Oil is a fossil fuel. It is made from the remains of tiny plants and animals called plankton. The plankton lived in the seas when dinosaurs still ruled the world. Over millions of years the tiny plants and animals have changed into oil.
These tiny planktons float in the sea.
Tiny plankton living in our seas today is similar to the prehistoric plankton from which oil is made. Like today’s plant plankton, the tiny prehistoric plants used energy from sunlight to make their food. When they were eaten by animal plankton, the Sun’s energy passed into the tiny animals. So, oil made from prehistoric plankton is actually stored from the Sun.
It takes millions of years for oil to form.
- Millions of years ago plankton died and fell to the seabed.
- Layers of dead plants and animals built up on to the seabed.
- Mud and sand (sediment) sank to the bottom of the sea and covered these layers of plankton.
- More layers of sediment piled up on top of the dead plankton. The bottom layers were squashed and became hotter.
- Slowly the muddy sediment turned into rock.
- The plankton rotted, giving off bubbles of gas, and turned into a thick liquid. This is crude oil.
- Crude oil and gas seeped up through the spongy rock, until they reached a solid rock. They stayed under the solid rock in a pool or reservoir.
