 Thurston (Nahuku) lava tube near summit caldera of Kilauea Volcano in Hawaii Volcanoes National Park |
Lava tube
Lava tubes are natural conduits through which lava travels beneath the surface of a lava flow. Tubes form by the crusting over of lava channels and pahoehoe flows. A broad lava-flow field often consists of a main lava tube and a series of smaller tubes that supply lava to the front of one or more separate flows. When the supply of lava stops at the end of an eruption or lava is diverted elsewhere, lava in the tube system drains downslope and leaves partially empty conduits beneath the ground. Such drained tubes commonly exhibit "high-lava" marks on their walls, generally flat floors, and many lava stalactites that hang from the roof. Lava can also erode downward, deepening the tube and leaving empty space above the flowing lava. |
 Scientist takes advantage of a skylight to measure height of lava flowing in a lava tube, Kilauea Volcano, Hawaii |
Skylight A skylight is an opening in the roof of a lava tube. Skylights usually form when part of the roof collapses into the tube, but they also occur where a roof failed to form over the lava channel. If the tube is active, a stream of glowing lava can be seen moving below. |