Formation of fossil fuels
Crude oil, coal and gas are Natural, finite fuel formed from the remains of living organisms, eg oil, coal and natural gas.. They were formed over millions of years, from the remains of dead organisms:
- coal was formed from dead trees and other plant material
- crude oil and gas were formed from dead marine organisms
Fossil fuels are A resource that cannot be replaced when it is used up, such as oil, natural gas or coal.. They took a very long time to form and we are using them up faster than they can be replaced - once they have all been used up, they cannot be replaced. Fossil fuels are also Resource that can only be used once and is in limited supply. For example, oil is a finite resource.. They are no longer being made or are being made extremely slowly.
How crude oil and natural gas were formed
Millions of years ago, huge numbers of microscopic animals and plants - plankton - died and fell to the bottom of the sea. Their remains were covered by mud.
As the mud sediment was buried by more sediment, it started to change into rock as the temperature and pressure increased. The plant and animal remains were altered chemically by this process, and slowly changed into crude oil and natural gas. The slideshow describes what happened and how we get oil from the ground today:
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The oil moved upwards through the spaces in permeable rock. It became trapped if it reached impermeable rock. Oil companies can drill down through the impermeable rocks to get it out. They are then able to turn it into products we can use, such as petrol and diesel.
