The
Rock Cycle
Chapters 5 & 6
What are the • Igneous rocks
• Form from cooling magma
types of
• Recall: magma is molten material
rock?
beneath Earth’s surface
• Sedimentary rocks
• Form from cementing and
compacting pieces of sediment
• Sediment is pieces of solid
material deposited on Earth’s
surface
• Metamorphic rocks
• Rocks that have been changed
from heat and pressure
Igneous
Rocks
• Formation of igneous rock
• Intrusive
• Formed by magma that cools
slowly
• Formed beneath the Earth’s
surface
• Coarse-grained
• Ex. granite
• Extrusive
• Formed by magma that cools
quickly
• Formed above the Earth’s
surface
• Fine-grained
• Ex. Rhyolite
• Properties of igneous rock
• Mineral composition
• Light colored = felsic
• Dark colored = mafic
• Grain size
• Coarse-grained = intrusive
• Fine-grained = extrusive
Sedimentary • Formation of sedimentary rock
• Weathering produces sediments
Rocks
• Physical weathering
• Happens when rock
fragments break off.
• Ex.
• Temperature changes
expand or contract rock
• Living organisms like
trees crack rocks
• Chemical weathering
• Happens when the
minerals in rocks are
chemically changed
• Ex.
• Dissolving
• Oxidation (rust)
• Erosion transports weathered
sediments from one place to
another
• Types of erosion
• Wind
• Moving water
• Gravity
• Glaciers
• Deposition is when sediments are
laid down on the ground or under
water
• This can cause sorting of
sediments into layers, which is
called bedding.
• Deposited sediments become
buried
http://www.classzone.com/books/earth_sci
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• Lithification happens when the
weight of overlaying sediments
forces grains closer together.
• Water is pressed out
• Sand is compacted
• High temperatures (~3-4km
deep) cause cementation
• New minerals can grow
between cemented sediments
• Properties of sedimentary rock
• Clastic—formed from deposits of
loose sediments
http://www.classzone.com/books/ea
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ons/es0605/es0605page01.cfm?c
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• Chemical—formed from
precipitation of minerals dissolved
in water
• Organic—formed from
accumulation and lithification of
dead organisms
• Ex. coal
Metamorphic • Formation of metamorphic rocks
• High temperatures and pressures
Rocks
increase with depth
• High temperature comes from
Earth’s internal heat or
intruding magma.
• High pressure comes from
overlying rock or the
compression of mountain
building
• Rocks do not melt, but change in
texture, mineralogy, or chemical
composition
http://www.classzone.com/books/ea
rth_science/terc/content/visualizati
ons/es0607/es0607page01.cfm?c
hapter_no=visualization
• Properties of metamorphic rocks
• Texture
• Foliated—wavy layers and
bands of minerals
• Nonfoliated—minerals form
blocky crystals
• Mineral composition
• Heat & pressure can
change one mineral into
another
• Chemical composition
• Hot fluids go in and out of
the rock during
metamorphism, changing
its chemistry
What is the
rock cycle?
• The rock cycle is the continuous
changing and remaking of rocks
• Any type of rock can turn into any
other type of rock
• Matter making up rocks is neither
crated nor destroyed, but simply
changed.
• Processes that power the rock
cycle
• Internal processes
• Uplift
• Heat & pressure
• Melting
• Cooling & crystallization
• External processes
• Uplift
• Weathering & erosion
• Deposition, burial, &
lithification