IGNEOUS ROCKS
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Transcript of IGNEOUS ROCKS
IGNEOUS ROCKS
Pg 99 text book
http://my.hrw.com
What you will learn
• Describe three ways that igneous rock forms. • Explain how the cooling rate of magma affects
the texture of igneous rock. • Distinguish between igneous rock that cools
within Earth’s crust and igneous rock that cools at Earth’s surface.
Igneous rock begins as magma
What is the origin of Igneous Rock?
http://www.webquest.hawaii.edu/kahihi/sciencedictionary/images/magma_flow_up.gif
There are three ways magma can form:
1. when rock is heated,
2. when pressure is released,
3. when rock changes composition.
What are the ways that magma can form?
Put a drawing like this on pg 37 in your nb
The longer it takes for the magma or lava to cool, the more time mineral crystals have to grow.
The more time the crystals have to grow, the larger the crystals.
The larger the crystals are the coarser the texture of the resulting igneous rock is.
What happens
to magma when it cools at different
rates?
The less time magma takes to cool, the less time crystals have to grow. Therefore, the rock that is formed will be fine grained.
What happens
to magma when it cools at different
rates?
Fine-grained igneous rock contains very small crystals, or if the cooling is very rapid, it contains no crystals.
What happens
to magma when it cools at different
rates?
What are the Compositions and Textures
of Igneous Rock?
What are examples of each type?
What is Intrusive Igneous Rock?
Magma that cools and solidifies deep within the Earth’s crust.
What is Intrusive Igneous Rock?
Magma that intrudes, or pushes, into surrounding rock below the Earth’s surface and cools.
What is Intrusive Igneous Rock?
Usually has a coarse-grained texture because it is well insulated by surrounding rock and cools very slowly. The minerals that form are large, visible crystals.
What are the different
masses of intrusive
igneous rock named and
why?
Masses of intrusive igneous rock are named for their size and shape
PlutonsBatholithsStocks Dikes
Plutons are large, irregular-shaped intrusive bodies.
The largest of all igneous intrusions are batholiths.
Stocks are intrusive bodies that are exposed over smaller areas than batholiths.
Dikes sheetlike intrusions that cut across previous rock units.
Sills are sheetlike intrusions that are oriented parallel to previous rock units.
Plutons
Batholiths
Stocks
Dikes
Sills
PLUTONS
Where would I find
Extrusive Igneous Rock?
Magma that erupts, or extrudes, onto the Earth’s surface. Extrusive rock is common around volcanoes.
Lava cools quickly on the surface and contains very small crystals or no crystals.
What type of texture
do extrusive igneous
rock have?
Does lava always
come from volcanoes?
Lava does not always flow from volcanoes. Sometimes lava erupts and flows from long cracks in the Earth’s crust called fissures.
Where do we
find fissures?
Lava flows from fissures on the ocean floor at places where tension is causing the ocean floor to be pulled apart.
When a large amount of lava flows out of fissures onto land, the lava can cover a large area and form a plain called a lava plateau.
Sedimentary Rock
Pg 44 in nbPg 102 in tb
What You Will Learn
• Describe the origin of sedimentary rock. • Describe the three main categories of
sedimentary rock. • Describe three types of sedimentary
structures.
Rock and mineral fragments called sediment
What are the origins of
Sedimentary Rocks?
sediment plume from Moore Creek entering Dog River.
http://www.usouthal.edu/geography/fearn/480page/98Gerrit/SedPlume.html
What are the agents
of weathering that make sediment?
1. Wind2. Water3. Ice4. Sunlight 5. Gravity
How do sediments
move from one place to
another?
Through the process of erosion.
1. Layers of sediment are deposited, they cover older layers.
2. Older layers become compacted.
3. Dissolved minerals separate from water that passes through the sediment.
4. Dissolved minerals form a natural cement
5. Cement binds the rock and mineral fragments together.
How are sedimentary rocks formed?
Sedimentary rock forms at or near the Earth’s surface. It forms without the heat and pressure that are involved in the formation of igneous and metamorphic rocks.
