(SI) Vabilo na sprehod po zeleni dolini Peračice, na iskanje zelenega kamna. In da izveste nenavadno zgodbo o potovanju kamnin tega območja z mesta nastanka.
PRED ZACETKOM:
Opis tega Geološkega zaklada je dolg. Prosimo, preberite ga in si zapisite naloge za vpis se pred obiskom zaklada!
GEOLOŠKI ZAKLAD IN NALOGE ZA VPIS
Koordinate zaklada so postavljene k spodnjemu slapu Peracice. Slap ni velik, zato pa je voda na tem mestu razkrila razlicne plasti kamnin. Na dnu slapa se pojavi plast kompaktne sive gline, nad njo pa lezijo plasti tufa.
1. Oglejte si tuf, ki ga razkriva skok Peracice pri slapu (tocka WE) in tuf, ki ga najdete nekaj deset metrov nad spodnjim slapom, na stezi proti drugemu slapu (tocka WQ)!
Bodite pozorni, da pri slapu pogledate kamnino iz tamkajsnje stene in ne kaksen kos, ki ga je prinesla voda! Opisite barvo in strukturo kamnine na obeh tockah in ju primerjajte.
2. Kaj opisuje tabla nad drugim slapom (tocka WG)? Prepisite prvi stavek.
3. Kje med prvim in drugim slapom se nahaja najožji del soteske?
4. Zelo bomo veseli, ce kaksno zanimivo fotografijo z mesta zaklada prilozite svojemu vpisu (logu) obiska.
POMEMBNO!
- Preden vpisete obisk zaklada, posljite odgovore preko GC profila ali neposredno na e-naslov vane.si.geo@gmail.com. Takoj potem lahko vpisete obisk zaklada na spletu – ne potrebujete dodatnega dovoljenja. Ce ste fotografirali, prosimo, prilozite kaksno fotografijo.
- Vpisi brez ustrezne spremljajoce e-poste, ki vsebuje pravilne odgovore, bodo najprej trajno kodirani, kasneje izbrisani!
- Vpisi, ki vsebujejo odgovor bodo izbrisani!
(ENG) Invitation to a hike through green forests of Peracica valley, to find the green stone. And to learn extraordinary truth about dislocation of these stone formations from original place.
BEFORE THE BEGINNING:
This EarthCache has a long description! Please, read it and write down logging tasks before visiting the EarthCache site!
EARTHCACHE AND LOGGING TASKS
EarthCache coordinates are set at first, or lower Peracica waterfall. The waterfall is not big, but its waters have revealed different stone layers there. There is a layer of compact grey clay at the foot of waterfall, and tuff layers above.
1. Take a look at tuff rocks disclosed by waterfall step (waypoint WE), and tuff rocks you find at the trail from first to second waterfall, just some tens of meters further (waypoint WQ)!
Be careful to observe rocks from the original layers at the first waterfall – not those transported from elsewhere by water! Describe the color and the structure of stones from both waypoints and compare them.
2. What is described at info-board above second waterfall (waypoint WG)? Write down first sentence.
3. Which part of the gorge between 1st and 2nd waterfall is the narrowest?
4. We would be glad if you added interesting photos from the EarthCache location to your log.
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.
(ENG) EXPLOSIVE ORIGIN, PEACEFUL FORMATION
This EarthCache takes you to a hike in the Peracica valley, to discover interesting green rock called tuff. While walking through the peaceful forest beside Peracica creek and observing unusually green pebbles, it is not easy to comprehend violent, volcanic genesis of those rocks!
There are two types of volcanic eruptions in terms of activity. Sometimes magma contains small quantities of dissolved gasses, and is characterized by the outpouring of lava onto the ground. If magma contains large quantities of dissolved gasses, eruption is explosive! Explosion expels ash, various gasses, various fragmental material called tephra (pumice, drops of cooled lava, pieces of older rocks torn from a vent). Large ejected pieces are called volcanic bombs, small are called lapilli. All solid pieces hurled through the air by volcano have a common name pyroclasts, and rocks formed from them pyroclastic rocks. These rocks are therefore volcanic by origin and sedimentary by formation.
