The Crowns of Croatian Islands

English:

The Crowns of Croatian Islands

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 telling 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.

Source: kornati.hr

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1.) Estimate the hight of the cliffs at the position.

2.) Which two tectonic plates are involved building the crowns? (as shown on the info panel / see additional waypoints)

3.) Of what two types of stone are the bottom layers of the crowns made of?

4.) At which location are the crowns rising 161m above the sea level?

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Enjoy your stay at dugi otok and the beautiful area.

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Hrvatski:

Krune

?uvene kornatske "krune" (strmci ili litice) okrenute prema otvorenom moru, a koje karakteriziraju ve?inu vanjskih otoka u Pu?inskom oto?nom nizu, posebna su odlika i vrijednost ovog prostora.

Pri?a o nastanku "kruna" globalnog je karaktera. Zbog razli?itih procesa koji se zbivaju u Zemljinoj unutra?njosti i golemih sila koje nastaju kao njihova posljedica, Afri?ka tektonska plo?a se ve? milijunima godina pomi?e prema istoku, sjeveroistoku i sjeveru i podvla?i (subducira) pod Euroazijsku tektonsku plo?u. Cijeli sredozemni prostor, a samim tim i jadranski i kornatski, le?i upravo na ovoj seizmi?ki aktivnoj zoni, u kojoj su se - kao posljedica - zbivala (i jo? uvijek se zbivaju) intenzivna boranja, rasjedanja i navla?enja Zemljine kore. Jedan od golemih rasjeda nastalih procesom subdukcije proteze se od istarskog poluotoka, pru?a se sasvim blizu jugozapadnih rubova sjevernih hrvatskih otoka, te zavr?ava negdje me?u srednjedalmatinskim otocima. Ovaj rasjed najljep?e se manifestira upravo u Kornatskim "krunama". Kornatske okomite litice zapravo predstavljaju paraklazu rasjeda po kojoj je do?lo do kretanja susjednih blokova zemljine kore na ovim prostorima. Procesi korozije, erozije i abrazije samo su dodatno ukrasili ovu golemu plohu koja se na nekim mjestima u Kornatima okomito spu?ta i preko 90 metara u morske dubine ("krune" otoka Piskera i Rasip). Najvi?a "kruna" u Kornatima nalazi se na otoku Klobu?ar (82 m iznad nivoa mora), a najdua (iznad nivoa mora) na otoku Mana (1350 m).

GEOLOSKA POVIJEST STVARANJA TERENA
Razli?ite paleontolo?ke, sedimentolo?ke i litolo?ke karakteristike stijena koje nalazimo u Kornatima pri?aju zanimljivu pri?u o evoluciji Zemlje kroz geolo?ku pro?lost.

Najstarije stijene koje nalazimo u Kornatima istalo?ene su u vrijeme mla?eg mezozoika, ili preciznije, u vrijeme prijelaza donje u gornju kredu, dakle prije nekih 100-tinjak milijuna godina. Ove stijene uglavnom su predstavljene dolomitima nastalim rekristalizacijom primarno istalo?enih vapnenaca u zapadnom dijelu tada?njeg plitkog, toplog i prozra?nog Zemljinog oceana zvanog Tethys. Zbog rekristalizacije i uni?tavanja primarne strukture, u dolomitima ne?emo na?i gotovo nikakav fosilni sadr?aj.

Iznad dolomita nalaze se gornjokredni vapnenci u kojima je, idu?i prema mla?im stijenama, sve manje dolomita. Vapnenci su uglavnom istalo?eni u plitkom, prozra?nom i toplom moru, ali u njima se ipak primje?uje i povremeno produbljavanje sedimentacijskog bazena u kojima su stvarani. Od fosila, prevladavaju ?koljkasi iz skupine hondrodonta (u starijim krednim naslagama) i brojni rudisti (u mla?im krednim naslagama).

Zavr?etkom krede (i mezozoika) prije nekih 65 milijuna godina, zbog unutarnjih Zemljinih sila i procesa podvla?enja (subdukcije) Afri?ke plo?e pod Euroazijsku, prostor dana?njih Kornata se borao, rasjedao i navla?io. Zbog tih tektonskih procesa morsko dno je izronilo i tada se bilje?e prvi procesi okr?avanja kornatskih karbonata. Kopnena faza je trajala relativno kratko, pa je ve? u paleogenu (po?etak kenozoika) nastupio novi prodor mora na ove terene i to u obliku ve?ih ili manjih, otvorenijih ili zatvorenijih bazena u kojima su od organizama kao biolo?kog i sedimentacijskog materijala dominirale foraminifere (jednostani?ni organizmi s vapnena?kom ljusturom). Foraminifere su dale prakti?ki sav gra?evinski materijal za vapnence iz tog vremena koje danas nalazimo na nekoliko mjesta u podru?ju Kornatskih otoka (Lavsa, Gustac, Ravni Zakan, Kurba Vela, Kornat).

Daljnje tektonski uvjetovano produbljavanje dijelova sedimentacijskog bazena rezultiralo je talo?enjem fliskih naslaga, koje u Kornatima nalazimo samo u podrucju uvale Gujak na otoku Kornatu. Krajem eocena (srednji dio paleogena), kornatski prostor je potpuno izronio.

Vrlo zna?ajan geoloski doga?aj u ovim prostorima zbio se relativno nedavno, tijekom posljednjih ledenih doba. Naime, za vrijeme zadnje glacijacije (würm) ? prije 15-tak tisu?a godina ? nivo mora je bio za preko 120 m ni?i nego danas (zbog goleme koli?ine vode zarobljene na Zemljinim polarnim kapama). Lako je zaklju?iti da su Kornati tada bili sastavni dio kopna i da je Jadransko more dopiralo samo do Jabucke kotline, do polovice svog danasnjeg pru?anja. Po zavr?etku ledenog doba, nivo mora je naglo porastao i "potopio" Kornatski prostor. Sada iz mora vire samo vrhovi nekada?njih brda.

Source: kornati.hr

To log this earthcache please send the answers to the following questions via profile to me. You may log this cache immediately, I will get back to you if the answers are wrong.

1.) Estimate the hight of the cliffs at the position.

2.) Which two tectonic plates are involved building the crowns? (as shown on the info panel / see additional waypoints)

3.) Of what two types of stone are the bottom layers of the crowns made of?

4.) At which location are the crowns rising 161m above the sea level?

I would be happy if you attach a picture to your log, but due to the guideline this is optional.

All non premium members that would like to log this cache can use this: Link

Enjoy your stay at dugi otok and the beautiful area.

  PrefixLookupNameCoordinate PH PHOTO Photo Location (Final-Position) N 43° 53.441 E 015° 09.407    Hinweis: PN PNL Info panel (Frage zur Beantwortung) N 43° 53.422 E 015° 09.463    Hinweis: