Imprints of the original vegetation often remain in the bituminous coal. According to this model, they grew prior to the catastrophe of the Flood and were then broken up and deposited on top of one another during the Flood. Subsequent to burial the layers of forest debris subsided to great depths, where they were subjected to pressure conditions which led to a rapid formation of coal. This depiction of coal formation within the creationist framework for Earth history suggests that at least the biomass of the plants which are present today as bituminous coal, but probably more than this, was present on the Earth prior to the Flood. A short, very rough estimate can give us an answer.
Bituminous coal is found in seams of varying thicknesses.
Bituminous and sub-bituminous coals vary in composition and density. However, lignites were formed from very different plants to those in the bituminous coals, the vegetation responsible more or less corresponding to today's angiosperms and gymnosperms. Just as the formation of bituminous coal seams is viewed as the result of swamp growth over millennia, so also is the origin of lignite. A study of the actual structure of the Tertiary lignites, however, indicates that here, too, their formation is due to a catastrophe. Prior to their final deposition and burial, they are presumed to have drifted on the post-Flood oceans as 'inhabited depots'.