1. Internal Forces of Change

2. Types of Boundaries Convergent Divergent Transform Come together
Pull apart
Transform
Slide past each other

3. Convergent Boundaries
Subduction
One plate dives beneath another
Forms volcanic mountains
Accretion
As one plate slides beneath another, a trench is formed
Overriding plate scrapes off the subducted plate, leveling off undersea mountains and ridges
Folding
Two continental plates collide, forming mountains

4. Divergent Boundaries Spreading Two sea plates pull apart
Magma rises, creating ridges or undersea mountain ranges (“new” land)

5. Transform Boundaries Fault
Crack in earth’s surface where two plates can slide past one another
When plates make a sudden, violent shift, earthquake!

6. External Forces of Change

7. Weathering
Definition: The breaking down of rocks on the earth’s surface into smaller pieces.
Different from erosion!
No movement

8. Physical Weathering
Caused by heat, water, ice, or pressure

9. Frost Wedging

10. Frost Heaving

11. Plant Roots

12. Burrowing of Animals

13. Temperature Changes

14. Acid rain has eaten away this limestone statue.
Chemical Weathering
Caused by chemical reactions.
Can be caused by water, carbon dioxide, oxygen, acid rain to
Acid rain has eaten away this limestone statue.

15. Water
Water weathers rock by dissolving it

16. Oxygen
Iron combines with oxygen in the presence of water in a processes called oxidation
The product of oxidation is rust

17. Acid Rain
Burning coal, oil and gas react chemically with water forming acids.
Acid rain causes very rapid chemical weathering

18. Erosion
Definition: The process by which water, ice, wind or gravity moves pieces of rock and soil
Different from weathering!
Movement

19. Water Erosion
Caused by fast-moving water such as rain, rivers, streams and oceans. Can eventually form a canyon or cliff (ocean).
Ex. Grand Canyon

20. Water Erosion

21. Wind Erosion
Caused by the movement of dust, sand and soil. Can create loess, a fertile soil carried by wind.
Ex. Great Plains

22. Wind Erosion

23. Glacial (Ice) Erosion
Caused by large pieces of ice moving across the earth’s surface. Can leave behind moraines (large piles of rock and debris).
Ex. Rocky Mountains

24. Glacial Erosion