chapter 4- rocks

Chapter 4Chapter 4

RocksRocks

The Rock CycleThe Rock CycleH.W. pg. 93 ques. 1-4H.W. pg. 93 ques. 1-4

A A rock rock is a mixture of is a mixture of minerals, rock minerals, rock fragments, volcanic fragments, volcanic glass, organic matter, glass, organic matter, and other natural and other natural materials.materials.

All rocks slowly change All rocks slowly change through time, and the through time, and the model that we use to model that we use to show this slow change show this slow change is called the is called the rock cyclerock cycle..

Discovery of the Rock CycleDiscovery of the Rock Cycle

James Hutton James Hutton recognized that rocks recognized that rocks undergo changes in undergo changes in 1788.1788.

Rock CycleRock Cycle As you can see the As you can see the

rock cycle shows 3 rock cycle shows 3 different types of rock: different types of rock:

1)1) Sedimentary Sedimentary 2)2) MetamorphicMetamorphic3)3) IgneousIgneous Also you see that all 3 Also you see that all 3

types can be formed in types can be formed in a number of ways.a number of ways.

This shows that any rock This shows that any rock can change into any of can change into any of the three major rock the three major rock types.types.

Rock CycleRock Cycle

Within the rock cycle rocks can be weathered Within the rock cycle rocks can be weathered to small rock and mineral grains.to small rock and mineral grains.

These grains could then be carried away by These grains could then be carried away by wind, water, or ice.wind, water, or ice.

This is what we callThis is what we call erosion erosion. This does not . This does not mean that the minerals and chemical elements mean that the minerals and chemical elements that make up rock are destroyed.that make up rock are destroyed.

The elements that make up rocks are not The elements that make up rocks are not destroyed they are just redistributed in other destroyed they are just redistributed in other forms.forms.

Igneous RockIgneous RockSection 4-2 H.W. pg. 97 questions 1-4Section 4-2 H.W. pg. 97 questions 1-4

Igneous rockIgneous rock forms when magma cools and forms when magma cools and hardens. hardens.

At certain within the Earth, the temperature At certain within the Earth, the temperature and pressure are just right for rocks to melt and pressure are just right for rocks to melt and form magma.and form magma.

Magma can be located at depths of 150km below Magma can be located at depths of 150km below the Earths surface. The temperature of this the Earths surface. The temperature of this magma can range between 650- 1,200magma can range between 650- 1,200ooC, C, depending on their chemical compositions and depending on their chemical compositions and pressures exerted on them.pressures exerted on them.

Igneous RockIgneous Rock The reason that these rocks melt is because of heat The reason that these rocks melt is because of heat

that is formed in the Earth’s interior.that is formed in the Earth’s interior. The heat comes from the decay of radioactive The heat comes from the decay of radioactive

material inside the Earth.material inside the Earth. Another source of this heat is actually heat that is left Another source of this heat is actually heat that is left

over from the formation of the planet, which was over from the formation of the planet, which was originally molten.originally molten.

Since magma is less dense than the surrounding rocks Since magma is less dense than the surrounding rocks it is forced upward toward the surface, like in a it is forced upward toward the surface, like in a volcano.volcano.

When magma reaches the Earths surface and flows When magma reaches the Earths surface and flows from volcanoes it is then called from volcanoes it is then called lavalava

Igneous RockIgneous Rock

So So magma magma is melted rock material composed of is melted rock material composed of common elements and fluids.common elements and fluids.

As magma cools atoms and compounds rearrange As magma cools atoms and compounds rearrange themselves into new crystals called themselves into new crystals called mineral grainsmineral grains. . And rocks form as these mineral grains grow And rocks form as these mineral grains grow together.together.

So rocks that form from magma below the Earths So rocks that form from magma below the Earths surface are called intrusive.surface are called intrusive.

These intrusive rocks stay underground until the land These intrusive rocks stay underground until the land above them are removed, either by erosion of by above them are removed, either by erosion of by physical means, and exposed to the surface.physical means, and exposed to the surface.


Intrusive rocksIntrusive rocks form form at deep depths of the at deep depths of the Earth. This causes the Earth. This causes the rocks to cool very rocks to cool very slowly. slowly.

Slowly cooled magma Slowly cooled magma will then produce very will then produce very large mineral grains that large mineral grains that we can see, within the we can see, within the intrusive rocks.intrusive rocks.


