volcanic (adj)

relating to or produced by or consisting of volcanoes

"volcanic steam"; "volcanic islands such as Iceland"; "a volcanic cone is a conical mountain or hill built up of material from volcanic eruptions"

volcanic (adj)

explosively unstable

"a volcanic temper"

volcanic (adj)

igneous rock produced by eruption and solidified on or near the earth's surface; rhyolite or andesite or basalt

"volcanic rock includes the volcanic glass obsidian"

volcanic (Adjective)

Of or pertaining to a volcano or volcanoes; as, volcanic heat.

volcanic (Adjective)

Produced by a volcano, or, more generally, by igneous agencies; as, volcanic tufa.

volcanic (Adjective)

Changed or affected by the heat of a volcano.

volcanic (Adjective)

Reminiscent of a volcano; explosive, violent, full of suppressed anger, energy etc.

volcanic

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. On Earth, volcanoes are most often found where tectonic plates are diverging or converging, and most are found underwater. 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. 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. 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. This results in hotspot volcanism, of which the Hawaiian hotspot is an example. Volcanoes are usually not created where two tectonic plates slide past one another. Large eruptions can affect atmospheric temperature as ash and droplets of sulfuric acid obscure the Sun and cool the Earth's troposphere. Historically, large volcanic eruptions have been followed by volcanic winters which have caused catastrophic famines.Other planets besides Earth have volcanoes. For example, Mercury has pyroclastic deposits formed by explosive volcanic activity.