The Rock Cycle
Section 3.2
• Vocabulary to know:
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Igneous rock
Magma
Lava
Extrusive igneous
rock
Intrusive igneous rock
Texture
Composition
Silicate
What are igneous rocks?
• Igneous rock– Form from molten rock
deep within the Earth
that has cooled…
OR…
– From molten rock that
has reached the
surface and cooled
lava
• Temperatures deep
within the Earth are
hot enough (14000F to
23000F) to melt rock
Where do igneous rocks come from?
• Volcanoes!
• Extrusive
igneous rock– Forms when
lava cools on
Earth’s surface
• Intrusive
igneous rock– Forms when
magma cools
within the
Earth
Textures of igneous rocks
• Texture = size of the rock’s mineral crystals
• Large crystals- slow cooling time
– Intrusive rocks commonly have large crystals
• Small/No crystals- fast cooling time
– Extrusive rocks commonly have small or no crystals
How can you tell the difference
between salt and sugar?
Answer = look at their composition!
• Igneous rocks are mainly made up of silicate minerals
Ship Rock
• Formed 1km below
Earth’s surface
• It was once intrusive
igneous rock
– It is what’s left behind of
magma that once fed a
volcano
• Through weathering
and erosion, surface
rock has been worn
away…
• …Ship Rock survives
because igneous rock
is usually harder than
other types of rocks
Section 3.3
• Vocabulary to know:
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Sedimentary rock
Sediment
Cementation
Coal
Limestone
Crossbeds
Ripples
What are sedimentary rocks?
• Sedimentary
rock– Forms from
loose material
(sediments) that
get pressed
together
(cemented) into
rock
– Sediments• Can be pieces
of rocks,
minerals,
plants, or
animals
Sedimentary rock formation…
• Rainwater washes
away rock particles…
• Flow downhill to
streams and rivers…
• Eventually these
sediments reach the
ocean…
• Settle on the bottom
of the ocean…
• Pressure eventually
forces these
sediments together…
• Sedimentary rock is
formed!
Fossils can also make sedimentary rock
• Coal– Made up of remains of
plants (dead wood,
bark, leaves, etc.)
– Started forming
millions of years ago
• Limestone– Made up of remains of
ocean organisms
(shells, bones, etc.)
– Pressure “squishes”
these materials
together into rock
Coal formation
• A- Dead pieces of
plant matter
collecting on lake
bottom
• B- sediments
applying pressure
on top of plant
matter
• C- Even greater
pressure applied
• D- Coal is created
Limestone towers (Mono Lake)
• Minerals can
dissolve in water …
• …and then re-form
as the water
evaporates
• Often they form
underwater…
• …and as the water
level drops they
become visible
Sedimentary rocks can teach us
about the past…
• Crossbeds– These layers were
once moving sand
dunes
• Ripples– The surface of this
sandstone preserves
ancient sand ripples
Section 3.4
• Vocabulary to know:
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Metamorphic rock
Metamorphism
Recrystallization
Foliation
Foliated rock
Nonfoliated rock
What are metamorphic rocks?
• Metamorphic
rock– Forms when
heat or pressure
cause older
rocks to change
into new types of
rocks
• Metamorphism– The process in
which existing
rock is changed
by heat or
pressure
Metamorphic rock formation
• During
metamorphism rocks
undergo many
changes
• Heat and pressure
can break the bonds
that join the atoms in
minerals… the atoms
then join together
differently
– Recrystallization
• Rocks do not melt
during this process!!!
Foliation
• Foliation– An arrangement of
minerals in flat or wavy
parallel bands
• Foliated rocks– Develop under pressure
– Minerals flatten out or
line up in bands
• Nonfoliated rocks– Develop if rock is made
up of only one type of
mineral
– May not be under
enough pressure
The Rock Cycle