Karst Features of the Moravian Karst: What a Sinkhole, Swallow Hole and Resurgence Are, and Where to See Them

Most visitors come to the Moravian Karst for the caves and overlook the fact that the entire landscape above them is one vast karst creation. A sinkhole (závrt) is a funnel through which water disappears underground. A swallow hole (ponor) is a spot where an entire stream flows into the rock. A resurgence (vyvěračka) is where the water comes back out again. Karren (škrapy) are fissured limestone laid bare at the surface. In the Moravian Karst, all of these features are easy to see from ordinary waymarked paths, and this article gives you specific places, complete with dimensions. The Protected Landscape Area Administration records 80 of them.

QUICK LINKS 🕳 Sinkholes · 🌊 Swallow holes and sinking streams · 💧 Resurgences · 🪨 Karren · 🌉 Natural rock bridges · 🗺 A route where you can see everything · ❓ Frequently asked questions

How it all works

Limestone slowly dissolves in water. Rain seeps down through cracks, widening them along the way, and over hundreds of thousands of years they become caves. Water that would elsewhere flow along the surface vanishes underground here and reappears kilometres away.

That is why karst landscapes have a vocabulary all their own. Once you understand the terms, the Moravian Karst stops being a collection of pretty views and starts to make sense as a single, connected system.

Sinkholes: where the landscape drains inwards

A sinkhole (závrt) is a funnel-, bowl- or well-shaped hollow through which surface water drains into the underground. There are hundreds of them on the karst plateaux, and they have always made life difficult for farmers, because you cannot plough in them and the soil from the surrounding land keeps washing into them.

Závrt Dolina is the second-largest bowl-shaped sinkhole in the whole Moravian Karst, with a diameter of 166 metres. It is shallow and can be farmed, which is unusual for a sinkhole. A Palaeolithic surface site was found right next to it.

Wanklův závrt has an exact date of birth. It collapsed on 5 April 1855, and what was originally a cylindrical shaft is now a funnel.

Uvala nad Amatérskou jeskyní is something different: when a series of sinkholes merge, an elongated depression forms, known as an uvala (compound sinkhole). This one is 1,100 metres long and 200 to 400 metres wide, the most fully developed in the whole karst. The latest interpretation is far more intriguing, though: it may not be merged sinkholes at all, but the remnant of an enormous tunnel cave whose roof has collapsed. A cave without a ceiling. It roughly follows the course of the Macocha Corridor of the Amatérská Cave, but lies some 250 metres to the east.

Tři Kotle is a group of three large cauldron-shaped sinkholes, while Bobří závrt is a textbook well-shaped example, 8 metres deep and 6 metres wide.

And then there is Malá Macocha u Babic, which is only half a karst feature. It is the remains of an old iron ore mine, with fossil karst funnels preserved in its walls. It was originally about 40 metres deep; today it is just 8, the rest having been filled in by time.

Sinkholes forming right now

This is not ancient history. The area below Šošůvka and U Trojičky is a place where new sinkholes keep forming, either through gradual subsidence or through sudden collapse to depths of up to 3 metres. And right by the road before Balcarka, a new sinkhole about 4 metres deep opened up in 2013, and it has been widening ever since as its walls slump.

Swallow holes and sinking streams: where a stream vanishes into the rock

While water merely seeps down through a sinkhole, a swallow hole (ponor) takes an entire stream underground in one go.

Rudické propadání is the most typical blind karst valley in Czechia, and it has a feature found nowhere else in the country: the Jedovnický potok flows freely into the cave straight through its portal and carries on through the passages. Elsewhere, water disappears into rubble and crevices. Here you can see a stream literally walk into the mountain. The Rudické propadání – Býčí skála underground system is roughly 13 kilometres long and delivers the water back to the surface in the Josefovské údolí.

Stará and Nová Rasovna near Holštejn are active swallow holes of the Bílá voda stream, with an overflow edge and flood swallow holes that only come into play when there is too much water. In the adjoining cave, Piková dáma, the Ledová chodba (Ice Passage) has ice formations almost all year round, the only one of its kind in the Moravian Karst.

Also belonging here are the Sloupské údolí with its system of swallow holes of the Sloupský potok, the propadání V Jedlích, U Domínky, the Habrůvecký ponor and the Hostěnické propadání in the southern part.

Resurgences: where water returns to daylight

Vývěr Punkvy is the largest karst resurgence in the Moravian Karst. Its hydrography has been altered: when the Punkva Caves (Punkevní jeskyně) were opened to the public, water levels were lowered and siphons were breached, so what you see is not entirely the natural state.

Vývěry Jedovnického potoka are three resurgences in a former quarry, separated by siphons from the continuation of the underground system.

