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. N. American* 6. Arabian 11. Indo-Australia* 2. Eurasian* 7. Phillippine* 12. Fiji 3. Juan De Fuca 8. S. American* 13. Nazca* 4. Caribbean 9. Caroline 14. Pacific* 5. Cocos 10. African* 15. Scotia 16. 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

Landform(s) & Examples Boundary Movement Picture Landform(s) & Examples Divergent Plates move AWAY from one another Landforms: Mid-ocean ridges & rift valleys Example: Mid-Atlantic Ridge Convergent Collision Plates move TOWARD each other and BOTH push upwards Large mountain ranges w/ lots of earthquakes Himalayan Mts in India Subduction Plates move TOWARD each other and one plate gets pushed under the other Deep ocean trenches, coastal mt. ranges & volcanoes Andes Mts in South America Transform Plates move past one another in opposite directions Faults that are visible on land San Andres Fault in California

divergent boundary transform boundary convergent / subduction boundary convergent / collision