Vents are openings in the Earth's crust from which magma and volcanic gases
escape onto the ground or into the atmosphere. Vents may consist of a single,
circular-shaped structure, a large elongated fissure and fracture, or a tiny
ground crack. The release of volcanic gases and the eruption of molten rock
result in a wide assortment of edifices, ranging from enormous shield volcanoes
and calderas to fumaroles and small hornitos.
Left: Steam rises from a vent on Mount Asahidake, a volcano on