(SI) Geološki zaklad je simpatično zaobljen griček, ki ga je pred seboj narinil daleč večji buldožer kot jih izdelujemo ljudje. Na delu bi ga videli pred kakimi 70.000 leti! To je bil Bohinjski ledenik!
PRED ZAČETKOM:
Opis tega Geološkega zaklada je dolg. Prosimo, preberite ga in si zapišite naloge za vpis se pred obiskom zaklada!
NALOGE ZA VPIS OBISKA
1. Voljčev hrib je del čelne morene Bohinjskega ledenika. Ce bi zakopali vanj (kar je danes prepovedano!), bi naleteli na nenavadno mešanico gradiva: nekaj običajnega ledeniškega drobirja – raznolike ostrorobe kamne, poleg tega pa veliko zaobljenih prodnikov, od katerih nekateri nosijo sledove razenja. Kako lahko razložite taksno sestavo materiala v tem delu čelne morene?
2. Ocenite velikost Voljčevega hriba: dolžino in širino v vznožju ter višino od vznožja do vrha hriba. Lahko si pomagate s svojo GPS napravo.
3. Stopite na najvišjo točko hriba, na koordinate zaklada, kjer betonski količek označuje trigonometrično točko. Uporabite kompas in poglejte v smer 291 stopinj. Približno na oddaljenosti 6 km v tej smeri stoji Blejski grad. Ce je viden, boste na tej razdalji lahko razločili veliko streho krito z rdečimi, opečnimi strešniki. Kaj ovira pogled v navedeno smer? Ali lahko vidite grad ali ne?
POMEMBNO!
- Preden vpišete obisk zaklada, pošljite odgovore preko GC profila ali neposredno na e-naslov vane.si.geo@gmail.com. Takoj potem lahko vpišete obisk zaklada na spletu – ne potrebujete dodatnega dovoljenja. Ce ste fotografirali, prosimo, priložite kakšno fotografijo.
- Vpisi brez ustrezne spremljajoče e-poste, ki vsebuje pravilne odgovore, bodo najprej trajno kodirani, kasneje izbrisani!
- Vpisi, ki vsebujejo odgovor bodo izbrisani!
(ENG) EarthCache is set on an attractive, prolonged wave of material, which has been pushed to its place by the far larger bulldozer than man has ever built. It has been last seen around here about 70.000 years ago! The Bohinj Glacier!
BEFORE THE BEGINNING:
This EarthCache has a long description! Please, read it and write down logging tasks before visiting the EarthCache site!
LOGGING TASKS
1. Voljcev hrib has been formed by Bohinj Galcier. It is a part of its terminal moraine. If you started to dig the hill (which is prohibited now), you would find a curious mixture of material there: some ordinary moraine debris – various sharp edged stones, but also a lot of rounded pebbles, some of them bearing scratch marks. How can you explain this kind of material in the moraine? Why is the hill made mostly of rounded pebbles, which have been shaped by running water?
2. Estimate the size of Voljcev hrib: length and width of the hill at the plain level, and height of the hilltop above the plain. You can use your GPS for these measurements.
3. Stand at the top-most point of the hill, there is a trigonometrical point almost exactly on EarthCache coordinates (concrete stake). Using your compass, take a look in the direction of 291 degrees. There is the Bled castle standing in this line of sight about 6 km from you. From this distance, you should recognize large, red tiles roof - if visible. What is obstructing view in that direction? Can you see the castle or not?
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 the answer 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.
Watch very interesting video animation The Bohinj Glacier, on the internet (reference No.2).
(ENG) UPPER CARNIOLA PLAIN
Upper Carniola plain is a large, western part of Ljubljana basin. Its present shape is a result of three main processes. The floor of the basin started to sink about 30 million years ago, so tectonic of wider region is the first actor in this story. Second and third are intermingled: Erosion power and transport capability of Sava River and climate change, which alternately caused ice ages and warmer periods in between.
Thorough research of the basin around Radovljica has started in 1909 by Brückner, followed by many others. It is now evident that the last two ice ages (Riss and Würm) have shaped major part of the modern basin landscape. Of course, Sava River and other streams have continued reshaping of the plain after the end of ice ages, but the imprint of the ice ages is still prevailing.
Figure 1: Topographic map and relief of the plain; red circle indicate position of Voljcev hrib, a pile of material pushed in front of advancing ice, and left there after the glacier retreated; reference No. 4;
You can compare relief with geomorphological map below (Figure 3) to identify some other remnants of the terminal moraine which have been deposited over fluvial terraces, or are protruding through their flat surface;
Fluvial deposits have filled basin floor during cold ice ages, while water eroded deposits in the warmer interglacial periods and carved deep valleys. Older gravel deposits slowly formed more compact conglomerate layers; only gravel of Würm deposits is still in loose state.
THE LARGEST BULLDOZER HAS COME...
Bohinj glacier, this huge product of the ice ages, contributed a large part of the rock debris. This debris may have been plucked off a valley floor as a glacier advanced, some of it have fallen off the valley walls as a result of frost wedging or landslide. At the end, huge quantities of glacial debris have been carried away, smoothed, and deposited by water, Sava River, in our case. This way thick fluvial deposits filled valleys and wider surroundings, leaving large, flat plain.
