Home / Learning / Science Topics / Earth Energy / Geothermal Energy / How is the heat created?

How is the heat created?

The heat generated internally in the earth, mainly by the decay of radioactive elements in rocks. This heat conducts slowly and continually to the surface along a temperature gradient which is normally 15°C to 30°C/km.

Superimposed over this normal heat flow are localised areas of higher heat flow associated with volcanic and geothermal activity. This occurs where tectonic plates:

  • move apart (divergent boundary), such as mid-ocean ridges;
  • collide (convergent boundary), such as in New Zealand where one plate is subducted below another;
  • or in “hot spots” under mid ocean volcanic islands, such as Hawaii, Iceland or Samoa

For more details about how volcanic activity occurs in New Zealand click here

NZ plate tectonics

Additionally, solar energy stored in the ground can be accessed for heating and cooling using geothermal heat pumps. A geothermal heat pump can also use groundwater or surface water as a heat source or sink.