the Dynamic Earth and Plate Tectonics

1. the Dynamic Earth and Plate Tectonics

2. Early Ideas on a moving Earth • Alfred Wegener proposed idea: “Continental Drift” • Stated that all continents used to be joined in Pangaea (meaning “all land”) that broke up into smaller continents, “drifted” to current locations • Geologic features such as mountains crumpled from this supercontinent moving apart

3. Continental Drift - Wegener’s hypothesis of continent movement after Pangaea broke apart Early evidence #1:Coastlines on early maps seem to fit like puzzle pieces

5. “Continental Drift”, Early evidence #2 Fossils of the same organism were on opposite land masses (puzzle pieces), known to have been joined at one time

8. “Continental Drift”, early evidence #3 Mountains and rocks continued on opposite puzzle pieces

10. “Continental Drift”, early evidence #4 Misplaced glacial remnants and tropical swamps can be explained if continents were once joined

11. Concluding evidence • Proof of seafloor spreading at the Mid-Atlantic Ridge (1947) • Rock at the ridge was dated much younger than continental rock • Paleomagnetismalso apparent • As magma solidifies, iron crystals align with Earth’s magnetic field like a compass. Geologists have known that this happens periodically throughout history, as magnetic poles flip flop.

13. Modern Theory of Plate Tectonics • Earth is made up of 9 primary plates and several microplates made up of continental and oceanic crust. • Upper lithosphere is crusty and moves about on plasticyasthenosphere. • Asthenosphere moves most likely due to convection in the mantledue to heat from core and radioactivity from mantle • Where plates meet is called a plate boundary • Types: Convergent, divergent, transform

14. PLATE BOUNDARIES • 1. Convergent Boundary • Ocean – Continent • Ocean – Ocean • Continent – Continent Continent – Continent convergence Ocean – Continent Convergence

15. 2. Divergent Boundary 3. Transform Boundary

16. Where in the World do we find those boundaries?