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Plate Tectonic Notes I. Continental Drift Theory A. proposed by Alfred Wegener in 1912 B. states that all continents were once one supercontinent (Pangaea) and have since “floated” apart over time C. Evidence to support theory 1. fossil records are similar on different continents 2. land forms such as mt. ranges and mineral deposits line up 3. coastlines of current continents appear to “fit together” like a puzzle II. Theory of Plate Tectonics A. states that the earth’s crust is broken into large moving pieces (plates) to which the continents are attached. B. Why Change the Theory? 1. new technology allows scientists to discover new information a) sonar b) SCUBA c) submarine improvements C. New Evidence 1. sea-floor spreading 2. earthquakes and volcanoes 3. actual recorded movement C. 16 plates (* means major plate) 1. 2. 3. 4. 5. N. American* Eurasian* Juan De Fuca Caribbean Cocos 6. Arabian 7. Phillippine* 8. S. American* 9. Caroline 10. African* 11. 12. 13. 14. 15. 16. Indo-Australia* Fiji Nazca* Pacific* Scotia Antarctic* III. Plate Boundaries A. locations where two plates meet B. where the forces that shape the earth’s surface occur 1. Constructive forces – create landforms 2. Destructive forces – destroy landforms C. three different types 1. Divergent a) plates move away from each other b) sea-floor spreading & ridges c) new crust is formed at this boundary type d) mid-Atlantic Ridge in Atlantic Ocean 2. Convergent a) plate move toward one another b) subduction- one plate forced underneath another > deep trenches, coastal mt. ranges, volcanoes > Andes Mts on west coast of S. America c) collision – both plates push upward > large mt ranges, earthquakes > Himalaya mt range in northern India 3. Transform a) plates move past one another in different directions b) faults visible at surface, large earthquakes c) San Andres Fault in California Boundary Movement Divergent Plates move AWAY from one another Convergent Collision Plates move TOWARD each other and BOTH push upwards Picture Landform(s) & Examples Landforms: Mid-ocean ridges & rift valleys Example: Mid-Atlantic Ridge Landforms: Large mountain ranges w/ lots of earthquakes Example: Himalayan Mts in India Landforms: Convergent Subduction Transform Plates move TOWARD each other and one plate gets pushed under the other Plates move past one another in opposite directions Deep ocean trenches, coastal mt. ranges & volcanoes Example: Andes Mts in South America Landforms: Faults that are visible on land Example: San Andres Fault in California divergent boundary transform boundary convergent / subduction boundary convergent / collision boundary