Chapter 5 and 6
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Section 5.1
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Igneous rocks are
formed from the
crystallization of
magma
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Igneous comes from
Latin ignis which
means fire
Lava is magma that
flow out onto earth's
surface
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Extrusive igneous rocks are fine-grained igneous
rocks that cool quickly on earth’s surface
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Intrusive igneous rocks are coarse grained igneous
rocks that cool slowly beneath the earth’s surface
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Pumice or obsididan
Granite is the most common
Studies of granite formations reveal they cut across
other formations, evidence of intrusion
 Magma
is a slushy mix of molten rock, gases
and mineral crystals
 Silica (SiO2) is the most abundant mineral in
magma and has the greatest effect on
magma characteristics
 Temperature,
pressure,
water content and mineral
composition affect magma
formation
 Temperature and pressure
increase with depth in the
Earth’s crust
 Pressure increases a
rocks melting point
o 1100 vs 1400
 Rocks
and minerals contain small
percentages of water which decreases a
rocks melting point
 Minerals have different melting points
 Rocks only melt at certain conditions
 MUST have the right temperature, pressure,
and mineral composition
 Rocks
are made of different minerals
 Minerals have different melting points so
parts of a rock will melt at different times
 Partial melting is a process where some
minerals melt at low temperatures while
others stay solid
 Just
as minerals melt at different rates, they
cool at different rates as well
 Fractional crystallization is a process where
minerals forma at different temperatures
 The last minerals to melt are the first
minerals to crystallize
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Section 5.2
Three
main groups of igneous rocks
o Felsic, mafic, intermediate
Felsic
rocks such as granite are: light
colored, high silica contents, contain
quartz and feldspars
Mafic rocks such as gabbro are dark
colored, and rich in iron and magnesium
 Igneous
rocks differ in the size of their grains
 Grain size is determined by the cooling rate
 When lava cools quickly, small grains form
 When lava cools slowly, large grains form
 Very
useful for building materials because
their interlocking grains make them strong
 Also resistant to weathering
 Granite is commonly used for building
 Ores
are minerals that contain a useful
substance that can be mined at profit
 Valuable ore deposits are often associated
with igneous intrusions
 Mineral
rich magma fills the cracks and
voids of surrounding rock
 During magma crystallization, water, silica
and any metals not common in minerals
(gold, silver, lead, copper) are left over and
eventually solidify to form veins
 Vein
deposits main
contain other valuable
resources in addition to
metals
 Veins of extremely large
grained minerals are
called pegmatites
 Rare elements and
crystals are found in
pegmatites
 Rare,
ultramafic rocks
that can contain
diamonds or other
minerals formed only
under very high
pressures
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Section 6.1
 Sediments
are pieces of solid material that
have been deposited on Earth’s surface by
wind, water, ice, gravity or chemical
precipitation
 When sediments become cemented
together, they form sedimentary rocks
 Weathering
is a set of physical and chemical
processes that break rock down
 Chemical weathering occurs when rocks are
dissolved or chemically changed
 Physical weathering occurs when rocks
break off but remain chemically unchanged
 Erosion
is the removal and movement of
surface materials from location to another
 4 main agents: Wind, moving water, glaciers
and gravity
 Deposition
occurs when sediments are laid
down on the ground or sink to the bottom of
water
 Sediments in water will create layers, with
large particles settling first
 Wind only moves fine sediments
 Glaciers and landslides move all sediments
equally
 Most
sediments are deposited in basins
where the building layers increase pressure
and temperature
 Increasing pressure and temperature cause
lithification, or the chemical and physical
processes that transform sediments into
sedimentary rocks
 Lithification
begins with compaction
 The weight of overlying sediments force sediments
together
 The temperature in earth's crust are high enough to
cause cementation
 Cementation occurs when mineral growth cements
sediments together into solid rock
 Two
types of
cementation
 New minerals can grow
between sediment
grains
 The same mineral
grows between the
sediment grains
 The
primary feature of sedimentary rocks is
horizontal layering called bedding
 Bedding with particle sizes that become
heavier at the bottom is called graded
bedding
 Cross-bedding is another type of bedding
where layers of inclined sediment move
forward across a horizontal surface
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Section 6.3
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 Meta
means change and morphe means forms
 During metamorphism, rocks change form while
remaining solid
 Pressure and temperature increase with depth
 Temperature comes from earths internal heat
 Pressure comes from overlying rocks or
compression during mountain building
 When
high temperature and pressure affect large
regions of crust, they produce large belts of
regional metamorphism
 When molten rock come into contact with solid
rock, a local effect called contact metamorphism
occurs
 When very hot water reacts with rocks and alters
its chemistry and mineralogy, hydrothermal
metamorphism occurs
o Occurs near igneous intrusions and active volcanoes
 Metamorphic
rocks have two textural groups:
foliated and nonfoliated
 Wavy layers and bands of minerals of flat crystals
characterize foliated metamorphic rocks
o Schist from shale (clay) and gneiss from granite
If I said you were gneiss, I’d be for of schist! lol
 Nonfoliated
rocks lack mineral grains with flat
crystals and instead have blocky crystal shapes
o Quartzite from quartz-rich sandstone and marble from
limestone
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The continuous changing and remaking of rocks is called
the rock cycle
Igneous rocks crystalize from magma
Sediments cement together to form sedimentary
Pressure and temperature form metamorphic rock
All rocks can change into one another!