Explain why, fossil fuels are exhaustible natural resources.

The amount of fossil fuels is very limited in nature. They can be exhausted by human activities. The formation of fossil fuels is a very slow process. These are formed under very high pressure and high temperature. For example, coal, petroleum and natural gas are fossil fuels. Coal was formed by the process of carbonisation. Carbonisation is the process by which plant material or vegetation buried deep under the earth was slowly converted into coal.