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Kraški Rob / Karst Edge

A cache by Vane Send Message to Owner Message this owner
Hidden : 06/08/2013
Difficulty:
2.5 out of 5
Terrain:
2.5 out of 5

Size: Size:   other (other)

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Geocache Description:


(SI) Geološki prerez po trasi avtoceste od Kozine do Kopra je v celoti odkril geološko zgradbo podrivnega pasu v severni Istri. Podrivni pas je nastal s podrivanjem Istre pod Zunanje Dinaride. Znotraj tega pasu se je izoblikovala geomorfološka stopnja, izrazit višinski preskok - KRAŠKI ROB, ki je nastal z narivom apnenca na fliš.

PRED ZAČETKOM:
Prosimo, preberite opis tega geološkega zaklada in si zapišite naloge za vpis se pred odhodom na teren!

NALOGE ZA VPIS ZAKLADA
1. Apnenčasti skladi Kraškega roba so narinjeni na flišne, v smeri proti jugozahodu. S koordinat Geološkega zaklada si oglejte oblikovanost pokrajine ležeče pod steno Kraškega roba. Ali po vašem mnenju sega čelna stena Kraškega roba ob svojem vznožju globlje pod površje ali se konča zelo blizu površine, ležeča na flišni podlagi? Obrazložite svoje mnenje.
2. Sprehodite se pod Kraškim robom med točkama UNDER1 in UNDER2. Vidite lahko, da je stena presenetljivo enotna, malo razčlenjena in ne zelo razpokana. Kompaktni apnenec je ostal precej nepoškodovan, ker je narinjen na mehke plasti fliša. V bližini točke UNDER1, ob stolpu z ostanki gradu, pa vidite nekaj kosov odmaknjenih od glavnega dela stene. Opišite jih.
3. Neobvezna naloga: Kateri dve zavarovani vrsti ptic imata na Kraškem robu eno svojih najpomembnejših gnezdišč v Sloveniji? Odgovor lahko najdete ob parkirišču PRKNG1 (če imate srečo in tam stoji informacijska tabla) ali na spletu.

POMEMBNO!
- Preden vpisete obisk Geološkega zaklada, pošljite odgovore preko GC profila ali neposredno na e-naslov vane.si.geo@gmail.com. Takoj potem lahko vpišete obisk Geološkega zaklada na spletu – ne potrebujete dodatnega dovoljenja. Če ste fotografirali, prosimo, priložite kakšno fotografijo.
- Vpisi brez ustrezne spremljajoče e-pošte, ki vsebuje pravilne odgovore, bodo najprej trajno kodirani, kasneje izbrisani!
- Vpisi, ki vsebujejo odgovore bodo izbrisani!


(ENG) Geologic profile along the highway Ljubljana - Koper, at the section between Kozina and Koper, has revealed the complete structure of underthrusting belt in northern Istria. A distinct geomorphologic step - KRAŠKI ROB - has formed inside this belt, where limestone is thrust over flysch rocks.

BEFORE THE BEGINNING:
Please, read the description of this EarthCache and write down logging tasks before visiting it in the nature!

LOGGING TASKS
1. Limestone layers of Karst Edge are thrusted over flysch layers, in the southwestern dirrection. Observe the terrain profile of the land beneath Kraški rob (Karst Edge). What do you think, how deep under the surface the front wall of Kraški rob extends? Does it end close to the surface, because limestone is laying on flysch layers, or deeper bellow? Explain your answer.
2. Take a walk under the cliff, between waypoints UNDER 1 and UNDER2. You can see that the cliff is surprisingly compact, only marginally indented and not very much fractured. The compact limestoneis almost undamaged, because it has been thrusted uppon softer flysch layers. But close to waypoint UNDER1, near the tower with the castle remains, you can find some large rocks chipped off the main cliff. Describe them.
3. Not obligatory task: Kraški rob (Karst Edge) is one of the major Slovenian nesting sites for two protected bird species. Which? You can find answer at the waypoint PRKNG1 (if you're lucky and an info board is standing there) or on the internet.

IMPORTANT!
- Send answers through GC profile or directly to e-mail vane.si.geo@gmail.com
before logging. After that you can log - you don't need an additional permission to log. Please, upload photos if you have taken them.
- Logs without an accompanying e-mail containing correct answers will be encrypted and later deleted!
- Logs containing answers will be deleted!


slovensko besedilo / Slovenian text
tocke poti in dnevniki / waypoints and logs

Visit our web-site Geološki zakladi / EarthCaches
for a complete list of our EarthCaches and a lot of additional information.

