This photo shows a curtain of fire during an eruption of Mauna Loa in Hawaii. Photo by Robin Holcomb, U.S. Geological Survey's Hawaiian Volcano Observatory, July 5, 1975. This map shows segments of the East Pacific Rise near the Clipperton Transform. The thick black lines show the location of the spreading axes along the rise. The thick red lines indicate portions of the rises where the presence of an axial magma chamber has been inferred.
Stars show the location of active hydrothermal vent areas.
Compare to the computer-generated topographic map at the top of this page. These magma chambers feed the fissure eruptions. The Moho marks the base of the crust and the top of the mantle. ASC is the Axial Summit Caldera. Layer 2a is made of extrusive volcanic rocks and intrusions of magma.