called
Differential Weathering
Chemical Weathering
Mechanical Weathering
Erosion

11. Which of the following weathering processes involves the constant freezing and thawing of water?
Unloading
Frost Wedging
Exfoliation
Spheroidal Weathering

12. Which of the following is not associated with mechanical weathering?
Frost Wedging
Unloading
Biological Activity
Reactions with Oxygen

13. What is responsible for the formation of exfoliation domes?
Frost Wedging
Biological Activity
Reactions with Oxygen
Unloading

14. What type of mechanical weathering is most common in mountainous regions in the middle latitudes?
Frost Wedging
Biological Activity
Oxidation
Unloading

15. When water freezes, its volume
Decreases slightly.
Increases.
Stays the same.
Decreases greatly.

16. Water is the most important agent of chemical weathering.
Chemical weathering is the transformation of rock into one or more new compounds.
The new compounds remain mostly unchanged as long as the environment in which they formed does not change.
Water is the most important agent of chemical weathering.
Water promotes chemical weathering by absorbing gases from the atmosphere and the ground.
These dissolved substances then chemically react with various minerals.
Oxygen dissolved in water reacts easily with certain minerals , forming oxides.
Ex: Iron-rich minerals get a yellow to reddish-brown coating of iron oxide (rust) when they react with oxygen.

17. Water that seeps into the ground also picks up carbon dioxide.
Water also absorbs carbon dioxide when rain falls through the atmosphere.
Water that seeps into the ground also picks up carbon dioxide.
The dissolved carbon dioxide forms carbonic acid, which reacts with many common minerals.
Carbonic acid is a weak acid found in carbonated drinks.

18. Water can also absorb the sulfur oxides in the atmosphere produced by the burning of fossil fuels (coal and petroleum).
Through a series of chemical reactions, these pollutants are changed into acids that cause acid precipitation.
Acid precipitation accelerates the chemical weathering of stone monuments and structures.

20. When granite (feldspar/quartz) is exposed to water containing carbonic acid, the feldspar is converted mostly into clay minerals.
As the feldspar is converted into clay, the quartz grains are released from the granite.
Sometimes it is then transported by rivers to the ocean where the tiny particles are carried far from shore and the quartz crystals are deposited near the shore where they become the main component of beaches and sand dunes.

21. When silicate minerals undergo chemical weathering, the sodium, calcium, potassium, and magnesium they contain, dissolve and are carried away by groundwater.
The three remaining elements are aluminum, silicon, and oxygen which usually combine with water and produce clay minerals.

23. This process is called spheroidal weathering.
Chemical weathering can change the physical shape of rock as well as its chemical composition.
Ex: When water enters along the joints in a rock, it weather the corners and edges most rapidly. As a result, the corners and edges become more rounded.
This process is called spheroidal weathering.
The rock takes on a spherical shape.
Spheriodal weathering sometimes causes the outer layers of a rock to separate from the rock’s main body.
Similar to exfoliation except that they are chemically weathered.

25. Which of the following is not related to chemical weathering?
Frost wedging.
Dissolution
Reactions with oxygen
Reactions with water

26. The gradual rounding of the corners and edges of angular blocks of rock is called
Exfoliation
Unloading
Spheroidal Weathering
Mechanical Weathering

27. Which of the following is the result of chemical weathering?
A rock that has been changed into one or more new compounds.
A rock that has been broken into tiny pieces.
A rock that has been split in two.
A rock that has lost its outer layers.

28. The chemical weathering of feldspar produces
Quartz.
Iron oxide
Clay minerals
Calcium carbonate

29. Whenever the characteristics and chemical composition of weathered materials have been altered, they have undergone
Chemical weathering.
Mechanical weathering.
Mass movement.
Frost wedging.

30. The atmospheric gas that forms a mild acid when dissolved in water is
Carbon Dioxide
Oxygen
Aluminum
Sulfur

31. Mechanical weathering affects the rate of chemical weathering.
By breaking rocks into smaller pieces, chemical weathering is increased due to the increased amount of surface area of the rock.
Two other factors that affect the rate of weathering are:
Rock characteristics
Climate

32. Rock Characteristics:
Physical characteristics of rock (cracks) are important in weathering because they influence the ability of water to penetrate rock.
Mineral composition also affects the rate of weathering.
Ex: Granite vs. Marble; granite is relatively resistant to chemical weathering while marble is not very resistant to chemical weathering (reacts with weak acids).

33. 2. Climate:
Climatic factors, especially temperature and moisture, have a strong effect on the rate of weathering (mechanical and chemical).
The climate most favorable for chemical weathering has high temperature and abundant moisture.
Slow in arid and polar regions.

34. Different parts of a rock mass often weather at different rates.
This process, called differential weathering, has several causes.
Differences in mineral composition is one cause.
More resistant rock protrudes as pinnacles, or high peaks.
Variations in the number and spacing of cracks in different parts of a rock mass is another cause of differential weathering.

36. What would cause the inscription on a marble gravestone to become harder and harder to read over time?
Frost wedging
Mechanical weathering
Exfoliation
Chemical weathering

37. Which of the following is not a factor that affects the rate of weathering in rocks?
Biological evolution
Climate
Rock characteristics
Amount of exposed surface area

38. Which of these factors affects the rate of weathering?
Climate
Chemical composition of the exposed rock.
Surface area of the exposed rock.
All of the above.

39. Rock features such as the sculpted pinnacles seen in Bryce Canyon National Park are the result of
Exfoliation.
Differential Weathering.
Unloading.
Frost Wedging.

40. Chemical weathering would be
Most effective in a warm, dry climate.
Most effective in a cold, dry climate.
Most effective in a warm, humid climate.
Equally effective in any climate.

41. If granite and marble were exposed in an area with a hot and humid climate,
The granite would weather most rapidly.
The marble would weather most rapidly.
Both rocks would weather at the same rate.
Neither rock would become weathered.