Krčnik – korita in naravni most / Natural Bridge EarthCache

(SI) Krčnik, senčna korita z naravnim mostom.

(ENG) Krčnik, shady gorge spanned by natural bridge.

(ENG)BEFORE THE BEGINNING:
Visit our website Geološki zakladi / EarthCaches
for complete list of our EarthCaches and a lot of additional information.

(ENG) KRČNIK
Krčnik Troughs are located on the Kožbanjšček brook under the village Kožbana in Goriška Brda. The brook carved very picturesque troughs into the limestone. They are about 40 meters long, up to 6 m deep and from 0,5 to 6 meters wide.
Just above the throughs you can see dam and remains of the mill. These remains, old as they are, somewhat diminish the feeling of Krčnik wilderness. But they don’t spoil the amazement of the visitor watching the nature’s workshop, displaying different rock formations, erosion potholes, waterfalls. Luckily, these were left untouched in the whole length of the Throughs.
Krčnik Throughs begin with large erosion pothole – a deep circular, bowl-shaped depression, formed by water with the help of abrasive sediments (sand, pebbles, boulders). When the water turbulence whirls rock particles, they slowly, but surely carve the bedrock. A natural bridge spans the pothole approximately at the middle. The rocky bridge is about 5 m long, 1.5 m thick and 1 m wide. Its surface is rounded and smooth, as it too has been formed by water in the process of abrasion. This natural bridge belongs to the most beautiful bridges in Slovenia. There are not many natural stone bridges of this kind in Slovenia, since they are mostly formed by weathering of rocks and have uneven surfaces and sharp edges.
Troughs continue with a narrow channel, only half a metre wide at places. Channel is interrupted with several potholes, up to 5 metres deep. At the end, Throughs open to the gorge with steep walls, and soon run into the narrow valley.


Image 1: Krčnik: A – dam above the troughs, B – first waterfall, C – upper part of troughs, D – lower part of troughs, E – life in the surroundings; photo kompaski

The naming of the natural bridge and Throughs has several explanations. One of the most popular is a story known by people from the surroundings: »In the past, boys from Kožbana region displayed their courage to one another by jumping from the natural bridge into the water. The mayor’s son didn’t want to be considered a coward. He jumped after the others, got leg cramps and drowned«. As cramp (involuntary muscle contraction) is called “krč” in Slovenian, this incident is said to have given the name to the bridge and Troughs.

Terminology:
Natural bridge: A bridge-like rock formation, formed by weathering and erosion,
Pothole: A kettlelike or circular depression, worn into the solid rock in a stream bed at falls and strong rapids by sand, gravel, and stones being spun around by the force of the current. Also called a kettle hole; swallow hole.

THE TROUGHS FORMATION
Water has carved the bedrock limestone (or rather limestone barrier), forming ever deeper channel, because of the increased altitude difference between the lower and upper flow of the Kožbanjšček. The reason is almost certainly to be found in the tectonic uplift of the Brda region – and with it lifting of the upper part of Kožbanjšček river basin.

ACCESS
This is a drive-in EarthCache, since you can drive a car or ride a bike right up to the natural monument. There is a parking area at the side of the road (EarthCache coordinates) and a simple info board with short description on three languages. Of course, you can reach Krčnik of foot as well – The international »Alpe-Adria Trail« runs right along the Kožbanjšček, for example.
Krčnik is only a couple of steps form the parking area. Access if free of charge and not limited. There is a strong safety fence along the troughs, but be careful all the same! Rocks can be slippery, especially when wet. Therefore, please, hold on your children’s hands and don’t boldly lean over the fence. It could be very dangerous. You are not allowed to climb natural bridge. If your children insisted on doing it, you could tell them the story about the Mayor’s son…

ADDITIONAL SIGHT SEEING
About 800 metres downstream from Krčnik, at waypoint KOTLIN, you can stop and look at another interesting part of Kožbanjšček. The brook negotiates about 10 metres of height difference with miniature troughs, rapids and small waterfalls. Water formed three large plunge pools, which are popular bathing place for local youth.


Image 2: Kotline: F – small troughs, G – water slide, H – black locust (Robinia pseudoacacia); photo kompaski

REFERENCES
- Podvodni atlas Slovenije (Underwater Atlas of Slovenia), specification sheet # 30, Krčnik gorge with Troughs and natural bridge, Matjaž Vidmar, 2012, Ljubljana,
- Moje najljubše poti, Željko Kozinc, Modrijan, 2009, Ljubljana,
- Web site www.kraji.eu/slovenija,
- Web site www.carga.si.

LOGGING TASK
Take a good look of the riverbed just above the start of the narrow troughs - between two artificial stone dams (upper – larger and lower – smaller). Then answer the questions:
1. What is the shape of the riverbed at this place?
2. How, in your opinion, has this shape of the riverbed been formed? Would you know to use a geological term to describe this formation?
3. How wide is the riverbed at this place? Just estimate.

IMPORTANT!
- BEFORE LOGGING send answers through GC profile or directly to e-mail vane.si.geo@gmail.com
After that you can log - you don't need an additional permission to log.
- Logs without an previous e-mail with answers will be encrypted and later deleted!
- Logs containing answers will be deleted!

