Download Rocks and Their Origins

Rocks and Their Origins
Petrologic Classification
Dynamic Earth Processes.
Objective- Identify and describe the three
classes of rocks.
California Science Standard (3a)- Students
know how to explain the properties of
rocks based on the physical and chemical
composition which they formed, including
plate tectonics processes.
Chapter 6-1 What are Rocks?
Rocks- mixture of minerals, generally
cemented together.
*All rocks are made up of one or more
minerals.
Petrologist- (petro is the Greek word for
rock.) Earth science specialists who study
rocks and minerals and their origin.
Chapter 6-1 Petrologic Cycle
(rock cycle)
Rock cycle- series of natural processes by which
rocks are slowly changed from one kind of rock
into another kind of rock.
*It shows the ways that one rock type is
changed to another.
Intrusive and
Extrusive changes
in rock types.
Classification Of Rocks
*
Classification- is the grouping of objects by
certain characteristics. Scientist classify objects
to make them easier to study.
* Petrologist classify rocks based on how they form.
• Igneous rock- rock formed by the crystallization
of hot molten rocks or minerals.
Chapter 6-2
How are igneous rocks formed
Objective- Identify two ways that igneous rocks are formed.
Molten Rock- melted rocks and minerals.
Magma- molten rock inside the earth.
* The cooling and hardening of molten rock produces rocks of
igneous classification.
Pluton- large body of igneous rock that can form into different
shapes when magma cools inside the Earth’s crust. Akaigneous intrusions.
* Igneous rocks that form here are classified as intrusive.
Intrusive- igneous rocks that form on the inside of the Earth
from cooling magma.
Lava- magma that reaches the Earth’s surface.
* Rocks that cool on the outside of the Earth from lava are
called extrusive.
Extrusive- igneous rocks that form on the outside of the Earth
from cooling lava.
Where igneous rocks form?
Chapter 6-2 How are igneous rocks
classified?
Objective- Identify and describe igneous rocks by
their minerals and textures.
*Igneous rocks are made up of aggregates
(combinations) of minerals.
*Six common igneous rock forming minerals; Quartz,
Mica, Amphibole, Feldspar, Olivine, Pyroxene.
Igneous Rock Classification
Crystal Size
* Crystal size in an igneous rock depends on the rate of
cooling.
* Large crystals form from slow cooling.
* Small crystals form from fast cooling.
Texture- size, shape and arrangement of a rocks crystals.
• Igneous rocks are classified based on their texture.
• Coarse texture- igneous rocks with large crystals.
• Fine Grain texture- rocks that have small crystals.
• Glassy- rocks that cool so fast they have no specific
crystals.
• Porphyry- rock with a set of different sized crystals.
Igneous Matrix
Igneous Rocks
Intrusive
(Acid magma)
High silica, thick slow
flowing,
Extrusive
(basic lava)
Low silica, hotter,
faster flowing
Slow Cooling
Fast Cooling
Large crystals
Small crystals
Coarse texture
Fine grain texture,
glassy
Light colored minerals
Dark colored minerals
(Quartz, Plagioclase
Feldspar)
(hornblende, dark mica,
augite)
Light colored rocks
(granite)
Dark colored rocks
(basalt)
Sedimentary
Rocks
Objective- Describe two ways that
sedimentary rocks are formed.
Sediment- rock particles carried and
deposited by water, wind, or ice.
Sedimentary- rocks made from the fragments
of existing rocks or organic remains.
Chapter 6-3 How are sedimentary
rocks formed?
*Most sedimentary rocks are formed in water.
*Sediments are deposited in layers or beds called
strata.
Deposition- the release of rock fragments into layers.
Stratification- layering of rock fragments.
* As the layers thicken, they become compressed.
* Water containing dissolved minerals seeps into the
layers and between rock particles, cementing the particles
together.
Cementation- minerals when evaporated and left behind bond
sedimentary particles together.
Lithification- the creation of solid rock layers through
cementation.
Sedimentary formation continued.
Chapter 6-3 Continued.
Sedimentary rocks from living things.
* When oceanic animals die they sink to
the bottom of the ocean floor.
* They get buried, compacted and
cemented together to form organic
sedimentary rocks.
Organic sedimentary- rocks made from the
remains of plants and animals.
Chapter 6-3 How are sedimentary rocks
classified?
Objective- Identify and describe the two main groups of
sedimentary.
There are two main groups of sedimentary rocks;
Clastic rock- sedimentary rock made up of fragments of
existing rock.
* Fragments of existing rock are carried by wind, water
and ice.
* They are classified according to their sizes and
shapes.
Sorting- separation of rock fragments by size.
Clastic Sedimentation
Conglomerate
Chapter 6-3 continued.
• Nonclastic Rock- sedimentary rock made up of
dissolved minerals or the remains of once living
things.
• Chemical- rocks formed from dissolved minerals.
• Precipitants- chemical sedimentary rocks formed when
minerals fall out of solution.
• Evaporite- chemical sedimentary rocks formed when minerals
are left behind after evaporation.
Chemical Sedimentation
Precipitant
(Limestone)
Evaporite
(Halite)
Limestone Formations
Dissolved minerals that drip from the tops of
caves form chemical deposits.
Stalagmites
Stalactites
Organic Sedimentary
• Story of Coal
• Peat- Loose, partially decomposed plant material.
• Lignite (brown coal)- more compacted, partially
decomposed plant matter.
• Bituminous (soft coal)- Highly compacted decaying
material that consist of 85% carbon.
• Anthracite (hard coal)- Metamorphosed bituminous coal,
90-95% pure carbon.
Types of Coal
Peat
Bituminous
Lignite
Anthracite
Sedimentary Matrix
Sedimentary
Clastic
Fragments
Sorting
Stratification
Cementation
Lithification
Conglomerate
Sandstone
Shale
Clay
Chemical
Chemical Action
Precipitant
Evaporite
Falls Out
Limestone
Organic
Remains
Coal
Left behind
Peat
Rock Salt
Lignite
Bituminous
Anthracite
Chapter 6-4 How are
metamorphic rocks formed?
Objective- Describe two ways in which
metamorphic rocks form.
Metamorphism- meta (change), morph (form)
Rocks that change in form as a result of heat
and pressure.
*Metamorphic Rock is formed by the effects
of heat and pressure upon igneous and
sedimentary rocks.
Chapter 6-4 Metamorphism
*Minerals in rock change chemically when
heated. Minerals go through chemical
changes at temperatures between 200°C
and 800°C. Above 800°C they change into
magma or molten rock.
* Forces within the Earth cause pressure,
which changes a rocks mineral form.
Chapter 6-4 How are
metamorphic rocks classified?
Dynamic Metamorphism
Objective- Explain the difference between foliated
and nonfoliated metamorphic rocks.
*Metamorphic rocks are classified based on their
texture; Foliated and nonfoliated.
Foliated- texture of a metamorphic rock that has
mineral crystals arranged in bands.
Granite
Gneiss
*Foliated rocks tend to break along their mineral crystal bands.
•
These rocks are formed under extremes of pressure and
some heat.
Chapter 6-4 Thermal Metamorphism
Nonfoliated- texture of a metamorphic rock
that does not have mineral crystals
arranged in bands.
* nonfoliated rocks do not break in layers.
* Formed under great heat and little
pressure, through recrystallization.
Limestone
Marble