Limestone is a sedimentary rock that is made up of horizontal blocks called bedding planes and vertical cracks called joints. Limestone is also a permeable rock which means that water can pass through its joints and cracks.
The chemical weathering is shown by the formula:
(limestone + carbonic acid → calcium hydrogen carbonate solution)
If carboniferous limestone is capped by impermeable rock, surface streams can run on to limestone. However, this water disappears from the surface, either by seeping through joints in the limestone or as streams disappearing down through swallow holes.
It is the action of water which is responsible for many of the distinctive features of upland limestone scenery.