Igneous Rocks Flashcards
rocks
aggregates of 1(+) minerals or mineraloids
igneous rocks
rocks which formed from melted rock that cooled
steps of the rock cycle
weathering
metamorphism
melting
recrystallization
weathering
mechanical/chemical processes that break a larger rock into smaller pieces or its chemical components
metamorphism
change that occurs in a rock due to extreme amounts of heat and/or pressure (NOT melting)
melting
when a rock becomes a liquid due to extreme heat
recrystallization
formation of new minerals under conditions of extreme heat or pressure
magma
melted rock below earth’s surface
lava
melted rock above earth’s surface
2 types of igneous rocks
intrusive and extrusive
intrusive rocks
form from magma cooling inside the earth; have larger crystals than extrusive rocks because they have more space and time to grow
extrusive rocks
form from lava cooling on earth’s surface; have smaller crystals than intrusive rocks since they cool rapidly
identifying factors of igneous rocks
texture
mineral composition
types of textures
pegmatitic
phaneritic
aphanitic
porphyritic
glassy
vesicular
pyroclastic
True or False: Pegmatitic and phaneritic textures are extrusive
False; they’re INTRUSIVE
True or False: aphanitic textures are extrusive
True
pegmatitic texture
has crystals larger than 30mm [very visible with the naked eye]
phaneritic texture
has crystals 1-30 mm in size [visible to the naked eye]
aphanitic texture
has crystals smaller than 1mm
porphyritic texture
a combo of phaneritic and aphanitic texture
glassy texture
created when lava cools so fast the minerals (crystals) can’t form; it is thus a mineraloid
vesicular texture
contains many tiny holes resulting from gases escaping from cooling lava
pyroclastic texture
contains fragments of broken volcanic rock because of explosive volcanism [a chaotic-looking mixture of vesicular & other rocks]
types of igneous mineral composition
felsic (light-coloured [& has lots of silicates])
intermediate (in-between light- and dark- coloured [gray])
mafic (dark-coloured [not as much silicates])
dikes
typically-vertical magmatic intrusions/openings in the rock below the surface; tend to flow against the grain of the rock
sills
typically-horizontal magmatic intrusions/openings in the rock below the surface; tend to flow with the grain of the rock
plutons (& their larger counterparts, batholiths)
large magmatic bodies below the surface
xenolith
solid rock around which magma crystallizes
Bowen’s reaction series
describes the sequence of mineral crystallization from cooling magma, illustrating how different minerals solidify at different temperatures, leading to the formation of various igneous rock types and textures.
True or False: Igneous rocks are usually the only rocks that can yield radioactive [not carbon] dates
True
