火山岩

Volcanic \Vol*can"ic\, a. [Cf. F. volcanique, It. vulcanico.]
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.