Limestone is an organic, sedimentary rock. This means it was formed from the remains of tiny shells and micro-skeletons deposited on the sea bed. They were compressed to form solid rock. Limestone is made up of calcium carbonate and reacts with diluted hydrocloric acid.
Limestone is formed in layers - called bedding planes.
These bedding planes contain vertical cracks called joints. Joints and bedding planes make the rock permeable. Erosion of Limestone Weathering is the breakdown of rock by physical, chemical or biological processes. Limestone areas are weathered when rainwater, which contains a weak cabonic acid, reacts with limestone. When it rains limestone is dissolved.