(ENG) GEOLOGY OF WIDER AREA
Some 50 million years ago a smaller part broke off the northern edge of African tectonic plate. It is called Adriatic micro tectonic plate, or simply »Adria«. African plate and its broken-off parts collided with Eurasian plate and caused Alpid orogeny – folding and »rise« of Alps and Dinaric mountains. Adria micro plate has later broken into two parts – western (Po) and eastern (Adriatic) part – roughly along the Kvarner fault. Western part, which includes Istria, has started to turn contra-clockwise, and its corner pushed towards Northeast, underthrusting Outer Dinarides. This way the so called Underthrusting Belt, shown at figure 1, has been formed.

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Figure 1 - Underthrusting of Istria under Dinarides:
A - Orientation sketch, Thrust subdivision of the Dinarides.
B - Istria – Friuli Underthrusting Belt - enlarged view of area indicated with red frame at figure 1A.


UNDERTHRUSTING BELT

Underthrusting Belt in the hinterlant of Istria is unevenly wide and encompasses several Thrust zones. The Belt is widest between Kozina and Koper / Capodistira – about 15 to 16 km. Visible part of the Underthrusting Belt extends from the Trieste Bay coast to Kvarner bay in Eastern Istria. 40 to 100 million years old carbonate rocks, and 30 to 50 million years old flysch form the surface of the Underthrusting Belt. Flysch is the result of the carbonate rocks disintegration.

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Figure 2a: Profile of Istria – Friuli Underthrusting Belt.

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Figure 2b: Geologic profile along the morotway A1, section Kozina – Koper / Capodistria.

Profile at figure 2b shows the cross-section along the motorway from Kozina to Koper /Capodistria, ortogonal to underthrusting structures. It represents the structure of the complete Zone, which consists of several thrust zones. Zones are not simply parallel to one another all along their length. They interwine, or they are segmented, and displacement of the thrusts laterally cross from one trust zone over to another. This complexity is shown at figure 1.

THRUST ZONES AND THRUST FAULTS
We can divide thrust zones into two groups, according to the differences in the structure. Thrust faults have main thrust plane (or main fault) fairly easy distinguishable from the accompanying faults. The thickness of the whole thrust zone is only up to few tens of meters. This kind of thrust faults are located in the carbonete rocks, to the Nort-East from the »karst edge« in the Istria – Friuli Underthrust Belt.
It is a different story to the South-West from the karst edge: Flysch is thrusted over flysch there and thrust zones can be up to several hundreds of meters thick! It is still possible to limit the width of the whole zone, or its here. But the main thrust plane can only be determined where the whole intersection of the zone with the surface is completely uncovered. It is more appropriate to use the general term thrust zone in these cases.
Looking at profile 2b in the direction from North-East to South-West, following thrust zones are marked: Trmun reverse fault (T), Prešnica reverse fault (P), Petrinje thrust fault (PE), Škrklovica thrust fault (ŠK), Kastelec thrust fault (K), Socerb thrust fault (SC) , and Palmanova thrust fault (PN) – this one is locally also known as Črni kal thrust fault (ČK). Then thrust zones are lined: Zanigrad (ZG), Hrastovlje (HR), Kubed (KU), Gračišče (GR), Sočerga (SO), and Buzet thrust zone (BU).
The main structural element of the Underthrust Belt is the Palmanova thrust fault (PN) . To the Notrheast from PN faults in the carbonate rocks have inclination of 25 to 35 degrees. Horizontal displacements along the faults is estimated from 400 meters at the first fault (Petrinje), to about 2900 meters at the third fault. But displacement of layers at Palmanova fault is much larger, estimated to about 10 kilometers! Thrust zones to the Southwest from the PN have ever decreasing inclination.
The Palmanova thrust fault caused the formation of the Kraški rob (Karst Edge) too.

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Figure 3: Underthrusting Belt map:
C - relief map: Red dots represent approximate outer limits of the Belt. Yelow dots follow the Palmanova thrust fault, part of which is named Kraški rob. Edges of several thrust faults are clearly visible at the reief map!
D - topo map: Railway makes long detours from the strait line because of the height difference between land north of the Underthrusting Belt and south of it.


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Figure 4: A part of Kraški rob - Karst Edge at aerial photo.

KRAŠKI ROB (KARST EDGE)
The distincitve geomorphologic step is only formed where carbonate layers are thrusted over softer rocks – these are flysch and transitonal marl. Step-like form is almost not visible or only slighty discernable where flysch is thrusted over flysch.
Only at the end of 20th century a term »Kraški rob« (Karst Edge) came into use. And it is necessary to distinguish between two terms – according to geologic and gemorphologic conditions. Kraški rob (Karst Edge) is now established geographic name for cliffs above Osp river and Upper Rižana river valleys. the term »kraški rob« (karst edge) in general, denotes geomorphologic step of vertical cliffs and steep carbonate slopes along the whole length of Underthrust Belt – between the Timavo river mouth and Učka mountain. These rocky cliffs and slopes mark the border between karstic plateaus Kras and Čičarija at one side, and flysch of Istria and Trieste coastline at the other side.

