The Physics of Volcanoes

Volcanic systems on Earth and the other rocky planets are defined by a collection of physical processes. The eruptive style of a volcano can be seen as a combination of magma composition, gas pressure, and temperature; impacting bubble formation and crystallization within the magma, in turn effecting viscosity and the eruption itself.

Volcanoes occur wherever there is a source magma to feed them. Hot mantle upwelling, melt from plate subduction, crustal rifting, and extreme tidal stresses from nearby celestial objects are the general cause of volcanism in our solar system. On Earth, we can expect that most volcanoes are tied to plate tectonics, such the volcanoes Redoubt and St. Helen's, or to mantle sourced magmas, such as Kilauea.

Volcanoes on Venus and Mars are (or were) likely due to similar tectonic processes as Earth's volcanoes. Mars' tectonic activity is slight, however, and as such volcanism tends to be old and most inactive at this point. Venus, however, was tectonically active and is warmed by its proximity to our sun, leading to a planet almost entirely covered in volcanic features. Although mostly quiet now, there are some indications for active volcanism on Venus.

The moons of Jupiter and Saturn have volcanoes as well, although the tectonic setting is somewhat complicated by the immense mass of the planets themselves. The Jovian moon Io is about the same size as Earth's Moon, too small for much of a planetary core, and yet is very volcanic. Jupiter's mass is so great that the tidal forces exerted on Io are enough to melt crust and, combined with the intense radiation from Io's proximity to Jupiter, drive spectacular volcanoes. Lava fields on Io can reach hundreds of kilometers in length.