(SI) Bregovi reke Kokre so res čudovito pisani, polni raznobarvnih, oblih prodnikov! Pestra pa ni le njihova obarvanost, temveč tudi izvor in način nastanka.
PRED ZAČETKOM:
Prosimo, preberite opis tega geološkega zaklada in si zapišite naloge za vpis se pred odhodom na teren!
NALOGE ZA VPIS ZAKLADA
1. Na koordinatah Geološkega zaklada je pisano prodišče na bregu reke Kokre. Pobliže si oglejte kako različnih barv in sestave so prodniki. Izberite dva različna in ju podrobneje opišite: barvo, strukturo, poskusite določiti za katero kamnino gre. Če ne gre drugače, vam lahko do odgovora pomaga namig.
2. Na točki PYRAMD si oglejte geološko piramido. Na vzhodni, severni in zahodni stranici so ločeno predstavljene kamnine različnega nastanka: karbonatne sedimentne, mehanske sedimentne, vulkanskega izvora . Na kateri stranici so zbrane mehanske sedimentne kamnine?
3. Na piramidi lahko vidite, da so stranice od nekaterih vgrajenih prodnikov navzdol temno rjavo zamazane. Ali veste iz česa so ti madeži in kaj v sestavi prodnikov omogoča nastajanje rjavih madežev?
POMEMBNO!
- Preden vpisete obisk Geološkega zaklada, pošljite odgovore preko GC profila ali neposredno na e-naslov vane.si.geo@gmail.com. Takoj potem lahko vpišete obisk Geološkega zaklada na spletu – ne potrebujete dodatnega dovoljenja. Če ste fotografirali, prosimo, priložite kakšno fotografijo.
- Vpisi brez ustrezne spremljajoče e-pošte, ki vsebuje pravilne odgovore, bodo najprej trajno kodirani, kasneje izbrisani!
- Vpisi, ki vsebujejo odgovore bodo izbrisani!
(ENG) Kokra river banks are full of colorful pebbles! They are not only variously colored, also their origin and way of formation is diverse.
BEFORE THE BEGINNING:
Please, read the description of this EarthCache and write down logging tasks before visiting it in the nature!
LOGGING TASKS
1. EarthCache coordinates are set on the Kokra river bank – at one of the gravel bars. There are many large and small pebbles scattered there. You can see how different the color and structure of these pebbles is. Choose two different pebbles, examine them, and describe: their color, structure, try to determine the type of the rock. If all else fails, the hint can help you get some answers.
2. Take a look at Geologic pyramide at waypoint PYRAMD. At eastern, northern and western side of the pyramid, rocks of different origin are presented separately: carbonate sedimentary rocks, mechanical sedimentary rocks, and rocks of volcanic origin. Which side presents mechanical sedimentary rocks?
3. You can see that parts of pyramid sides are stained with something brown - under the level of some particular pebbles. What are these stains, and what in the structure of pebbles »produce« brown stains?
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) WHERE DO PEBBLE STONES COME FROM AND WHY ARE THEY ROUND
The rocks that constitue the pebble stones scattered on the Kokra gravel bars originate from Karavanke Mountains and Kamnik Alps. Under the steep rockwalls of these mountains, sharp-edged rubble is formed. Part of it is scooped by the waters of the Kokra river. Its great water power, especially during Spring snow melting and after heavy rainfall, shifts and rolls these stones down the river floor, where they rub against each other. In the course of time they thus become round and smooth. Pebbles of various sizes and shapes are formed, while tiny grains constiture sand and silt. All this material is deposited in gravel bars as soon as water current power is not strong enough to transport the load.
GEOLOGIC PYRAMID
Pebble stones from gravel bars near the village of Visoko are built into the pyramid at waypoint PYRAMD. While its south side shows the gravel bars diversity, pebbles at each of other three sides consist of the rocks with common way of formation:
- carbonate sedimentary rocks,
- mechanical sedimentary rocks,
- rocks formed during (or because of) volcanic activities.
The colourful pebbles are one of the special featuies of gravel bars on the Kokra River, as the rock composition of the Karavanke Mountains Is exceptionally diverse - owing to the turbulent geological everts in tne past.
Figure 1 – Geologic pyramid, and river bank full of pebbles.
PEBBLES FROM CARBONATE SEDIMENTARY ROCKS
The commonest are limestone and dolomite pebbles. Limestones and dolomites belong to the group of carbonate biochemical sedimentary rocks that constitute the largest part of the hinterland and bedrock of the Kokra catchment. Most of the carbonate rocks are white, the others mostly pink, grey and black. The colours are given to them by mineral, chemical and organic admixtures.
