Limestone Labs: The Science of Caves

The Science of Cave Carving

Karst landscapes are created through chemical weathering, where slightly acidic water slowly dissolves a specific type of rock called limestone.

• The Key Rock: The formation begins with limestone, a bedrock made almost entirely of the mineral calcite (calcium carbonate).
• The Acid Weapon: Rainwater is naturally slightly acidic because it absorbs carbon dioxide (CO₂) from the air. When H₂O and CO₂ mix, they form carbonic acid.
• Dissolution Power: The carbonic acid chemically reacts with the limestone (calcite), slowly dissolving the rock over thousands of years to carve out huge underground passages.

Features of a Karst Landscape

The defining features of a Karst region are its unique surface geology and the striking mineral formations inside the caves.

Sinkholes: Bowl-shaped depressions formed when the roof of an underground cave collapses.

Cave Formations (Speleothems): Water dripping through the     cave ceiling leaves behind dissolved calcite, which slowly recrystallizes into formations:

• Stalactites: Formations that hang TIGHT to the ceiling.
• Stalagmites: Formations that grow MIGHTY tall from the ground.

Cave life: Many creatures adapt to darkness—pale fish, bats, insects—often with slow growth and keen senses.

Fun Facts

Here are some interesting facts about caves and karst:

• The largest known cave system, Mammoth Cave in Kentucky, is over 675 km (420 miles) long—longer than the entire state of Rhode Island!
• Cave formations can trap clues about past climates (ancient rain patterns) in their layers.
• A stream can vanish into a sinkhole in karst areas and reappear miles away as a spring.
• Cave formations grow incredibly slowly, often less than 1 centimeter every 100 years.

Review

Let’s quickly recap what we learned about caves and karst:

• What type of rock is dissolved to form a Karst landscape? Limestone
• What is the weak acid created when rainwater absorbs carbon dioxide? Carbonic Acid
• What cave formation grows up from the floor? Stalagmite
• What is the name for the bowl-shaped depression caused by a collapsed cave roof? Sinkhole