The most remarkable of all, though, is the Hádecká estavela in the southern part of the karst. An estavela is a spot that acts as a swallow hole at one moment and as a resurgence at another, depending on water levels. This one is the only estavela currently functioning in the Moravian Karst: either the Říčka disappears into it, or the underground Hostěnický potok flows out of it. The protected landscape area’s administration adds, however, that its function has not yet been reliably proven. There is more in the article The Říčka Valley and Pekárna Cave.

Karren: limestone laid bare to the bone

Karren (škrapy) are grooves, channels and sharp ridges etched into bare limestone by water. When there are many of them together, they form a karren field, and the hillside looks as if someone had hacked it to pieces.

The best karren fields in the karst:

• Macošská stráň — right by the Macocha Abyss, the easiest to reach
• Vilémovická stráň — also the type locality of the Vilémovice limestone, the place after which that rock is named
• Vykydalova stráň near Blažkův závrt
• Balcarova skála above the Balcarka Cave
• Lysá hora above the Říčka valley
• Hádecká planinka on the southern edge

Incidentally, the karren slopes are the reason sheep are grazed in the karst. Flocks are brought onto them to stop them from becoming overgrown with scrub.

Natural rock bridges: what is left when a cave falls apart

Caves do not last for ever. When a roof collapses, all that remains of the passage is a piece of vault, and that is a natural rock bridge.

Čertův most in the Suchý žleb is the finest example: the wreck of a cave in the form of two bridge arches. Just below the valley rim above it you will find the Čertova vrátka, the remains of a cave in the shape of a short rock passage.

Čertova branka in the Pustý žleb is a rock gate. And the Skalní most nad Punkevními jeskyněmi formed differently, from a sinkhole at the edge of the gorge.

Where to see the most karst features on a single route

The Suchý žleb from Skalní Mlýn to the Macocha Abyss is the best for this. Along the way you will pass Čertův most, the Kateřinská Cave (Kateřinská jeskyně), the karren on Macošská and Vilémovická stráň, and finish at the edge of the largest abyss. A detailed description is given in the guide to the Pustý žleb and the guide to the Macocha Abyss.

Rudice and surroundings is the second option. It is a short walk from the windmill to the Rudické propadání, and on the way you will see the only swallow hole of its kind in Czechia, the Kolíbky rock amphitheatre above it, and the remains of an old mining field. More in the article about Rudice and about the Rudice geodes.

The Holštejnské údolí is the quietest of the three. Swallow holes in the Sloupské údolí, Stará and Nová Rasovna, a ruined castle and the Lidomorna Cave.

Macocha: about 138 metres to the water

While we are on the subject of numbers, the Macocha Abyss is about 138 metres deep down to the surface of the Dolní jezírko (Lower Lake). Below the surface, however, a flooded section continues, and sources disagree about it: AOPK gives a total depth of 188.5 metres in its analyses, while other sources say 187.5 metres. The Caves Administration estimates the depth of the lake itself at roughly 40 metres, and nobody has yet reached the bottom, so the final figure is still waiting for divers. In technical terms it is a light hole, an abyss formed by the collapse of the roof of a large underground chamber, through which light then penetrates from above.

Hidden in the walls of the abyss are a number of further caves and chasms that you cannot make out from the viewing platforms: Podmůstkové, Červíkovy, Pasovského, Erichova or Hankensteinova.

And one more figure worth remembering: the entire Amatérská Cave system, including the caves connected to it, is about 40 kilometres long and is the longest in Czechia. Both the Punkva Caves and the Sloup–Šošůvka Caves (Sloupsko-šošůvské jeskyně), which you can tour with a guide, are part of it, so you are in fact exploring a small piece of one gigantic system.

Frequently asked questions

What is the difference between a sinkhole and an abyss? A sinkhole forms from above, through dissolution and subsidence of the surface. An abyss forms from below, through the collapse of the roof of an underground chamber. Macocha is an abyss; Dolina is a sinkhole.

Can you fall into a sinkhole? Into most, no; they are gentle, grass-covered funnels. Take care at the fresh collapses below Šošůvka and U Trojičky and at the one from 2013 near Balcarka, as these have vertical walls that continue to slump.

What are blind and semi-blind valleys? A blind valley ends in a rock wall into which the stream disappears, and goes no further (Rudické propadání). A semi-blind valley has a dry continuation beyond the swallow hole, through which water flows only in flood (Stará and Nová Rasovna).

How many karst features does the Moravian Karst actually have? The protected landscape area’s administration keeps a list of 80 significant features of inanimate nature. There are over 1,100 registered caves, of which 5 are open to the public.

Source: AOPK ČR, Rozbory předmětu ochrany CHKO Moravský kras (August 2017), chapter 3.10.

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