Convection and the Mantle

1. Convection and the Mantle How is heat transferred?

2. What makes an object hot? • Movement of particles • Heat moves toward colder areas

3. 3 Types of Heat Transfer • Radiation • Conduction • Convection

4. Radiation • Transfer of energy through space • No direct contact between heat source and an object. • Can you think of examples of Radiation? • Sunlight warming us during the day • Being warmed by a fire

5. Conduction • Heat transfer within a material, or between materials that are touching. • The particles heat up, move faster, and bump into other particles that do the same.

6. Conduction: Examples • A spoon sitting in a boiling pot of soup. • Hot sand at the beach. • Cold hands after making a snow ball.

7. Convection • Heat is transferred by the movement of fluids and gases. • Heated particles begin to flow, and transfer heat from one particle to another. • This is caused by differences in temperature and density* in a fluid. • Density = a measure of how much mass there is in a substance. Example: Rock is much denser than water.

8. Convection Currents • How does hot liquid move? • Think of the boiling pot of soup: • The soup on the very bottom of the pot is the hottest, and therefore, less dense. It begins to float towards the top. • Once at the top, it cools, which increases its density. It becomes heavier, and due to gravity, falls back to the bottom of the pot.

9. Convection currents take on a circular motion. • This is how the mantle rock moves inside the earth.

10. Changes in Density • The heating and cooling of a fluid changes its density. • What a fluid is heated, it’s particles move farther apart at a faster speed than when it was cold. As the particles spread out they take up more space. • The particles of the fluid are now being stretched over a larger area, and therefore, the density of the fluid decreases.

11. Inside the Earth • Heating and cooling of a fluid, changes in the fluid’s density, and the force of gravity combine to set convection currents in motion. • Heat from the core and mantle causes these types of convection currents in the mantle.

12. The flowing mantle • Plumes of mantle rock rise slowly from the bottom of the mantle toward the top. • The hot rock eventually cools, and sinks back through the mantle. • This cycle of rising and sinking is repeated over and over. • This has been happening inside our earth for more than 4 billion years!

13. Convection Currents in Action: • http://duedall.fit.edu/wholeearth/PHysical%20geology%20animations/0053.swf