Mine Subsidence Awareness Month

Subsidence is soil sinking to fill voids in the strata (or soil layers).  These voids can be caused by water erosion, uneven soil compaction, or the collapse of mine shafts.

Sometimes, vast amounts of coal are discovered in a single deposit.  It is often the result of an ancient lake or other body becoming completely filled with peat and turning to coal.  These are called �fields�.  In order to remove a field, vast excavations occur.  This means that timbers are constructed to keep the soil crust above from caving in.  During the mining process, portions of the coal, or other earth, would be left in pillars to help reduce the risk of cave in.   As the mine tapped out the remaining coal in the area, these pillars would eventually be removed as well and replaced with rubble, or timber.  Naturally, the pillars do not last forever.  When the soil crust above the field collapses, large areas of subsidence occur.  This subsidence usually happens quickly with dramatic results.

Check back next week for helpful checklists and answers to the most commonly asked questions about subsidence!