What is Extrusion?
'''Extrusive''' means to the mode of [[igneous rock|igneous]] [[volcano|volcanic]] [[Rock (geology)|rock]] formation in which hot [[magma]] from inside the [[Earth]] flows out (extrudes) onto the surface as [[lava]] or explodes violently into the [[atmosphere]] to fall back as [[Pyroclastic rock|pyroclastic]]s or [[tuff]]. This is opposed to [[intrusion|intrusive]] rock formation, in which magma does not reach the surface. [[File:Extruded aluminium section x3.jpg|thumb|250px|right|Cross-sections of extruded aluminium]] '''Extruded''' when talking about an artificial material like soft metals like aluminium, plastic or glass means that it is pushed out of a nozzle when the material is in a soft state. The shape of the nozzle will vary depending on the shape required in the finished product {{sci-stub}} [[Category:Geology]]