Kratek in preprost EarthCache.
Kaj je konglomerat?
Preprosta znanstvena razlaga pravi, da je konglomerat debelozrnata, klastična, sedimentna kamnina, ki nastane s sprijetjem prodnikov.
Pri čemer lahko poljudno razložimo besede:
- Prodniki: kosi kamnine z obrušenimi robovi,
- Debelozrnata kamnina je za geologe tista, v kateri so zrna kamnine večja od 2 milimetra, to pomeni, da so v konglomeratu zaobljeni kamenčki veliki 2 mm ali več,
- Klastična: je kamnina sestavljena iz klastov ali kosov,
- Sedimentna je kamnina, ki nastane z usedanjem delcev kamnin, mineralov, organskih in drugih snovi.
Beseda konglomerat izhaja iz latinske conglomerare, ki pomeni kopičenje. Slovensko lahko konglomerat imenujemo tudi sprimek, ponekod ga imenujejo tudi labora.
Konglomeratu podobna je breča, ki pa vsebuje ostrorobe kamne.
Kje in kako nastane konglomerat?
Konglomerat nastaja iz proda na mestih, kjer so ga vodni tokovi odložili v zadostnih količinah. To je lahko v vršajih, kjer struga vodotoka postane položnejša ter posledično izgubi hitrost in s tem moč prenašati prodnike. Druga možnost so poplavne ravnice, na katerih vodotok odlaga prod med poplavljanjem ali v času povečanega vodostaja. V obeh primerih vodni tok najprej odloži masivnejše prodnike.
V produ se pod težo mlajših plasti, ki se usedajo nanj, začne proces kompaktiranja, oziroma stiskanja. Pri tem je praznega prostora med prodniki vse manj, hkrati jih med seboj prične sprijemati vezivo. Vezivo je lahko mineralni cement, ki se izloča iz vodne raztopine kamnin (pri nas je to najpogosteje kalcit iz apnenca), lahko pa je drobnozrnata osnova (peščena, glinena ali lapornata) ali pa oboje. Vezivo postopoma zapolni tudi preostale prazne prostore med prodniki. Tako v procesu, imenovanemu diageneza, iz proda nastane kamnina konglomerat.
Na koordinatah zaklada
Konglomeratne kamnine so najpogosteje razkrite očem v pobočjih nad rečno strugo, kjer je vodni tok poglobil dno doline, ustvaril sotesko ali spdjedel pobočje ob katerem teče. Na mestu konglomeratne stene tega EarthCache zaklada je reka tekla pred več tisoč ali deset tisoč leti, zdaj pod njo teče železnica. Stena je dolga približno sto metrov in je preprosto dostopna, saj ob njej vodi sprehajalna steza z nekaj stopnicami. Najdete jo v bližini velikega geolovskega dogodka, Block Party 2025, ki se bo odvil / se je zgodil na gradu Zaprice.
Konglomeratna stena / Conglomerate wall, foto / photo: Vane, kompaski
Vprašanja za vpis zaklada
1. Oglejte si del kamnite stene. Ali gre za zelo kompakten konglomerat z malo ali nič zračnimi prostorčki ali zlahka najdete večje število luknjic in špranj v kamnini?
2. Koliko so veliki povprečni prodniki v tej konglomeratni steni (gledano najdaljšo mero prodnika)? od 2 do 10 mm / 10 do 30 mm / več od 30 mm.
3. Dodatno, neobvezno vprašanje: Kaj menite, zakaj so prodniki tega konglomerata v tem velikostnem razredu? Kako je to povezano z vodnim tokom, ki jih je tu odložil?
4. Če boste fotografirali steno, sebe ali kaj drugega, tega ne storite blizu konglomerata. Hvala.
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Odgovore pošljite preko GC profila preden vpišete najdbo. Po pošiljanju odgovorov ne potrebujete dodatnega dovoljenja za vpis. Prosimo, naložite fotografije, če ste jih posneli.
Vpisi brez predhodnega sporočila s pravilnimi odgovori bodo šifrirani in kasneje izbrisani!
Vpisi z odgovori bodo izbrisani!
Viri / References:
Proteus, marec 2009, Ljubljana, članek ' Konglomerat − kamnina leta 2009'
Short and easy EarthCache.
What is a conglomerate?
A simple scientific explanation says that a conglomerate is a coarse-grained, clastic, sedimentary rock formed by the adhesion of pebbles.
We can explain the fancy words:
- Pebbles: pieces of rock with rounded edges,
- For geologists, coarse-grained rock is one in which the rock grains are larger than 2 millimetres, this means that the conglomerate contains rounded pebbles 2 mm or larger,
- Clastic: is the rock composed of clasts or pieces,
- Sedimentary is a rock that is formed by the settling of rock particles, minerals, organic and other substances.
The word conglomerate comes from the Latin conglomerare, which means accumulation.
Breccia is similar to conglomerate, but it contains sharp-edged stones.
Where and how is conglomerate formed?
Conglomerate is formed from pebbles in areas where watercourse has deposited it in sufficient quantities. This can be in alluvial fan, where the riverbed becomes flatter and consequently loses speed and thus the energy to transport pebbles. Another possibility is floodplains where the watercourse deposits pebbles during flooding or during periods of increased water levels. In both cases the larger pebbles are deposited first.
In the layers of pebbles, the process of compaction, or compression, begins under the weight of younger layers that are covering them. In time, there is less and less empty space between the pebbles, and at the same time, abinder or cement begins to adhere them to each other. The binder can be a mineral cement formed by the disolution of rocks (in our country this is most often calcite from limestone), or it can be a fine-grained base (sand, clay or marl), or both. The binder gradually fills most of the remaining empty spaces between the pebbles. Thus, in a process called diagenesis, a rock conglomerate is formed from pebbles.
At the coordinates of the EarthCache
Conglomerate rocks are most often revealed to the eye in the slopes above the riverbed, where the water flow has deepened the valley floor, created a gorge or carved the slope along which it flows. At the site of this EarthCache, a river flowed thousands or tens of thousands of years ago – now just a footpath runs along the rock wall.
The wall is about a hundred meters long and is easily accessible, since a path with a few steps leads along it. It is situated near the venue of the big geocaching event, Block Party 2025, which will take place / took place at Zaprice Castle.
Grad Zaprice v bližini EarthCache točke / Zaprice Castle close to EC, foto / photo: Vane, kompaski
Logging tasks
1. Look at a section of rock wall. Is it a very compact conglomerate with little or no air pockets, or can you easily find many holes and cracks in the rock?
2. What is the average size of the pebbles in this conglomerate wall (the longest dimension of the pebble)? 2 to 10 mm / 10 to 50 mm / more than 50 mm.
3. Additional answer – not obligatory: Why do you think the size of the pebbles in this conglomerate is in this dimension range? How is this connected to the water course that transported them?
4. If you are going to take a photo of the wall, yourself, or anything else, do not do it near the conglomerate. Thank you.
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Logs containing the answer will be deleted!
Viri / References: Proteus, marec 2009, Ljubljana