Underground features

A cross section of a limestone pavement before the effects of chemical weathering have taken placeThe formation of a limestone cave – before chemical weathering

A crosssection of a limestone pavement showing what a limestone cave looks like after the effects of chemical weathering have taken placeThe formation of a limestone cave – after chemical weathering

Underground CaveUnderground cave

Inside a cave with stalactites and stalagmites
Inside a cave with stalactites and stalagmites

Inside the cave are a number of distinctive features, which have formed over thousands of years. They are all the result of water permeating the rock and dissolving the limestone.

  • Large caverns can form underground in carboniferous limestone landscapes. They form when chemical solution is more active.
  • They can also be enlarged by the usual processes of river erosion – hydraulic action, corrosion and corrasion.
  • As water flows underground it dissolves the limestone around it.
  • The dissolved limestone (calcium carbonate) is carried away by the water in solution.

The video below talks about the formation of caves.

Caves

Stalactites, stalagmites and pillars

Inside of a limestone cave showing stalctites hanging from the ceiling and stalagmites on the ground
  • Water drips from the roofs of caverns very slowly and evaporates. As the water evaporates, through a process known as gas diffusion, solid calcium carbonate is deposited on the cavern roof.
  • This will build-up over time to form long, thin deposits which grow downwards and look like icicles hanging from the ceiling of a cavern - these are called stalactites.
  • Some drops of water fall to the floor of the cavern where they splash and evaporate.
  • The splash spreads the deposit of calcium carbonate and as more and more calcium carbonate builds up on the floor, short, wide, dumpy features grow upwards from the ground - these are called stalagmites.
  • Occasionally stalagmites and stalactites grow towards one another and join to form a rock pillar.