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This Earthcache is located inside the Krka Nationalpark. To go there you need to pay an entrance fee.
Travertine is a form of limestone deposited by mineral springs, especially hot springs. Travertine often has a fibrous or concentric appearance and exists in white, tan, and cream-colored varieties. It is formed by a 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 raised pCO2. On emergence, waters degas CO2 due to the lower atmospheric pCO2, resulting in an increase in pH. Since carbonate solubility decreases with increased pH, precipitation is induced. Precipitation may be enhanced by factors leading to a reduction in pCO2, for example increased air-water interactions at waterfalls may be important, as may photosynthesis. Precipitation may also be enhanced by evaporation in some springs.
Both calcite and aragonite are found in hot spring travertines; aragonite is preferentially precipitated when temperatures are hot, while calcite dominates when temperatures are cooler. When pure and fine, travertine is white, but often it is brown to yellow due to impurities.
Travertine, (visit link)
On the given coordinates you will find a dead travertine an a sign.
in order to log this Earthcache you will have to answer the following questions.
1.) How old are the travertines of Skradinski buk
2.) How old are the oldest dead travertines found in the area of the former river
3.) How many mm does the travertine grow per year
Send the answers of these questions to firstname.lastname@example.org
There is no need to wait for a logging permission, if there is something wrong i will contact you.
It would be great if you could post a photo of you in front of the travertine.
(No hints available.)