The opening grew into underwater streams and rivers. When the water was gone, these underground waterways became cave tunnels and caverns. It can take from 10,000 to 100,000 years to make a cave that is large enough for humans to explore. Water drips constantly in caves. The water carries minerals that accumulate into formations, as the water dries out.
Cave formations grow over thousands of years.
Visit the cave map below to learn about caves near you. Encourage your students to e-mail or write to the national park or other organizations that are responsible for caves and ask for information and materials. Each student or pair should produce a tourist brochure for the chosen cave. Make your own stalagmites and other cave formations in the classroom. You will need 2 cups hot water, charcoal briquettes, and Epsom salts.