Download Igneous rocks

What is a rock?
• A rock is a
combination
of minerals.
For
example:
Granite is
composed
of biotite,
quartz, and
feldspar.
Metamorphic Rocks
The Rock Cycle
• Any rock can be
changed into any
other type of rock.
• The rock cycle
is the continuous
changing and
remaking of rocks.
The Rock Cycle
• Igneous and sedimentary rocks may be
transformed by heat, pressure and chemical
reactions into metamorphic rocks.
• Metamorphic rocks may be changed or
metamorphosed into other metamorphic rocks.
They may also be remelted into and igneous
rock. Or a metamorphic rock can be weathered
to form a sedimentary rock.
• Any rock can be changed into any other type of
rock.
Metamorphic Rocks
Other Possible Paths
• There is more than one path in the rock cycle.
• The rocks of Earth’s
crust are constantly
being recycled
from one type
to another.
• The processes
that help shape
Earth’s landscapes
are also part of
the rock cycle.
What are igneous rocks?
What are igneous rocks?
• About 95% of rocks on the earth are igneous or
metamorphic although mostly sedimentary cover
the surface due to weathering and erosion.
• Igneous rocks are rocks are formed from
volcanoes
• Igneous rocks are formed from the crystallization
of magma
What are igneous rocks?
Types of Igneous Rocks
• Intrusive igneous rocks are coarse-grained
igneous rocks that cool slowly beneath
Earth’s surface. (INside the earth)
• Granite is the most common intrusive
igneous rock.
• Extrusive igneous rocks are fine-grained igneous
rocks that cool quickly on Earth’s surface.
(Ex=Out of)
• An example is basalt or obsidian.
What are igneous rocks?
Types of Igneous Rocks
• Careful study of granite rock formations revealed
that they cut across other rock formations.
• These cross-cutting
relationships are
evidence that the
granite was intruded,
or forced into,
existing rocks.
Magma cools slowly beneath
Earth’s surface and forms
course-grained igneous rocks
such as granite.
What are igneous rocks?
Composition of Magma
• Magma is often a slushy mix of molten rock,
gases, and mineral crystals.
• The elements found in magma are the same
major elements found in Earth’s crust:
oxygen (O), silicon (Si), aluminum (Al), iron (Fe),
magnesium (Mg), calcium (Ca), potassium (K),
and sodium (Na).
Classifying Igneous Rocks
Classifying Igneous Rocks
• Igneous rocks are broadly classified as intrusive
or extrusive.
• Igneous rocks are further classified by their
mineral compositions and texture.
• Composition refers to the minerals that make up
a rock.
Classifying Igneous Rocks
Mineral Composition
• The two main groups of igneous rocks are felsic
and mafic are classified according to their mineral
compositions.
– Felsic rocks, such as granite, are light-colored
and have high silica contents. (L=Light!)
– Mafic rocks, such as gabbro, are darkcolored, have lower silica contents, and are
rich in iron and magnesium.
Classifying Igneous Rocks
Grain Size
• In addition to differences in their mineral
compositions, igneous rocks differ in the
sizes of their grains.
Cooling Rates
– When lava flows on Earth’s surface, it cools quickly and
there is not enough time for large crystals to form.
– Extrusive igneous rocks have no visible mineral grains.
– When magma cools slowly beneath Earth’s surface,
there is sufficient time for large crystals to form.
– Intrusive igneous rocks may have crystals larger
than 1 cm.
Classifying Igneous Rocks
Texture
• Often, it’s easier to observe the sizes of mineral
grains than it is to observe their shapes.
• Many mineral grains have interlocking edges.
• As the grains crystallize from magma, they grow
together and form irregular edges.
• Texture gives clues for the identification of various
igneous rocks.
• Texture is the size, shape, arrangement and
distribution of minerals in the rock.
Glassy Texture
• An example of glassy texture is obsidian.
Fine grained texture
• An example of fine grained is basalt or gabbro.
Coarse grained texture
• An example is granite.
Classifying Igneous Rocks
Texture Porphyritic Texture
– A rock that has a porphyritic texture is
characterized by large crystals
surrounded by finer-grained crystals.
– Porphyritic textures indicate a complex
cooling history wherein a slowly cooling
magma suddenly began cooling rapidly.
Pumice
• Pumice can float!
• Pumice is used as an abrasive cleaner.
More Uses of Igneous Rocks
Uses of Igneous rocks- granite
countertops
Scoria is a landscaping material
Igneous Rocks
• Igneous rock - Wikipedia, the free encyclopedia
Metamorphic Rocks
• Metamorphic rock - Wikipedia, the free
encyclopedia
Uses of Metamorphic Rocks
• Marble
chips for
landscaping
Classifying Igneous Rocks
Igneous Rocks as Resources
• Igneous rocks have several characteristics that
make them especially useful as building materials.