LIMESTONE is composed of calcite mineral (CaC03). Most often, it is formed in seas and oceans from the fragments of shells and skeletons of marine animals, bound into solid rock by calcite binder, which is chemically extracted from water. The petrified remains of former living beings that are found in it are called fossils.
DOLOMITE is composed of dolomite mineral CaMg (C03)2, which is mostly formed in seas from calcite through the replacement of calcium with magnesium. This process is called dolomitization. In dolomite, fossils are rarely found, given that the limestone's basic composition and often structure is totally changed.
PEBBLES FROM MECHANICAL SEDIMENTARY ROCKS
The grains, which were formed through the weathering of older rocks, travelled from the place of disintegration under the influence of mechanical forces, gravity, with water, wind or glaciers and sank or settled in certain places, when their power of transport was finally reduced. Mechanical sediment, or sediment in short, was formed. Later on, the binder bound the sediment's free-flowing grains into a solid mechanical sedimentary rock.
BRECCIA is composed of angular grains. This is usually cemented rubble, but can also be formed from technically (owing to the inner Earth's forces) broken and again cemented rock. CONGLOMERATE is composed of rounded grains - pebbles. The hardest of gravel bars is quartz conglomerate, which is mostly composed of quartz pebbles cemented with quartz binder. SANDSTONE is made up of grains ranging from 0.063 to 2 mm in size, while SILSTONE is composed of grains smaller than 0.063 mm, which can no longer be seen with the naked eye. On gravel bars, mostly red quartz sandstones and siltstones can be found. The red colour is given to them by iron minerals (hematites).
PEBBLES FROM ROCK OF VOLCANIC ORIGIN
On its way, the Kokra River uncovers and carries away the rocks formed during volcanic eruptions taking place in deep seas as well as on land. The commonest are green and reddish QUARTZ CERATOPHYRES - volcanic rocks made of silicate melt - magma or lava. Effusions of lava from thevolcanic crater were accompanied by effusions of gases as well as of solid and melted material. This solid and melted matter called pyroclastic material, forms volcanic bombs and blocks and finerer volcanic ash. The volcanic ash is called TUFF, while the cemented blocks are known as VOLCANIC BRECCIA. The most notable on the Kokra gravel bars are, apart from pebbles of quartz ceratophyres, the green tuffs.
EARTHCACHE AND ACCESS
In Kranj take direction Jezersko and drive to the village Visoko. At waypoint TURN1 turn left – towards Kokra River. You can park your car at waypoint PRKNG1, it is almost at the EarthCache coordinates. Go to the EarthCache coordinates at the Kokra river bank and solve task #1. Walk to the waypoint PYRAMD, and take a look at the interesting geological pyramid and info board. Answer the questions #2 and 3.
We recomned you to walk along the rest of the trail (towards Hotemaže village in the north) too – it is just over 1 kilometer long. There are four additional info-boards on the trail to give you more geologic, natural and historical information.
References:
- Information board; text: Dragomir Skaberne, Tadeja Šubic, Mirka Trajanova; photo: Marko Engerlman, Milan Krišelj, Tadeja Šubic; erecting and financing: Šenčur Community, Geological Survey of Slovenia, The Institute of the Republic of Slovenia for Nature Conservation; 2012.
Slovensko besedilo
Obiščite našo spletno stran Geološki zakladi / EarthCaches
za seznam vseh naših Geoloških zakladov in mnogo dodatnih podatkov.
(SI) OD KOD PRIHAJAJO PRODNIKI IN ZAKAJ SO OKROGLI
Kamnine, ki sestavljajo prodnike kokrških prodišč, izvirajo iz Karavank in Kamniških Alp. Pod njihovimi strmimi skalnimi stenami nastaja ostrorobi grušč. Del grušča zajamejo vode reke Kokre. Njena vodna sila jih premika in kotali po dnu, kjer se drgnejo drug ob drugega. Tako se sčasoma ostri robovi zaoblijo in zgladijo. Nastanejo prodniki različnih velikosti in oblik, drobnejša zrnca pa predstavljajo pesek in mulj.
GEOLOŠKA PIRAMIDA
V piramido na točki PYRAMD so vgrajeni prodniki s prodišč v bližini Visokega. Južna stranica prikazuje raznolikost prodišča, ostale tri pa ločeno predstavljajo izbrane prodnike iz kamnin enakega izvora:
- iz karbonatnih sedimentnih kamnin,
- iz mehanskih sedimentnih kamnin in
- iz kamnin nastalih med vulkanskim delovanjem (ali kot posledica tega delovanja).
