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Rocks
Granite is a mixture of:
Feldspar
Quartz
Mica
Hornblende
Combinations of
different minerals
Rocks
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Rocks are made up of a mixture of
minerals:
1. They can be formed in many different
ways.
2. Rocks come in many different shapes
and colors.
3. The components are not in any fixed
proportion.
Types of Rocks
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Igneous
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Sedimentary
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Metamorphic
The Rock Cycle
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Model that shows how one kind of rock changes into
another kind of rock.
The diagram of the rock cycle shows how the earth's
rocks are changed again and again.
Has no beginning and no end, rocks are continually
changing from one form to another.
The changes that take place in the rock cycle never
destroy or create matter. The elements are just
distributed in other forms.
Sedimentary Rock
Heat and
Pressure
Compaction
and
Cementation
Sediment
Weathering,
Erosion,
and
Deposition
Weathering,
Erosion,
and
Deposition
Metamorphic Rock
Melting
Weathering,
Erosion,
and
Deposition
Igneous Rock
Heat and
Pressure
Magma
Cooling and
Crystallization
Rocks are changed by processes
such as:
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Weathering
Erosion
Deposition
Compaction
Cementation
Crystallization
Heat and Pressure
Melting
Weathering
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The breaking down of solid rock by
chemical or physical forces.
Results in small particles and/or new
chemicals.
Example:
- Physical change – Some of the mineral matter in mountains is broken
off by wind, water, or ice but otherwise remains the same.
- Chemical change – Some of the mineral matter is carried away in
streams as individual particles we cannot see. These particles are free
to react with other particles to produce new minerals.
Erosion
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When weathered particles are carried
(transported) by agents of erosion, such
as wind, water, ice, or gravity.
Deposition
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When weathered material is laid down,
generally in layers, in a new location.
Compaction
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When deposited particles are compressed
into smaller volume.
Cementation
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When the deposited particles are “glued”
together by a cementing agent or by
pressure.
Crystallization
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When liquid rock (magma or lava) freezes
into a solid form.
Heat and pressure
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Created by deep burial or by close contact
with molten rock (lava or magma).
Melting
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Changing a solid into a liquid by
heat/pressure.
Igneous Rocks
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The most abundant type of rock on Earth.
Most igneous rocks are produced deep
underground by the cooling and hardening
of magma.
Classification of Igneous Rocks
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Classified according to how the magma
cools and hardens (crystallizes).
Composition-refers to the minerals that
make up the rock.
Texture-shape, size, arrangement and
distribution of minerals that make up the
rock.
Composition
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Extrusive- Formed from lava; volcanic
Obsidian
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Pumice
Intrusive- Formed deep within the earth;
plutonic Granite
Intrusive vs. Extrusive Rocks
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Intrusive – Magma solidifies deep within the
earth. The slow cooling causes large crystals to
form and the texture is coarse-grained.
 Think: INside. Formed inside the earth.
Extrusive – Magma flows to the surface (now
called lava) and cools very rapidly. This rapid
cooling causes small or no crystals to form and
the texture is fine-grained.
 Think: EXit. These rocks exited the Earth
Textures
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Glassy
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Obsidian
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Fine-grained
Basalt
Coarse-grained
Granite
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Porphyritic
Granite
Gabbro vs. Basalt
Diorite vs. Andesite
Granite vs. Rhyolite
Sedimentary Rocks
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Forms from cementing together of Earth’s
materials called sediment (clay, sand, pebbles,
gravel, plants or animal remains).
75% of the rocks at Earth’s surface are
sedimentary rocks.
Sedimentary rocks can be categorized into three
groups based on sediment type.
Clastics
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Clastic rocks are composed of grains or
fragments of rocks and minerals that have been
eroded, transported, deposited, and cemented
together.
During the transport process, the particles that
make up these rocks often become rounded due
to abrasion or can become highly sorted.
Non-clastics
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Non-clastic rocks are created either from
chemical precipitation and crystallization,
or by the lithification of once living organic
matter.
Identification of non-clastics requires
identification of the primary mineral.
Classification of
Sedimentary Rocks
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Clastic (fragmental) – formed from the
broken pieces of other rocks (clastics).
Organic – forms from accumulation of
dead plants and animals.
Chemical – form when dissolved minerals
precipitate out or are left behind when a
solution evaporates.
Clastic Rocks
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Conglomerate
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Sandstone
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Shale
Organic Rocks
Organic rock comes remains of plants and animals
Coquina
Fossiliferous Limestone
Chemical Rocks
Chemical rocks come from minerals that are
dissolved in a solution and crystallize
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Limestone
Metamorphic Rocks
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Formed when high heat and pressure
changes the original or parent rock into a
completely new rock.
The parent rock can be either
sedimentary, igneous, or even another
metamorphic rock.
Metamorphic Rocks
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Metamorphic means “change in form”.
Two categories:
Regional Metamorphism – the deeper a layer
of rock lies within the earth’s crust, the more it
will be affected by temp and pressure.
Contact Metamorphism – common in regions
of volcanic activity since hot magma may heat
the preexisting rock layers.
Foliated
When mineral grains flatten and line up in
parallel layers.
Light and dark bands.
Unfoliated
The mineral grains
change, grow and
rearrange but they
don’t form bands.