What is "volcanic bomb"

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.

Bomb \Bomb\, n. [F. bombe bombshell, fr. L. bombus a humming or buzzing noise, Gr. ?.]

1. A great noise; a hollow sound. [Obs.]

   A pillar of iron . . . which if you had struck, would make . . . a great bomb in the chamber beneath.
   --Bacon.

2. (Mil.) A shell; esp. a spherical shell, like those fired from mortars. See Shell.

3. A bomb ketch.

   Bomb chest (Mil.), a chest filled with bombs, or only with gunpowder, placed under ground, to cause destruction by its explosion.

   Bomb ketch, Bomb vessel (Naut.), a small ketch or vessel, very strongly built, on which mortars are mounted to be used in naval bombardments; -- called also mortar vessel.

   Bomb lance, a lance or harpoon with an explosive head, used in whale fishing.

   Volcanic bomb, a mass of lava of a spherical or pear shape. ``I noticed volcanic bombs.''
   --Darwin.

n. A tephra, larger than 64 mm (2.5 inches) in diameter, formed when a volcano ejects viscous fragments of lava during an eruption.

A volcanic bomb is a mass of molten rock ( tephra) larger than 64 mm (2.5 inches) in diameter, formed when a volcano ejects viscous fragments of lava during an eruption. They cool into solid fragments before they reach the ground. Because volcanic bombs cool after they leave the volcano, they are extrusive igneous rocks. Volcanic bombs can be thrown many kilometres from an erupting vent, and often acquire aerodynamic shapes during their flight. Bombs can be extremely large; the 1935 eruption of Mount Asama in Japan expelled bombs measuring 5–6 m in diameter up to 600 m from the vent. Volcanic bombs are a significant volcanic hazard, and can cause severe injuries and death to people in an eruption zone. One such incident occurred at Galeras volcano in Colombia in 1993; six people near the summit were killed and several seriously injured by lava bombs when the volcano erupted unexpectedly.

Volcanic bombs are known to occasionally explode from internal gas pressure as they cool, but contrary to some claims in popular culture (specifically, the 1997 film Volcano), explosions are rare; in most cases most of the damage they cause is from impact, or subsequent fire damage. Bomb explosions are most often observed in "bread-crust" type bombs.