Coal seams are formed by peat (trees, foliage, plants, and life) becoming trapped by massive catastrophes such as volcanic eruptions and flooding. Sedimentary layers trap peat and press this material into coal seams. This process does not happen under normal decay processes, the catastrophe that laid down the coal seams we observe today was unimaginably massive.
https://answersingenesis.org/age-of-the-earth/stumping-old-age-dogma/