Karst landscape

The word karst derives from the name of a region, the Carso, at the border between Italy and Slovenia, which is characterized by this type of landscape. Karstik environments develop in places with calcareous rocks, which are highly soluble like limestones, dolomites and evaporitic rocks. Carbonates and evaporites are rocks made of minerals that are very soluble in the water and for this reason they are easily shaped by rainfalls. Also raindrops manage to melt these rocks and dig holes, sometimes very deep ones. The erosion of calcareous rocks in a Karstik territory is called corrosion.
The soil
The dark red colour of karstik soil is due to oxides and the clay content of calcareous rocks. When soluble minerals are melted by water and detached from the rock, some residual deposits are left on the spot. They consist of insoluble minerals, like iron oxides and clay minerals.
Superficial shapes
The most evident superficial phenomena are dolines: funnel-shaped depressions, 1-30 metres deep and hundreds of metres wide. The continuous action of water can favour the widening and union of several nearby dolines. In this way a single depression is formed, which is called uvala. A continuous corrosion leads to the creation of a wider and wider depression, on a flatland, called polje. These depressions can host small lakes that still have some little protuberances of harder and un-dissolved rocks.
Polje can be seen in the Italian and Slovenian Carso, where they are called  piani or campi, like campo Imperatore on Gran Sasso.
The karstik landscape that we can see has no stable hydrographic network, with a total absence of water streams or rivers. The water, by dissolving carbonate rocks, digs the subsoil, where it creates typical underground shapes.
Underground shapes
In large karstik landscapes there are no rivers or streams running on the surface. Water streams run deep underground and, after spending some time underground, they come back to the surface. The underground karstik cavities are made up of caves and canals that can host underground water streams. An example of them is the Timavo river, in Carso in Trieste area: after running on the surface, close to San Canziano, the river goes underground and re-emerges 40 kilometres afterwards, near Monfalcone.
The walls of caves that no longer host rivers are full of juts and encrustations. The most famous are stalactites that hang from the ceiling, and stalagmites that lift from the cave floor. The two protuberances, with time, can join and form columns.

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