Volcanic bomb most of the damage they cause is from impact, or subsequent fire damage. Bomb explosions are most often observed in "bread-crust" type bombs. Bombs are named according to their shape, which is determined by the fluidity of the magma from which they are formed. Volcanic bomb 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.
Calc-alkaline magma series to increase as the melt is depleted of iron-poor crystals. (Magnesium-rich olivine solidifies at much higher temperatures than iron-rich olivine.) However, a calc-alkaline magma is oxidized enough to (simultaneously) precipitate significant amounts of the iron oxide magnetite, causing the iron content of the magma to remain more steady as it cools than with a tholeiitic magma. The difference between these two magma series can be seen on an AFM diagram, a ternary diagram showing the relative proportions of the oxides of NaO + KO (A), FeO + FeO (F), and MgO (M). As magmas cool, they precipitate out significantly more