Tufa phenomenon

A complex natural process creating tufa on the karst rivers was best described by A. B. Kostić, a Croatian scientist, when he named it a process of eternal circulation of living and non-living matter.

Tufa is a type of porous calcium carbonate created by the sedimentation of calcite from the water with the assistance of tufa-forming organisms thus creating barriers and small lakes. Important for the creation of tufa are also favourable physical and chemical conditions. Karst rivers, including Slunjčica, represent a solution of calcium carbonate as they flow through the limestone soil. While water runs in thin layers through the barriers, carbonate from the water creates deposits. When it bursts into small drops, some of the water evaporates, while the calcium carbonate crystallises. The speed of the sedimentation of tufa depends on the fall and the form of the riverbed as well as the roughness of the surface onto which it is deposited. The creation of the tufa depends on the illumination of the water defining the types of biocenosis in the waterfalls. Optimum conditions for the development of the tufa-forming vegetation are habitats with little light and high water temperatures, while the development of animal life is favoured by the habitats with strong light and colder water.