Shield Volcano

Image of the Martian shield volcano, Olympus Mons taken during the Mars Global Surveyor (MGS) mission in 2000. Vertical is exaggerated 10:1. Image Credit: NASA/MOLA Science Team

Volcanic construction of a central type formed by repeated effusion of fluid (usually basaltic) lava. The shield is characterized by a shallow flank, the steepness of which can vary from ~1° to 8°, however typical values are closer to ~5°. There often are one or more caldera craters near the summit, like broad saucer-shaped cavities with steep walls. One of the largest shield volcanoes in the solar system is Olympus Mons on Mars, with a diameter 624 km and height 25 km. It covers nearly the same area as the state of Arizona. The largest shield volcano on Earth is Mauna Loa on the Big Island of Hawaii with a diameter of 120 km and height of 10 km. An excellent explanation of why volcanoes are larger on Mars can be found at

Some or all content above used with permission from J. H. Wittke.