Sunlight from a very long time ago
What Is Crude Oil?
Oil is the squashed remains of tiny sea creatures, holding sunlight they caught hundreds of millions of years ago.
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Step 1 of 5
It starts as tiny sea life.
Not dinosaurs — mostly microscopic drifting creatures. When they died in still, airless water they did not rot away, and layer upon layer of them built up on the sea floor.
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Step 2 of 5
Pressure and heat do the rest.
Buried deeper and deeper, that layer gets squeezed and warmed for millions of years. Nothing burns, because there is no air — instead the remains slowly change into a thick black liquid.
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Step 3 of 5
It is the sunlight they caught.
Those creatures grew by capturing sunlight. Burning oil today releases exactly that energy — you are running an engine on a summer's afternoon from before there were flowers.
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Step 4 of 5
Crude oil is a mixture, so it gets sorted.
Out of the ground it is useless sludge. Heated in a tall tower, the light parts rise high and the heavy ones stay low, so it separates into petrol, diesel, jet fuel, oil and tar.
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Step 5 of 5
Most of it does not get burned as fuel.
Oil is also the raw material for plastics, paint, medicines and fabric. Nearly everything plastic around you started as the same black liquid that fills a fuel tank.
It took millions of years to make and a couple of centuries to use most of the easy parts, which is the whole argument in one sentence.
The short version
Crude oil is ancient sea life cooked under rock, and burning it releases sunlight caught hundreds of millions of years ago.
Try it yourself
Look at a plastic bottle, a candle and a car. All three are the same buried sunlight, sorted into different parts.
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