Longwall mining is the most destructive form of underground mining possible.
Long gone are the days when hundreds of miners were employed to chip away at a coal seam with hand picks.
Now huge machines called shearers rip through a “wall” of coal typically 250 – 400 metres wide. As the shearer removes coal, hydraulic supports hold the roof of the coal seam up. As the shearer moves forward, the roof collapses behind it. This causes subsidence (vertical sinking) and fissures to appear in the ground above.