Q.  How were coal deposits formed?

A.  From huge forests floating as rafts on the surface of shallow seas.

Q.  Does this apply to all sorts of coal?

A.  No, only the hard coals formed during the Carboniferous and Permian periods.

Q.  How can such an extreme explanation be justified?

A.  It is the only explanation which explains some distinctive features of coal deposits.

Q.  Such as?

A.  First, coal seams are interlaid by layers of certain sedimentary rocks (limestones and shales) which are formed in seas, distant from shores.