Convection Currents and the Mantle

Heat Transfer

The movement of energy from a warmer object to a cooler object is called heat transfer.

The direction of heat transfer is always from a warmer substance to a cooler substance.

There are three types of heat transfer:

1.  Radiation

Radiation is the transfer of energy through empty space.

Heat transfer by radiation takes place with no direct contact between a heat source and an object.

Example: Radiation enables sunlight to warm Earth’s surface.

2.  Conduction

Conduction is heat transfer by direct contact of particles of matter.

In conduction, the heated particles of a substance transfer heat to other particles through direct contact.

3.  Convection

Convection is the transfer of heat by the movement of a heated fluid.

During convection, heated particles of a fluid begin to flow, transferring heat energy from one part of the fluid to another.

Convection currents continue as long as heat is added to the fluid.

Variables of Convection

Three factors contribute to set convection currents in motion:

1.      heating and cooling of the fluid,

2.      changes in the fluid’s density, and

3.      force of gravity

Convection Currents in the Earth

Convection currents flow in the asthenosphere.

1.      The heat source for these currents is heat from Earth’s core and from the mantle itself.

2.      Hot columns of mantle material rise slowly.

3.      At the top of the asthenosphere, the hot material spreads out and pushes the cooler material out of the way.

4.      This cooler material sinks back into the asthenosphere.

5.      Convection currents like these have been moving inside Earth for more than 4 billion years.