What is a cave?

Have you ever peeked into a dark hole in a hillside and wondered how deep it goes? That hole might be the start of a cave — a big hollow space hidden inside the Earth.

A cave is a hollow space underground

A cave is like a giant empty room, but made of rock and tucked away below the ground. Some caves are small enough to crawl into. Others are so huge you could fit a whole house inside! Caves are usually cool, quiet and very, very dark.

How does a cave get made?

Many caves are carved out by water. Rain trickles down through cracks in the ground and slowly dissolves soft rock — a tiny bit at a time. Drip by drip, year by year, the water washes the rock away and leaves an empty space behind. This takes thousands of years, so caves are super old.

Dripping stone shapes

Inside many caves you can find pointy stone shapes. Stalactites hang down from the ceiling like stone icicles. Stalagmites grow up from the floor. They form as water drips and leaves behind tiny bits of mineral, building up slowly over a very long time.

Wonder fact: Some caves are home to animals that have no eyes at all — in the total darkness, they don’t need them to find their way!