1. Convection Wednesday, February 29, 2012

2. 3 Modes of Heat Transfer: 1.Conduction: heat transfer through direct contact 2.Radioactive exchange: heat transfer via electromagnetic waves 3.Convection: heat transport by a moving fluid (gas or liquid).

3. 3 Modes of Heat Transfer:

4. What is Convection? = the up and down movement of gases and liquids (fluids) caused by heat transfer Hot material expands, becomes less dense, and rises Hot material begins to cool Cold material contracts, becomes more dense, and sinks

5. What was happening in the lab? 1.The hot plate heated water at the bottom of the beaker. 2.This water expanded, became less dense than the surrounding water, and rose to the top. 3.Water cools as it moves away from the heat source. 4.As it cools, the water contracts, gets denser, and sinks.

6. Video Intermission

7. What does this have to do with plate tectonics? This figure shows a convection in the mantle. Colors closer to red are hot areas and colors closer to blue are cold areas. A hot, less-dense lower boundary layer sends plumes of hot material upwards, and cold material from the top moves downwards. Convection occurs in the mantle! Rising hot material Sinking cooler material

8. How does convection fit in with plate tectonics? Earth’s core is made up of radioactive materials that give off a lot of heat. Heat is transferred to the mantle.

9. How does this fit in with plate tectonics? The asthenosphere is heated by the Earth’s core. Hot material in asthenosphere rises while the cooler material sinks. This motion drags the overlying tectonic plates.

10. How does convection fit in with plate tectonics? Convection in the mantle causes the tectonic plates to move like a conveyor belt on top of the asthenosphere.

11. How does mantle convection create different plate boundaries? What kind of boundary occurs where the hot material rises? DIVERGENT BOUNDARIES What kind of boundary occurs where the hot material sinks? CONVERDENT BOUNDARIES

12. VIDEO INTERMISSION