Convection and the Mantle

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Convection and the Mantle

• How is heat transferred?

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What makes an object hot?

• Movement of particles
• Heat moves toward colder areas

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3 Types of Heat Transfer

• Radiation
• Conduction
• Convection

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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

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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.

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Conduction Examples

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

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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.

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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.

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

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Changes in Density

• The heating and cooling of a fluid changes its
  density.
• What a fluid is heated, its 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.

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Inside the Earth

• Heating and cooling of a fluid, changes in the
  fluids 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.

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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!

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Convection Currents in Action

• http//duedall.fit.edu/wholeearth/PHysical20geolo
  gy20animations/0053.swf