The source of the glacier has been at the heart of Julian Alps, above Lake Bohinj valley. At the time of the largest extent glacier has been over 800 m thick, and its terminus has reached somewhat north-east of Radovljica.
The slow movement of enormous and heavy river of ice has reshaped, widened, deepened valleys. It has transported glacial debris and deposited it along glacier edges. It has also pushed a lot of material in front of its tip as it extended ever further – displacing older fluvial deposits too! When glacier melted and retreated, large terminal moraines remained at the end of its reach, lateral moraines along each side of its trail and ground moraines at the bottom of the valley. It has also left large, empty terminal depression, carved into older deposits.
Figure 2: Bohinj Glacier presented at the time of almost maximal extent; reference No. 2;
... AND HAS GONE!
Of course, you can’t see the bulldozer – the glacier - any more! But heaps of material, which it has pushed and transported are still there! Two belts of terminal moraines can be traced today in the surroundings of Radovljica. First has been left behind the glacier at the end of the first cold peak of Würm ice age, about 70.000 years ago. Irregular heaps and hills of material have been partly covered by thick gravel deposits in the following interglacial (terrace III at Figure 3). Gravel deposits reached up to 40 m in thickness. The Second belt of terminal moraine marks the reach of the glacier during the Würm second cold peak, about 55.000 years ago.
Figure 3: Fluvial terraces and glacier moraines; Geomorphologic map of Pleistocene in the Radovljica plain, Dusan Kuscer, additional map to the article, reference No. 1; legend expanded and colors added by kompaski;
EARTHCACHE
EarthCache coordinates are set at the top of the grassy, distinctly wave-shaped, small hill called Volcji or Voljcev hrib. It is positioned between towns Radovljica and Lesce. It represents one of the smaller remains of the terminal moraine from the first Würm cold maximum. Not entire size and height of the hill is visible today, since its surroundings has been filled up and flattened by Sava River deposits in the following period. This way, at the top of the hill you are standing on a kind of an island, stranded here in time. You actually get quite a nice view from this small hill!
Neighboring Obla gorica hill has the same origin. It is larger, but covered with trees, and it doesn’t offer such a great view. Still, there are some interesting sites there to visit too. At the foot of the hill you can take a look at the “geological column”, presenting collection of rocks from Radovljica municipality.
Both hills have been declared natural monuments. They are accessible on foot, without restrictions. There is no entrance fee and no fence.
Figure 4: Vojcev hrib today; A popular destination for locals, dog-walkers and geocachers; photo: kompaski;
REFERENCES
1. Prispevek h glacialni geologiji radovljiske kotline, Dusan Kuscer, magazine Geologija Volume 6, No. 3, Geological survey Ljubljana and Slovenian Geological Society, Ljubljana, 1955;
2. The Bohinj Glacier, animation, Narodni muzej Slovenje; screenplay: Milos Bavec, Timotej Knific; expert advisor for geomorphology and glaciology: Milos Bavec; geomorphology consultant. Jurij Kunaver; paleozoology consultant: Vida Pohar; photographer: Joze Hanc;
3. The Quaternary valley fills of the Sava River and neotectonics, Dusan Kuscer, magazine Geologija, No. 33, Faculty of Natural Sciences and Technology, Geological institute, Ljubljana, 1990;
4. Geopedia.si, web atlas;
Slovensko besedilo
Obiščite našo spletno stran Geološki zakladi / EarthCaches
za seznam vseh naših Geoloških zakladov in mnogo dodatnih podatkov.
Oglejte si zelo zanimivo video animacijo Bohinjski ledenik na spletu (vir st.2).
(SI) GORENJSKA RAVAN
Gorenjska ravan predstavlja velik, zahodni del Ljubljanske kotline. Njena današnja podoba je v veliki meri rezultat treh procesov. Tektonski procesi so pred približno 30 milijoni let povzročili pogrezanje dna kotline. Drugi in tretji proces sta močno prepletena: Erozijska moč in transportna sposobnost reke Save ter klimatske spremembe, ki so izmenično povzročale ledene dobe in vmesna toplejša obdobja.
Temeljitega preučevanja kotline okoli Radovljice, se je prvi od raziskovalcev lotil Brückner leta 1909, sledili pa so mu številni drugi. Zato je znano, da sta današnjo podobo kotline v veliki meri izoblikovali zadnji dve ledeni dobi, Riss in Würm. Seveda so Sava in ostali vodotoki po koncu ledenih dob nadaljevali preoblikovanje, vendar je odtis ledenih dob se vedno prevladujoč.
Slika 1: Topografska karta in relief ravnine; rdeča kroga kažeta položaj Voljčevega hriba, kupa gradiva, ki ga je pred seboj potiskal napredujoči ledenik, in je tu ostal po umiku ledenika; vir st. 4;
Primerjate lahko relief in geomorfološko karto spodaj (slika 3) in določite se nekaj drugih ostankov čelne morene, ki so bili odloženi preko rečnih zasipov ali pa kot hribčki kukajo skozi kasnejše rečne zasipe;
Rečni zasipi so zapolnjevali dno kotline v času ledenih dob, v vmesnih toplejših obdobjih pa je vodna erozija zasipe odnašala in vrezovala globoke doline. Starejši prodni zasipi so se počasi sprijeli v kompaktnejše konglomeratne plasti, le prod zasipov iz Würma je se nesprijet.
