Wigan Album

1980. Derek Winstanley. Diagram to show how coal seams outcrop at the surface at one place and are nearly two thousand feet below the surface not far away. In this case, nine feet of high quality Orrell coal seams outcrop at or near the surface in Winstanley Estate and were mined there first, starting in the 17th century. The technology did not exist then to go very deep. Between Winstanley and Blundell's Pemberton Collieries (just over a mile away) are major geological faults that throw rocks, including coal seams, down a couple of thousand feet. When technologies (steam engines etc) were developed in the 19th Century, this allowed Blundell to go much deeper to mine the same Orrell coal seams, and the other coal seams above - for a total of 71 feet of coal. The shallowest coal seams were the ones mined by opencast during WWII and in the 1980s.