Fine-grained rock, with grains smaller than 2 mm in diameter, is called tuff. Tuff forms from volcanic ash, which is consolidated and compacted by the weight of ever new deposits above. Rock with grains sized up to 64 mm is called lapilli-tuff. Rock with even larger and sharp-edged particles is called tuff-breccia, the one with rounded particles tuff-conglomerate.
Figure 1: Tuff rocks in Peracica valley: green pebbles in the creek channel, and tuff layers at Peracica waterfall; photo: vane_si.
WHERE HAS PERACICA TUFF FORMED?
In Oligocene, about 24 million years ago, Smrekovec volcanism became active. The Smrekovec Oligocene basin has been an aquatic environment at that time. Magma composition changed over time. First effusive, non-violent lava-flows predominated, and formed volcanic breccia because of quick cooling and breaking of lava in the contact with seawater. Explosive eruptions prevailed later. A tall, conical stratovolcano formed from layers of dust, ash and lava. Thick pyroclasts deposits have often slided from steep slopes and mixed. Extended composite rock layers of underwater landslides formed this way. Andesite and andesic tuff are most common, and appearing between layers of aquatic sedimentary rocks.
Figure 2:
A - Stratovolcano: 1-ash plume, 2-volcanic ash rain, 3-lava dome, 4-volcanic bomb, 5-pyroclastic flow, 6-layers of lava and ash, 7-stratum, 8-magma conduit, 9-magma chamber, 10-dike; Reference No. 5.
B – Volcanic ash cloud, eruption of Cleveland volcano, Aleutians; Reference No. 5.
Peracica tuff has been named after quarries in Peracica valley near village Brezje. Quarry Peracica has been used from 16th to beginning of 20th century. Peracica tuff contains plagioclase, quartz, zeolites and spar. Distinctively green color of the rock is caused by mineral chlorite, which is largely substituting primary biotite. Light-green, very fine-grained tuff, and coarse-grained lapill-tuff specimens with dark-green larger fragments are prevailing.
WHAT DOES SAVA FAULT HAVE TO DO WITH PERACICA TUFF LOCATION?
Major part of rocks produced by Smrekovec volcanism is situated in the rather close surroundings of Smrekovec mountain today. Therefore researchers have not linked Peracica tuff origins with it at first. Studies, especially in the second part of 20th century, have shown the structure of rocks is the same at both locations. The fact that they are more than 60 km apart has not helped to find an answer to the Peracica tuff origin.
The Sava fault comes at scene here. The Sava fault is the most southern accompanying fault of the Periadriatic fault zone. It represents the boundary between Karnian Alps, Karavanke and Savinja Alps in the north, and the Julian Alps and Eastern Sava folds in the south. It has been known that Sava fault is dextral, where land block north of fault slides towards right, or eastwards, while block south of fault slides in the opposite direction. Since the researchers have not known where Sava fault continues in the east, they estimated the displacement of land-blocks along the fault to be maximum 25 km. Only recent detailed investigations have shown that Celje fault is in fact the eastern extension of Sava fault! This new evidence has set entirely new light to the locality of Peracica tuff, which lies south of the Sava fault!
The right slip along the Sava fault must have occurred in the post-Oligocene, possibly even post-Miocene times. And the displacement of Peracica tuff helped to determine the length of slip better. According to now known data this is 65 to 70 km!
Figure 3: Regional scheme: Slovenian borders are shown with white line. Blue color depicts locations of Oligocene pyroclastic rocks of Smrekovec series (after Buser, 1977; Mioc in Znidarsic, 1987; Premru, 1983). SF=Sava Fault; PAF=Periadriatic fault zone; SAF=South-alpine thrust zone; Reference No. 1.
