page_title: Volcano
section_title: Erupted material
hierarchical_section_title: Volcano / Erupted material
caption_attribution_description: English: The Island of Stromboli, Shot 2004 Sep 28 by Steven W. Dengler. Autor&#160;: Contact steven[at]dengler[point]net for larger resolutions of this photo, or to inquire about commercial use.
context_page_description: A 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.
  Earth's volcanoes occur because its crust is broken into 17 major, rigid tectonic plates that float on a hotter, softer layer in its mantle. Therefore, on Earth, volcanoes are generally found where tectonic plates are diverging or converging, and most are found underwater. For example, a mid-oceanic 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. Volcanoes can also form where there is stretching and thinning of the crust's plates, e.g., in the East African Rift and the Wells Gray-Clearwater volcanic field and Rio Grande Rift in North America. This type of volcanism falls under the umbrella of "plate hypothesis" volcanism. Volcanism away from plate boundaries has also been explained as mantle plumes. These so-called "hotspots", for example Hawaii, are postulated to arise from upwelling diapirs with magma from the core–mantle boundary, 3,000 km deep in the Earth.
caption: The Stromboli stratovolcano off the coast of Sicily has erupted continuously for thousands of years, giving rise to its nickname "Lighthouse of the Mediterranean"
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