(SI) Presihajoči studenec ob Savinji je zanimiva zaganjalka, oziroma izvir v katerem pretok niha v enakomernih časovnih presledkih zaradi posebne oblikovanosti dovodnega kanala ali drugih hidravličnih mehanizmov.
PRED ZAČETKOM:
Prosimo, preberite opis tega geološkega zaklada in si zapišite naloge za vpis se pred odhodom na teren!
NALOGE ZA VPIS ZAKLADA
Opazujte gladino vode v izviru med enim ciklom polnjenja in praznjenja:
1. Izmerite razliko med najvišjo in najnižjo gladino.
2. Zabeležite čas enega cikla – koliko časa preteče med dvema zaporednima napolnitvama izvira?
Če je izvir suh in se voda v času vašega obiska sploh ne pojavi v koritu izvira, tega zaklada žal ne morete vpisati!
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(ENG) Visit »Presihajoči studenec« - literally »Intermittent Spring« in Slovenian. Combination of geologic conditions and hydraulics causes water level in Intermittent sources to rise-and-fall rhytmically. And also to complete drying-up several times during the year.
BEFORE THE BEGINNING:
Please, read the description of this EarthCache and write down logging tasks before visiting it in the nature!
LOGGING TASKS
Observe the water level in the trough during one filling-and-emptying cycle:
1. Measure the height difference between lowest and highest level.
2. Note the time of one cycle – how much time does it take between two consecutive maximums?
If the spring is dry and water doesn't appear during your visit at all, I am really sorry, but you can not log the EarthCache.
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) THE INTERMITTENT SPRING AT SAVINJA
The intermittent sources are not very rare natural phenomenon. But in the past their periodic rise-and-fall nature has inflamed various speculations about what is causing unusual water source behaviour: ordinary people and even academics have given all sorts of wilde and fantastic explanations – including dragons and divine magic. Well, today we know, that combination of geologic conditions and hydraulics is at work here. Even thou the truth is much more dull than people used to imagine, seeing the source »in action« is no less interesting or »magical« today.
INTERMITTENT SOURCES IN SLOVENIA
There are several intermittent sources in Slovenia. Some of them are more known than others. Here is a short description of three sources.
Zaganjalka is one of them, to be found in the hills above Cerkno, western part of Slovenia. The Slovene verb »zaganjati« means something like to start, to spring or to push forward. Unfortunately the Zaganjalka source has been affected by the renovation of the nearby forest road.
Lintvern is the name of another intermittent source at Vrhnika, near Ljubljana. Today its water are used for the water supply, the source is walled-in with concrete and access locked. Therefore, its performance is obstructed. The water springs from a karstic cave. Before people started to exploit the source, the water used to roar in the depth of the cave, before the waterflow appeared. It is supposed to have brought out the cave amphibia Proteus anguinus Laurenti, curiosity of the Dinaric karst. People were convinced that they were the dragon offspring. Moreover, the roar of the dragon was to be heard beneath. That is why this intermittent source is called Lintvern, which is a popular deformation of the German word Lindwurm = a dragon.
The third source, simply called The intermittent Spring, is the one you are invited to visit with this EarthCache. It is located in the valley of the Savinja river not far from the beautiful glacial valley Logarska dolina. Surmounting the source there is a pointed rock leaning against the slope at one place and right underneath there is a narrow crevice. It appears like a needle with an eye, that is why it was given the name »Igla« - Slovene word for a needle.
The Intermittent Spring has been designated a natural monument together with »Igla« in 1948.
HOW DOES THE INTERMITTENT SOURCE FUNCTION?
We can find very interesting explanation of the activity of such sources in the book »Kamniške ali Savinjske Alpe« of Ferdinand Seidl, geologist and seismologist, where he describes the geological structure of the Slovene mountain chain Kamnik or Savinja Alps (see refrence #1). And the principle of the mechanism is still thought to be correct.
Image 1: Explanatory cross-section of the intermittent source (according to F. Seidl).
There is a system of crevices in the stone cliff behind the source, some of them are functioning as water channels. The water channel (c) which is supplying the source is narrow at first. The channel widens into the more spacious cavity or reservoir (n), which is followed by a syphon and a kind of the barrier or a treshold. When the water fills the cavity higher than the edge of the treshold, water starts to flow through the syphon. All the water above outflow opening (level a-a) is pulled out from the cavity. Channel leading from the syphon towards the source (b-i) drains larger quantity of water than the channel (c) supplies to the cavity (n) –this enables the rhytmycal filling and emptying of the cavity.
WHEN AND HOW TO OBSERVE THE SOURCE
In short: don't come in the dry season or in the cold winter, because the spring performance depends on the amount of water. In the time of low water it could be completely dry. The best time for observation is time of high waters! Then the fucntioning of the source is obvious and very interesting to observe!
What do you do when you get to the source? First take a look at the spring trough. If it contains any amount of water, you will not be dissapointed! Take some time to observe the changes and be patient, because the rise and fall of the water level can be slow and hard to notice. The best way is to observe the water surface on a distinctive place (e.g. top of a stone).
If there is no water in the trough when you came, but the sand and pebles at the floor were wet, seat down at the bench for some time and observe: it is possible that you will see what you came for – but it could take some time. If nothing changed in 20 minutes, just go and find the traditional cache in the vicinity...
If the floor of the trough was dry – too bad! You'll need more luck - next time!
Image 2: Difference between the high and low water level (photo: Vane).
REFERENCES
1. Collection »Slovenska zemlja«, Kamniške ali Savinjske Alpe, njih zgradba in njih lice, Ferdinand Seidl, Matica Slovenska, Ljubljana, 1907 in 1908.
