Natural heritage
Geology

KARST

An impressive contrast of avaricious, seemingly halfdesert and inhospitable land on one hand, and biologically and geomorphologically very diverse and rich underwater on the other hand, is one of the basic traits of this area.

Causes of this contrast must be sought primarily in the phenomenon known as the “karst”, which is without doubt one of the most valuable natural resources in Croatia at all.  In Kornati carbonate rocks (limestone and dolomites), which have already been exposed to atmospferic influence and intense processes of carbonization (corrosion and erosion) for 65 million  years -  with longer and shorter pauses - , one can find  almost every karst form  as in the rest of Croatian karst area (caves, pits, karrens, etc.). Because of being unexplored, or at least unsufficiently explored, this “angry” Kornati karst still conceals numerous secrets - both in geological and biological terms.

CROWNS
The famous Kornati “crowns” (steeps and cliffs) are turned towards open see, and they characterize majority of outlying islands in offshore island series. They are a unique characteristic and value of this area.

The story about the creation of the “crowns” has a global   connotation. Because of different processes that took place in Earth’s interior and enormous forces which appeared as their results, the African tectonic plate has been moving east-, northeast-, and northward for millions of years and it has been subducing under the Eurasian tectonic plate. The whole Mediterrenean area, and consequently the Adriatic and Kornati, is lying precisely on this seismic active zone, in which   - as a consequence -  intensive foldings,  faults  and haulings have been  occurring.  One of huge faults that exists due to the prcess of subduction is spread from Istrian peninsula, along the southwest border of the Croatian northern islands, and it finishes somewhere among the middle Dalmatian islands. This fault is manifested most beautifully through the Kornati “crowns”. These vertical cliffs actually represent the fault line along which the movement of adjacent blocks of the Earth’s crust has occurred. Processes of corrosion, erosion and abrasion have just further adorned this huge surface, which in some places in Kornati vertically goes downhill even over 90 meters deep into the sea (the “crowns” of Piskera and Rasip). The highest “crown” in Kornati is on the island od Klobucar (82 m above sealevel), and the longest (above the sealevel) on the island of Mana (1350 m).

GEOLOGICAL HISTORY OF TERRAIN FORMATION
Distinct palaeontological, sedimentological and litosphere characteristics of rocks that we find in Kornati are teeling us an interesting story about the evolution of the Earth through the geological past.

The oldest rocks found in Kornati  were precipitated during early Mesozoic, or more precisely, during the transition period from early to late stage of Cretaceous, approximately 100 million years ago. These rocks are mainly dolomites created due to the process of recrystallization of primarily precipitated limestones in the western part of the then shallow, warm and ethereal Earth's ocean called Tethys. Due to recrystallization and destruction of primary structure, we will hardly find any fossil content in the dolomites.

Above the dolomites one will find limestones which date from the late stage of Cretaceous in which, going towards younger rocks, there is less and less dolomites.  Limestones are mostly precipitated in the shallow, transparent and warm waters. However, one can note the occasional deepening of the sediment basin in which the limestones where created.  When speaking about fossils, bivalves from the group hondrodonta are the most numerous (in the older Cretaceous deposits) and numerous rudist bivalves (in the early Cretaceous deposits).

Upon completion of the Cretaceous (and Mesozoic) some 65 million years ago, due to internal forces of the earth and processes of underscoring (subduction) of the African Plate under the Eurasian Plate, the present area of Kornati folded, faulted, and slipped over. Due to these tectonic processes the seabed has emerged, and the first karstination process of the Kornati carbonates were recorded. Ground phase lasted a relatively short time, so that already in the Paleogene (beginning of the Cenozoic) a new breakthrough of sea in these grounds appeared, either in the form of larger or smaller, more open or more closed pool in which the organisms as biological and sediment materials were dominated by foraminifera (single-celled organisms with limestone shell). Foraminifera gave practically all the building material for limestone from that time which is still found in few places in the area of the Kornati islands (Lavsa, Gustac, Ravni Zakan, Kurba Vela, Kornat).

Further tectonically driven deepening of sediment basin parts resulted in flysch deposits, which are found in the Kornati area only in Gujak bay on the island of Kornat. At the end of the late Eocene (the middle part of Paleogene), the Kornati area was fully emerged.

Very important geological event in this region occurred relatively recently, during the last ice ages. In fact, during the last glaciation (Würm) – about 15 thousand years ago - the sea level was more than 120 m lower than today (because of the huge amount of water trapped in the Earth's polar caps). It is easy to conclude that Kornati were then an integral part of the mainland and the Adriatic Sea reached only to the Jabuka Pit, to half of its present-day spread. Upon completion of the ice age, sea level suddenly rose and sunk the "Kornati” area. Now only the peaks of former hills can be seen above the sealevel.