Geology of Coal

Coal is a fossil fuel—an energy source whose beginnings can be traced to once-living organic materials. It is a combustible mineral, formed from the remains of trees, ferns, and other plants that existed and died in the tropical forests 400 million to 1 billion years ago. Over vast spans of time, heat and pressure from Earth's geological processes compressed and altered the many layers of trees and plants, slowly transforming these ancient vegetal materials into what we know as coal today. The several kinds of coal now mined are the result of different degrees of alteration of the original material.

It is estimated that approximately 0.9 to 2.1 m of reasonably compacted plant material was required to form 0.3 m of bituminous coal. Different ranks of coal require different amounts of time. It has been estimated that the time required for deposition of peat sufficient...