Volcanic Textures

Question 1

Vitric

Answer 1

Glassy (no crytals)

Ex. Obsidian

Question 2

Vitrophyric

Answer 2

Glass with skeltal crytsals

Question 3

Intersertal

Answer 3

Glass in space between crystals

Question 4

Intergranular

Answer 4

Crystals in spaces between other crystals

Question 5

Porphyritic

Answer 5

Bimodal size distribution

Large crytals (phenocrysts) in finer grained rock

Question 6

Trachytic

Answer 6

Elongated minerals aligned with the flow

Imbricated due to magma flow

Question 7

Poikilitic

Answer 7

Large crystals enclosing smaller crystals

Generic term

Question 8

Ophitic

Answer 8

Large pyroxene crystals enclosing smaller plagioclase crystals

Question 9

Subophitic

Answer 9

Large pyroxene crystals partially enclosing plagioclase crystals

Question 10

Eutaxitic

Answer 10

Flattened clasts fragments aligned with the flow of pyroclastic rock

Volcanic ash

Clastic texture

Question 11

Pyroclastic

Answer 11

Ejected volcanic debris

Sediment texture

Glass shards

Question 12

Xenolith

Answer 12

Foreign

Pieces of pluton roof can sink into magma chamber and then magma crystallizes around it

Erupting magma rips off rock from magma chamber

Question 13

Vesicular

Answer 13

Holes

Gas has now escaped thus leaving voids

Question 14

Amygduloidal

Answer 14

Filled vesicles

Desposited later due to precipitation by groundwater