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  23.06.2020, 11:35h


How it all began: travertine is the builder of waterfalls on which the living world of the Krka River rests

 

Travertine or tufa is the name for calcium carbonate (limestone) rock that is formed in rivers when minerals from the water settle onto different types of surfaces. Travertine is the fundamental phenomenon of Krka National Park: the creation and development of travertine barriers has shaped the present day appearance of the river bed and the characteristics of the living world of the Krka River. Travertine is frequently found in the surface watercourses of the Dinaric karst, though rarely does it build waterfalls like those on the Krka. That is why in the cycle of publications How It All Began, after the relief, tufa is presented through ten texts. Time has ended a great whole about the origin of the Krka, the primordial actions that created the landscapes we know today. Now we have to get to know the living world that is in them.

For centuries prior to the proclamation of Krka National Park, travertine (tufa) was used as a building material in the areas along the Krka River. Even the Church of St. Nicholas at Skradinski buk waterfall was constructed entirely of travertine. Preserving the good ecological condition of water at the barriers is a top priority task of ecological protection, as the development and survival of the living communities on the barriers depends on it.

 The travertine-building process is constant and dynamic and is based on the mutual action of physicochemical conditions and the living organisms in the water. Travertine can only be formed in water containing sufficient quantities of dissolved calcium bicarbonate. Plants, especially mosses, serve as a substrate on which calcite is excreted from the water But calcium carbonate dissolved in the water is not enough to result in the formation of travertine (limestone). Temperature is also an important factor, especially in the summer (vegetative) period. Other importance factors are water aeration, splashing of water particles, pH value, speed of water flow and the substrate of the riverbed. In this process, the travertine-building organisms (algae and mosses) play a very important role, with the ability to retain precipitated calcium carbonate and to create tufa deposits. The most common forms of travertine in karst watercourses are the underwater sheaths, thresholds and barriers found at the base of the karst rapids, curtains and consoles.

The process of travertine building began in the Pleistocene, the last ice age, and with occasionally interruptions has lasted until the present day. Most of the travertine at the waterfalls is less than 10,000 years old. Outside the present-day course of the Krka River, in the area of the river's previous course near Knin that which was active during the time of the river’s geological development, we find travertine about 125,000 years old – fossil travertine. According to the structure and size of travertine barriers, it can be seen that the largest amount of travertine was deposited near the river, where the speed of water flow was lower. Skradinski buk is the largest travertine barrier on the river Krka and the longest travertine barrier in Europe.

The travertine waterfalls of the Krka River are a natural and karst phenomenon with appropriate values of world scientific interest. With a total flow drop of 224 m, from the source are Bilušića buk (22.4 m), Brljan (15.5 m), Manojlovac (59.6 m), Rošnjak (8.4 m), Miljacka (23, 8 m), Roški slap (25.5 m) and Skradinski buk waterfall (45.7 m). Waterfalls have a very delicate structure and a dynamic purposeful complex sensitive to natural changes and all human activities. Only with the constant growth of travertine it is possible to preserve the survival of waterfalls, which are the backbone of the hydrogeological and landscape image and the foundation of the biological diversity of the Krka National Park.