A volcano is a geological landform (usually a mountain) where a substance, usually magma (rock
of the Earth's interior made molten or liquid by extremely high temperatures along with a reduction in pressure and/or the
introduction of water or other volatiles) erupts through the surface of a planet. Although there are numerous volcanoes (some
very active) on the solar system's rocky planets and moons, on Earth at least, this phenomenon tends to occur near the boundaries
of the continental plates. However, important exceptions exist in hotspot volcanoes.
The name "volcano" originates from the name of Vulcan, a god of fire in Roman
mythology. The study of volcanoes is called vulcanology (or volcanology in some spellings).
Mud volcanoes are formations which are often not associated with known magmatic activity. Active mud
volcanoes tend to involve temperatures much lower than those of igneous volcanoes, except when a mud volcano is actually a
vent of an igneous volcano. This article describes igneous volcanoes.
