In the Plitvice Lakes National Park, barriers between the lakes over which are falling magnificent waterfalls and the small falls, have been created in a special, natural way. Under certain physical / chemical and biological conditions, calcium carbonate (CaCO3) is being extracted from the water, and then is being deposited on the bottom of the lake, and on the submerged items. It also creates underwater thresholds and barriers which are elevating above the water growing constantly in height and width. The barriers are chalky creations, which are hard, porous and fragile limestone, full of remains of microscopic mosses and petrified water mosses that are growing up at the falls. That kind of creation is called sedra, travertine, tufa, bigar, vapneni macak. Travertine which is fonned and created by plants, is called plant - formed travertine.
The famous explorer of traveitine creating process at the Plitvice Lakes, I.Pevalek, wrote in 1926: "The essence of the Plitvice Lakes is in travertine and in travertine - forming plants, namely algae and mosses. Immense number of waterfalls, various barriers between the lakes and the unique caves have all been created by travertine - forming plants."
Permanent and continuous creation of plant - formed travertine at the Plitvice Lakes is the fundamental phenomenon of the National Park and condition for their existence.
Due to the special qualities of karst base (limestone, dolomite), the water of the Plitvice Lakes is rich of dissolved calcium carbonate which is present in form of calcium bicarbonate Ca(HCO3)2. To explain the chemistry - water of the Plitvice Lakes is "super - saturated" with this chemical compound. It comes to that when rainwater, while going through superficial soil - stratum, absorbs carbon dioxide (CO2), thus creating carbonic acid (H2CO3) which dissolves limestone and dolomite - thereby the water becomes significantly mineralized, super - saturated with calcium and magnesium - bicarbonate. When it breaks through on the surface, at the tapids and specially at the travertine barriers, the water splashes and thereby the chemical balance is being disturbed, calcium carbonate is being secreted in the form of microcrystals that are being deposited. The super saturation of water by calcium salts is the basic condition for travertine creation. Besides, the water has to be clean, must not contain increased concentration of organic substances which are the serious obstacle for the unique process of travertine creation at !he Plitvice Lakes, (proved by SRDOC and associates in 1958). Down the Korana river from the Korana bridge, travertine creation ends quite quickly, inspite the supersaturation with calcium bicarbonate, because of the increasement of concentration of the organic substance in the water. The presence of water - algae and some mosses is also a condition for travertine creation at the Plitvice Lakes, particularly as a factor that forms chalky secretions. Those water plants are giving form to the created travertine, and the Plitvice Lakes waterfalls can thank mosses for their feature, and depending on various species, we could also differ various biological types of travertine. Let's have a look at mosses on the travertine barriers over which water is falling down. Young shoots of mosses are green and soft, they are mostly without travertine, the ones from the last year are already forming travertine while the old shoots are of yellow color, completely covered and petrified, thus being the famous sight of the Plitvice Lakes - the plant - formed travertine. Recent researches have proved that millions of algae and bacteria living on the mosses shoots, are secreting mucus that is adhered to by the first microcrystals of calcite. Very quick, the other microcrystals are going to be deposited on that, thus creating the travertine. This process goes far back in geological past, but only under the conditions of warm and humid climate, similar to those of today. 2000 years ago, during the last cooling which effected Europe, travertine was not created at the Plitvice Lakes. Yet today travertine is being created much faster during the summer, than in the winter.
To log this cache do the following:
Submit a photo of you and your GPS with a map of the lakes (spoiler).
Send to an e-mail address firstname.lastname@example.org
answers to these questions:
1 - the date of declaration Plitvice lakes as a National park
2 - name at least 4 of the lakes the national park is made of
3 - what kind of material the underlay of lower lakes is made of
* 1.1.2011 edit - since the groundspeak changed their terms & conditions, you are no longer obligated to include photos as a proof of your visit. Due to this change, you may choose to send a photo or write to the e-mail what exactly awaits park visitors on given coordinates besides the info panel.