Shield Volcanoes
Courtesy of the U.S. Geological Survey.
(Above) The comparison of the profile and size of a shield volcano and a stratovolcano. The volcanoes are drawn to the same scale.
Shield volcanoes are the largest volcanoes on Earth. Mauna Loa is over 30,000 feet (9,000 m) tall (from base to summit) and has a volume of more than 9,700 cubic miles (40,000 cubic km). At sea level, Mauna Loa is 60 miles (100 km) wide. The volume of a typical eruption is 0.05 cubic miles (0.22 cubic km).
Photo by J.D. Griggs, U.S. Geological Survey, March 25, 1984.
The 1984 eruption of Mauna Loa produced long curtains of fire and large lava flows. However, the eruption was relatively non-violent (VEI=0) compared to those at stratovolcanoes.
Because of their basaltic composition, Hawaiian magmas have a low viscosity, and gases can escape prior to an eruption. Hawaiian eruptions are noted for their non-explosive nature and approachability. Hawaiian-type volcanoes are associated with hot spots, areas of unusually high heat flow and magma production in the Earth's mantle.