Extrusive igneousExtrusive igneous rocks rocks are formed by the cooling of are formed by the cooling of lava on the surface of the lava on the surface of the Earth. Earth.

When lava cools on the When lava cools on the surface it could be exposed surface it could be exposed to water and air. This to water and air. This causes the lava to cool causes the lava to cool quickly and does not allow quickly and does not allow large mineral grains to form.large mineral grains to form.

Therefore extrusive igneous Therefore extrusive igneous rock looks fine grained.rock looks fine grained.

Classifying Igneous RockClassifying Igneous Rock Besides intrusive and extrusively forming. The Besides intrusive and extrusively forming. The

type of igneous rock also depends on the type of igneous rock also depends on the magma from which it forms.magma from which it forms.

An igneous rock can form from basaltic, An igneous rock can form from basaltic, andesitic, or granitic, magma.andesitic, or granitic, magma.

The type of magma that rocks form from The type of magma that rocks form from determines important chemical and physical determines important chemical and physical properties of that rock.properties of that rock.

These include mineral composition, density, These include mineral composition, density, color, and melting point.color, and melting point.

Basaltic RockBasaltic Rock

These are dense dark colored igneous rock that These are dense dark colored igneous rock that form from magma that is rich in magnesium form from magma that is rich in magnesium and iron, and lack in silica. and iron, and lack in silica.

The iron and magnesium give these rocks the The iron and magnesium give these rocks the dark color.dark color.

This basaltic magma flows, largely from the This basaltic magma flows, largely from the mountains in Hawaii, which explains the black mountains in Hawaii, which explains the black color of Hawaii’s beaches.color of Hawaii’s beaches.

Basaltic RockBasaltic Rock

Granitic RockGranitic Rock

These are light colored igneous rock that have These are light colored igneous rock that have a lower density than basaltic rocks.a lower density than basaltic rocks.

Granitic magma has more silica and less iron Granitic magma has more silica and less iron and magnesium then basaltic magmaand magnesium then basaltic magma

Andesitic RockAndesitic Rock This type of magma has a This type of magma has a

chemical composition that chemical composition that is between basaltic and is between basaltic and granitic rock, when dealing granitic rock, when dealing with silica, magnesium and with silica, magnesium and iron.iron.

It has more iron and It has more iron and magnesium than granitic magnesium than granitic and less silica than granitic.and less silica than granitic.

Usually found in volcanoes Usually found in volcanoes along the Pacific Coast.along the Pacific Coast.

Metamorphic RockMetamorphic RockSection 4-3 H.W. pg 102 ques. 1-4Section 4-3 H.W. pg 102 ques. 1-4

Rocks that have changed because of changes in Rocks that have changed because of changes in temperature and pressure or the presence of hot, temperature and pressure or the presence of hot, watery fluids are called watery fluids are called Metamorphic Rock.Metamorphic Rock.

These changes can be in the form of the rock or in its These changes can be in the form of the rock or in its composition or both.composition or both.

Metamorphic rocks can form from igneous, Metamorphic rocks can form from igneous, sedimentary or from other metamorphic rocks.sedimentary or from other metamorphic rocks.

Ex: When you add heat and pressure to granite, the Ex: When you add heat and pressure to granite, the mineral grains are flattened and a metamorphic rock mineral grains are flattened and a metamorphic rock called gneiss is formed.called gneiss is formed.

Granite & GneissGranite & Gneiss

How heat and Pressure effect rocks.How heat and Pressure effect rocks.

Rocks beneath the Earth’s surface are under great Rocks beneath the Earth’s surface are under great pressure from the rock layers above them. Also, pressure from the rock layers above them. Also, temperature increases as the depth of the Earth temperature increases as the depth of the Earth increases. increases.

In some areas under the Earth’s surface the Temp and In some areas under the Earth’s surface the Temp and pressure is just right to allow rock to melt and magma pressure is just right to allow rock to melt and magma to form.to form.

In other areas, melting doesn’t occur but some In other areas, melting doesn’t occur but some mineral grains change by dissolving and mineral grains change by dissolving and recrystallizing, in the presence of liquids.recrystallizing, in the presence of liquids.


