How Volcanoes Work

 Image Described in Caption
Soutwest rift zone, Kilauea -- This rift zone of en echelon fractures emanates from the Kilauea summit caldera to the southwest. These fractures develop above blade-like intrusions of basaltic magma at depth. The darker shiny lava flows erupted from the fissures on September 24, 1971. Courtesy of J.D. Griggs, USGS.