1. Internal Forces
of the Earth

2. Inner Structure of the Earth

3. Inner Structure of the Earth
Inner Core—dense and solid
4000 miles below surface
Outer Core—Molten or liquid
Both are mostly hot and made of hot metal (iron)
Appro 1,400 miles thick
3. Mantle—thick layer of rock (1800 miles thick); mostly solid, but has pockets of magma (melted rock)

4. 4. Crust—very thin layer; rocky surface
Below the oceans, the crust is about 2 miles thick. Below the continents it averages 75 miles in thickness.

5. Internal Forces that Shape Landforms
Volcanoes—form when magma inside the earth breaks through the crust. Lava flows and may produce a large, cone-shaped mountain

6. Divergent Plate Boundary Features
Faults
Earthquakes
Intrusions
Volcanoes
Crust 6
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7. 2. Fault—a break in the earth’s crust
2. Fault—a break in the earth’s crust. Movement along a fault can send out shock waves, causing an earthquake.

8. The Big Burp

9. The Plate Tectonic Theory
The lithosphere—the earth’s crust and upper layer of the mantle—are broken into a number of large, moving plates.
The plates slide very slowly over a hot, pliable layer of mantle.
3. The earth’s oceans and continents ride atop of the plates.

10. Plate Boundary Features
To view this animation, click “View” and then “Slide Show” on the top navigation bar. 10

11. The Ring of Fire
A circle of volcanic mountains that are surrounding the Pacific Plate

12. 2. Hot Spots: hot regions deep within the mantle that produce magma, which rises to the surface. Volcanic island chains form as oceanic plates drift over the hot spot. Example: Hawaiian Islands.

13. What Happens When Plates Meet?

14. Collision/Spreading Zones
To view this animation, click “View” and then “Slide Show” on the top navigation bar. 14

15. Convergent Plate Boundaries
They collide and push slowly against each other and form a collision or converging zone.
Ocean - Continent
Ocean - Ocean CC
Continent-Continent
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16. Converging (Collision) Zone
If 2 continental plates collide, mountains are formed. Example: Himalayas

17. Continental Crush (Collide)

18. If 2 oceanic plates collide, 1 slides under the other
If 2 oceanic plates collide, 1 slides under the other. Islands often form this way. Example: Japan

19. Ocean – Ocean Convergent Plate Boundary

20. Subduction zone.
*If an oceanic plate collides with a continental plate, the heavier oceanic plate will slide under the lighter, continental plate. Results: volcanic mountain building and earthquakes.

21. Ocean-Continent Convergent Plate Boundary

22. South American Subduction22

23. SPREADING ZONE
Plates pull away from each other and form a spreading zone. These areas are likely to have earthquakes, volcanoes, and rift valleys (a large split along the crest of a mountain).

24. Red Sea Spreading Center

25. East African Rift Valley
National Geographic Society.

26. Fault
At a FAULT, the plates will grind or slide past each other rather than colliding. Example: San Andres Fault.

27. Motion at Transform Boundaries
To view this animation, click “View” and then “Slide Show” on the top navigation bar. 27

28. San Andreas 28

29. External Forces of the Earth

30. Weathering
Breaks down rock at or near the earth’s surface into smaller pieces

31. Mechanical weathering
rock is actually broken or weakened physically.

32. Mechanical weathering
Frost Wedging: most common form; water freezes to ice in a crack (water expands 10% when frozen). Ice widens the crack and splits the rock.

33. Mechanical weathering
Seeds: Seeds will take root and grow in the cracks of a rock. As the plant grows, the rock will split.

35. Chemical Weathering
Alters the rock’s chemical make-up by changing the minerals that form the rock. Most important forces are water (H2O) and carbon dioxide (CO2).
H2O + CO2 + CaCO3  --> Ca+2 + 2HCO3-

36. Chemical Weathering
Carbonic Acid: CO2 from the air or soil combines with H2O to make carbonic acid. When the acidic water seeps into the cracks in certain rocks (limestone) it dissolves the rocks away. Examples: caves

37. With the snow-draped Sierra Nevada as a backdrop, unique erosion formations called sand tufa stand like giant cauliflower stalks in a dry Arizona lake bed. Before this alkaline lake went dry, tufa formed when a freshwater spring percolated from below and formed calcium carbonate deposits. When the lake's level dropped, these fragile formations surfaced, and wind went to work removing the sand beneath the deposits.

38. Chemical weathering
Acid Rain: Chemicals in the polluted water combine with water vapor and then fall back to the earth as acid rain.

39. Acid Rain is known to be caused by industrial pollution, volcanic activity, and acid producing agents in the oceans.

40. A stand of withered red spruce and Fraser fir trees blights a green vista in North Carolina's Mount Mitchell State Park.

41. Erosion
The movement of weathered materials such as gravel, sand, and soil.
An agent of mechanical weathering
Three common forms
Wind
Water
Glaciers

42. Erosion—Wind Most damaging in areas that are dry and with few plants
Wind-blown sand carves and/or smooths natural and man made formations

43. Desert winds sculpted these gentle swirls out of the limestone hills in Black Gap Wildlife Management Area, Texas. This remote, 100,000-acre (40,470-hectare) area in West Texas contains some of the lowest, driest, and hottest areas in the Chihuahuan Desert.

44. Erosion—Water Moving water carries sediment
Grinds away rock like sandpaper
Forms canyons and valleys

45. Erosion—Glaciers Huge, slow moving sheets of ice
When melted, leave behind piles of rock/debris called moraines
Great Lakes formed by glaciers

46. The Bernard Glacier in Alaska's Saint Elias Mountains looks like a huge alpine highway. Glaciers are slow but highly effective shapers of the land, essentially carrying away anything in their path—from soil and rocks to hills and even the sides of mountains.