Depending on the amount of pressure and Depending on the amount of pressure and temperature applied, one type of rock can temperature applied, one type of rock can change into several different metamorphic change into several different metamorphic rocks, and every metamorphic rock can come rocks, and every metamorphic rock can come from several different parent rocks.from several different parent rocks.

Ex: The sedamentary rock shale will change Ex: The sedamentary rock shale will change into slate.into slate.

As you increase pressure slate turns into As you increase pressure slate turns into phyllite, then schist and then eventually gneiss.phyllite, then schist and then eventually gneiss.


Lastly, schist can also form basalt.Lastly, schist can also form basalt.

How Hot Fluids Effect RocksHow Hot Fluids Effect Rocks

Some fluids can move through rock. These Some fluids can move through rock. These fluids are usually hot and mostly water with fluids are usually hot and mostly water with dissolved elements, COdissolved elements, CO22 and compounds. and compounds.

When these fluids pass through rocks they When these fluids pass through rocks they react chemically with the rock to change its react chemically with the rock to change its composition. composition.

This occurs a lot when rock surrounds a hot This occurs a lot when rock surrounds a hot magma body and the fluids from the magma magma body and the fluids from the magma react with the surrounding rock.react with the surrounding rock.

How to Classify Metamorphic RockHow to Classify Metamorphic Rock

Metamorphic rocksMetamorphic rocks can form from igneous, can form from igneous, sedimentary, or other metamorphic rocks sedimentary, or other metamorphic rocks through their interaction with heat pressure through their interaction with heat pressure and hot fluids.and hot fluids.

We classify these rocks by their We classify these rocks by their composition composition and texture.and texture.

First is First is FoliatedFoliated rocks rocks. A metamorphic rock . A metamorphic rock is said to have foliated texture when mineral is said to have foliated texture when mineral grains in the rock line up in parallel layers.grains in the rock line up in parallel layers.

Metamorphic foliated rockMetamorphic foliated rock

Two examples of Two examples of foliated rocks are slate foliated rocks are slate and gneiss.and gneiss.

Metamorphic foliated rockMetamorphic foliated rock Slate forms from a Sedimentary rock called Slate forms from a Sedimentary rock called

shale.shale. The minerals in shale arrange into layers when The minerals in shale arrange into layers when

they are exposed to heat and pressure. This they are exposed to heat and pressure. This allows slate to separate easily along these allows slate to separate easily along these foliation layers.foliation layers.

The pressure is so great during this change that The pressure is so great during this change that the minerals in slate get pressed so tightly that the minerals in slate get pressed so tightly that water cannot pass through it, making it water cannot pass through it, making it virtually water tight. virtually water tight.

This unique property makes slate the optimal This unique property makes slate the optimal rock for the use of patios and paving around rock for the use of patios and paving around pools.pools.

Metamorphic foliated rockMetamorphic foliated rock Gneiss, another foliated Gneiss, another foliated

rock, forms when granite is rock, forms when granite is changed. The foliation in changed. The foliation in gneiss shows up as gneiss shows up as alternating light and dark alternating light and dark bands.bands.

This is because during the This is because during the transformation from granite transformation from granite to gneiss the light atoms of to gneiss the light atoms of quartz and feldspar are quartz and feldspar are separated from the darker separated from the darker atoms of mica.atoms of mica.

Non Foliated metamorphic RockNon Foliated metamorphic Rock

In In non foliated metamorphic rocknon foliated metamorphic rock layering does not layering does not occur. The mineral grains grow and rearrange but do occur. The mineral grains grow and rearrange but do not form layers.not form layers.

This produces a non foliated texture. This produces a non foliated texture. An example is when sandstone, a sedimentary rock An example is when sandstone, a sedimentary rock

composed of mostly quartz grains, is exposed to heat composed of mostly quartz grains, is exposed to heat and pressure.and pressure.

The quartz grains here grow in size and become The quartz grains here grow in size and become interlocking like a jigsaw puzzle.interlocking like a jigsaw puzzle.

The resulting rock is called quartzite.The resulting rock is called quartzite.


Another example of non foliated metamorphic rock is Another example of non foliated metamorphic rock is marble.marble.

Marble forms from the sedimentary rock limestone, Marble forms from the sedimentary rock limestone, which is rich with the mineral calcite.which is rich with the mineral calcite.

