The Carbon Cycle

The fossil fuels that we rely on so much come from ancient organisms. Over a span of millions of years, many marine organisms and swamp plants died, decayed, and became buried in thick layers of sediment. Like all living things, their bodies contained carbon, and that carbon was trapped in the sediment that buried them. It stayed there for millions of years. Intense heat and pressure turned the carbon-rich sediment into carbon-bearing fossil fuels, namely oil, natural gas, or coal.

Fossil fuels come from the decay of plants. Since wood comes from trees, why is wood not considered one of the fossil fuels?

Wood is derived from trees that are still alive or that died only recently. To be a fossil fuel, the substance must be derived from the decay of organisms that died and were buried deep in Earth for hundreds of millions of years.

Because they contain massive amounts of carbon, fossil fuel deposits are an important carbon supplier on Earth. The carbon interacts with the environment once we bring these fossil fuels to the surface and burn them. When fossil fuels are burned, they release all that stored carbon into the atmosphere and interact in Earth’s carbon cycle. Roll over the numbers on the diagram to explore the steps of the carbon cycle.

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