VHP Photo Glossary: Effusive Eruptions

`A`a lava flows pour down Mauna Loa Volcano, Hawai`i

Photograph by R.W. Decker on 25 March 1984

Mauna Loa Volcano, Hawai`i.

Lava erupts from a fissure high on the northeast rift zone of Mauna Loa (about 3400 m) on the morning of March 25, 1984. Fountains are 10 to 50 m high along the fissure, and lava output is estimated at 1-2 million m3/hour. This fissure fed a narrow `a`a lava flow that moved only about 5 km downslope (lower right) before new vents became active farther downrift. See eruption summary from the USGS Hawaiian Volcano Observatory for more information and images about the 1984 eruption of Mauna Loa.
Caldera of Kaguyak volcano, Alaska

Photograph by Juan Carlos Gavilanes on 3 December 1998; Universidad de Colima

Colima Volcano, Mexico.

A stubby andesite lava flow advances 900-1,200 m down the southwest side of Colima Volcano. Lava was first observed in the summit crater on November 20 and began spilling over the crater rim the next day. Colima Volcano is the most historically active volcano in Mexico. For more information about Colima, see the volcanic activity reports provided by the Smithsonian Institution's Global Volcanism Program.
Caldera of Ugashik volcano, Alaska

Photograph by S.R. Brantley on 29 July 1998

Obsidian flow, Long Valley Caldera, California.

Viscous rhyolite lava was erupted to form several circular-shaped lava flows, often referred to as domes, following a series of explosive eruptions from the Mono-Inyo Volcanic Chain. The eruptions occurred about 550-650 years ago. Obsidian flow (foreground) is about 1.5 km wide (left to right). A smaller lava dome, Wilson Butte, was erupted about 1,400 years ago (left of Obsidian flow), also following a series of explosive eruptions.

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