The introduction of large-scale mining operations occasioned technological innovations which, in turn, permitted more methodical exploration and exploitation of coal seams several hectares in extent and of relatively uniform thickness. The "pillar and bord" or "room and pillar" system of mining, introduced by the G.M.A., facilitated more extensive utilization of a seam. Once the seam's location and magnitude were determined, usually by extensive drilling, certain areas or "pillars" were left intact to support the roof of the mine as shafts stretched farther from the surface. Careful planning allowed several levels to be worked simultaneously. Once the coal was extracted from any given area, the pillars were also mined. This system of mining resulted in the wide distribution of miners throughout the various shafts and rendered direct supervision by management problematic. Most miners at the face would not encounter their supervisors more than once a day. Improved haulage and ventilation equipment allowed for the use of greater numbers of men in the larger mines and, as a result, the expansion of mining communities.
Later in the twentieth century the "long wall" system of continuous mining replaced the "room and pillar" system in most mines. Instead of dividing the mine into a series of blocks for individual miners, a long wall of coal was prepared for cutting and loading and the miners worked together in an interdependent producing unit. Traditional mining skills were gradually displaced as more miners were required to perform maintenance work associated with the automatic cutting and loading machinery which became an integral part of the long wall system.
