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.


Travertine builders

Species that have the ability of encrusting calcite crystals are called travertine-builders. Algaes and mosses play an important role in the formation of travertine.


Several forms of travertine are known, based on the plants or animals that participate in the construction of these limestone deposits, named after species of travertine building mosses (Cratoneurum commutatum, Brium vebtricosum and Didimodon tophaceus), and chironomid, gastropod and trichoptera, named after travertine building animal groups, the midges (Chironomida), snails (Gastropoda) and caddisflies (Trichoptera).

Species that have the ability of encrusting calcite crystals are called travertine-builders. Algaes and mosses play an important role in the formation of travertine.


Forms of travertine


The most common forms of travertine in flowing karst rivers are underwater shelves, thresholds and barriers, that are found at the bottom of karst rapids, curtains and consoles that arise where the water flows down vertical cliffs, and tufts, troughs and pipes that are created where large quantities of water fall, forming waterfalls.




Dead and live travertine

Outside the present day course of the Krka River, travertine that is about 125,000 years old, called “dead” travertine has been found in the area of the former water course near Knin that was active during geological development.


This travertine was formed during the climatically warm Ris/Würm interglacial period. The active travertine waterfalls of the Krka River, i.e. the parts of the barriers that are found within the present day watercourse, are biodynamic creations that are continually growing through new calcification, and are thus called “live” travertine.

– See more at: