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It is not how it looks, I am a responsible dad. Photo by Helen Kelleher.

Caves are the one of the most noticeable features of a karst. The word “karst” may come from the Slovenian. It is characterized by karst phenomena that apart from caves also include canyons, sinkholes and abysms. A karst can only occur in water soluble rocks such as limestone, dolomite or gypsum. As the rain water is slightly acidic due to its content of carbon dioxide, it dissolves those soluble types of rocks. If you want to rewind this process in high speed, throw a piece of limestone into vinegar, or vice versa, pour a drop of vinegar onto limestone. Chemistry for beginners, not dangerous, but spectacular. The Bohemian Karst where I do my hiking tours is a limestone karst. This area has plenty of caves to look out for, and plenty of undiscovered caves.

Where does the water find its way on the limestone.

Where the water find its way on the limestone.

But it takes a long time before the water finds its way through the rock. In a karst area, this process is hardly noticeable at the beginning. But once a pit is big enough to carry other particulates such as clay or sand, the pit or channel gets rapidly wider and deeper. The abrasive forces of clay, sand and stones help to accelerate this process.

If the rain water seeps through the soil, it is enriched by even more carbon dioxide and becomes even more acidic. There is more carbon dioxide in soil than in air due to the activities of organisms in the soil. If there is enough of this acidic seepage, it speeds up the chemical dissolution of the limestone bedrock. Once the pit in the ground is big enough to fit a human being inside, we can call it a cave. Calcium deposits from seeping water may create stalactites or stalagmites as can be seen in many caves in Bohemian Karst. The genesis of caves and other karst phenomena is therefore always connected with water activity.

While hiking above ground in Bohemian Karst today, it is very likely that beneath the surface you are walking on is a system of corridors and caves. And many of them are still unknown. You can see and even step inside many fully formed caves in Bohemian Karst, like for example the cave at a waterfall called Bubovické vodopády on the red hiking trail from Karlštejn to Beroun.

The Berounka River and the longest Karst valley in the Czech Republic

As far as I know, rain water seepage no longer plays an important part in the creation of caves in Bohemian Karst. But some caves are still being forged by water deep down in the limestone bedrock. Most importantly the Berounka River is still forming and shaping caves in Bohemian Karst. The Berounka River flows through the longest karst valley in the Czech Republic. Throughout history the river valley deepened as the water eroded the rock beneath it. You can see lots of caves formed by the river on both banks while hiking through this valley to Beroun for example. Many of these caves are unchanging because they are now untouched by the river which now runs far below them. Other caves are still being formed by flood water from the river which pushes its way into underground spaces through fractures, holes and caves on the river bank.

Koněpruské jeskyně caves By Hadonos – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=30766670

The best known caves in Bohemian Karst are Koněpruské Jeskyně. These caves are a tourist destination, they are accessible and you have to pay for a guided tour in order to see them. And as I mentioned earlier, it is very likely you might hit, or spot caves while hiking in the Bohemian Karst. And if you are curious enough to climb into an unknown dark hole in the ground, good luck with that! Happy hiking in Bohemian Karst!