Limestone is a rock that is softer than other kinds of rocks.
It formed in wet places so there are shells in it.
Rain water drips through cracks in limestone and dissolves it to make caves.
Inside the caves there are shapes called stalagmites and stalactites.
Limestone is a sedimentary rock. It is formed by layers of small pieces of rock and stones pressed hard together.
The stone forms in wet areas which means it also contains shells and waste matter from organisms that live in water.
Limestone caves are formed when rainwater seeps through cracks in limestone rock and dissolves it.
Limestone is generally formed in a warm shallow sea where plants and animals thrive. When they die, the skeletons and shells of the animals settle on the seabed, and give out a mineral known as calcium carbonate. Over time, the shells, skeletons and calcium are mixed with algae, sponges and the remains of other sea life to form hard layers of the rock we know as limestone.
Limestone turns into the metamorphic rock marble when it is subjected to high amounts of pressure and heat. Marble can be polished and is used in buildings as floors, and as wall tiles. It can be in many different colours.
Movement under the Earth’s crust lifts the sedimentary rock up out of the water to create mountains and hills. Trees and plants grow on the hills and cause the rock to crack. As rainwater pours through the cracks in the stone, the limestone begins to dissolve, and caves begin to form underground. As the water continues to dissolve the rock, large pieces of the rock fall from the ceiling of the cave and more underground chambers form.
Stalactites and stalagmites
Interesting features of limestone caves are stalactites and stalagmites. Stalactites are icicle-like deposits of calcium carbonate formed by the dripping of water from the ceiling. Stalagmites are deposits of calcium carbonate formed on the floor of a cave by the dripping of water.
Uses of limestone
- Limestone is important to making cement.
- It is used in glass making.
- Layers of crushed limestone are placed underneath roads and underneath railroad tracks.
- It helps clean drinking water and treat sewage.
- Fertilizer used by farmers contains ground up limestone. It is a food for the plants and is good for the soil.
- Animal feed also contains some limestone.