Volcano Learning zone > Volcano Glossary
Lava Tubes form where a channel of fast moving basaltic lava roofs over. The sides gradually cool and extend over the flow enclosing the lava flow in a covered conduit. A wide lava front will be supplied by several lava tubes with lava flowing at speeds up to 60km/hr. When the lava has stopped erupting at source the lava runs out leaving a tunnel with a flat floor and basalt stalactites hanging from the roof. Skylights are openings in the roof of the tube.
Etna and Hawaii have lava tubes you can walk and crawl through. The Thurston lava tube in Hawaii is a tourist attraction.