NAJVEČJI BULDOŽER JE PRISPEL...
Bohinjski ledenik, velikanski rezultat ledenih dob, je prispeval velik del kamnitega drobirja. Drobir je bil med premikanjem ledenika postrgan z dolinskega dna, nekaj pa ga je pristalo na vrhu ledene reke, kot rezultat razpadanja skal ob zmrzovanju, plazov in spodjedanja sten na obeh strani ledenika. Na koncu je ogromne količine kamnitega ledeniškega drobirja voda odnesla, obrusila in odložila v zasipih. V našem primeru je to bila reka Sava. Na ta način so doline in širšo okolico napolnili debeli rečni zasipi in ustvarili ravnico.
Ledenik je zrasel v osrčju Julijskih Alp, nad dolino Bohinjskega jezera. V času svojega največjega obsega je njegova debelina presegala 800 m in je segal nekoliko severovzhodno od današnje Radovljice.
Počasno premikanje neznansko težke ledene reke je preoblikovalo, razširilo, poglobilo doline. Ledenik je prenašal skale in kamniti drobir ter ga odlagal vzdolž svoje poti. Čelo ledenika pa je med svojim napredovanjem gradivo tudi potiskalo pred seboj ter na ta način premeščalo tudi starejše rečne zasipe! Ko se je ledenik topil in umikal, je na mestu svojega skrajnega dosega pustil velike čelne morene, na vsaki strani svoje poti stranske morene ter talne morene na dnu doline. Poleg tega je zapustil tudi veliko, prazno čelno kotanjo, ki jo je izgrebel v starejših zasipih.
Slika 2: Bohinjski ledenik, predstavljen v času svojega (skoraj) največjega obsega; vir st. 2;
... IN ODŠEL!
Seveda, danes buldožerja – ledenika – ne morete več videti! A kupi gradiva, ki ga je potiskal in premeščal, so se vedno tu! Danes lahko v okolici Radovljice sledimo dvema lokoma čelnih moren. Prvi je ostal po umiku ledenika po koncu prvega hladnega maksimuma v Würmu, pred približno 70.000 leti. Nepravilni griči in razmetani kupi gradiva so bili kasneje delno prekriti z debelimi nanosi rečnih zasipov (terasa III na sliki 3). Zasipi so visoki do 40 m. Drugi lok čelne morene označuje doseg ledenika v drugem hladnem višku Würma, pred približno 55.000 leti.
Slika 3: Rečne terase in ledeniške morene; Geomorfološka karta pleistocena v okolici Radovljice, Dušan Kuščer, karta dodana članku, vir st. 1; legendo dopolnil in barve dodali kompaski;
GEOLOŠKI ZAKLAD
Koordinate Geološkega zaklada so postavljene na vrh travnatega, kot val oblikovanega griča, imenovanega Volčji ali Voljčev hrib. Leži med Radovljico in Lescami. Predstavlja enega od manjših ostankov celne morene iz prvega hladnega viska v Würmu. Danes ni vidna celotna višina hriba, ker je njegovo okolico Sava kasneje zasula in zravnala. Tako je vrh hriba, na katerem stojite, ostal nekakšen otok v času. Z vrha se odpira presenetljivo lep razgled!
Sosednja Obla gorica je nastala na enak način kot Voljčev hrib. Je večja, a poraščena z drevjem in ne nudi kakšnih posebnih razgledov. Kljub temu ponuja več zanimivosti, ki si jih je vredno ogledati. V njenem vznožju so postavili tudi »geološki steber«, v katerem so predstavljene kamnine Radovljiške občine.
Oba hriba sta bila razglašena za naravna spomenika. Pes sta dostopna brez ovir.
Slika 4: Voljčev hrib danes; Pogost cilj sprehodov za domačine, pasje sprehajalce in zakladolovce; foto: kompaski;
VIRI:
1. Prispevek h glacialni geologiji radovljiške kotline, Dušan Kuščer, Geologija Letnik 6, st. 3, Geološki zavod Ljubljana in Slovensko geološko društvo, Ljubljana, 1955;
2. Bohinjski ledenik, animacija, Narodni muzej Slovenje; scenarij: Miloš Bavec, Timotej Knific; strokovni sodelavec za geomorfologijo in glaciologijo: Miloš Bavec; svetovalec za geomorfologijo. Jurij Kunaver; svetovalka za paleozoologijo: Vida Pohar; fotograf: Joze Hanc;
3. Kvartarni savski zasipi in neotektonika, Dušan Kuščer, Geologija st. 33, Fakulteta za naravoslovje in tehnologijo, Institut za geologijo, Ljubljana, 1990;
4. Geopedia.si, spletni atlas;
tocke poti in dnevniki / waypoints and logs