2. ProGeo News - A ProGeo newsletter, No. 3/1997, Pro Geo: European Association for the Conservation of the Geological Heritage, Oslo, 1997.
Slovensko besedilo
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(SI) ZAGANJALKA OB SAVINJI
Zaganjalke, imenovane tudi presihajoči izviri, niso posebno redek naravni pojav. Vendar so s svojim mehanizmom ponavljajočega naraščanja in upadanja vode v preteklosti razplamtevale domišljijo in različna ugibanja o vzrokih nenavadnega obnašanja vode. Preprosti ljudje in tudi naravoslovci so zanje našli vse mogoče in nemogoče razlage, vključno z zmaji in božjim posredovanjem. No, danes vemo, da ta pojav poganja kombinacija geoloških pogojev in hidravličnih mehanizmov. Čeprav je resnica precej bolj dolgočasna kot so nekoč mislili ljudje, ni danes nič manj zanimivo in »čudežno« opazovati takšen izvir »v akciji«.
POZNANE ZAGANJALKE PRI NAS
V Sloveniji imamo več zaganjalk, nekatere bolj znane od drugih. Na kratko bomo opisali tri.
Zaganjalka, po kateri je ime prišlo v strokovno izrazoslovje, se imenuje Zaganjalka. Najdemo jo v Volkovi grapi pod Cerkljanskim vrhom, blizu domačije Zakrog. Žal je bil izvir prizadet med prenovo bližnje gozdne ceste.
Lintvern se imenuje poznana zaganjalka pod Planino pri Vrhniki, kjer voda izvira iz kraške jame. Danes izvir služi za oskrbo s pitno vodo, obdan je z betonskimi stenami in zaklenjenimi vrati. Njegovo naravno delovanje pa je okrnjeno ter nedostopno. Preden so izvir zagradili, je voda v globinah jame bučala vsakič pred izbruhim na površje. Pravijo, da je s seboj prinašala tudi človeške ribice, za katere so bili ljudje prepričani, da so zmajevi mladiči. Kako tudi ne, saj so jasno slišali zmajevo rjovenje v globinah! Tako so izvir poimenovali Lintvern, s popačeno različico nemškega izraza za zmaja – Lindwurm.
Tretji izvir se preprosto imenuje Presihajoči studenec. Tja vas tudi vabi ta geološki zaklad. Izvira izpod skalne stene ob Savinji, nedaleč od ledeniške Logarske doline. Skoraj tik nad izvirom se v nebo pne Igla, 40 metrov visok skalni obelisk, Izgleda kot šivanka ali igla. Od matične stene jo loči približno dva metra široka razpoka, skoznjo je vse do leta 1894 vodila edina dolinska pešpot iz Luč v Solčavo.
Presihajoči studenec in Igla sta bila že leta 1948 razglašena za naravni spomenik.
KAKO DELUJE ZAGANJALKA?
Zelo zanimivo razlago, katere princip še vedno drži, lahko preberemo v knjigi Kamniška ali Savinjske Alpe, avtorja Ferdinanda Seidla, slovenskega geologa in seizmologa (vir št.1).
Slika 1: Skica prereza z razlago delovanja (po F. Seidlu).
Skalno steno za izvirom prepreda sistem razpok, nekatere med njimi za svojo pot uporablja voda. Vodni kanal (c), ki napaja izvir, je sprva ozek. Kanal se kasneje razširi v prostornejšo votlino ali rezervoar (n). Temu sledi sifon in neke vrste ovira ali skalni prag. Ko voda napolni votlino nad nivo skalnega praga, prične odtekati skozi sifon. Vlek iz votline potegne za seboj vso vodo, ki je nad zgornjim robom odprtine odtoka iz votline (nivo a-a). Kanal, ki od sifona vodi do izvira (b-i) odvaja večjo količino vode, kot jo v votlino (n) lahko dovede kanal (c). – s tem je omogočeno ritmično polnjenje in praznjenje votline.
KDAJ IN KAKO OPAZOVATI IZVIR
Pridite po deževju ali spomladi, ko se topi sneg. Nikar v sušnem obdobju ali v mrzli zimi! Delovanje izvira je namreč odvisno od količine vode. V času nizkih voda in suše povsem presahne. Jasno vidno delovanje zaganjalke, resnično zanimivo za opazovanje, omogočajo visoke vode.
Kaj torej storiti, ko pridete do izvira? Najprej si oglejte ograjeni deli izvira. Če je v njem voda, ne glede na višino, vas izvir ne bo razočaral! Vzemite si čas za opazovanje in bodite potrpežljivi, saj je lahko sprememba višine vode zelo poćasna in jo je težko opaziti. Najbolje, če si za orientacijsko točko vzamete rob ali vrh kakšnega kamna, do kamor sega gladina vode.
Če ob vašem prihodu v koritu ni vode, pesek in prod na tleh pa je moker, le sedite na bližnjo klopco in si vzamite nekaj časa za opazovanje: možno je, da boste videli tisto zaradi ćesar ste prišli – a lahko traja nekaj več časa. Če se nič ne zgodi v 20 minutah, pojdite in poiščite tradicionalni zakladek v bližini...
Če so peščena tla v koritu suha – res škoda! Več sreče – prihodnjič!
Slika 2: Razlika v višini gladine, posneto v mokri pomladi (foto: Vane).
VIRI
1. Zbirka slovenska zemlja, Kamniške ali Savinjske Alpe, njih zgradba in njih lice, Ferdinand Seidl, Matica Slovenska, Ljubljana, 1907 in 1908.
2. ProGeo News - A ProGeo newsletter, No. 3/1997, Pro Geo: European Association for the Conservation of the Geological Heritage, Oslo, 1997.
tocke poti in dnevniki / waypoints and logs