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The features of volcanoes are much more complicated and their structure and behavior depends on a number of factors. The most common perception of a volcano is of a conical mountain, spewing lava and poisonous gases from a crater at its summit however, this describes just one of the many types of volcano. Skjaldbreiður, a shield volcano whose name means 'broad shield' Plate tectonicsįurther information: Types of volcanoes Lakagigar fissure vent in Iceland, the source of the major world climate alteration of 1783–84, has a chain of volcanic cones along its length. The study of volcanoes is called volcanology, sometimes spelled vulcanology. The word volcano is derived from the name of Vulcano, a volcanic island in the Aeolian Islands of Italy whose name in turn comes from Vulcan, the god of fire in Roman mythology. For example, Mercury has pyroclastic deposits formed by explosive volcanic activity. Other planets besides Earth have volcanoes.

Historically, large volcanic eruptions have been followed by volcanic winters which have caused catastrophic famines. Large eruptions can affect atmospheric temperature as ash and droplets of sulfuric acid obscure the Sun and cool the Earth's troposphere. Volcanoes are usually not created where two tectonic plates slide past one another. This results in hotspot volcanism, of which the Hawaiian hotspot is an example. Volcanism away from plate boundaries has been postulated to arise from upwelling diapirs from the core–mantle boundary, 3,000 kilometers (1,900 mi) deep in the Earth. Volcanoes can also form where there is stretching and thinning of the crust's plates, such as in the East African Rift and the Wells Gray-Clearwater volcanic field and Rio Grande rift in North America. For example, a mid-ocean ridge, such as the Mid-Atlantic Ridge, has volcanoes caused by divergent tectonic plates whereas the Pacific Ring of Fire has volcanoes caused by convergent tectonic plates.

On Earth, volcanoes are most often found where tectonic plates are diverging or converging, and most are found underwater. For broader coverage of this topic, see Volcanism.Ī volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.

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