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.
This type of topography indicates that water is close to soluble bedrock such as limestone, dolomite, gypsum and rock salt. Karst topography is found throughout the world; in the U.S. it is particularly important for mapping large cave formations such as Mammoth Cave and the Fisher Ridge Cave System in Kentucky, Jewel Cave and Wind Cave in South Dakota, and the Friars Hole System in West Virginia.