Barviti prodniki so ena izmed največjih zanimivosti prodišč ob Kokri, saj je kamninska sestava Karavank zaradi burne geološke preteklosti izjemno pestra.
Slika 1 – Geološka piramida in rečni breg poln prodnikov.
PRODNIKI IZ KARBONATNIH SEDIMENTNIH KAMNIN
Najbolj pogosti so apnenčevi in dolomitni prodniki. Apnenci in dolomiti spadajo v skupino karbonatnih biokemičnih sedimentnih kamnin, ki oblikujejo največji del zaledja in podlage povodja reke Kokre. Barvo jim dajejo mineralne, kemične in organske primesi.
APNENEC je sestavljen iz minerala kalcita (CaC03). Najpogosteje nastaja v morjih in oceanih iz drobcev lupin in skeletov morskih živali, ki jih v trdno kamnino povezuje iz vode kemično izločeno kalcitno vezivo. V njem nastopajoče okamnele ostanke nekdanjih živih bitij imenujemo okamnine ali fosili.
DOLOMIT sestavlja mineral dolomit CaMg (C03)2, ki nastaja v morju iz kalcita, z nadomeščanjem kalcita z magnezijem. Ta proces imenujemo dolomitizacija.
PRODNIKI IZ MEHANSKIH SEDIMENTNIH KAMNIN
Zrna, ki so nastala s preperevanjem starejših kamnin, so potovala s kraja preperevanja pod vplivom mehanskih sil, težnosti, z vodo, vetrom ali ledeniki in se usedla, obmirovala na določenem mestu, ko se je njihova transportna moč zmanjšala. Nastal je mehanski sediment ali usedlina. Kasneje je sipka zrna sedimenta povezalo vezivo v trdno mehansko sedimentno kamnino.
KONGLOMERAT sestavljajo zaobljena zrna - prodniki. Na prodišču je najtrši kremenov konglomerat, ki je sestavljen večinoma iz kremenovih prodnikov, zlepljenih s kremenovim vezivom.
PEŠČENJAK sestavljajo zrna, velika od 0,063 do 2 mm, MULJEVEC pa zrna, manjša od 0,063 mm, ki jih s prostim očesom ne vidimo več. Na prodišču najdemo prevsem rdeče kremenove peščenjake in muljevce. Rdečo barvo jim dajejo železovi minerali (hematit).
PRODNIKI IZ KAMNIN VULKANSKEGA IZVORA
Kokra na svoji poti razkriva in odnaša kamnine, nastale med izbruhi vulkanov v globokem morju in na kopnem. Najpogostejši so zeleni in rdečkasti KREMENOVI KERATOFIRJI - predornine, nastale iz silikatne taline - lave. Izlive lave iz vulkaskega žrela so spremljali tudi burni izbruhi plinov, trdnega in staljenega materiala. To trdno in staljeno tvarino imenujemo piroklastični material in predstavlja večje vulkanske bombe in bloke ter drobnejši vulkanski pepel. Sprijeti vulkanski pepel imenujemo TUF, sprijete bloke pa VULKANSKO BREČO. Poleg prodnikov kremenvih keratofirjev so na kokrškem prodišču najbolj opazni zeleni tufi.
GEOLOŠKI ZAKLAD IN DOSTOP
Iz Kranja se po cesti proti Jezerskem pripeljete v vas Visoko. Na točki TURN1 zavijete levo – proti Kokri. Parkirajte na točki PRKNG1, ki je povsem zraven koordinat Geološkega zaklada in točke QUEST1. Tam rešite prvo nalogo. Potem se sprehodite do točke PYRAMD, kjer si ogledate zanimivo geološko piramido ter informativno tablo in odgovorite na drugo in tretje vprašanje.
Oglejte si še preostali del učne poti ob Kokri, proti Hotemažam. Pot je komaj več kot kilometer dolga in opremljena še s štirimi informativnimi tablami s podatki o geologiji, naravi in zgodovini.
Viri:
- Informacijska tabla, besedilo: Dragomir Skaberne, Tadeja Šubic, Mirka Trajanova, fotografije: Marko Engerlman, Milan Krišelj, Tadeja Šubic, postavitev: občina Šenčur, Geološki zavod Slovenije, Zavod Republike Slovenije za varstvo narave, 2012.
tocke poti in dnevniki / waypoints and logs