You are a US citizen and: 1  You are a first time applicant age 18 or older. 2  OR your most recent U.S. Passport was issued when you were under age 16. 3  OR your previous U.S. passport was issued more than 15 years ago.
Cave formations are called speleothem, from the Greek word spelaion, cave and thema meaning deposit. Almost all of them are made of calcite, the crystal of calcium carbonate. Different minerals and different movements in the water account for an incredible variety of cave formations.
How do cavern and cave diving. Cavern diving is the exploration of permanent, naturally occurring overhead environments while remaining within sight of their entrances. It differs from cave diving in that, while cave divers may penetrate thousands of yards, cavern divers generally go no further than 130 feet from the surface.