More detailsSome people have proposed coal forms from floating mats of dead plant material deposited in deep water in a short amount of time. Although not too far from the conventional explanation (dead plant material, sometimes transported), it can not explain the majority of coal deposits. Most coals are found in sedimentary rocks deposited in terrestrial river floodplains. They have river channels, levees, and fossil soil horizons. Often soil horizons are found immediately below coal seams, and these are often filled with plant roots (see the "polystrate trees" FAQ, for example). All these structures are similar to modern peat-forming environments. The common occurrence of rooted upright trees that can not be transported (because they have delicate rootlets embedded in the sediment) is compelling evidence that most coals form near the surface in terrestrial environments (see the "polystrate trees" above). However, even more convincing is the co-occurrence of dinosaur footprints and upright trees on the top surface of several coal seams at a Cretaceous-age locality near Price, in southeast Utah:
It is impossible to interpret these deposits as formed by a single event of short duration. The plants that form coal take time to grow, coal takes time to accumulate and decay, and trees take many years to grow. There are multiple coal seams and multiple tree and footprint horizons, and this is only in one short interval of the geologic record in one area. There are many other areas of similar coal deposits (e.g., Joggins, Nova Scotia). Rather than being a significant problem for conventional geology, coal is explained quite easily by analogy to modern peat environments. Coal deposits and associated sediments are an immense problem for any interpretation involving a "global flood".