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.
Ice caves come in two forms. A cave formed entirely of ice is actually called a glacier cave and as the name implies, forms in glaciers. Water runs through or under the glacier and forms a cave. Glacier caves are very dangerous to enter and explore because of shifting and melting ice. They are a little too adventurous for the novice. The other type of ice cave can be any cave type (limestone, lava tube, etc.) that has ice in it year round. These caves trap cold air. Water entering the cave freezes and stays frozen year round.