1. CONVECTION CURRENTS: GO with the FLOW

2. A temperature increase produces a decrease in the density of a substance
Density is defined as mass divided by volume (D=M/V)
Less dense substances float on more dense substances
Convection is defined as the circulation of a fluid at a non-uniform temperature due to the variation of its density and the action of gravity

3. COLD, HIGHER DENSITY HOT, LOWER DENSITY Hot rising Cool Cool current
descending
current
Cool
descending
current
HOT, LOWER DENSITY

6. Circular Paths of Food Coloring Gel Created by
Convection Currents in Heated Water
Water at the bottom is warmer and less dense; food coloring gel rises
Water at the top is cooler and denser; food coloring gel sinks

7. A radiator in your home or classroom uses the principle of convection currents as a heat source.

8. A bulb at the bottom of the lamp heats up the two liquids in the lamp
One liquid expands more than the other, becomes less dense and rises
The liquid cools at the top; becomes denser; and sinks
As long as the lamp is on, this cycle continues
Lava lamp serves a model for internal processes occurring
in the Earth’s mantle producing convection currents causing
tectonic plate movement
LAVA LAMPS:

9. HOW DO TECTONIC PLATES MOVE?
Heat for convection comes from deep within the earth
Two main sources: radioactive decay and residual heat
Primary mechanism for mantle convection is seafloor spreading
“Ridge Push” caused by magma intrusion also provides additional force
“Slab Pull” caused by subduction now considered to be major driving force

10. Convection Current crust mantle
Hot material rises, cooler material sinks,
creating a Convection Current or Cell

12. “RIDGE PUSH” and “SLAB PULL”

13. LET’S REVIEW
Continents are continuously slowly moving on the Earth’s crust --- only
a few cm a year. Convection currents are what move the Earth’s continents.

14. THE END