Lava tube
![Valentine Cave in Lava Beds National Monument, California. This shows the classic tube shape and the curbs on the wall mark former flow levels.](/Images/godic/202501/23/Valentine_Cave2543.JPG")
![Thurston Lava Tube in Hawaii Volcanoes National Park, Hawaii. The step mark, more visible on the right wall, indicates the depth at which the lava flowed for a period of time.](/Images/godic/202501/23/Thurston_Lava_Tube,_Big_Island2543.jpg")
![A rare characteristic of lava tubes are lava pillars. This is the Manjanggul lava pillar located in the Manjanggul lava tubes on the island of Jeju-do, Korea.](/Images/godic/202501/23/Manjanggul_Lava_Tower2544.jpg")
![Lavacicles on the ceiling of Mushpot Cave in Lava Beds National Monument](/Images/godic/202501/23/Lavacicles_82382544.jpg")
A lava tube is a natural conduit formed by flowing lava which moves beneath the hardened surface of a lava flow. Tubes can be actively draining lava from a volcano during an eruption, or can be extinct, meaning the lava flow has ceased and the rock has cooled and left a long, cave-like channel.