Here's why:
* Sedimentation: Coal forms from layers of dead plant matter that accumulate in swamps. Over time, these layers are buried by more sediment (sand, mud, etc.). This process is called sedimentation.
* Superposition: The principle of superposition states that in undisturbed rock sequences, the oldest rocks are at the bottom and the youngest rocks are at the top.
* Coal Formation: The layers of rock below the coal represent the sediment that was already there when the coal-forming plants were growing. The layers above the coal were deposited *after* the coal formation was complete.
So, the layers of rock above the coal are younger because they were deposited later, while the layers of rock below the coal are older because they were there first.
