1. Evidence for Plate Tectonics Example Power Point Earth Science

2. Standard:Dynamic Earth Processes • Students know features of the ocean floor (magnetic patterns, age, and sea-floor topography) provide evidence of plate tectonics

3. Vocabulary • Transform faults: faults that run across a mid-ocean ridge • Mid-ocean ridges: undersea mountain chain where new ocean floor is produced: a constructive (divergent) plate boundary

4. Mid-ocean ridge

5. Vocabulary • Ocean-floor spreading:process in which old ocean floor is pushed away from a mid-ocean ridge by the formation of new ocean floor • Trenches:V-shaped valley on the ocean floor where old ocean floor is subducted; a convergent plate boundary

6. Ocean Floor spreading • Volcanic and earthquake activity occurs at the mid-ocean ridges. • As lava erupts and hardens, ocean floor moves away on either side of the ridge

7. Deepest Parts of the Oceans • As older ocean floor moves away from mid-ocean ridges, it moves down deep into Earth along trenches. • Trenches are found close to continents or near strings of islands such as Alaska’s Aleutian Islands.

8. Magnetic Patterns • Basalt rock on the ocean floor records the earths magnetic field when it hardens • The pattern of magnetic stripes is identical on both sides of a mid-ocean ridge

9. Summary • Ocean floor topography • Underwater mountains - mid-ocean ridges • Deep underwater trenches • Evidence • Age of rock on ocean floor • Magnetic patterns • Ocean floor is spreading at mid-ocean ridges

10. Quiz 1. Where is the youngest rock in the ocean formed? 2. Where is the deepest part of the ocean? 3. Name three pieces of evidence that supports plate tectonics?

11. Acknowledgement • Books:Exploring Earth Science • Prentice Hall • Internet: www.usgs.gov • Dynamic Earth