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What is
strata?
Layers of sedimentary
rock.
http://davidkanaga.blogspot.com/2011/07/sediments-and-sedimentary-rocks.html
Sedimentary rock is classified by the way it forms.
Clastic, Chemical, and Organic
How is sedimentary
rock is classified?
Clastic sedimentary rock is made of fragments of rocks cemented together by a mineral such as calcite or quartz.
What is clastic Sedimentary Rock?
By the size of the fragments from which the rock is made.
How is clastic
sedimentary rock is
classified?
Pg 103
Chemical sedimentary rock forms from solutions of dissolved minerals and water.
How is chemical sedimentary rock formed?
Halite, one type of chemical sedimentary rock, is made of sodium chloride, NaCl, or table salt.
What is Organic
Sedimentary Rock and what are
some examples.
Limestone forms from the remains, or fossils, of animals that once lived in the ocean.
Coal forms underground when partially decomposed plant material is buried beneath sediment and is changed into coal by increasing heat and pressure.
fossiliferous limestone
coal
What are some
Sedimentary Rock
Structures?
Stratification is the process in which sedimentary rocks are arranged in layers.
Ripple marks, record the motion of wind and water waves on lakes, oceans, rivers, and sand dunes in features called Structures called mud cracks
ripple marks
http://www.answersincreation.org/curriculum/geology/geology_chapter_6.htm
Mud Cracks
Metamorphic rockspg 106 text
pg 48nb
Origins of Metamorphic
Rock
If the temperature or pressure of the new environment is different from the one in
which the rock formed, the rock will undergo metamorphism.
The word metamorphism comes from the Greek words meta, which means “changed,” morphos, which means “shape.”
Contact metamorphism is a change in the texture or structure of a rock resulting from the contact of invading magmatic material.
Texture and structure of
metamorphic rocks
Texture and structure of
metamorphic rocks
Regional metamorphism is metamorphism that affects rocks over large areas, instead of in only a local area.
107
p107
Hornfels is a fine-grained nonfoliated metamorphic rock with no specific composition. It is produced by contact metamorphism. Hornfels is a rock that was "baked" while near a heat source such as a magma chamber, sill or dike.
http://www.geol.umd.edu/~jmerck/geol100/lectures/16.html
Regional metamorphic area
The minerals calcite, quartz, and hematite combine and recrystallize to form the metamorphic mineral garnet. P.108
Scientists can understand a metamorphic rock’s history by observing the minerals the rock contains. Theses minerals are called index minerals
p108
index minerals,
Textures of Metamorphic
Rock
The texture of metamorphic rock in which the mineral grains are arranged in planes or bands
Foliated.
Textures of Metamorphic
Rock
The texture of metamorphic rock in which the mineral grains are not arranged in planes or bands
Nonfoliated.
The effects of metamorphism depend on the heat and pressure applied to the rock. see what happens to shale, a sedimentary rock, when it is exposed to more and more heat and pressure.
. Pg 109
Metamorphic Rock
Structures
Deformation is a change in the shape of a rock caused by a force placed on it. These forces may cause a rock to be squeezed or stretched.
These large folds occur in metamorphosed sedimentary rock along Saglet Fiord in Labrador, Canada
Slate is a fine-grained, foliated metamorphic rock that is created by the alteration of shale or mudstone by low-grade regional metamorphism
Shale sedimentary rock
Slate metamorphic rock
created by the alteration of shale or mudstone by low-grade regional metamorphism
Gneiss is foliated metamorphic rock that has a banded appearance and is made up of granular mineral grains.
Granite igneous rock
Gneiss metamorphic rock
Marble is a non-foliated metamorphic rock that is produced from the metamorphism of limestone.
Limestone sedimentary rock
Marble metamorphic rock
Quartzite is a non-foliated metamorphic rock that is produced by the metamorphism of sandstone. It is composed primarily of quartz.
Sandstone sedimentary rock
Quartzite metamorphic rock