Geothermal heating is a process where we gain heat and energy from the depth of the earth. As you know, the interior of our planet is very hot and only the very surface is cool. Below the Earth’s crust is magma and it emits heat into the crust as well. If you could travel down deeper into the earth, you would discover that the temperature of the surrounding rocks would increase on average by 25 degrees for every kilometer that you go down. In some places, where there are volcanoes and magma is closer to the surface, such as Iceland, temperature increases even faster. What some people do is that they drill into these hot rocks below, pump water in them, let water absorb heat from surrounding hot rocks and then pump it back up. The hot water then can be used for heating. Once it is cooled down, it can be pumped back into rocks and reused. If you can get water into rocks that are hot enough, it will actually turn to steam. The steam then can be used in turbines to generate electricity. As you can see, there are no chemicals involved and no greenhouse gas emissions, so this way of energy generation is considered very environment friendly.