Limestone
How limestone is eroded
Limestone is a sedimentary rockA type of rock formed by the deposition of material at the earth's surface. that is made up of horizontal blocks called bedding planesLayers of sedimentary rock. and vertical cracks called jointsA crack in a rock formed when the rock dried out or pressure is released.. Limestone is also a permeable rockA type of rock which allows water to pass through its joints and cracks, eg limestone. which means that water can pass through its joints and cracks.
Limestone is made of calcium carbonateThe main chemical composition of limestone. which is dissolvedWhen something is broken up in a liquid and no longer exists. by rainfall, a weak carbonic acidWhen the gas carbon dioxide mixes with water to form an acidic solution.. This process is called chemical weathering.
Chemical weathering of limestone pavement
The chemical weatheringThe erosion of rocks by chemicals that react with their minerals. is shown by the formula:
(limestone + carbonic acid 鈫 calcium hydrogen carbonate solutionWhen chemicals in the water dissolve minerals in the rocks, causing them to break up (also called corrosion).)
Limestone landscapes
If carboniferous limestoneA type of sedimentary rock formed between 363 and 325 million years ago. is capped by impermeable rockRock which does not allow water to pass through it, eg granite., 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.