History

About 300 million years ago,

the land we know as England was much nearer to the equator and had a tropical climate. It was covered by a shallow tropical sea and the shells and bones of dead creatures sank to the sea bed, when compressed these formed chalk or limestone.≈ Over the following 100 million years or so  the sea level fluctuated. When sea level was low, a huge swampy area developed.

The plants were huge and vegetation was lush. The action of heat and pressure caused the decayed tropical vegetation to be firstly converted into peat and then into coal, and the intervening sediments into rock strata. It is these Carboniferous sediments that form the solid geology of the area—the Lancashire Coalfield. If we travel down through these rocks for nearly 3,000 feet [ 750m] we find alternating bands of fireclay, coal, mudstone, shale and sandstone. The coal seams themselves vary in thickness from a few inches to about nine feet [2.7m], and are separated from each other by up to several hundred feet of rock. The coal varies in quality and it is not economical to work the very thin seams.

However, seams of good quality coal as thin as fourteen inches [35 cm.] have been worked and there are some miners who actually preferred to work under these difficult conditions. In the Wigan area, these coal measures were downfolded into a basin, with the oldest rocks outcropping along the Billinge Ridge to the west and at Haigh to the east.

The bending of the rocks means that the horizontal beds of rock strata have been severely faulted and fragmented, with the result that coal seams crop out very frequently at the surface. It is at these points that they are easily reached and worked. From the outcrop, many seams dip steeply underground. The sloping, narrow coal seams mean that getting coal in this area was not easy.