1. Chapter 7 Weathering, Erosion, and Soil
I. Weathering (process by which Earth’s materials are broken down) and Erosion (the removal and transport of these sediments.
A. Mechanical Weathering-physical weathering by which rocks are broken down but not chemically changed.
1. Temperature-when water freezes it expands by 10% in volume and can break apart rock.
a) Frost wedging (frost action)
i. Responsible for many pot holes

3. 2. Pressure: Is another factor in mechanical weathering
a).The weight of overlying rocks causes pressure below
i. When top layers are removed, this allows for expansion of lower layers.
ii. Long curved cracks then form known as joints.

5. 2 Continued…
b. Exfoliation- Process by which outer rock layers are stripped away over time (like layers of an onion)
Ogres are also like onions (not cakes), they have layers to!

8. B. Chemical weathering Process by which rocks and minerals undergo a change in their composition as a result of chemical reactions.
1. There are 4 main agents of chemical weathering.
a) Water - Hydrolysis
b) Oxygen - Oxidation (rusting of rocks)
c) Carbon dioxide - creates carbonic acid
d) Acids - Dissolve the rocks

9. C. What Affects the rate of weathering?
1. Climate: Variables include precipitation, temperature, and evaporation.
a) Warm and wet climates: Chemical weathering is dominant
i) Produce thick soils that are rich with organic matter.

11. 2. Cool and dry climates: Physical weathering is dominant
a)Water undergoes repeated freezing and thawing
ex: The Adirondacks featured here

12. 3. Rock Type and Composition
a) Sedimentary rocks are easily weathered
b) Igneous and metamorphic rocks are tougher
Sedimentary rocks Igneous rocks

13. 4. Surface Area
a) The more surface area, the more weathering occurs and with a faster rate

14. 5. Topography and other Variables
a) More weathering occurs on a slope because
gravity pulls down the loose material which
exposes more surface area.

15. II Erosion and Deposition
A. Erosion is the transport of materials
1. Deposition:
a) When sediments and materials are dropped off. This is the final stage of erosion.

16. 2. Gravity:
a) is the force responsible for most agents
of erosion by pulling materials down slope.

17. 3. Running water:
a) Moves the most amount of sediment annually
b) Rill erosion: The erosion of running water in small channels

18. 3. Continued...
c) Gully erosion: When a channel becomes wide and deep
i. This can be a problem in grazing areas for cows

19. 4. Coastal Deposition and Erosion
a) Each year running water carries billions of tons of sediment to the coast
b) When a river enters a larger body of water, it slows down, and deposits materials
c) Sediments are deposited by size, shape and density.

20. 5. Glacial Erosion
a) Glacier is a large mass of ice that can move large amounts of rock as it travels
b) Covers less than 10% of Earth’s surface
c) Carves out “U” shape valleys, parallel scratches in bedrock, lake beds, and leaves unsorted deposits

21. 6. Wind Erosion
a) Major agent of erosion in environments with limited precipitation and high temps (deserts)
b) Wind blown sediments can be very abrasive
c) Poor agricultural practices and wind caused the dust bowl in the 1930’s
d) Wind barriers such as trees planted in strips helped to break up the wind and reduce top soil losses

22. 7. Erosion by Plants, Animals and Humans
a) The least effective form of erosion
b) Move sediments through life processes

23. III Formation of soil A. Development of Soil
1. Soil is the loose covering of broken rock particles and decaying organic matter.
a). Process begins with chemical and physical weathering, and biological activity over a long period of time.

24. B. Soil Composition
1. Residual Soil- soil that was formed in place, and remains above its parent bedrock
2. Transported soil- soil that was moved from where it was formed.
a) Long Island is a glacial deposit of transported soils.

25. C. Soil Profiles-Vertical sequence of soil layers
1. The three major horizons are (O included) A, B, C
2. Topography (shape of the land)
a) On a slope, the soil is thin, and at the valley where the sediments are deposited, the soil is thicker.

26. D. Soil Types
1. Polar Soils
2. Temperate Soils
3. Desert Soils
4. Tropical soils