Geography
Why Limestone Karst Landscapes Develop Sinkholes and Underground Drainage Systems
Quick fact
Some karst regions have more than a thousand sinkholes per square kilometer, and extensive cave networks can stretch for hundreds of kilometers beneath the surface.
Why this is interesting
Have you ever seen a lake that suddenly drains away, or a cave that swallows an entire river? In karst landscapes, water can flow right through solid rock as if it were a sponge.