Lesson 4: Igneous Rocks Flashcards
Formed by cooling and crystallization of magma
Igneous Rock
Molten rock underground
Magma
forms within crust/blow ground
surface; takes centuries – millions of years to form
Intrusive Igneous Rock
forms above ground surface;
takes seconds to years to form
Extrusive Igneous Rock
Molten rock above ground surface
Lava
Volcanic Rocks
Extrusive
Plutonic Rocks
Intrusive
Magma from _____melting is the source of nearly all Igneous rocks
Partial
Only certain parts of the rock melt (not all of
it) due to each component of a rock having different melting points
Partial Melting
determines how far the
reaction process reaches (based on available silica) and what kind of rock it will harden into.
Magma Composition
has the most SiO2
Felsic
45%-55% SiO2
Mafic
SiO2 < 45%
Ultramafic
result to mafic rocks
Mafic magma
mafic rocks will have different names depending on
where it ________
Crystallized
Has low viscosity associated with (relatively) calmer
volcanic eruptions
Mafic magma
fluid’s resistance to flow
viscosity
show how minerals are formed as magma
cools and becomes igneous rocks.
Bowen’s reaction series
branches of Bowen’s reaction series
Discontinuous, continuous
Plagioclase Feldspar will have calcium rich core
and then covered with more sodium-rich Plagioclase Feldspar shell/cover.
Zoning
magma formed at ~750-800°C (assuming there are still silica left)
Quartz, Potassium feldspar, muscovite mica
Large part of the remaining Silica goes into
calcium-rich Plagioclase
Remaining part of Silica (if there are any) transforms Olivine to
Pyroxene
Mafic magma typically cools into
Gabbro (intusive) or basalt (extrusive)
Intermediate magma usually cools into
Diorite (intrusive form) or
Andesite (extrusive form)
Felsic magma do not have to be so hot to maintain liquid form so they crystallize/harden at
lower temperatures
A felsic magam that cools starts at
Pyroxene and Plagioclase
Felsic magma commonly cools into
Granite (intrusive form) or
Rhyolite (extrusive form)
the _____ separates the ferromagnesian silicates on the upper right
from the non-ferromagnesian silicates on the lower left.
red line
Mafic rocks tend to be darker than felsic rocks due to the
ferromagnesian silicates
• Mafic rocks can have _______ ferromagnesian silicates
50-100%
Intrusive rocks tend to be _______. This is because they ________under the ground, the crystals ______
rougher, cool slower, grow
crystallization of minerals in certain
sequence, and separation of the ones already formed.
Fractional Crystallization
settling of crystals already formed to the bottom
of a magma chamber
Crystal settling
have exposed area at the surface of more than 100
km2
batholiths
a pluton that is sheet-like and is parallel to the existing
layering of the underground materials.
sill
similar to sill but perpendicular to the existing layering
of underground materials.
dyke
sill that has expanded and pushed the rock above it.
LACCOLITH
a “cylindrical” conduit (may have any cross-sectional shape)
that serves to allow movement of magma from one point to another.
PIPE