– The interlocking grain textures of igneous rocks help
to give them strength.
– Many of the minerals found in igneous rocks are
resistant to weathering.
Classifying Igneous Rocks
Ore Deposits
• Ores are minerals that contain a useful substance
that can be mined at a profit.
• Valuable ore deposits are often associated
with igneous intrusions.
• These deposits sometimes occur as veins.
Classifying Igneous Rocks
Section Assessment
1. Match the following terms with their definitions.
___
B felsic
___
D mafic
___
A ultramafic
___
C porphyritic
A. igneous rocks that have low silica
content and very high levels of iron
and magnesium
B. igneous rocks that are light-colored,
have high silica contents, and
contain quartz and feldspars
C. texture characterized by wellformed crystals surrounded by
finer-grained crystals
D. igneous rocks that are darkcolored, have lower silica contents,
and are rich in iron and magnesium
Chapter Resources Menu
Study Guide
Section 5.1
Section 5.2
Chapter Assessment
Image Bank
Section 5.1 Study Guide
Section 5.1 Main Ideas
• Igneous rocks are formed by the cooling and
crystallization of magma. Intrusive rocks form inside
Earth’s crust, and extrusive rocks form on Earth’s
surface. Extrusive rocks, which cool more rapidly than
intrusive rocks, are generally more fine grained.
• Magma is a slushy mix of molten rock, gases, and
mineral crystals. The elements found in magma are the
same major elements found in Earth’s crust: oxygen (O),
silicon (Si), aluminum (Al), iron (Fe), magnesium (Mg),
calcium (Ca), potassium (K), and sodium (Na).
Section 5.1 Study Guide
Section 5.1 Main Ideas
• Silica (SiO2) is the most abundant compound in magma.
Magmas are classified as basaltic, andesitic, and
rhyolitic, based on the amount of SiO2 they contain.
• Different minerals melt and crystallize at different
temperatures in the processes of partial melting and
fractional crystallization. Minerals crystallize from magma
in a sequential pattern known as Bowen’s reaction series.
Section 5.2 Study Guide
Section 5.2 Main Ideas
• Igneous rocks are classified as felsic, mafic, intermediate,
and ultramafic, depending upon their mineral
compositions. Felsic rocks such as granite are lightcolored, have high silica contents, and contain quartz and
feldspars. Mafic rocks such as gabbro are dark-colored,
have lower silica contents, and are rich in iron and
magnesium. Intermediate rocks have moderate silica
levels. Ultramafic rocks have low silica contents and very
high levels of iron and magnesium. Igneous groups can be
further identified by crystal size and texture.
• Early forming minerals may have well-shaped crystals,
while later-forming minerals have irregular shapes.
Porphyritic textures contain both large and small crystals.
Section 5.2 Study Guide
Section 5.2 Main Ideas
• Igneous rocks such as granite are often used as building
materials because of their strength, durability, and beauty.
• Valuable ore deposits and gems are often associated with
igneous intrusions. Ores of rare elements such as lithium
and beryllium are found in veins of extremely largegrained minerals called pegmatites. Diamonds are found
in rare types of igneous intrusions known as kimberlites.
Chapter Assessment
Multiple Choice
1. The process wherein different minerals form at
different temperatures is called ____.
a. partial melting
b. Bowen’s reaction series
c. fractional crystallization
d. crystal separation
Partial melting is when some minerals melt at low
temperatures while others remain solid. Bowen’s
reaction series describes in what order minerals form.
Crystal separation is a hypothesis that answers
questions about Bowen’s reaction series.
Chapter Assessment
Multiple Choice
5. Extrusive igneous rocks generally have small
mineral grains because ____.
a. they cool slowly.
b. the minerals in extrusive rocks do not
form crystals under any condition.
c. they cool quickly.
d. there is too much water in the magma.
By quickly cooling, the minerals in extrusive igneous
rocks do not have enough time to form large crystals.
Chapter Assessment
Short Answer
6. What characteristics make igneous rocks useful
as building materials?
Igneous rocks are useful as building materials
because the interlocking grain textures of
igneous rocks help to give them strength and
many of the minerals found in igneous rocks
are resistant to weathering.
Chapter Assessment
Short Answer
7. What causes a porphyritic texture to form in
certain rocks?
A porphyritic texture indicates a complex
cooling history wherein a slowly cooling
magma suddenly began cooling rapidly.
Image Bank
Chapter 5 Images
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Chapter 5 Images
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Chapter 5 Images