Shield Volcanoes
Photo by Jack Lockwood, U.S. Geological Survey, September 12, 1980.
Mauna Loa is a classic example of a shield volcano. Hilo and Hilo Bay are in the foreground.
Photo by Jack Lockwood, U.S. Geological Survey, March 26, 1984.
Shield volcanoes are made of thousands of thin basalt lava flows. Because the lava has a relatively low viscosity (low resistance to flow) the lava can travel far from the vent, the location where the lava reaches the surface. The resulting volcanic landform has a broad base and very gentle slopes, much like a warrior's inverted shield. This photo shows an aa lava flows that is about 7.5 miles (12 km) from its vent on the upper northeast rift zone of Mauna Loa. Note powerline poles for scale.
