1. Earth Notes Chapter 2 ~ Section 2 Forces of Change

2. The Earth’s Interior Inner Core – about 4,000 miles below the surface of the Earth Outer Core – 1,400 miles thick, temperature reaches 8500°F

3. Earth’s Interior (con’t) • Mantle: layer of hot, dense rock – MAGMA

4. Earth’s Interior (con’t) • Crust: rocky shell forming Earth’s surface. • The crust is broken into slabs of rock called plates. • Natural forces interact with the crust, creating landforms on the surface of the earth. • Below the oceans, the crust is about 5 miles thick. Below the continents it averages 22 miles in thickness.

5. Earth’s Interior (con’t) • Plates - float on a melted layer in the upper mantle - carry the earth’s oceans and continents

6. Internal Forces of Change

7. The Plate Tectonic Theory • The lithosphere — the earth’s crust and upper layer of the mantle — is broken into a number of large, moving plates.

8. The Plate Tectonic Theory • The plates slide very slowly over a hot, pliable layer of mantle. • The earth’s oceans and continents ride atop of the plates. • It’s along the plate boundaries that most earthquakes and volcanoes occur due to friction and pressure that produces heat.

9. Plate Movement Plate movement: creates oceans and mountain ranges

11. Plate Movement • Continental Drift: the theory that the continents were once joined and then slowly drifted apart

12. Plate Movement Pangaea: gigantic super continent which eventually broke apart

14. Observe an animation of the breakup of Pangaea • http://www.classzone.com/books/earth_science/terc/content/visualizations/es0806/es0806page01.cfm?chapter_no=visualization

15. Examine an animation of plate movement predicted for the future • http://www.classzone.com/books/earth_science/terc/content/visualizations/es0807/es0807page01.cfm?chapter_no=visualization

16. Ring of Fire • A circle of volcanic mountains surrounding the Pacific Ocean • It is one of the most earthquake-prone & volcano-prone areas on the planet. • Hot Spots are 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 • http://www.classzone.com/books/earth_science/terc/content/visualizations/es0904/es0904page01.cfm?chapter_no=visualization

18. Volcanoes • Form when magma inside the earth breaks through the crust. Lava flows and may produce a large, cone-shaped mountain • They often form along plate boundaries • Magma splits the earth’s surface when plates collide

20. Fault—a break in the earth’s crust. Movement along a fault can send out shock waves, causing an earthquake.

22. San Andreas Fault

23. San Andreas Fault

24. A devastating fire followed the 1906 earthquake in San Francisco

25. The San Fernando earthquake of 1971 collapsed freeway overpasses in southern California

26. Converging/Collision Zone • Plates collide and push slowly against each other and form a collision or converging zone. • If 2 oceanic plates collide, 1 slides under the other. Islands often form this way. • If 2 continental plates collide, mountains are formed. Example: Himalayas

27. Continental Crush / Collide

28. 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). http://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/es0804page01.cfm?chapter_no=visualization

30. Spreading Zone

31. Subduction They meet, or CONVERGE and form a subduction zone. *If an oceanic plate collides with a continental plate, the heavier oceanic plate will slide under the lighter, continental plate. This results in volcanic mountain building and earthquakes.

33. Subduction

34. External Forces of Change

35. External Forces • What other forces can create landforms? • Weathering – a process that breaks down rock at or near the surface into smaller pieces. - This is a VERY slow process – thousands to millions of years. • Mechanical (or Physical) Weatheringoccurs when rock freezes – it can cause Frost Wedging, a crack in the rock caused by freezing.

42. Chemical Weathering– alters the rock’s chemical makeup by changing the minerals. This can actually change one kind of rock into another. • Important forces in Chemical Weathering are moisture and carbon dioxide. • Through this process caves are created. • Acid Rain causes another type of chemical weathering that destroys forests, pollutes water and kills wildlife.

43. Over thousands of years, areas with limestone rocks can develop caves. • Groundwater dissolves a network of tunnels in the rock. If the water table is lowered by a change in climate or tectonic uplift of the area, groundwater drains out of the tunnels, leaving the caverns exposed to air. http://www.classzone.com/books/earth_science/terc/content/visualizations/es1405/es1405page01.cfm?chapter_no=visualization

44. EROSION • Erosion is the movement of weathered materials including gravel, soil and sand. • The most common agents of erosion are water, wind and glaciers.

45. WATER AND EROSION • Moving Water (rain, rivers, streams and oceans) is the greatest agent of erosion. • Sediment – small particles of soil, sand, and gravel - is carried by the moving water and works like sandpaper to grind away rocks.

46. ErosionSullivan Falls Rickett’s Glen State Park Pennsylvania

47. Sediment • Sediment from the River Rhône flowing into Lake Geneva.

48. Sediment • http://www.classzone.com/books/earth_science/terc/content/visualizations/es0604/es0604page01.cfm?chapter_no=visualization

49. Floodplains Sediment creates new landforms such as floodplains & deltas. Deltas form at the mouth of a river

50. Wind Erosion • The second major cause of erosion is wind, especially where there is little water and few plants. • Wind Erosion can devastate one area while benefiting another – HOW? • Loess – windblown deposits of mineral-rich dust