USAGE OF PERACICA TUFF
Artistically carved stone has been used in all sorts of buildings: farm houses, rich town houses, manors, churches and chapels. Pastel-green stone is one of the most characteristic features of houses in Upper Carniola (Gorenjska). It can still be found as a prominent building element in many places. Especially Radovljica and surroundings boast marvelous green church and house portals, window frames, colonnades…
Figure 4: C - Podvin castle, close to Peracica, is a proper exhibition of green tuff stone: courtyard driveway, base of exterior walls, window frames, columns under the balcony, portal of the main entrance, basement portals and other elements; D – Beautiful portal in Radovljica; E – Window frames; F – Artwork in stone! Carving in church of St. Lucy; Reference No. 5.
Tuff stone elements are not particularly durable when exposed to fresh air. Conservators therefore face all sorts of problems when trying to protect Peracica tuff elements against permanent damage. They are grinding andesic tuff into a stone meal of different grain-sizes, and use it to prepare quality reparation materials. They are using pozzolanic reaction, which is substituting cement in mortar. In this way, appearance of repaired elements is close to original but much more durable.
ACCESS TO THE EARTHCACHE
You are invited to hike through green, wooded Peracica valley. Local tourist club has renovated and signposted the trail a couple of years ago, and appropriately named it Brezje peace trail.
Trail has many possible routs, but we suggest one about 5 km long. Park your car near basilica in village Brezje. There is some parking fee to pay. Continue on foot from there, and use proposed waypoints for easier orientation:
- W1, crossroads in village Brezje,
- W2, start of descent in the Peracica valley, and entrance into the woods,
- WE, first Peracica waterfall, and EarthCache coordinates,
- WQ, trail from first to second waterfall, answer the question,
- WG, viewpoint above small second waterfall and gorge in green tuff,
Suggested return trail: return short part of the trail from the waterfalls, and then:
- W3, start of trail towards Crnivec village,
- W4, entrance in Crnivec village,
- W7, branching of trail across meadows, towards Brezje village,
- W8, turn on the trail across meadows,
- PK, parking area in Brezje;
Trail through woods is signposted with yellow round markings on trees, yellow colored direction signposts and brown marking poles with sign of trail and an arrow. There are some information boards at more interesting points of the trail.
Figure 5: EarthCache point; First Peracica waterfall, in solid state! Photo: vane_si.
Note: You use trails at your own risk. Use only trails you are fit to. Be safe and enjoy!
References:
1. Vanja Kastelic, 2008: Petrological and mineralogical characteristics of Peracica tuff, RMZ – Materials and Geoenvironment 55-3, 377-388. Ljubljana, University of Ljubljana, Faculty of Natural Sciences and Engineering, Dept. of Geology.
2. Ladislav Placer, 1996: Displacement along the Sava fault, magazine Geologija 39, 283-287, Geological Survey of Ljubljana, Institute for Geology, Geotechnic and Geophysics.
3. Matjaz Novak, 2010, Geological Survey of Slovenia: Ko se vulkanski pepel usede na zemeljsko povrsje (When volcanic ashes settles down at the Earth surface), article in a daily newspaper Delo.
4. DEDI, Encyclopedia of Slovenian natural and cultural heritage web-site, Opusceni kamnolom tufa ob Peracici (Abandoned tuff quarry at Peracica), authors of text: Janko Cretnik, Mateja Golez, Slovenian National Building and Civil Engineering Institute.
5. Photos and sketch:
A – Pelean eruption, en.wikipedia.org; B - NASA Photo of Eruption of Cleveland Volcano in the Aleutian Islands; C – Castle Podvin, sl.wikipedia.org; D – Detail of portal in Radovljica, www.radolca.si; E – Window frame at Finzgar house, sl.wikipedia.org; second window frame from reference No. 3; F – relief carving inside the church of St. Lucy in Zadnja vas, www.radolca.si.
