1. PLATE TECTONICS

2. 1950’s scientists first knew earth’s plates were moving.
Alfred Wegener proposed in 1915
Fossils on different continents match.

3. Continental Drift
Sir Francis Bacon maps Atlantic Ocean and notices parallelism of opposite shores
Alfred Wegener proposes Pangea breaks apart & ocean fills gaps. Based on fossil evidence, rock types and rock structures
Magnetic Studies - Outer core generates magnetic field (polarity of North & South Poles). Patterns of polarity reversals in mid-ocean ridge and volcanic rocks where magma reaches surface. magnetic field & seafloor spreading

5. New ocean crust is being created, pushing continents apart.
Youngest rock
Oldest rock
Mid Atlantic Ridge
New ocean crust is being created, pushing continents apart.

6. Earthquakes occur along moving plate boundaries.
Mid Atlantic Ridge
Ring of Fire
Earthquakes occur along moving plate boundaries.
Four plates

7. Oceanic plates generally made of basalt (more dense & darker)
Continental plates (crust) generally made of granite. Less dense than oceanic plates
Oceanic plates generally made of basalt (more dense & darker)
When these two plates meet, oceanic plate is forced under the continental plate.

8. What happens at each type of boundary? PLATE BOUNDARIES
2 continental plates = Himalayas
2 continental plates = Rift Valley
2 oceanic plates = Islands
2 oceanic plates = sea floor spreading (ridge)
2 plates = earthquakes
Practice

9. Plate visual
ucation_and_outreach/aotm/interactive/ DynamicPlanet-EQs&Volcanoes.swf

10. Movement of plates is driven by convection currents.
Hot interior of earth rises, cools and sinks.

11. Examples: Hawaii, Yellowstone, Galapagos, Iceland, others.
HOT SPOTS - places where magma is close to surface, but not necessarily at a plate boundary
Examples: Hawaii, Yellowstone, Galapagos, Iceland, others.

12. VOCABULARY
Plate tectonics
transform boundary
convergent boundary
divergent boundary
rift
ridge
seafloor spreading
magnetic reversal
hot spot
convection