As they accumulate over millions of years they gradually infiltrate the microscopic cavities of the sea floor sediment and rock where they decay. The resulting oil remains trapped in these spaces, forming oil reserves which can be extracted through large drilling platforms. The use of oil increased significantly after the Second World War. Improved energy efficiency has caused oil consumption to decline in many developed, industrialised countries, as well as shifts to other fuels such as natural gas and nuclear energy. Decreasing use of oil is also resulting from tougher environmental restrictions concerning its use in some regions.
Natural gas is formed in the same way as oil, from the remains of marine microorganisms.
From the mid-1960s, up until the present day, there has been a dramatic increase in the amount of proven reserves of natural gas. Consequently, natural gas has become the fastest-growing energy resource. Natural gas provides an alternative to oil or coal in the provision of energy, and in terms of acidic pollution it is a cleaner fuel. Some estimates indicate the reserves of natural gas may be available for up to 400 years. Air Quality Print Topic Websites FossilFuels.