Marble. Marble is a metamorphic rock that forms from the recrystallization of limestone due to heat and pressure in the Earth's crust.

The chemical formula of chalk or limestone is calcium carbonate (CaCO3).

Limestone is a compound composed mainly of calcium carbonate minerals. It is not an element, as it is made up of multiple elements (carbon, oxygen, and calcium). It is also not a mixture, as its composition is consistent throughout.

limestone is a soluble rock that can be easily eroded and form caves and sinkholes. As water infiltrates into the ground through these features, it may not flow as surface streams but instead travel underground through interconnected cavities in the limestone. This can result in few visible surface streams in limestone regions.

The Nullarbor Plain was once under the ocean and accumulated layers of limestone over millions of years. The limestone caves formed through a combination of chemical weathering and erosion processes, such as the dissolving of limestone by acidic groundwater and the carving out of caverns by flowing water. This resulted in the unique landscape of the Nullarbor Plain being riddled with limestone caves.