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How is travertine formed?

The creation of travertine barriers is a dynamic process of the combined action of physical and chemical factors and living organisms in the water.

Travertine structures are formed in water with high concentrations of dissolved calcium bicarbonate Ca(HCO3)2.

The formation of travertine begins at the rapids, at uneven places in the river bed, on submerged branches and the like. As the water splashes, the chemical balance of the water is disturbed and CO2 is released. Calcium carbonate (CaCO3) then precipitates out of the water and is deposited on submerged objects. Bacteria, algae and mosses must be present for the deposition of travertine, as travertine attaches to the surface of the moss in the form of microcrystals of calcite that adhere to the sticky secretions of blue-green algae and some species of diatomaceous algae. Both organic and anorganic particles (fragments of animal shells, grains of limestone and dolomite rock, etc.) can be encrusted on these secretions, thus forming a core upon which the calcite crystals will grow. Therefore, these microscopic plants have the role of “catching” the microcrystals of calcite and creating a core around which more calcite will be encrusted, i.e. travertine will be deposited, thus forming a new “brick” in the building of the waterfall.

The process of travertine-building and the growth of travertine barriers is only possible in waters that are oversaturated in calcium carbonate, with a low concentration of organic matter and pH greater than 8. In addition to these three fundamental conditions, travertine-building is greatest at higher air temperatures and water flows faster than 0.5 to 3.5 m/s. The youngest travertine structures will encrust blue-green algae, which then allows for the settlement of light mosses and more vegetation. More vegetation shade the waterfalls and allow for the development of shady mosses, which most stimulate the growth of travertine.