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Over time, the old forest grew, died, and fell down, one layer after another. The vegetation began to decay and new plants grew. These new plants died and fell down over the partly and fully decayed plants. Centuries passed. Layers upon layers built up over old roots, leaves, tree trunks, and other plant material. The layers built up faster than it could be decomposed by bacteria. The layers stayed waterlogged and had little oxygen. A thick, brown, spongy layer of plant material called peat formed. Many more centuries passed before the spongy peat became hard, black coal. How did this happen?

A lot of pressure built up over the peat swamps. In certain regions, large areas of the land sunk. Water, sand, and mud settled over these sunken areas which are called basins. More and more pressure came from the upper layers pressing moisture out of the peat and making it harder.

After more than hundreds of thousands of years, the great pressure and heat, changes in the climate, environment, and earth caused the rock-like material to change into shiny, black coal.

Let's fast forward.

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