CHPTR 3/4 Igneous Rocks Flashcards
magma
molten rock beneath the surface of the Earth
parts of magma
molten rock, crystals, dissolved water, gas
what negative ion is lava made of
SiO4^4- (silicate ion)
lava
magma once it reaches the surface
plutonic
intrusive - cools slowly underground - larger crystals
volcanic
extrusive - cools quickly at the surface - smaller crystal grains
felsic lava
high silica, lower melting point, high viscosity
mafic lava
low silica, higher melting point, low viscosity
interlocking grains
similar to a camo pattern - evidence that the rock crystallized from liquid state
pyroclastic texture
rock formed from particles that travelled from volcano through the air. when they land on the ground they weld together
glassy
cooling is so fast that there is no time for crystals to form
vesicular
voids formed by bubbles of volatiles that expanded close to the surface and could not escape from the lava/magma
amygdaloidal
vesicles that have been filled in with secondary minerals long after the flow cooled
frothy
vesicular rock and very light - more air than rock
phaneritic texture
slow cooling, crystals visible - like camo pattern
porphyritc
mixed rate of cooling. starts cooling then phenocrysts form. cooling is then faster and remaining melt forms groundmass - big rock in small rock
groundmass
the small crystals in porphyritic rocks
phenocrysts
large crystals within a porphyritic rock
aphanitic
fast cooling produces fine grained rock and crystals not visible - “looks like a rock”
pegmatitic
large grains formed in water rich magma. crystals larger than 1cm
felsic rock intrusive and extrusive rock pairs
intrusive: granite - extrusive: rhyolite
intermediate rock intrusive and extrusive rock pairs
intrusive: diorite - extrusive: andesite
mafic rock intrusive and extrusive rock pairs
intrusive: gabbro - extrusive: basalt
ultramafic rock intrusive and extrusive rock pairs
intrusive: peridotite - extrusive: komatiite
tabular
flat body
massif
not flat - shapeless
concordant
parallel to sedimentary layers
discordant
cut across existing rock layers
dykes
tabular, discordant pluton
sills
tabular, concordant plutons
laccoliths
dyke extends upwards and forms a little rock mound to bulge upwards