Currents and the Mantle
The movement of energy from a warmer object to a cooler object is called heat
The direction of heat transfer is always from a warmer substance to a cooler substance.
There are three
types of heat transfer:
Radiation is the transfer of energy through empty space.
by radiation takes place with no direct contact between a heat source and an object.
Example: Radiation enables sunlight
to warm Earth’s surface.
Conduction is heat transfer by direct contact of particles of
In conduction, the heated particles of a substance transfer heat to other particles through direct contact.
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,
in the fluid’s density, and
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.
currents like these have been moving inside Earth for more than 4 billion years.