Rocks and the
Rock Cycle
ROCKS!
Rocks are: naturally formed solid that is usually
made up of one or more types of minerals.
They are divided into three groups based on how
they form.
The 3 types are:
1. Igneous Rocks: formed when
molten rock cools and becomes
solid.
a. Made from—molten rock or
magma
b. Classified according to origin,
texture, and mineral composition
c. Four textures
i. Glassy
ii. Fine Grain
iii. Coarse Grain
iv.Porphyritic—has large crystals scattered
on a background of much smaller
crystals
d. 2 main categories of igneous rocks are:
i. Intrusive—forms when magma cools
inside Earth
ii. Extrusive—forms when lava cools on
Earth's surface
Basalt Forming--Extrusive
Textures
• Glassy
• Coarse-grained
Obsidian
• Fine-grained
Basalt
Granite
• Porphyritic
Granite
• Extrusive- Formed from lava; volcanic
Obsidian
Pumice
• Intrusive- Formed deep within the earth
Granite
Uses of Igneous Rock
• *Many igneous rocks are hard, dense, and
durable – These qualities make them very useful
for tools and building materials.
• *Granite is one of the most abundant igneous
rocks and it has a long history of being used as
a building material.
• *Basalt is crushed to make gravel that is used in
construction
• *Pumice has a rough surface which makes it a
good abrasive for cleaning and polishing.
• *Perlite comes from obsidian and is often mixed
with soil for starting vegetable seeds.
2. Sedimentary Rocks:
forms when pieces
of older rocks,
plants, and other
loose material get
pressed or
cemented together.
a. Made from-particles
deposited by wind
and water after
being eroded
from other rock.
Lithification
•
•
*The process by
which sediment
becomes
sedimentary rock.
*The four steps that
make sedimentary
rock.
1.
2.
3.
4.
Erosion
Deposition
Compaction
Cementation
Erosion
• *Occurs when water
or wind loosens rock
and soil and carries it
away.
• *Erosion is a
destructive force.
Deposition
• *The process by which
the sediment settles out
of the water or air
carrying it.
• Sediment is deposited
when the wind or water
slows down.
• *After sediment has been
deposited, the processes
of compaction and
cementation change the
sediment into
sedimentary rock.
Compaction
• As the sediments settle they will loosely fit on
top of each other.
• As the years go by, more and more sediment is
added.
• *The bottom layers get compacted by the weight
of the layers above them.
• *Compaction is the process that presses
sediments together.
b. Classified into 3 categories according
to—what they are made of.
c. These categories are:
i. Clastic: formed when rock
fragments are squeezed together.
ii. Organic: formed from the remains
of living things.
iii.Chemical: formed when dissolved
minerals crystallize
Common Clastic Sedimentary
Rocks
Organic Rocks
Limestone
Coquina
Fossiliferous
Limestone
Coal
• *Formed from the
remains of ancient
swamps.
• *As layer upon layer of
dead plants built up, the
bottom layers were
compacted into coal.
• Stored chemical energy
from the sun.
• Fossil fuel.
Chalk
• *Formed from the
shells of ancient sea
life.
Seven Sisters in Sussex
Chemical Sedimentary Rocks
Halite – Forms large crystals
Uses of Sedimentary Rock
• Sandstone and Limestone as building
materials.
• *Whitehouse in Washington D.C. is built of
sandstone.
• Limestone has many industrial uses,
including being used in smelting iron ore
and making cement.
3. Metamorphic rocks: rock that has changed
from one form to another.
a. Made when--heat or pressure causes older
rocks to change into new types of rocks
b. This is called a metamorphism.
Metamorphic Rock Pictures
c. Divided into 2 basic
groups based on—the
arrangement of the
grains
d. These 2 groups are:
i. Foliated–the thin
layering found in
many metamorphic
rocks. These rocks
will split along these
bands.
ii. Nonfoliated-Mineral grains are
randomized. Do
not split into layers.
Granite to Gneiss-foliated
• *Granite becomes
gneiss when subjected
to heat and pressure.
• *The atoms end up lining
up in bands.
• *Gneiss is foliated.
Shale to Slate-foliated
• *Slate is formed when
shale is subjected to
pressure.
• *Slate is denser, more
compacted than shale
and the slate
becomes foliated.
• Slate produces flat
plates when broken.
Slate to Schist-foliated
• *If slate is subjected
to even greater
pressure and
moderate
temperatures, schist
is formed.
Quartzite-Nonfoliated
• *Occurs when
sandstone is
compressed by
pressure.
• *It is formed
when weakly
cemented quartz
particles in
sandstone
recrystallize.
• Usually very
hard.
Marble - Nonfoliated
• *Formed from
metamorphed
limestone.
• *Much harder and
denser.
Economic Importance of Minerals
•
•
Minerals are in many things we see and
use everyday such as; bricks, glass,
cement, plaster, iron, gold.
*Marble is extremely useful for building
for these reasons:
1) *It has a fine, even grain.
2) *It is relatively easy to cut into thin slabs.
3) *It can be polished easily.
•
The Taj Mahal in Agra, India is made of
gleaming white marble.
Taj Mahal
Coral Reefs
Coral reefs are responsible for the creation of one
of the 2 types of organic sedimentary rocks:
limestone.
Limestone is produced from: the hard shells of
coral left behind when they die and become
compressed and cemented together.
Coral reefs only live in: warm, clear, shallow
tropical water
Two locations they can be found in the U.S. are:
1. Florida
2. Hawaii
There are 3 types of coral reefs:
1. Fringing reef
2. Barrier reef
3. Atoll
Limestone from coral can be found: on
continents in places where uplifting has raised
ancient sea floors above sea level.
Fringing Reef – Polynesian island
of Mooréa
Barrier Reef – The Great Barrier Reef
in Australia
Atoll – Maldives in the Indian Ocean
The Rock Cycle
• *The rock cycle is a series of processes
on Earth’s surface and inside the planet
that slowly change rocks from one kind to
another.
• *Earth’s constructive and destructive
forces – including plate tectonics – move
rocks through the rock cycle.
• *The rock cycle can follow many different
pathways.
IGNEOUS
Crystallization
MAGMA
Weathering
Volcanic
IGNEOUS
Plutonic
Crystallization
Uplift
MAGMA
Weathering
SEDIMENT
Volcanic
IGNEOUS
Plutonic
Crystallization
Uplift
MAGMA
Weathering
SEDIMENT
Erosion
Transport
Deposition
Volcanic
SEDIMENTARY
IGNEOUS
Plutonic
Crystallization
Uplift
MAGMA
Weathering
SEDIMENT
Erosion
Transport
Deposition
Volcanic
SEDIMENTARY
IGNEOUS
Plutonic
Crystallization
Uplift
MAGMA
Weathering
SEDIMENT
Erosion
Transport
Deposition
Volcanic
SEDIMENTARY
IGNEOUS
Plutonic
Increased P&T
METAMORPHIC
Crystallization
Burial
Uplift
MAGMA
SEDIMENT
Weathering
Erosion
Transport
Volcanic
Can you see
IGNEOUS
any shortcuts?
Deposition
SEDIMENTARY
Plutonic
Increased P&T
METAMORPHIC
Crystallization
Melting
Burial
Uplift
MAGMA
Weathering
SEDIMENT
Erosion
Transport
Deposition
Volcanic
SEDIMENTARY
IGNEOUS
Plutonic
Increased P&T
METAMORPHIC
Crystallization
Melting
Burial
Uplift
MAGMA
The Rock Cycle
• The diagram of the rock cycle shows how the
earth's rocks are changed again and again
Distribution of Rocks in the U.S.