Caves and karst landscapes

In short: Karst forms when water dissolves soluble rock such as limestone over a long period of time. This creates caves, funnel-shaped hollows in the ground and underground rivers.

In more detail: Rainwater absorbs carbon dioxide from the air and soil and becomes slightly acidic. This weak carbonic acid dissolves limestone along cracks and joints and, over thousands of years, widens them into cavities.

In detail

• Name: The term goes back to the Karst region on the border between Slovenia and Italy, where these landforms were described early on.
• Rocks: Karst forms mainly in limestone and dolomite, but also in gypsum and salt.
• Sinkholes: Funnel-shaped hollows, called dolines, form when rock is dissolved from below or a cave roof collapses.
• Disappearing rivers: In karst areas streams often vanish into swallow holes and reappear elsewhere as powerful karst springs.
• Dripstones: Where lime-rich water drips into a cave, calcium carbonate is deposited; stalactites hang from the ceiling and stalagmites grow upwards from the floor.
• Slow growth: Dripstones usually grow very slowly, so touching or breaking them can cause damage that lasts for a very long time.
• Examples: Well-known karst areas include the Swabian Jura, Franconian Switzerland, the tower karst around Guilin in China and Ha Long Bay in Vietnam.
• Other types of cave: Besides karst caves there are lava tubes formed from solidified lava, ice caves and sea caves carved out by waves.
• Vulnerable groundwater: Water flows quickly through karst and is hardly filtered, so pollutants easily reach springs and drinking water (gebirge-und-berge-der-erde, fluesse-und-seen-der-erde).