Depression, a collapsed bell pit, evidence of early coal mining in Middleton Woods
A bell pit is a primitive method of miningcoal, iron ore or other minerals where the coal or ore lies near the surface. A shaft is sunk to reach the mineral which is excavated by miners, transported to the surface by a winch, and removed by means of a bucket, much like a well. It gets its name because the pit in cross section resembles a bell.
Typically, no supports were used and mining continued outwards until the cavity became too dangerous or collapsed at which point another mine was started, often in close proximity. This type of mine was in use in prehistoric times, the Middle Ages and a few continued in use until the early 20th century in the region around Ford, Northumberland. Such pits are common at prehistoric flint working sites such as Grimes Graves in Norfolk.
Bell pits often flooded due to a lack of a drainage system. This, plus the lack of support and the likelihood of collapse, meant they had a limited lifespan. The remains of bell pits can sometimes be identified by depressions left when they collapsed. They were not very effective for mining.