Vents in the surface of the Earth through which magma and associated gases erupt; also, the forms or structures, usually conical, that are produced by the erupted material. [Glossary of Geology, 4th ed.]
Episodes during which gases, ash, and lava (molten rock) escape from vents in the earth's crust, accompanied by minor tremors.
A volcanic rock defined modally by Q/(Q+A+P) < 20% or F/(F+A+P) < 10%, P/(A+P) > 90%, and M < 35
Landmasses that project conspicuously above their surroundings. [USGS Circ 1048]