Rudland Rigg Spoil Heaps, North Yorkshire
These spoil heaps on open moorland are the remains of an 18th-century colliery. From around the mid 1850s, shafts following a thin seam of coal were sunk to a depth of between 9 and 12 metres. The shafts, spaced 40 metres apart, were then connected at the bottom by a series of passages from which coal was mined, leaving a pillar of unexcavated material between each shaft to support the roof. Excavation rubble from these operations created this uniform series of mounds.
