1. A solid mass of mineral or mineral like
ma
tt
er that occurs naturally as part of
our planet
• The three major type rocks are:
• Igneous – Made from hardened magma or lava
• Sedimentary – Made from pieces of other
rocks or precipita
ti
on of minerals from water.
• Metamorphic – Made from heat and pressure
deep within the earth.
ROCKS
2. HOW ROCKS FORM/ROCK CYCLE
• The ROCK CYCLE is
the movement from
one rock type to
another.
• Interac
ti
ons among earth’s water, air, land, and
living things can cause rocks to change from one
type of rock to another. The con
ti
nuous processes
that cause rocks to change make up what is known
as the Rock Cycle.
3. EXAMPLES OF ROCK CYCLE
• When magma hardens beneath the surface of the earth it
forms Igneous rock. If this Igneous rock is placed under heat
and pressure without mel
ti
ng it could change to a
metamorphic rock. If the metamorphic rock is subjected to
weathering the pieces known as sediments could erode,
deposit, compact and cement together to form a
sedimentary rock. These are all parts of the rock cycle.
• Sedimentary rock
• Metamorphic rock
• Igneous rock
4. PROCESSES THAT DRIVE THE ROCK
CYCLE
• The earth system is driven by two
processes, the sun and earth’s interior
heat. These two processes also drive the
rock cycle.
5. PROCESSES THAT DRIVE THE ROCK
CYCLE
• Processes driven by
the earth’s interior
heat are responsible
for the forma
ti
on of
Igneous and
Metamorphic rocks.
6. PROCESSES THAT DRIVE THE ROCK
CYCLE
Processes powered
by energy from the
sun drive external
processes such as
weathering that
drive the forma
ti
on
of sedimentary
rocks.
7. IGNEOUS ROCKS
• Igneous rock forms from magma when it hardens. Magma is simply
melted or molten rock that is underground. When magma reaches the
surface of the earth it is called lava.
The only di
ff
erence between magma and lava is magma is underground
and lava is out of the ground. Magma also loses most of the gas it contains
when it reaches the surface through processes such as volcanoes.
8. IGNEOUS ROCK TYPES
• When magma hardens out of the ground, then
known as lava, it forms what is called an Extrusive
Igneous Rock. Volcanoes normally produce
extrusive igneous rock as lava hardens and also
intrusive igneous rock as previously hardened
magma is thrown out of the volcano.
• Extrusive Igneous Rock
• Intrusive Igneous Rock
• When magma hardens within the ground it forms what is
called an Intrusive Igneous Rock.
9. IGNEOUS ROCK CLASSIFICATION
• Igneous Rock is classi
fi
ed by both texture and
composi
ti
on.
• Texture is the structure of the rock.
• Composi
ti
on is what the rock is made of.
• Texture and composi
ti
on only applies to
Igneous rocks.
• We will study 4 textures and 4 composi
ti
ons.
10. IGNEOUS ROCK TEXTURES
• Coarse Grained Texture is formed when magma
hardens deep within the earth over a long period of
ti
me. The slow cooling allows large crystals to form.
11. IGNEOUS ROCK TEXTURES
• Fine Grained Texture occurs when the rock cools fast,
not allowing
ti
me for large crystals to form.
12. IGNEOUS ROCK TEXTURES
• Glassy Texture occurs when the magma or lava cools
very fast, such as a volcanic erup
ti
on, and no crystals
have
ti
me to form. The rocks appear as glass.
13. IGNEOUS ROCK TEXTURES
• Porphyri
ti
c Texture occurs when both large and
fi
ne
grains appear in the same rock. Di
ff
erent minerals cool
and harden at di
ff
erent rates and causing the di
ff
erent
sizes.
14. COMPOSITION OF IGNEOUS ROCKS
• Grani
ti
c Composi
ti
on is made up of light
colored silicate materials mixed with a few
dark crystals.
15. COMPOSITION OF IGNEOUS ROCKS
• Basal
ti
c Composi
ti
on is made up mostly of
dark colored materials.
16. COMPOSITION OF IGNEOUS ROCKS
• Andesi
ti
c Composi
ti
on is a mixture of light and
dark materials.
18. SEDIMENTARY ROCKS
• We will study two ways sedimentary rocks form; from weathered bits of
other rocks and from materials precipita
ti
ng out of solu
ti
ons.
• Clas
ti
c Sedimentary Rocks are made up of
bits of other rocks that go through a 5 step
process described later. They are classi
fi
ed
by the size of the sediments contained in the
rock. Examples are shale, sandstone and
breccia.
• Chemical Sedimentary Rocks form as
minerals are le
ft
behind from evapora
ti
on of
water through a process known as
precipita
ti
on. Examples are limestone and
gypsum.
• A third, known as Organic Sedimentary
Rock, forms when pieces of dead
organisms accumulate such as shells in the
ocean. An example is chalk. Our book puts
this in chemical.
• Sedimentary Rocks are used to
fi
gure out
history. They are the only rocks to contain
fossils. The oldest rocks are at the bo
tt
om of the
bo
tt
om of the rock forma
ti
on. Ripple marks
indicate the rocks formed near water.
19. CLASTIC SEDIMENTARY ROCKS
• The order is always Weathering, Erosion, Deposi
ti
on, Compac
ti
on and
Cementa
ti
on.
Clas
ti
c Sedimentary Rocks begin to form when exis
ti
ng rocks are broken down into
sediments by the process of Weathering. Weathering occurs by the forces of water,
wind, ice, etc.
Erosion is the process by which the broken down rock is moved to di
ff
erent
loca
ti
ons. Water, wind, ice and gravity are examples of agents of erosion.
When the energy that moves the sediments is lost the sediments are placed
by a process known as Deposi
ti
on.
• Compac
ti
on is the process that squeezes or compacts the sediments.
• Cementa
ti
on is the process that takes place when dissolved minerals are
deposited in the
ti
ny spaces among the sediments and hardens the rock.
20. METAMORPHIC ROCKS
• Metamorphic rocks are formed from heat and pressure deep
within the earth, usually a few kilometers down (at 8 km the
temperature is 150 to 200 C.
• Metamorphic rocks can be made from any of the three rock
types.
• Contact Metamorphism occurs when
magma moves into the cracks
between rocks and the rock being
touched changes form but does not
melt into the magma. This is called
low grade metamorphism.
• Contact metamorphism could also result from a hydrothermal
solu
ti
on traveling between rocks.
• Agents of Metamorphism are heat, pressure and hydrothermal
solu
ti
ons.
21. Regional Metamorphism
• Regional Metamorphism is also known as high
grade metamorphism.
• Extreme heat and pressure are present during
this process.
• Regional metamorphism normally involves
large scale deforma
ti
on.
• This from of
metamorphism normally
occurs during plate
movement and results in
mountain building.
22. Metamorphic Rocks
• Nonfoliated Metamorphic rocks do not have
bands or layers and many
ti
mes contain only
one type of mineral. See
fi
gure 19 in our book.
• Foliated Metamorphic rocks have a banded
appearance or a layered look. See
fi
gure 18 in our
book. Many
ti
mes this is a result of di
ff
erent
minerals being in the same rock.
