Geological base and hydrogeology of the area of the lakes

Geological base of the area which is located within the borders of the Plitvice Lakes National park, as well as its large surrounding area, is a part of a large carbonic environment with layers of Mesozoic era on the immediate surface. The basic kinds of stone that we can differentiate are a limestone and dolomite with a number of varieties which are visible in relief differences and in either absence or presence of water on the surface.

Formation and feature of todays relief in this part of Croatia is the result of numerous occurrences in geological past which took place in a large area of Dinaric ranges during the formation of mountain ranges such as todays Velebit, Velika and Mala Kapela and Licka Pljesevica. While that was happening, a very porous and low porous area were created by movement and erection of large blocks of stone, broken by regional and local faults. Due to the colder and more humid climatic conditions in Pleistocene era - water as a factor which destroys, corrodes and dissolves the carbonic layers both mechanically and chemically - was penetrating in different ways into the rocky base and by incising formed gradually what is todays relief. The compact or imporousness of mostly dolomite stratums of Mesozoic era had, as a consequense, water penetration up to the different depths in existing mountain ranges and the other areas with the changeable superficial and subterranean waterflow, and more or less visible process of karstening that was taking place on the rocky relief.


The proposition of low porous dolomites in regards to karstened and Jurassic layers of limestone system, has conditioned the final - todays appearance of the whole area within and around borders of the National park. Specific hydrogeological characteristics of dolomite rocks have conditioned possibility of lake creation, but also canyon incisions in the chalky layers of Cretaceous age.


Certain chemistry of water conditioned by litology of rocky layers, then water accumulation in karsted subterraine with permanent in and outflow, have made possible and helped the development of biological component (appearance of vegetable organisms) along with origin of various travertine - forming - plants and travertine deposit and with creation and growth of travertine barriers in the lake water. Dolomite base of Triassic age has made possible accumulation of lake water in the area from todays Proscensko, through Ciganovac, Galovac and Gradinsko jezero (lake) to the end of the lake Kozjak. Accumulation is now still being fed continuously and abundantly by waterfluws from the White and Black river (Bijela i Crna rijeka) and from the Brook from existing subterranean accumulation as well as from superficial water of melted snow and from numerous small but permanent springs.


On the enclosed hydrogeological profile, a drainage basin is shown in the hinterland of the Plitvice Lakes. There are layers of karsted limestone with a dolomite interlayers of Jurassic age (blue color and mark "J" on the sketch). White arrows are indicating movement of subterranean waterflows towards springs of the White and Black river. From Proscansko jezero (lake) to the end of Kozjak, the base is made of dolomites of Triassic Age (mark "T" on the light - violet base), while lower Lakes and the Korana canyon are increased in karsted rudistic limestone rocks of Cretaceous Age (mark "K" on the green base). The drawings above are showing in circles the process of limestone rocks karstening which water penetrates in, then karst spring next to the edge of field Brezovac, through which that very water siniks in subterrain through the funnel shaped holes. That water appears again in the spring of the Black river, and after creating a lake, spreads between afforested mountain slopes - as for example in Gradinsko lake next to which are located dolomite rocks. Schematic cross - section of travertine barrier shows the halt of water between the Lakes, permanently growing up, while the last drawing presents incised canyon where the Lower Lakes a situated, as well as the Korana river flow. 



Geological attractions along the promenades


At the Entrance point 1, the main attraction is a view on the Plitvica stream fall over vertical cliff that is 70 metres high. By a strong retroactive erosion, water has formed a scar which resembles a kettle in which everything is rumbling from a large waterfall drop during the spring floods. It is a classic example of erosion and corrosion of waterstream.


Right across Sastavci, at the level of the stream fall, our view from a lookout point is discovering a big entrance of the cave Supljara which is located just above the lake Kaluderovac, but it was broken through and surrounded by work of water in the geological past, as well as "a tunnel" of upper Kaluderovac cave which inclines towards the "kettle" under the Plitvica stream fall. Going downwards from the Entrance point 1 towards Sastavci and towards the lower path along the Lakes, have a look at the gray limestone rock on the second curve. Irregular sediment of rudist traces can be perceived in the level of your eyes - prehistoric animal of clam which formed limestone layers of Cretaceous geological period.


On the sharp curve on the road above Glibovita draga of Kozjak lake and above the lake Gradinsko, from a panoramic train a ruined dolomite layers which look like spring of permanent outflow can be observed. We can also see beautiful dolomite rocks and mountain spurs next to the western path, between the lake Galovac and Gradinsko lake.


We can also notice a soft travertine on the northern side of the lake Gradinsko, close to Burgeti and origin of travertine and growth of travertine - forming - plants can bee seen at the waterfalls where a walkway made of small wooden bridges goes.