|Image: The entrance to Škocjanske Jame is located in a green dolina, a few hundred meters from Škocjan.|
In covered karst, the vegetation covers the limestone. This has two important effects on the geology:
It is rather difficult to see, if a certain area is a karst region, if it is a covered karst area. But if you know the signs, it is pretty easy:
Karst areas have a typical soil and vegetation. There is no ground water, so there will be no vegetation that depends on it. The soil may dry regularily, so the vegetation will be used to this and be able to store some water.
The soil is formed by the residuals of limestone dissolution, which are mostly silt minerals. If there is any iron in the limestone, which is rather common, the soil will in most cases have the colour of the iron oxide, as iron oxides are very good pigments. Red soils are formed only in sub-tropic and tropic climate zones while beige soils are typical for temperate climates. The reason are two different chemical classes of iron oxides, the +2 and +3 oxidation states. In tropical and subtropical climates, the colour is red (terra rossa). The colour is caused by rust or ferric oxides, iron(III) oxides, also called trivalent iron compounds. In colder climates the colour is beige, a very typical yellowish brown, caused by ferrous oxides, iron(II) oxides, or divalent iron compounds. This chemical specialty of iron gives us a good marker to determine the temperature of the time when the residual was formed.