Download Metamorphic and Igneous

Metamorphic Rocks
Metamorphic Rocks
• produced from preexisting igneous, sedimentary, or from other
metamorphic rocks (called parent rock)
• Metamorphism means to “change form”
• leads to changes in the mineralogy, texture, and sometimes the
chemical composition of rocks.
Recrystallized
Minerals
Can
Be
More
Stable
Metamorphic Rocks
• Causes include changes in temperature, pressure (stress), and
the introduction to chemically active fluids.
1. Heat is the most important of metamorphism because it
provides the energy to drive chemical reactions that result
in the recrystallization of existing materials and/or the
formation of new materials.
Earth’s internal
heat comes
mainly from
radioactive
decay within the
Earth’s interior.
Metamorphic Rocks
2. Pressure, like temperature,
increases as you get deeper into
the Earth. Buried rocks are
subjected to:
• Confining pressure – equal
squeezing and minerals closer
together; dense
• Differential pressure –
unequal squeezing and
develops folds or foliation
Metamorphic Rocks
3. Chemically active fluids
• the circulation of hot, mineralladen fluids through rock bodies
Metamorphic Rocks
Metamorphic Rocks
• slight changes (low-grade metamorphism) shale turning into
slate because of not terribly high pressures or temperatures. Fine
grained
• substantial changes (high-grade metamorphism). Slight melting
may occur, as well as folds or obliteration of fossils in the parent
rock. Coarse grained
Examples of
Metamorphic Rocks
Gneiss
Slate
Schist
Marble
Quartzite
Phyllite
Metamorphic Rock Textures
Texture is used to describe the size,
shape, and arrangement of grains
within a rock.
2 types:
• Foliated
• Non-foliated
quartzite
Examples of Foliated Textures
Schist has minerals (such as
mica) that have grown large
enough to be seen by the unaided
eye
Slate is a rock with
excellent rock cleavage, as
it breaks in flat slabs.
Gneiss results from high-grade
metamorphism
Foliated Metamorphic Rocks
Gneiss
Slate
Schist
Phyllite
Nonfoliated Metamorphic Texture
Marble (Parent rock
of Limestone)
Quartzite (Parent rock
of sandstone)
Porphyroblasts are large grains
that are surrounded by a finegrains of other minerals.
GARNETS
The exterior of the Taj Mahal is constructed mainly of the
metamorphic rock marble.
Metamorphic Environments
Hydrothermal metamorphism occurs when hot fluids circulate
through fissures and cracks that develop in rock. This hot fluid
chemically alters rocks and is closely related to igneous activity.
Metamorphic Environments
There are a number of environments in which metamorphism
occurs. Most are in the vicinity of plate margins, and many are
associated with igneous activity.
Contact or thermal
metamorphism
occurs when rocks
immediately
surrounding a molten
igneous body are
“baked” and therefore
altered from their
original state.
Metamorphic Environments
Regional metamorphism occurs where rocks are squeezed
between two converging lithospheric plates during mountain
building.
Igneous Rocks
Igneous rock forms when magma
cools and makes crystals.
Magma is a hot liquid made of
melted minerals. When magma
pours onto the earth’s surface it
is called lava. The minerals can
form crystals when they cool. Fast
cooling results in small crystals.
Igneous rock can form
underground, where the magma
cools slowly and results in large
crystals. Or, igneous rock can
form above ground, where the
magma cools quickly.
The crystals grow together and
form one igneous rocks.
What kind of igneous rocks form when
molten lava cools and hardens?
Extrusive = forced out
while molten through
cracks in the earth's
surface
What is the Latin word that the word igneous
comes from and what does it mean?
ignis = fire
Extrusive Igneous Rocks
Formed by lava on the Earth’s surface
Intrusive Igneous Rocks
Form from magma below the earth’s surface
What is the difference between
magma and lava?
Magma = molten rock
below the earth’s
surface
Lava = molten rock
flowing on the earth’s
surface
What are the 8 elements that make up
magma?
Silicon, oxygen, aluminum,
iron, calcium, sodium,
potassium, magnesium
Basaltic rocks are low in silica. They are dark colored
and dense. Basaltic rock is called “MAFIC”
Granitic rocks have high silica content, are light in
color, and have lower densities. Granitic rock is
called “FELSIC”
Look at the granite rock and the rhyolite rock
Granite
Rhyolite
In what ways are the two rocks similar?
Both are from melted rock
Their composition is the same – quartz and feldspar
In what ways are the two rocks different?
Granite
Rhyolite
Granite – coarse texture, made from magma
Rhyolite – fine texture, made from lava
What causes the two rocks to be different?
Granite
Rhyolite
Granite – Slow cooling below the earth’s surface
Rhyolite – Quick cooling on the earth’s surface
Why do you think some rocks are
heavier than others?
Some are denser – less air space between particles
Which rock would have greater density?
Pumice
Granite
Which is EXTRUSIVE?
Andesite
Pegmatite
Gabbro
Basalt
These 2 are related. They form
the oceanic crust.
1. Which one is most likely
on the surface of the crust?
2. Are they mafic or felsic?
Pumice
Obsidian
Both Pumice and Obsidian are extrusive.
1. Why don’t they exhibit crystalline structure?
2. The pumice has “vesicles” like a slice of bread. How do
those form?
3. Which one has such low density that it floats in water?
Slow cooling magma will form rocks with a
a. coarse grained texture.
b. fine grained texture.
c. glassy texture.
d. porphyritic texture.
Rapid cooling magma will form rocks with a
a. coarse grained texture.
b. fine grained texture.
c. glassy texture.
d. porphyritic texture.
Imagine magma cooling slowly, deep in
Earth’s crust. Suddenly, it is moved
higher in the crust and some erupts
onto the surface. What type of texture
would result?
a. coarse grained texture.
b. fine grained texture.
c. glassy texture.
d. porphyritic texture.
Bet Cha’ Weren’t Expecting A….
POP QUIZ!!!!!*
1. What are the three types of rock?
2. Which type of rock has been formed by magma
or lava?
3. What do we classify rocks by?
4. How do sedimentary rocks form (in order)?
5. Metamorphic rocks are rocks that have
?(fill in the blank)
6. What is the process of sediments forming a
sedimentary rock?
7. What does “ignis” mean in the word igneous?
*Answers are on next slide!
ANSWERS!!!!
1.
2.
3.
4.
Igneous, Sedimentary, and Metamorphic
Igneous
Texture, Color, and Mineral Composition
Erosion, Deposition, Compaction,
Cementation
5. Morphed
6. Lithification
7. “ignis” means fire