Why do some rivers disappear underground in karst regions?
Quick Answer
In karst landscapes, water dissolves soluble rocks like limestone, creating sinkholes and cave passages. The river can sink into these openings and flow below ground.
The Full Story
Karst terrain develops where acidic rainwater and groundwater dissolve limestone, dolomite, or gypsum over long periods. This creates cracks, caves, and sinkholes that can capture surface streams. Once a river enters an underground passage, it may travel through a cave system for kilometers before reemerging. The Nullarbor region in Australia and parts of Slovenia and Kentucky have striking examples of karst drainage. Because the rock is soluble, the drainage pattern can change suddenly as new openings form and old ones collapse.
Key Facts
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