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Figure 5: Kraški rob (Karst Edge) close to EarthCache coordinates (photo Vane).
E – view towards west: The motorway bridges the step with a tunnel on the upper side and viaduct on the lower side of the Edge.
F – view towards east: This used to be a real Heaven for birds, since people only seldom wandered here. Two sections of the cliff, where climbing is allowed (near Osp and Črni kal villages) are almost overburdened with climbers today.


EARTHCACHE AND ACCESS
Motorway exit Kastelec, direction Podgorje, leave road to Podgorje at waypoint ACCES1, turn right at crossroads – waypoint ACCES2, park your car at parking site – waypoint PRKNG1. Take a walk to the castle and EarthCache coordinates. They are set at the edge of the cliff, at a marvelous viewpoint close to the ruins of the old castle.

Note: You use trails at your own risk. Use only trails you are fit to. Be safe and enjoy!
References:
- Kraški rob (landscape term) –Geologic section along the motorway Kozina – Koper (Capodistria), magazine Geologija 50/1, Geološki zavod Slovenije, Ljubljana, 2007;
- The bases for understanding of the NW Dinarides and Istria Peninsula tectonics, magazine Geologija 53/1, Geološki zavod Slovenije, Ljubljana, 2010;
- relief, topo map, and satelite image are taken from web-atlas Geopedia, www.geopedia.si.



Slovensko besedilo

Obiščite našo spletno stran Geološki zakladi / EarthCaches
za seznam vseh naših Geoloških zakladov in mnogo dodatnih podatkov.

(SI) GEOLOGIJA ŠIRŠEGA OBMOČJA
Pred približno 50 milijoni let se je od afriške tektonske plošče na severu odtrgal manjši kos, ki ga imenujemo Jadranska mikro tektonska plošča ali na kratko »Adria«. Afriška plošča in njeni odlomljeni deli so »trčili« v Evrazijsko ploščo ter povzročili gubanje Dinarskega gorovja in Alp. Adria se je kasneje razlomila na padski in jadranski del, približno ob Kvarnerskem prelomu. Ob zasuku padskega dela v smeri nasproti urinemu kazalcu, se je njen vogalni del, na katerem leži polotok Istra, podrinil proti severovzhodu, pod Zunanje Dinaride. Nastal je podrivni pas prikazan na sliki 1.

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Slika 1 - Podrivanje Istre pod Dinaride:
A - Pregledna skica, pregled delitve narivnih območij Dinaridov.
B - Podrivni pas med Trstom in Buzetom. Povečan prikaz območja označenaga z rdečim okvirčkom na sliki 1A.


PODRIVNI PAS
Podrivni pas v zaledju Istre in Tržaškega zaliva je sestavljen iz več narivnih con in je različno širok. V najširšem poznanem delu med Kozino in Koprom doseže 15-16 km. Mejo pasu tvorita na severovzhodu in jugozahodu mejni narivni coni. V vidnem območju se podrivni pas vleče od obale Tržaškega zaliva do obale Kvarnerskega zaliva v vzhodni Istri. Podrivni pas na površju sestavljajo karbonatne kamnine stare od 40 do 100 milijonov let ter 30 do 50 milijonov let star fliš, ki je rezultat razpadanja karbonatnih kamnin.

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Slika 2a: Prerez Istrsko-Furlanskega podrivnega pasu.

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Slika 2b: Geološki prerez vzdolž avtoceste A1, na odseku Kozina – Koper.

Prerez na sl. 2b poteka po trasi avtoceste med Kozino in Koprom, pravokotno na narivne strukture. Na njem je prikazana zgradba celotnega podrivnega pasu, ki je sestavljen iz več narivnih con. Te cone niso kar preprosto vzporedne ena drugi. V vzdolžni smeri (gledano na večjih razdaljah) se prepletajo med seboj, ali pa so ločene (segmentirane) in premiki narivanja bočno prehajajo od ene narivne cone na drugo. Kompleksnost tega neenakomernega razporeda je razvidna na sliki 1.

