Pahoehoe near the coast of Kilauea. Photo by Steve Mattox, 1989.

Photo of the "fire hose" flow, a small lava tube pouring into the ocean. Photograph by J.D. Griggs, U.S. Geological Survey, November 27, 1989.

Igneous rocks begin as magma. Intrusive igneous rocks, like granite, form when magma cools inside the Earth. Extrusive igneous rocks, like the basalt lava flow in this photo, form at the Earth's surface. Volcanic rocks are extrusive igneous rocks. Photograph by Steve Mattox, July 1990.

Measuring the temperature of lava is one method used to monitor volcanic eruptions. Photograph by R.L. Christiansen, U.S. Geological Survey, January 9, 1973.

The lava at Mount St. Helens is not like the type of lava that erupts from Hawaii's Kilauea Volcano. Kilauea's lava easily flows across the ground while Mount St. Helen's lava oozes onto the dome, like taffy candy being squeezed from a giant tube. Photo courtesy of the U.S. Geological Survey.

The Kilauea Iki eruption began on the morning of November 14, 1959, three months after a rapid increase in inflation of the ground surface and the number and size of earthquakes. Photo courtesy of the U.S. Geological Survey.

During the second phase of the Kilauea eruption, lava spilled from the lava lake in the deeper east crater and began to flow into the west crater. Photo courtesy of the U.S. Geological Survey.

After many eruption episodes the unstable walls of the Kilauea growing cinder cone collapsed into the lava lake. Photo courtesy of the U.S. Geological Survey.

The Kilauea eruption continued for 4 more weeks and included 16 additional eruptive phases. Each eruptive phase produced a lava fountain. The views of the fountain and lava lake at night were spectacular. Photograph by Jerry Eaton, U.S. Geological Survey, 6:30 pm, December 5, 1959.