Pamukkale mineral terrace. Limestone (calcium carbonate) terraces at the Pamukkale (meaning inscastle of cottonins) hot spring site, Turkey. The terraces are comprised of semi-circular basins which cascade down a hillside. They are created because hot water emerging from the ground experi- ences a sudden reduction in pressure. This causes the carbon dioxide in the water to vaporise, leading to the dissolved calcium carbonate precipitating out of solution. The terrace layers of Pamukkale have an average length of 3 kilometres and an average width of 300 metres. Hot springs like this are common in areas where geothermal heat is brought close to the surface.