The Rock Cycle
What is the rock
cycle?
What exactly is a ROCK?
• A rock is a naturally occurring solid. It is
a mixture of one or more minerals &
organic matter.
• Rocks are always changing; this process
of new rocks forming from old rocks is
called the Rock Cycle
Are rocks useful?!
Absolutely!
• What were they used for?
• Uses of rocks: Hammers &
other tools &…
chert
obsidian
knives
arrowheads
Rocks were not only used to make tools…
Rocks were also used to make
buildings, monuments & roads.
Limestone, a sedimentary Washington Monument in
D.C.-made of marble,
rock was used to make
granite & sandstone
the pyramids
What processes make & destroy
rocks?
Geological processes such as
erosion & deposition
influence the type of rock
that is formed on Earth’s
surface
• Sediment: small particles
(usually dirt) that was
suspended in water and has
settled to the bottom of water.
Erosion is the process of removing
sediment from its original location.
Usually carried away by water or
air; (it is displaced)
Deposition is the sediment that is carried
away (or displaced) by erosion, is
dropped off in
a new location.
Feeling the Heat & Pressure
Sediment that is buried, can be squeezed by weight of
layers on top of it to form sedimentary rock.
When the pressure & temperature is high enough, the
rock can change into metamorphic rock.
If the rock gets hot enough inside the earth, the rock
melts. The melted rock becomes magma; which
then cools & forms igneous rock.
Igneous Rock
cooling
melting
Weathering
Magma
Heat & pressure
sediment
melting
Compaction &
cementation
Weathering
Metamorphic
Rock
Weathering
Heat & pressure
Sedimentary Rock
Round & round the cycle goes
Buried rock is brought to the Earth’s surface by
erosion & uplift (movement in the Earth, that
brings rocks inside the Earth to the Earth’s
surface).
On the Earth’s surface weathering, erosion &
deposition occur.
How are rocks classified?
• All rocks can be classified into 3 main classes of rock
based on how it is formed:
–igneous, sedimentary & metamorphic
• Each rock class can be divided further; also by how
they form.
– Ex: Igneous rock can form beneath Earth’s surface &
other igneous rock can form above Earth’s surface
What is looked @ to classify rocks?
• Composition:
the minerals that the rock
contains
• Texture:
the size, shape & grain position
that make up the rock
Aragonite
5%
Calcite
95%
Calcite
Mineral
Composition
of Limestone
Mineral
Composition
of Granite
Quartz
35%
Feldspar
55%
Biotite
mica
10%
Rock Textures can Vary
Sedimentary rock can be:
Medium grained
Fine grained
Coarse grained
Varying Rock Textures Continued…
Igneous Rock can be fine grained or coarse grained,
depending on how much time the magma has to
cool.
Metamorphic rock can also be fine or coarse grained,
depending on the amount of pressure &
temperature the rock is exposed to.
Rock Type
Fine Grained
Sedimentary
X
X
X
Igneous
Metamorphic
Medium
Grained
X
Coarse
Grained
X
X
X
Why do we care to look @ the
texture anyway?!
• For clues to tell us where & how the rock was
formed
Sandsto
ne
Basal
t
Let’s see what we’ve learned!
Fill in the Blank:
1. The minerals that a rock is made of
determine the __________ of that rock.
2. ______ is a naturally occurring, solid
mixture of crystals of one of more
minerals.
Sediments are transported or moved
from their original source by a
process called:
a) deposition
b) erosion
c) uplift
d) weathering
Describe 2 ways that rocks have
been used by humans.
Explain the difference between
composition & texture
Look @ the table below
to answer the question
Texture
Particle Size
Coarse grained
Medium grained
Fine grained
> 2mm
0.06 – 2 mm
<0.06 mm
Sandstone is a type of sedimentary
rock. If you had a sample of
sandstone that had an average
particle size of 2 mm, what texture
would your sandstone have?
Power Point Presentation made by
Ms. Luck