The properties and behaviour of volcanoes, from the genesis of magmas to their ascent and emission at the surface of the Earth (or other planetary environments).

The field of volcanology includes study of the formation, distribution, and classification of volcanoes; their structures; the types of material erupted (e.g. lava, ash, pyroclastic flows, gases); research into relationships between volcanic eruptions and other large-scale geologic processes; and eruption prediction.