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(SI) KRČNIK
Naravni spomenik Krčnik je soteska potoka Kožbanjšček v Goriških Brdih, s koriti in naravnim mostom. Potok Kožbanjšček je v pasu apnenca izdolbel izredno slikovita korita z imenom Krčnik. Korita so dolga okoli 40 metrov, globoka do 6 metrov in na posameznih mesti samo pol metra široka.
Tik nad tesnijo so ostanki mlina in klavž, ki morda nekoliko zmotijo naravno prvinskost Krčnika. Seveda pa ne ustavijo ljubitelja narave, da ne bi osupel zrl v njeno delavnico, v skalne tvorbe, Kožbanjščkove kotlice, skočnike in slapove. K sreči so ti na celotni dolžini korit ostali nedotaknjeni.
Korita se začnejo z veliko kotlico ali draslo, globoko kroglasto kotanjo v strugi, ki jo je oblikovala voda s pomočjo peščenega in prodnega materiala. Ko vodni tok v vrtincu zavrti kamniti material, počasi, a zanesljivo dolbe stene in dno svoje struge. Približno na sredini kotilice se pne naravni most. Obok mostu je približno 5 metrov dolg, 1,5 m debel in do 1 m širok. Je lepo zaobljen in gladek, saj je tudi to nenavadno obliko ustvarila deroča voda z brušenjem. Taki mostovi so v Sloveniji zelo redki – večinoma so bolj robati in ostrorobi, nastali s preperevanjem in odpadanjem kosov kamnine.
Korita se nadaljujejo z ozkim žlebom, mestoma širokim komaj pol metra, ki ga prekinjajo drasle, globoke do 5m. Na spodnjem koncu se korita odprejo v sotesko s strmimi stenami in kmalu razširijo v ožjo dolino.


Slika 1: Krčnik: A – jez nad koriti, B – prvi slap, C – zgornji del korit, D – spodnji del korit, E – življenje v okolici; foto kompaski

Naravni most in tudi vsa korita so poimenovana Krčnik. Razlag za nastanek imena je več. Ena od pripovedi med domačini pravi: »V preteklosti so mladi fantje iz Kožbanjskega kota drug drugemu dokazovali pogum tako, da so z naravnega mosta skakali v vodo. Tudi županov sin ni hotel zaostajati za njimi. Skočil je v tolmun, zgrabil ga je krč in je utonil. Tako je skrivnostna soteska dobila ime Krčnik.« Druga razlaga je manj romantična in ime preprosto razloži s tem, da si je moral potok prehod skozi skalne sklade »izkrčiti«.

Razlaga izrazov:
Naravni most: mostu podobna oblika v kamnini, ki je nastala zaradi preperevanja in erozije,
Kotlica / drasla / erozijski lonec: skledasta vdolbina ali kotanja v skalni rečni strugi, nastala zaradi vrtinčenja proda v vodi,
Skočnik: manjši slap, višine od 2 do 5 metrov

NASTANEK KORIT
Voda je korita v apnenčevo podlago, oziroma prečno potekajoči apnenčev prag, izdolbla zaradi povečanja padca vodne struge. Razlog za povečanje višinske razlike med zgodnjim in spodnjim tokom Kožbanjščka je po vsej verjetnosti tektonsko povzročeno dvigovanje Brd – in s tem tudi povirja potoka.

DOSTOP
Z avtom ali kolesom se pripeljemo prav do naravnega spomenika. Ob cesti je prostor za parkiranje (izhodiščne koordinate zaklada) in enostavna informativna tabla. Krčnik je oddaljen le nekaj korakov. Ima urejeno kratko sprehajalno pot opremljeno z varovalno ograjo ob koritih. A skale, še posebej, kadar so mokre, so lahko zelo drseče. Zato je tu treba otroke držati za roko in se izogibati kakšnem drznejšem nagibanju čez ograjo. Zdrs v tesen je lahko smrtno nevaren.

DODATNI OGLED
Na točki KOTLIN, približno 800 metrov nizvodno od Krčnika, si lahko ogledate še eno znamenitost Kožbanjščka. Dobrih 10 metrov visoko skalno stopnjo tukaj potok premaguje z miniaturnimi koriti, brzicami in slapovi. Voda je izoblikovala tudi tri tolmune, ki so poleti priljubljeno kopališče briške mladine. Vredno ogleda, v poletni vročini pa tudi primerno za ohladitev.


Slika 2: Kotline: F – mala koritca in prelivi, G – vodni tobogan - slapišče, H – robinija (Robinia pseudoacacia); foto kompaski

VIRI
- Podvodni atlas Slovenije, popisni list št. 30, Soteska Krčnik s koriti in naravnim mostom, Matjaž Vidmar, 24.7.2012, Ljubljana,
- Moje najljubše poti, Željko Kozinc, Modrijan, 2009, Ljubljana,
- spletna stran www.kraji.eu/slovenija,
- spletna stran www.carga.si.

NALOGA ZA VPIS OBISKA
Oglej si obliko struge tik pred začetkom korit – med obema umetnima kamnitima pregradama (večjo, zgornjo in manjšo spodnjo) in odgovori na vprašanja:
1. Kakšna je oblika struge na tem delu?
2. Kako je po tvojem mnenju nastala oblika struge, kakršno vidiš? Bi jo znal/a poimenovati z geološkim izrazom?
3. Približno koliko je struga na tem delu široka?

POMEMBNO!
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