The Earth is made up of different layers, from the unbelievably hot core (up to 6000?!) to the hard crust on the surface, on which we all live. In some places, this crust is quite thick (up to 70km thick) and in others e.g. Iceland it is very thin (6km). Here, the hot molten rock is not far underground and it can work its way up to the surface through cracks and faults in the crust. Rain seeps into these cracks and heats up – instant hot water right under your feet! Iceland gets 90% of its hot water like this.

The steam from this hot water can also be used in geothermal power stations to produce electricity.

But of course there are both good things and bad things about geothermal energy:

* It works 24 hours a day, every day. And it is renewable.

* No fossil fuels are used so no extra greenhouse gases are pumped into the atmosphere.

* No transport is needed to get the power to houses – it is right underfoot!

* These countries don?t need to buy in expensive fuels like coal, oil and gas from other countries.

The downsides are:

* Only a few places in the world are situated where the earth?s crust is thin enough to use geothermal energy. It is difficult and expensive to transport geothermal energy to places away from where it is produced.

* The hot spots are not necessarily stable and conditions can change abruptly as the plates in the earth?s crust shift.