Coal is compressed plant matter that over millions of years transformed into a high-carbon material. Age, type of initial vegetation, and location of deposit formation are all significant factors in the quality of a coal deposit. Scientific research indicates that the first plants to grow on land appeared more than 400 million years ago during the Silurian and Devonian periods of the Paleozoic Era. This early vegetation consisted mostly of leafless shoots. Some 375 million years ago, extensive forests covered much of the world, and it is approximately from this time that coal deposits have been dated. The period from 350 to 275 million years ago is known as the Carboniferous period, and during this time many coal deposits originated. This was a period of globally warm temperatures, which encouraged plant growth. Indeed, plants and vegetation grew to unimaginable sizes when compared to our current world. Giant ferns and plants the size of current-day mature trees were quite common.

At the end of the Carboniferous period and for about 135 million years thereafter coal formation in the Northern Hemisphere greatly diminished. With the onset of the Cretaceous period in the Mesozoic Era (around 135 million B.C.), plant growth and coal formation resumed, although by this time more complex vegetation, including plants and trees with protected seeds, had begun to dominate the landscape. Thus, the coal that we use today developed over hundreds of millions of years from a wide variety of vegetation. What was the process behind coal formation?

To understand...