Times are changing in the coal trade, and while April marked the end of one era (the last pit pony in the UK died), on the other had we have the renewed interest, and debate over, the use of coal as a source of liquid fuels for a variety of vehicles, including aircraft. So I thought it worth trotting out some more facts that might help put the current (and future) situations in context. (Plus we haven't had a Techie talk in a bit).

The late Bob Stefanko has written that the Great Dismal Swamp is probably the best current place that represents the type of conditions under which, back in Carboniferous times (about 355 to 290 million years ago) the various vegetative fragments fall into the water, and are slowly compressing to form a layer of peat. The peat layer in the swamp is about 7 ft thick, which would convert to about 20 inches of coal. The swamp is slowly sinking, allowing the vegetative mat to continue to deepen and slowly built to a greater thickness. Back in the Carboniferous he noted that the speed at which the layers formed was likely about twice that at which the current Swamp is growing, and that, due to the different levels of pressure required to form them, it would have taken about 160 years to lay down what is now a 1 ft thick layer of lignite; 260 years for a foot of bituminous, and about 490 years for a foot of anthracite. Since it is more worthwhile to mine thicker coal, and eight-feet is a nice working height, this would have required about 2,100 years of steady growth to lay down the layer of vegetation that formed the Pittsburgh seam in Pennsylvania. The original areas over which these forests and swamps grew were vast, and the cycles of deposition grew as the land distorted, with multiple seams being deposited in some cases, and a single thick seam in others. But how has it survived? How much is really there, and how much can we actually produce?