Slovensko besedilo
Obiscite naso spletno stran Geološki zakladi / EarthCaches
za seznam vseh nasih Geoloških zakladov in mnogo dodatnih podatkov.
(SI) OGNJEVITA PRETEKLOST
Med obiskom doline Peracice, in opazovanjem spokojne narave si ni lahko predstavljati silovitih dogajanj, ki so botrovali nastajanju zanimive zelene kamnine – peraciskega tufa. Tuf je namrec vulkanskega izvora!
Ognjeniki material izbruhajo na dva nacina. Ce je v magmi majhna kolicina lahkohlapnih snovi, se razlije skozi vulkansko zrelo v obliki tokov lave in nastanejo predornine. Kadar pa je lahkohlapnih snovi v magmi veliko, bo izbruh eksploziven! Eksplozija ob izbruhih izvrze pepel in prah, pogosto tudi pline, kose starejsih vulkanskih kamnin, iztrgane iz ognjeniskega zrela, drobce plovca iz na hitro ohlajenih kapljic lave in kose raztaljene kamnine iz ohlajajoce se lave. Velike izvrzene delce imenujemo vulkanske bombe drobnim pa recemo lapili. Vse trdne delce, ki jih izbruha vulkan, imenujemo piroklasti (iz grscine: pyros – ogenj, klasis – lomljenje), kamnine, ki iz njih nastanejo, pa piroklasticne kamnine ali piroklastiti. Po izvoru so te kamnine torej magmatske, po nastanku pa sedimentne.
Piroklasticno kamnino iz najdrobnejsih delcev, ki ne presezejo velikosti 2 mm, imenujemo tuf. Tuf nastane iz usedlega vulkanskega pepela, stisnjenega pod tezo vedno novih plasti usedlin, ki se odlagajo nad njim. S casom tako nastane plastovita kamnina. Tufsko kamnino, ki vsebuje tudi delce velikosti do 64 mm, imenujemo lapilni tuf, táko s se vecjimi kosi pa tufska breca, ce so kosi ostrorobi, oziroma tufski konglomerat, ce so zaobljeni.
Slika 1: Peraciski tuf v dolini Peracice: zeleni prodniki v strugi potoka in plasti tufa pri slapu Peracice; foto: vane_si.
KJE JE NASTAL PERACISKI TUF?
V oligocenu, pred priblizno 24 milijoni let, je na danasnjem ozemlju Slovenije zazivel smrekovski vulkanizem. Vulkanizem je potekal v morskem okolju, sestava magme pa se je spreminjala. Najprej so prevladovali neeksplozivni izlivi tokov lave, ki so se zaradi hitrega ohlajanja ob stiku z morsko vodo drobili v ostrorobe delce in nastala je vulkanska breca. Pozneje so prevladovali eksplozivni izbruhi. Iz slojev prahu, pepela in lave je nastal visok stozcast ognjenik, kakrsnim recemo stratovulkani. Pogosto so debeli nanosi piroklastov splazeli po strmih pobocjih in se pomesali. Tako so na Smrekovskem pogorju nastale zelo razsirjene plastnate kamnine sprijetih podmorskih plazov. Med vulkanskimi kamninami sta najbolj razsirjena predornina andezit in sedimentni andezitni tuf, ki se pojavljata med plastmi morskih sedimentnih kamnin.
Slika 2:
A – Plastoviti ognjenik ali stratovulkan: 1-izbruh pepela, 2-dez pomesan z vulkanskim pepelom, 3-lavin pokrov, 4-vulkanska bomba, 5-piroklasticni tok, 6-sloji lave in pepela, 7-podlaga, 8-ognjenisko zrelo, 9-magmatska komora, 10-magmatska zila; Vir st. 5.
B – Oblak vulkanskega pepela ob izbruhu ognjenika Cleveland, Aleuti; Vir st. 5.
