Volcanos This paper will define and discuss the volcano to include: types of volcanoes, formation of a volcano, and elements of a volcano; such as, lava, rock fragments, and gas. This paper also tells a little bit about volcanic activity in different parts of the world. What is a volcano? A volcano is a vent in the earth from which molten rock and gas erupt. The molten rock that erupts from the volcano forms a hill or mountain around the vent. The lava may flow out as a viscous liquid or it may explode from the vent as solid or liquid particles. Kinds of Volcanic Materials Three basic materials that may erupt from a volcano