Vol·can·ic a.
 1. Of or pertaining to a volcano or volcanoes; as, volcanic heat.
 2. Produced by a volcano, or, more generally, by igneous agencies; as, volcanic tufa.
 3. Changed or affected by the heat of a volcano.
 Volcanic bomb, a mass ejected from a volcano, often of molten lava having a rounded form.
 Volcanic cone, a hill, conical in form, built up of cinders, tufa, or lava, during volcanic eruptions.
 Volcanic foci, the subterranean centers of volcanic action; the points beneath volcanoes where the causes producing volcanic phenomena are most active.
 Volcanic glass, the vitreous form of lava, produced by sudden cooling; obsidian.  See Obsidian.
 Volcanic mud, fetid, sulphurous mud discharged by a volcano.
 Volcanic rocks, rocks which have been produced from the discharges of volcanic matter, as the various kinds of basalt, trachyte, scoria, obsidian, etc., whether compact, scoriaceous, or vitreous.

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