Pg.no. 97
24. Formation of Coal and Soil
Coal formation:
Coal is a solid, black, readily combustible fossil fuel that contains a large amount of carbon-
based material - approximately 50% of its weight. The formation of coal takes a significant
amount of time, with coal beginning to form 290-360 million years ago, in a time known as
the Carboniferous or "coal-bearing" Period. As well, there are extensive coal deposits from
the Cretaceous age - about 65 to 144 million years ago.
The formation of coal begins in areas of swampy wetlands where groundwater is near or
slightly above the top soil. Because of this, the flora present produces organic matter quickly
- faster in fact than it can be decomposed. In these areas, layers of organic matter are
accumulated and then buried. It is these layers of organic material that then form coal. The
energy in coal initially comes from the Sun, and is energy from sunlight trapped by dead
plants.
Figure 24.1 (Coal formation)
Process
The process that creates coal varies slightly in different areas depending on the plants and
conditions that are present, but the overall process is similar. There are two main phases in
coal formation: peatification and coalification. Bacterial activity is the main process that
creates the peat during peatification. Increasing temperature and pressure from burial are the
main factors in coalification.To form coal, the following steps are followed
1. Plant matter in mires and wetlands, such as ferns, shrubs, vines, trees, and algae dies and
accumulates on the surface. Initially the organic matter is decomposed by bacteria, yielding
carbon dioxide and methane.
2. The plant matter becomes buried, and is no longer exposed to air. Anaerobic bacteria then
starts to decompose the material. Burial and accumulation can occur for several thousands of
years, producing several meters of partially decayed plant matter known as peat.