The hard rocks surrounding the Krka River were once seabed.
This sea was part of the ancient Tethys Ocean that the Dinarides rose from. The Dinarides mountain range is primarily built of carbonate rock (limestone and dolomite), created by the deposition of seashells through the eras of the Mesozoic that included the Triassic, Jurassic and Cretaceous periods.
The water solubility of carbonate rock is perhaps the most important condition for the karstification process. In essence, this is a chemical process that has taken place for millions of years, and is still ongoing. Water corrodes the carbonate rocks, creating fissures, which make it impossible for the rock to retain water. Both tectonic and mechanical processes play a part in this process. The present day appearance of the Krka Canyon is the result of tectonic movements, and superficial karstification processes in the carbonate deposits of Mesozoic and Tertiary age. From the rocks surrounding the Krka River, we can read their geological timeline. If the limestone layers that we see on the canyon walls are of varying composition, purity and thickness, then we know that they settled under differing conditions, and the position and types of deposits explains how the sea surface rose or fell.
Hollowness and fissures are the main features of the rock of karst landscapes. This leads to the formation of numerous pits and caves. The karstification process is also responsible for the formation of the ornamentation within these structures. Under special conditions, it is possible that this process is reversed: where calcium carbonate is again secreted, and instead of wearing, the rock grows. That results in the formation of stalagmites and stalactites, as well as travertine (tufa), the fundamental phenomenon of Krka National Park.
Like the sight of living water flowing through its opposite, hard rock, so too is the dual nature of karst: rugged, and yet so vulnerable to pollution, which can easily enter the groundwater due to the permeability of the rock. However, this is also its value, as the constant two-way circulation of water creates a diversity of habitats on the surface and underground, ensuring living conditions for so many different species, including rare, threatened and endemic species.
Now that we know what karst is, it is easier to understand the eons that it took for the Krka River to be born and to grow, creating the plateaus, cutting the canyons and raising up the travertine barriers. Karst here is the main feature: in addition to creating the landscape around us, it has also defined the way of life for the people living here. The karst regions of Croatia, which forms an uninterrupted belt 50 – 100 km wide along the entire Adriatic coast, covers about 46% of the nation’s land territory. It is our duty and responsibility to protect it, so that our future generations can also read their history from its rock.