Jacob's Well -- Wimberly, Tx: One of the most significant natural geologic treasures in the Texas Hill Country. It is one of the longest underwater caves in Texas and an artesian spring. Jacob’s Well surges up thousands of gallons of water per minute.
East of Reykjavik lies a mountain named Hengill. Hengill was formed from a Palagomite tuff and its highest point is around 800 metres above sea level. Hengill is a central volcano and has a giant magma chamber beneath it.