Lava Flows and Lava Tubes
40-minute video uses spectacular and unusual footage of erupting volcanoes from Hawaii and around the world to explain the features found in many of our volcanic national parks and monuments, and to show how they form. It presents up-to-date scientific ideas about lava flows: how they move, how they change, and how they create lava tubes.
 Lava moves across the ground as a pahoehoe flow, Kilauea Volcano, Hawaii |
Lava
Lava is the word for magma (molten rock) when it erupts onto the Earth's surface. Geologists also use the word to describe the solidified deposits of lava flows and fragments hurled into the air by explosive eruptions (for example, lava bombs or blocks). Lava is from the Italian word for stream, which is derived from the verb lavare--to wash. |
 Sketch of a magma reservoir beneath a volcano and a conduit leading up to a lava dome at the surface. Arrow indicates direction of magma movement from a deeper source. |
Magma Magma is molten or partially molten rock beneath the Earth's surface. When magma erupts onto the surface, it is called lava . Magma typically consists of (1) a liquid portion (often referred to as the melt); (2) a solid portion made of minerals that crystallized directly from the melt; (3) solid rocks incorporated into the magma from along the conduit or reservoir, called xenoliths or inclusions; and (4) dissolved gases. |
National Geographic's Restless Earth Collection
Asteroids Deadly Impact Volcano Nature's Fury. The devastating powers of earthquakes, hurricanes, tornadoes, volcanoes and other earth-shattering forces of nature in dramatic scenes of destruction and inspiring human courage captured by the acclaimed filmmakers of National Geographic