Elements or compounds that bubble out of magma or lava in gaseous form.

Volcanic gas is contained within magma. As the magma rises to the Earth's surface the gases are exsolved and can become a very important factor in the violence of an eruption. Because some gases are toxic they can suffocate people. Examples of volcanic gases include steam, sulphur dioxide and carbon dioxide.

Dissolved gases contained in the magma are released into the atmosphere during volcanic eruptions. Gases may also escape continuously from volcanic vents, fumaroles, and hotsprings. The most common gas released is steam (H2O), followed by CO2 (carbon dioxide), SO2 (sulfur dioxide), (HCl) hydrogen chloride and other compounds. See the USGS for more information on volcanic gases .

Gases released from a volcano or vent that were previously dissolved in magma.

Volcanic gases include a variety of substances given off by active (or, at times, by dormant) volcanos. These include gases trapped in cavities (vesicles) in volcanic rocks, dissolved or dissociated gases in magma and lava, or gases emanating directly from lava or indirectly through ground water heated by volcanic action.