NARIVNE CONE IN NARIVNI PRELOMI
Potrebno je omeniti razliko v zgradbi narivnih con, ki jih lahko ločimo v dve skupini. Pri narivnih prelomih je razmeroma lahko določiti glavno narivno ploskev, oziroma glavni narivni prelom, od spremljajočih, debelina celotne narivne cone pa je le do nekaj deset metrov. V obravnavanem podrivnem pasu so takšni narivni prelomi v karbonatnih kamninah, severovzhodno od kraškega roba. Jugozahodno od kraškega roba, v narivih fliša na fliš, pa dosežejo narivne cone debelino tudi do več sto metrov in je le v primerih popolne razkritosti mogoče določiti glavno narivno ploskev. Povsod pa je mogoče omejiti širino narivne cone, oziroma njen presek s površjem. Zato je na takšnem primeru ustreznejši kar splošen izraz narivna cona. Na prerezu (slika 2b) so v območju podrivnega pasu označene naslednje narivne cone (od severovzhoda proti jugozahodu): trmunski narivni prelom (T), preški reverzni prelom (P), petrinjski narivni prelom (PE), škrklovski (ŠK), kastelski (K), socerbski (SC) in palmanovski narivni prelom (PN) – ta je lokalno znan tudi kot črnokalski narivni prelom (ČK). Sledijo narivne cone: zanigradska (ZG), hrastoveljska (HR), kubejska (KU), gračiška (GR), sočerska (SO) in buzetska narivna cona (BU). Osrednji strukturni element podrivnega pasu je palmanovski narivni prelom (PN) . Severovzhodno od njega imajo narivni prelomi v karbonatnih kamninah nagib 25 do 35°, zamiki plasti ob njih pa znašajo od približno 400 metrov pri prvem (petrinjskem) do približno 2900 m pri tretjem prelomu. Pri palmanovskem narivnem prelomu pa je zamik plasti znatno večji, ocenjen na 10 kilometrov! Jugozahodno od PN imajo narivne prelomne cone v flišu postopoma vse manjši nagib. Palmanovski narivni prelom je povrzočil tudi nastanek Kraškega roba.

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Slika 3: Karta podrivnega pasu:
C - relief: Rdeče pike označujejo približne zuanje meje pasu. Rumene pike sledijo palmanovskemu narivnemu prelomu, katerega del nosi pokrajinsko ime Kraški rob. Na reliefni karti so jasno vidni robovi večine narivnih prelomov! Najizrazitejši je prav palmanovski (ali črnokalski).
D - topografska karta: Železnica zaradi višinske razlike med ozemljem severno in južno od podrivnega pasu zavije daleč vstran od ravne linije proti morju.


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Slika 4: Del Kraškega roba na orto-foto posnetku.

KRAŠKI ROB
Izrazita geomorfološka stopnja je opazna le tam kjer so karbonatne kamnine narinjene na mehkejše kamnine, to sta fliš ali prehodni laporovec. Tam kjer je fliš narinjen na fliš »stopničasta« zgradba ni vidna ali pa je neizrazita. Za del geomorfološke stopnje se je šele konec 20. stoletja uveljavil izraz Kraški rob. Glede na geološke in geomorfološke danosti, je treba razlikovati dva pojma. Kraški rob je danes uveljavljeno pokrajinsko ime za stene nad dolinama Osapske reke in zgornje Rižane. Izraz kraški rob v splošnem pomenu, pa označuje geomorfološko stopnjo iz prepadnih sten in strmih karbonatnih pobočij v celotni dolžini med izlivom Timave in Učko. Te kamnite stene in pobočja tvorijo mejni pas med kraškim planotastim svetom Krasa in Čičarije na eni strani ter flišno Istro s tržaškim flišnim obalnim pasom na drugi.

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Slika 5: Kraški rob blizu koordinat geolškega zaklada (foto Vane).
E – pogled proti zahodu: avtocesta premošča Kraški rob s tunelom in vsekom na zgornji strani in viaduktom na spodnji.
F – pogled proti vzhodu: Dolgo časa je bil to pravi raj za ptice, saj so ljudje sem le občasno zašli. Danes sta dva odseka stene, kjer je plezanje dovoljeno (pri Ospu in Črnem kalu), kar preobremenjena s plezalci.


GEOLOŠKI ZAKLAD IN DOSTOP
Avtocestni izvoz Kastelec, smer Podgorje, cesto proti Podgorju zapustite na točki ACCES1, na križišču ACCES2 zavijte desno, parkirajte na prostoru PRKNG1. Sprehodite se do gradu in Geološkega zaklada. Koodrinate zaklada so postavljene na rob stene, oziroma Kraškega roba, na razgledišče s širnimi razgledi, blizu ruševin starega gradu.

Opomba: Poti uporabljate na lastno odgovornost! Hodite le po poteh za katere ste ustrezno pripravljeni! Zelimo vam varno pot in veliko uzitkov!
Viri:
- Kraški rob – Geološki prerez vzdolž AC Kozina – Koper, revija Geologija 50/1, Geološki zavod Slovenije, Ljubljana, 2007;
- Osnove razumevanja tektonske zgradbe NW Dinaridov in polotoka Istre, revija Geologija 53/1, Geološki zavod Slovenije, Ljubljana, 2010;
- relief, topo karta in orto-foto posnetek so povzeti iz spletnega atlas Geopedia, www.geopedia.si.



tocke poti in dnevniki / waypoints and logs

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