Photoglossary

Lava Lakes,Tubes, and Fountains   Lava Lakes      Lava lakes form when molten lava becomes trapped in a volcanic crater or depression. The term is used to describe lakes that are completely molten, as well as those that are partially or completely solidified. Lava lakes can be as deep as 120 m (400 ft), and can take as long as 30 years to cool and solidify.   Lava Tubes     Lava tubes are tunnels which form when the outer layer of a lava flow cools and solidifies, but the lava beneath the surface remains fluid and continues to flow. A large lava flow typically has one main lava tube plus several smaller tubes which supply lava to the front of one or more separate flows. Empty lava tubes commonly have lava stalactites hanging from their roofs, and a flat floor which develops as lava drains through the tube. Lava tubes can be as small as about a meter (3 ft) across or as large as a railway tunnel.   Lava Fountains    Lava fountains are jets of lava that spurt into the air from vents, fissures, and from within active lava lakes. They form when gas bubbles in molten rock rapidly expand as they reach the surface, forcing the lava to be erupted high into the air. Most lava fountains rise to about 10 to 100 meters (30 ft. to 330 ft) in height, although they occasionally reach even greater heights. This highest lava fountain ever recorded occurred in 1986 on the Izu-Oshima volcano in Japan. It reached a height of 1,600 meters (5,200 ft).         Photo Credits: E.W. Wolfe, USGS (top) Hawaii Volcanoes National Park (middle) J.D. Griggs, USGS        Io Home Page  Photoglossary Home Page