1. DYNAMIC PLANET INVESTIGATION 3 NOTES

2. CONVECTION CELLS Definition – a motion in a fluid that is caused by heating from below and cooling from above

3. Examples Heating of the corn syrup demonstration Oatmeal demonstration Home heating systems Convection oven

5. Convection Cells When a fluid is heated, it expands and lowers its density slightly The expanded fluid (less dense) rises  reaches cooler surroundings  shrinks, becoming more dense  sinks  heated again… Forms CONVECTION CELLS

6. Convection of the Earth’s Mantle The mantle convects in the form of gigantic convection cells

7. Material movement Many materials act like solids on short time scales but like liquids on much longer time scales –Examples include: Silly Putty Glass Wax

8. These materials flow and take on a new shape, even though it seems like a solid The Earth’s mantle behaves in the same way The speeds of flow in the mantle are only a few centimeters per year OR as fast as your fingernail grows

9. The Lithosphere and Asthenosphere

10. The Lithosphere Outermost part of the Earth Cooler temperature Remains rigid Does not convect Made up of the crust & uppermost part of the mantle Consists of several pieces called lithospheric plates

11. The Asthenosphere Below the lithosphere Zone where mantle rocks are just hot enough & under enough pressure to deform & change shape Able to convect  moving the lithosphere

12. Mid-Ocean Ridges All the Earth’s oceans have a continuous mountain range, called a mid-ocean ridge Located above rising currents in the mantle convection cells Stand high because they are heated by hot rising material which expands the rocks

13. As hot mantle rock rises, some melts forming magma Magma is less dense than surrounding rock, rises to form volcanoes along the ridge As rock rises, temperature stays the same but pressure decreases (less weight of rock above)

14. Melting temperature decreases as pressure decreases, why some rising rock forms magma Magma reaches surface, solidifies to form basalt

16. New crust is formed, moves away from the crest of the ridge Due to movement of the mantle Due to downhill slope of the ridge away from the crest

17. Movement of new oceanic crust in both directions  sea floor spreading