The exhaustible natural resources which are formed from the dead remains of living organisms or fossils are known as fossil fuels. For example, coal, petroleum and natural gas are fossil fuels. The fossil fuel such as petroleum is formed from the dead animals under the sea. As these organisms died, their bodies settled at the bottom of the sea. They got covered with layers of sand and clay. Over millions of years, in the absence of air, with high temperature and high pressure, these the dead organisms were transformed into petroleum and natural gas. The main constituents of petroleum are petroleum gas, petrol, diesel, lubricating oil, paraffin wax and kerosene. Petroleum can be extracted from under the sea bed. It can be extracted with giant drilling machines. The layer containing petroleum oil and gas is above that of water.