Volcanic Bombs

Volcanic bomb is a pyroclastic formation which was semi-molten (viscous) while ejected from a volcanic vent and is
therefore shaped while in flight. The term “Volcanic Bomb” is a term often mistakenly used by non-volcanologists to describe all sizes of formations that fall to earth already hardened. By definition volcanic bombs are larger than 64 mm in diameter. Smaller pyroclastic bombs are officially called Lapilli (plural) or Lapillus (singular).

Lapilli are a size classification term for Tephra, which is material that falls out of the air during a volcanic eruption or during some meteorite impacts. Lapilli mean "little stones" in Latin. By definition lapilli range from 2 mm to 64 mm in diameter. A pyroclastic particle greater than 64 mm in diameter is known as a volcanic bomb when molten, or a volcanic block when solid. Pyroclastic material with particles less than 2 mm in diameter is referred to as volcanic ash.

Lapilli are spheroid, teardrop, dumbbell or button-shaped droplets of molten or semi-molten lava ejected from a volcanic eruption that fall to earth hardened, or may be partially molten. These formations are the direct result of liquid rock cooling as it travels through the air. The Teardrop or almond shape occurs when a blob of lava is ejected with a spin which pulls the lava into a shape which cools and hardens before falling to the surface. We shall call these volcanic rocks “Lava Bombs” based to how they were formed. They are the smaller brothers and sisters to volcanic bombs.