Ovaj se Earthcache nalazi unutar Nacionalnog parka Krka. Ovdje su vrlo zanimljive sedimentne stijene ...
Geologija
Na početnim koordinatama nalazi se stjenoviti izdanak sedre.
Travertin je oblik vapnenca koji se taloži u mineralnim izvorima, posebno vrelima. Travertin često ima vlaknasti ili koncentrični izgled i postoji u bijelim, žutosmeđim i kremastim sortama. Nastaje postupkom brze oborine kalcijevog karbonata, često na ušću vrućeg izvora ili u vapnenačkoj špilji.
Moderna sedra nastaje iz geotermalno zagrijanih prezasićenih alkalnih voda, s povišenim pCO2. Po izbijanju vode degaziraju CO2 zbog nižeg atmosferskog pCO2, što rezultira povećanjem pH. Budući da se topljivost karbonata smanjuje s povećanim pH, dolazi do taloženja. Oborine mogu pojačati čimbenici koji dovode do smanjenja pCO2, na primjer povećane interakcije zrak-voda na slapovima mogu biti važne, kao i fotosinteza. Padavine mogu biti pojačane isparavanjem u nekim izvorima.
I kalcit i aragonit nalaze se u sedrenicama vrućih izvora; aragonit se prioritetno taloži kad su vruće temperature, dok kalcit dominira kada su temperature hladnije. Kad je čist i fin, sedra je bijela, ali često je smeđa do žuta zbog nečistoća.
Zadaci:
1. Kako je nastao lokalni sedri?
2. Je li ova pojava i danas?
3. Vidite li neke fosile u pješčenjaku?
4. Slikajte se sa sobom ili s GPS-om s travertinom.
Pošaljite mi odgovore putem profila, a zatim se normalno prijavite.
Izvori: wikipedia
English:
This Earthcache is located next to the Krka National Park. Here are very impressive sedimentary rocks ...
Geology
At the initial coordinates there is a rocky shoot of travertine.
Travertine is a form of limestone that is deposited in mineral springs, especially hot springs. Travertine often has a fibrous or concentric appearance and exists in white, yellow-brown and creamy varieties. It is formed by the process of rapid precipitation of calcium carbonate, often at the mouth of a hot spring or in a limestone cave.
Modern travertine is formed from geothermally heated supersaturated alkaline waters, with elevated pCO2. After the outbreak of water, they degas CO2 due to lower atmospheric pCO2, which results in an increase in pH. As the solubility of carbonates decreases with increasing pH, precipitation occurs. Precipitation can be amplified by factors leading to a decrease in pCO2, for example increased air-water interactions at waterfalls can be important, as can photosynthesis. Precipitation may be intensified by evaporation in some springs.
Both calcite and aragonite are found in the travertines of hot springs; aragonite precipitates primarily when temperatures are hot, while calcite dominates when temperatures are colder. When clean and fine, the tufa is white, but is often brown to yellow due to impurities.
Tasks:
1. How did the local travertine originate?
2. Is travertine still formed here today?
3. Do you see any fossils in travertine?
4. Take picture with you or with your GPS with travertine.
Send me answers via profile, then log in normally.
Sources: wikipedia