Heat Transfer on Earth

How is Heat Transferred?

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

• There are 3 types of heat transfer:

• Radiation

• Conduction

• Convection

Radiation

• The transfer of energy that is carried in rays like light

• Ex: the Sun transfers heat and light through the air, warming your skin

Conduction

• Heat transfer between materials that are touching

• Ex: Grabbing a hot pan transfers heat to your hand

Convection

• Heat transfer by the movement of a fluid (liquid or gas)

• Ex: Eagles can glide on warm air currents produced by rising heat from the ground

Convection Currents

• Density - a measure of how much mass there is in a given volume

• Convection Current - the flow that transfers heat within a fluid

• Convection currents work by warmer, less dense, fluid rising and colder, more dense, fluid sinking

Convection Currents

• ***These 3 things set convection currents in motion***

• Heating and cooling of a fluid

• Changes in the fluid's density

• The force of gravity

Convection Currents in Earth

• Heat from the core and the mantle itself cause convection currents inside the mantel

• The middle portion of the mantel, the asthenosphere, is plastic-like due to this heat

• As lower parts of the asthenosphere are heated, they become less dense and begin to rise

• When this section reaches the top, it spreads out, cools off, and begins to sink back to the bottom

Convection Currents in Earth continued...

• When the section of asthenosphere reaches the top it transfers heat to the lithosphere through conduction

• Convection currents also occur inside the outer core

• The outer core is mostly liquid iron and nickel

• These currents cause Earth's magnetic fields