1. Changing Earth’s Surface …
WEATHERING, EROSION, DEPOSITION
Changing Earth’s Surface …

2. WEATHERING
Surface processes that work to break down rock into smaller and smaller pieces
The small pieces are called sediments which become part of the process of soil-formation.

3. 2 Types of Weathering
Mechanical &
Chemical

4. Mechanical Weathering
Occurs when rocks are broken apart by physical processes
The Chemical composition of the rock stays the same (same substance—different shape or form.)
SAME

5. AGENTS OR CAUSES OF MECHANICAL WEATHERING
WIND --carries sand and debris which scrapes away at rocks.

6. AGENTS OR CAUSES OF MECHANICAL WEATHERING
WATER –as it flows over rocks
Big Bend–
Water erosion from the
Rio Grande River

7. AGENTS OR CAUSES OF MECHANICAL WEATHERING
PLANTS –roots, seeds fall into cracks and sprout, breaking them apart more.

8. http://img. geocaching. com/cache/d4fb66d9-ebf4-4328-b116-507cd6ecf624

10. AGENTS OR CAUSES OF MECHANICAL WEATHERING
ANIMALS– burrowing or pounding of feet on rocks
Hey kid, get off the rock!

11. AGENTS OR CAUSES OF MECHANICAL WEATHERING
PRESSURE– force of something –other rocks falling, movement etc.-causes rock to break

12. AGENTS OR CAUSES OF MECHANICAL WEATHERING
TEMPERATURE CHANGES
(hot days—rocks expand; cold nights—rocks contract and this causes rocks to crack)

14. AGENTS OR CAUSES OF MECHANICAL WEATHERING
ICE/FROST WEDGING--

15. CHEMICAL WEATHERING
Occurs when chemical reactions dissolve the minerals in rocks or change them into different minerals.
This changes the chemical composition of the rock, which can weaken/dissolve it.

16. AGENTS OR CAUSES OF CHEMICAL WEATHERING
1. WATER—MOST IMPORTANT agent of chemical weathering. (many minerals dissolve in water; water mixes with and carries other substances)
2. OXYGEN –oxidation-oxygen reacts with something else (rust, etc.)
weakens rocks.

17. A AGENTS OR CAUSES OF CHEMICAL WEATHERING
3. LICHENS AND PLANT ACIDS—roots of some plants or when they decay on rocks, lichens give off acids that break down rock.
4. OTHER ACIDS—
Carbonic acid –dissolves minerals in limestone—caves
(carbon dioxide + water=carbonation)
-Acid rain caused by
burning fossil fuels
TEXAS CAVES

18. Factors that affect the rate of weathering (how fast they weather)
1. Climate –pattern of weather that occurs in a particular area over many years.
*Chemical—more rapid * Mechanical –more rapid
in warm, wet (tropical) climates in cold climates (ice)

19. Factors that affect the rate of weathering (how fast they weather)
2. ROCK TYPES— can also affect the rate of weathering in a particular area because some minerals dissolve easier than others
Example: limestone etc.
3. The more surface area (outside) that is exposed to weathering, the faster the rock will weather
A B.
“B” would weather faster than “A” because more is exposed to the elements

21. EROSION
*Process that wears away surface and moves them from one place to another (sediments are moved.)

22. CAUSES/AGENTS OF EROSION
1. Wind (blows)
2. Water (flows)
3. Gravity (pulls)
4. Glaciers (scrape)
Click here.

23. MASS MOVEMENT
Any type of erosion that happens as gravity moves materials downslope.
Ex. landslides—rockslides, mudslides, creep, etc.

24. TAIWAN LANDSLIDE 2010

25. Dropping of sediments that occurs when agents of erosion lose energy
DEPOSITION
Dropping of sediments that occurs when agents of erosion lose energy

27. and dropped elsewhere (when agents or erosion lose energy)
Sediments are broken off
Carried Away
Weathering
Erosion
Deposition
These processes work together in a cycle that constantly changes Earth’s surface (landforms, shorelines, coastlines, etc.)
These processes also help in the formation of soil.

28. SOIL
Mixture of weathered rock, decayed organic matter, mineral fragments, water, and air that can take thousands of years to develop.

29. SOIL EROSION Removal or loss of soil due to wind or water.
It is harmful in 2 ways:
Plants need soil to grow
Eroded fertile soil causes sedimentation in (clogs) waterways and releases agricultural pollution into surface waters
*Can happen naturally or by humans

30. SOIL EROSION
Soil is eroded when it is moved from where it formed and it occurs when water flows along Earth’s surface or when wind picks up and moves sediment.
Many human activities disturb
the natural balance between
soil formation and soil erosion.

31. SOIL EROSION
2 Main Categories (Human activities contributing to soil erosion)
1. Construction
Remove vegetation, breaking up dirt, etc.
Prevention – covering the site with mulch mats, plastic, etc., wetting dirt, plastic fencing around the site.

32. SOIL EROSION
2. Farming –
Plowing soil, animals overgrazing, removing crops over and over again.
Prevention—Alternating crops, shelter belts of trees, terracing on sloped fields which makes shorter slopes, no-till farming.
Shelter belts of trees
Terracing

33. NO-TILL FARMING

34. STRIP CROPPING

35. The Basics: Earth's Changing Surface
CLICK THIS PICTURE FOR VIDEO :
The Basics: Earth's Changing Surface