lava tube

Valentine Cave, a lava tube in Lava Beds National Monument, California shows the classic tube shape; the grooves on the wall mark former flow levels. 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. Rare characteristics 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. Lavacicles on the ceiling of Mushpot Cave in Lava Beds National Monument Close-up of a skylight on a coastal plain, with lava stalactites forming on the roof of the tube, Hawaii Volcanoes National Park Entrance of a lava tube, Big island, Hawaii

A lava tube, more rarely called a pyroduct or lava tunnel, is a natural roofed conduit along which molten lava flows from a volcanic vent. If lava in the tube drains out, it will leave an empty cave. Lava tubes are common in low-viscosity volcanic systems. Lava tubes are important as they are able to transport molten lava much further away from the eruptive vent than lava channels. A tube-forming lava flow can emplace on longer distance due to the presence of a solid crust protecting the molten lava from atmospheric cooling. Lava tubes are often considered when preparing hazard maps or managing an eruptive crisis.