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Volcanoes A volcano is a vent in the earth’s crust through which magma (molten rock) and gas are released. The magma, once it reaches the surface, is called lava. The lava forms a hill around the vent or opening. The lava can flow out as a viscous liquid, or it may explode from the vent as solid or liquid particles. Types of Volcanoes There are three different types of volcanoes that can be formed around a vent. The ways to identify each type are what it is composed of and what into what shape it is formed. The shield volcano, which takes its name form its resemblance to the shields of early Germanic warriors, is a quietly erupting flow that forms gently slopping mountains. The dome that is formed over a period of time involving multiple one to ten meter thick lava flows. This type of volcano is found mostly in Hawaii and Iceland. The second type of volcano dome formation is the cinder-cone. This volcano has high gas content and high viscosity (the thickness of the lava), therefore producing a much more explosive eruption than that of the shield volcano. These volcanoes blew volcanic bombs and cinders into the air which land beside the vent to form a step-sided