Peraciski tuf je svoje ime dobil po kamnolomih v dolini Peracice pri Brezjah. Kamnolom Peracica je deloval od 16. do zacetka 20. stoletja. Peraciski tuf je sestavljen iz plagioklazov, kremena, zeolitov in sljud. Zeleno barvo mu daje mineral klorit, ki v veliki meri nadomesca primarni biotit. Najbolj znacilni so svetlozeleni drobnozrnati razlicki in bolj grobo zrnati lapilni tufi s temnozelenimi vkljucki.
KAJ IMA SAVSKI PRELOM OPRAVITI Z LEGO PERACISKEGA TUFA?
Velik del kamnin nastalih v casu delovanja smrekovskega vulkana je razporejena bolj ali manj v bliznji okolici Smrekovca, zato izvora peraciskega tufa najprej niso povezovali z njim. Predvsem v drugi polovici 20. stoletja so raziskave pokazale, da imajo kamnine na obeh obmocjih enako sestavo in skoraj zanesljivo skupen nastanek. Tezava je bila v tem, da kamnine v okolici Smrekovca lezijo vec kot 60 kilometrov vzhodneje! Kako bi torej lahko imele skupen izvor?
Tu v zgodbo vstopi Savski prelom. Savski prelom je najjuznejsi od spremljajocih prelomov Periadriatske prelomne cone. Predstavlja mejo med Karnijskimi Alpami, Karavankami in Kamnisko-Savinjskimi Alpami na severu ter Julijskimi Alpami in Posavskimi gubami na jugu. Znano je bilo, da je Savski prelom tako imenovan desnozmicni, kjer ozemlje severno od preloma drsi desno, oziroma proti vzhodu, ozemlje juzno od preloma pa v nasprotno smer. Raziskovalci v preteklosti niso vedeli kje se na vzhodu nadaljuje Savski prelom, in so predpostavljali dolzino zmika ob Savskem prelomu na najvec 25 kilometrov. Sele leta 1996 je bila potrjena domneva, da je Celjski prelom le vzhodni podaljsek Savskega preloma. To pa je v povsem novo luc postavilo lego peraciskega tufa, ki lezi juzno od Savskega preloma!
Do desnozmicnega premika ob Savskem prelomu je prislo ob koncu oligocena ali v miocenu. Prav razmik v legi obeh delov kamnin smrekovskega vulkanizma je pomagal tocneje dolociti velikost tega zmika, ki po dosedanjih raziskavah znasa 65 do 70 kilometrov!
Slika 3. Regionalna skica: meje Slovenije so zacrtane belo. Z modro barvo so podane lokacije Oligocenskih piroklasticnih kamnin Smrekovske serije (po Buser, 1977; Mioc in Znidarsic, 1987; Premru, 1983). SF=Savski prelom; PAF=Periadriatska prelomna cona; SAF=Juzno-alpska narivna meja; Vir st. 1.
UPORABA PERACISKEGA TUFA
Umetelno obdelan kamen so uporabljali v zelo razlicni objektih: preprostejsih hisah, premoznih domacijah, trskih in mescanskih hisah, grascinah, cerkvah in kapelah. Pastelno zeleni kamen je bila ena najznacilnejsih posebnosti gorenjskih his. Se danes ga najdemo v mnogih krajih po Gorenjskem. Posebej Radovljica in njena okolica je se danes polna cudovitih, pastelno zelenih poudarjenih elementov objektov, kot so cerkveni in hisni portali, okenski okvirji, stebrisca in drugi stavbni cleni.
Slika 4: C – Peracici bliznji grad Podvin razkazuje zbirko pastelno zelenega kamna: pot h gradu, spodnji deli obodnih zidov, okenski okviri, stebri pod balkonskim vhodom, obok nad vhodom, kletni portali; D – Detajl cudovitega portala v Radovljici; E – primer dveh okenskih okvirjev; F – Umetnina v kamnu! Izklesan relief v cerkvi sv. Lucije; ; Vir st. 5.
