Volcanic Textures Flashcards
(14 cards)
Vitric
Glassy (no crytals)
Ex. Obsidian
Vitrophyric
Glass with skeltal crytsals
Intersertal
Glass in space between crystals
Intergranular
Crystals in spaces between other crystals
Porphyritic
Bimodal size distribution
Large crytals (phenocrysts) in finer grained rock
Trachytic
Elongated minerals aligned with the flow
Imbricated due to magma flow
Poikilitic
Large crystals enclosing smaller crystals
Generic term
Ophitic
Large pyroxene crystals enclosing smaller plagioclase crystals
Subophitic
Large pyroxene crystals partially enclosing plagioclase crystals
Eutaxitic
Flattened clasts fragments aligned with the flow of pyroclastic rock
Volcanic ash
Clastic texture
Pyroclastic
Ejected volcanic debris
Sediment texture
Glass shards
Xenolith
Foreign
Pieces of pluton roof can sink into magma chamber and then magma crystallizes around it
Erupting magma rips off rock from magma chamber
Vesicular
Holes
Gas has now escaped thus leaving voids
Amygduloidal
Filled vesicles
Desposited later due to precipitation by groundwater
