🇸🇮 NALOGE ZA VPIS:
1. Kaj je pradaselj?
2. Kako sta nastali soteski (kamnita korita) Veliki in Mali Predaselj?
3. Katera vrsta erozije deluje v zgornjem delu reke, tudi tukaj, blizu izvira Kamniške Bistrice?
4. Oceni globino soteske z mostu na katerem stojiš.
5. Vpisu dodaj fotografijo sebe / lista s svojim imenom / svoje GPS naprave s Predasljem v ozadju.
Preden vpišeš najdbo, mi pošlji odgovore v Središču za sporočila (Message Center). Potem lahko vpišeš najdbo na spletu. Če bo z odgovori kaj narobe, se bom oglasila.
🇬🇧 LOGGING TASKS:
1. What is a predaselj?
2. How were the gorges (rocky canyons) Veliki and Mali Predaselj formed?
3. Which type of erosion acts in the upper course of the river, also here near the source of the Kamniška Bistrica?
4. Estimate the depth of the gorge from the bridge you are standing on.
5. Add a photo of yourself / a paper with your nickname / your GPS device with Predaselj in the background.
Before you log the find, please, send me a message with the answers to the logging tasks through the Message Center. After you send the message, you can log the find without waiting for my reply. If there is something wrong with the answers, I will contact you.
🇸🇮 SLOVENSKO
PREDASELJ
Beseda predaselj označuje naravni most, ki povezuje dva bregova reke. Takšen most je nastal v dolini Kamniške Bistrice približno 800 m pod njenim izvirom. Reka je v trde apnenčaste kamnine vrezala korita Veliki Predaselj dolga približno 280 metrov. Korita zaznamujejo velika globina, ozkost in slikovita podoba z zagozdeno skalo. O tem naravnem pojavu je poročal že Ferdinand Seidl leta 1909: »Tu si je zarezala Bistrica v čvrst apnik celih 20 m globok, a le približno 5 m širok jarek z navpičnimi stenami in ga še sedaj poglablja počasi pa vztrajno. Ta jarek zovejo »Veliki Prédoselj.«
Veliki Predaselj leži tik nad bližnjim Mali Predasljem. Zaznamujejo ga slikovite stene, ki jih je zaoblila velika erozijska moč vode, ki s seboj prinaša apnenčaste prodnike. Z betonskega mostu nad koritom Velikega Predaslja si lahko ogledamo okoli 5 m visok slap in naravni most, ki je velika zagozdena skala. Malo verjetno je, da bi bila tam od konca ledene dobe in je na to mesto verjetno prišla ob skalnem odlomu.
EROZIJA REKE
Rečna erozija je pojav, ko voda s svojim tokom (in materialom, ki ga prenaša s seboj), poglablja in razjeda površino, po kateri teče.
Moč in učinek rečne erozije sta odvisna od padca reke, količine vode v rečni strugi in kamninske podlage. Erozijska moč vode je večja v nesprijetih kamninah, ki jih voda lažje erodira. Rečna erozija deluje mehansko s trganjem kamninskih delcev v rečnem koritu, z njihovim premikanjem in prenašanjem. Pri tem delci zadevajo ob trdno dno in ga s tem poglabljajo, hkrati pa trkajo drug ob drugega ter se tako postopno oblijo in manjšajo. Velikost delcev se tako dolvodno zmanjšuje, grušč se preoblikuje v prod. Poleg tega rečna voda kemično raztaplja kamnino v strugi.
EROZIJA V ZGORNJEM TOKU REKE
V zgornjem toku ima reka velik strmec in veliko erozijsko moč, ki je največja na dnu rečnega korita. Reka s tako imenovano globinsko erozijo poglablja rečno korito. Posebna globinska erozija poteka v gorskem svetu, kjer se voda vrtinči ob skalnih stenah v nasprotni smeri vodnega toka, pri tem pa dolbe in širi strugo.
🇬🇧 ENGLISH
PREDASELJ
The word predaselj refers to a natural bridge that connects two riverbanks. Such a bridge was formed in the valley of the Kamniška Bistrica River, about 800 m below its source. The river carved the Veliki Predaselj gorge into hard limestone rocks, stretching approximately 280 meters in lenghth. The gorge is marked by its great depth, narrowness, and picturesque appearance with a wedged rock. This natural phenomenon was already reported by Ferdinand Seidl in 1909:
"Here the Bistrica cut into the solid limestone a trench 20 m deep, but only about 5 m wide, with vertical walls, and it still deepens it slowly but steadily. This trench is called ‘Veliki Prédoselj’."
Veliki Predaselj lies just above the nearby Mali Predaselj. It is characterized by picturesque walls shaped by the strong erosive power of water carrying limestone pebbles. From the concrete bridge above the Veliki Predaselj gorge, you can see a 5 m high waterfall and the natural bridge formed by a large wedged rock. It is unlikely that the rock has been there since the end of the Ice Age; it probably ended up in this place due to a rockfall.
RIVER EROSION
River erosion occurs when water, with its flow (and the material it carries), deepens and erodes the surface it flows across.
The strength and effect of river erosion depend on the river’s gradient, the volume of water in its bed, and the type of rock substrate. The erosive power of water is greater in loose rocks, which water erodes more easily. River erosion acts mechanically by tearing rock particles from the riverbed, moving and transporting them. While moving, these particles hit the solid bottom, deepening it further, and also collide with one another, gradually becoming rounded and smaller. Thus, downstream, the particle size decreases, and gravel is transformed into pebbles. In addition, river water chemically dissolves the rock in the bed.
EROSION IN THE UPPER COURSE OF A RIVER
In its upper course, a river has a steep gradient and strong erosive power, which is greatest at the bottom of the riverbed. With so-called vertical erosion, the river deepens its bed. Special vertical erosion occurs in mountainous areas, where water whirls along rock walls in the opposite direction of the water flow, drilling into and widening the channel.
Viri (sources):
http://www.dedi.si/dediscina/507-veliki-predaselj
http://www.dedi.si/dediscina/506
https://isjfr.zrc-sazu.si/sl/terminologisce/slovarji/geografski/iskalnik?iztocnica=pr%C3%A9daselj
https://eucbeniki.sio.si/geo1/2501/index4.html