Tuf na zraku ni zelo obstojen, zato se varuhi stavbne dediscine danes srecujejo s stevilnimi konservatorsko-restavratorskimi problemi, pri ustrezni zascititi elementov iz peraciskega tufa pred trajnimi poskodbami. Kamnino andezitni tuf meljejo tudi v agregate razlicnih zrnavosti, iz katerih pripravljajo kakovostne sanacijske materiale. Pri tem se izkoriscajo pucolanske lastnosti reaktivnega silicijevega dioksida v agregatu, ki v maltah nadomesca cementno vezivo. S tem se videz obnovljenih elementov pribliza originalnemu, trajnost pa se poveca.
DOSTOP DO GEOLOŠKEGA ZAKLADA
Vabimo vas na sprehod po gozdnati dolini potoka Peracica. Domacini so pot pred nekaj leti uredili, oznacili in primerno poimenovali Brezjanska poti miru.
Predlagamo pot skupne dolzine dobrih 5 kilometrov. Parkirajte pri baziliki v vasi Brezje, kjer boste placali nekaj parkirnine. Nadaljujte pes, s pomocjo dodatnih tock poti (waypoints):
- W1, krizisce v vasi Brezje,
- W2, zacetek spusta v dolino Peracice kjer vstopite v gozd,
- WE, prvi slap Peracice, to so tudi koordinate Geološkega zaklada,
- WQ, steza od prvega k drugemu slapu, odgovorite na vprasanje,
- WG, razgledisce nad malim, drugim slapom in sotesko v zelenem tufu,
Predlagana vrnitev: od obeh slapov se odpravite kratek kos poti nazaj, potem pa:
- W3, zacetek poti proti vasi Crnivec,
- W4, prihod v Crnivec,
- W7, odcep poti cez travnike proti vasi Brezje,
- W8, ovinek na poti cez travnike,
- PK, parkirisce v Brezju;
Pot skozi gozd je oznacena z rumenimi markacijami, rumeno obarvanimi smernimi tablami in rjavimi kolicki z znakom poti in puscico. Na zanimivejsih tockah je ob poti tudi nekaj informativnih tabel.
Slika 5: Koordinate Geološkega zaklada; Prvi slap Peracice, v trdnem stanju! Foto: vane_si.
Opomba: Poti uporabljate na lastno odgovornost! Hodite le po poteh za katere ste ustrezno pripravljeni! Zelimo vam varno pot in veliko prijetnih trenutkov!
Viri:
1. Vanja Kastelic, 2008: Petroloske in mineraloske znacilnosti Peraciskega tufa. RMZ – Materials and Geoenvironment 55-3, 377-388. Ljubljana, Univerza v Ljubljani, Naravoslovnotehniska fakulteta, Oddelek za geologijo.
2. Ladislav Placer, 1996: O premiku ob Savskem prelomu, Geologija 39, 283-287, Geoloski zavod Ljubljana, Institut za geologijo, geotehniko in geofiziko.
3. Matjaz Novak, 2010, Geoloski zavod Slovenije: Ko se vulkanski pepel usede na zemeljsko povrsje, clanek v casopisu Delo.
4. DEDI, Enciklopedija naravne in kulturne dediscine na slovenskem, Opusceni kamnolom tufa ob Peracici, avtorja zapisa: Janko Cretnik, Mateja Golez, Zavod za gradbenistvo Slovenije.
5. Fotografije in skice:
A – Pelejski izbruh, en.wikipedia.org; B - NASA fotografija izbruha ognjenika Cleveland na Aleutskih otokih; C – Grad Podvin, sl.wikipedia.org; D – Detajl portala v Radovljici, www.radolca.si; E – Okenski okvir Finzgarjeve hise, sl.wikipedia.org; drugi okvir povzet iz vira st. 3; F – reliefno rezbarjen kamen v cerkvi sv. Lucije v Zadnji vasi, www.radolca.si.
tocke poti in dnevniki / waypoints and logs