Photoglossary

Shield Volcanoes   Shield volcanoes are volcanic mountains built up by the eruption of fluid, basaltic lava flowing out of a central vent. They have broad bases with very gentle slopes, and are the largest volcanoes on Earth. The volcano gets its name from its resemblence to the slightly domed shape of a warrior's shield. The largest volcano in the solar system is Olympus Mons, a shield volcano on Mars. It rises to an incredible height of 24 km (15 miles), and its base is so large it would cover almost the entire state of Missouri. The largest shield volcano on Earth is Mauna Loa in Hawaii which rises from its base on the seafloor to a height of 17 km (10.5 miles). Mt. Everest, by comparison, rises only a little over 8 km (5 miles) above sea level.     Shield volcanoes do not erupt violently. Rather, fluid, basaltic lava erupts onto the surface and flows freely across the ground for great distaces forming a broad cone. Lava tubes can form beneath the surface of the lava flow which allows the lava to flow for tens of kilometers (miles) without cooling. Each successive flow increases the size of the shield volcano.           Photo Credit: D. Little, USGS Illustration Credit: Lutgens, F./Tarbuck, E., FOUNDATIONS OF EARTH SCIENCE, 2/e, © 1999 Electronically reproduced by permission of Prentice Hall, Upper Saddle River, New Jersey.       Io Home Page Photoglossary Home Page