Marble that is a different color than white is due to Marble that is a different color than white is due to the presence of other minerals besides calcite that is the presence of other minerals besides calcite that is present.present.

Hornblende gives marble a black or greenish colorHornblende gives marble a black or greenish color And hematite gives marble a reddish color.And hematite gives marble a reddish color.

Sedimentary RockSedimentary RockSection 4-4 H.W. Pg 109 ques. 1-5Section 4-4 H.W. Pg 109 ques. 1-5

Igneous rocks are the most common rocks on Earth. Igneous rocks are the most common rocks on Earth. However we don’t see them a lot because they are However we don’t see them a lot because they are mostly beneath the Earths surface.mostly beneath the Earths surface.

75% of the rocks that are exposed at the surface are 75% of the rocks that are exposed at the surface are sedimentary rockssedimentary rocks..

Sediments are loose materials such as rock fragments, Sediments are loose materials such as rock fragments, mineral grains, and bits and pieces of shell that have mineral grains, and bits and pieces of shell that have been moved by wind, water, or icebeen moved by wind, water, or ice

These sediments come from already existing rock that These sediments come from already existing rock that were weathered or eroded. were weathered or eroded.

Sedimentary rock forms when these sediments are Sedimentary rock forms when these sediments are pressed together by great pressure, or when minerals pressed together by great pressure, or when minerals form in solution.form in solution.

Stacked RocksStacked Rocks

Sedimentary rocks often form in layers. The Sedimentary rocks often form in layers. The older layers are on the bottom layers because older layers are on the bottom layers because they were deposited first.they were deposited first.

Sometimes these layers can be disturbed by Sometimes these layers can be disturbed by the forces of nature. This will sometimes the forces of nature. This will sometimes overturn the layered sedimentary rock and the overturn the layered sedimentary rock and the oldest will no longer be on the bottom.oldest will no longer be on the bottom.

Classifying Sedimentary Rocks Classifying Sedimentary Rocks The sediments that form sedimentary rocks The sediments that form sedimentary rocks

can be almost anything that is found in nature.can be almost anything that is found in nature. Sediments can come from weathered or eroded Sediments can come from weathered or eroded

igneous, metamorphic, sedimentary rocks.igneous, metamorphic, sedimentary rocks. And the composition of sedimentary rocks And the composition of sedimentary rocks

depends on the composition of the sediments depends on the composition of the sediments that formed that rock.that formed that rock.

Like the other rocks we spoke of, sedimentary Like the other rocks we spoke of, sedimentary rocks are classified by their composition and rocks are classified by their composition and are classified as: are classified as: detrital, chemical, or detrital, chemical, or organic.organic.

Detrital Sedimentary RockDetrital Sedimentary Rock Detrital Detrital means “to wear away” in Latin, and are means “to wear away” in Latin, and are

made from broken fragments of other rocks.made from broken fragments of other rocks. These broken fragments are compacted together by These broken fragments are compacted together by

pressure and cemented together to form solid rock.pressure and cemented together to form solid rock. These broken fragments of rocks can form in a These broken fragments of rocks can form in a

number of ways. One way is by weathering and number of ways. One way is by weathering and erosion.erosion.

When rock is exposed to air, water, or ice it is When rock is exposed to air, water, or ice it is unstable and breaks down chemically and unstable and breaks down chemically and mechanically. mechanically.

This process, which breaks down rocks into smaller This process, which breaks down rocks into smaller pieces, is called pieces, is called weathering weathering and the actual movement and the actual movement of these smaller pieces is called of these smaller pieces is called erosionerosion..

Detrital Sedimentary RockDetrital Sedimentary RockH.W. pg 114 questions 1-10H.W. pg 114 questions 1-10

Compaction is also a part of sedimentary rock Compaction is also a part of sedimentary rock formation.formation.

Erosion moves sediments to a new location, Erosion moves sediments to a new location, where they will be deposited. Now layer upon where they will be deposited. Now layer upon layer of sediment builds up.layer of sediment builds up.

Pressure from all of the built up layers pushes Pressure from all of the built up layers pushes down on the lower layers causing the small down on the lower layers causing the small fragments to form solid rock. This process is fragments to form solid rock. This process is called called compaction.compaction.

Detrital Sedimentary RockDetrital Sedimentary Rock If the fragments are large, like the size of pebbles or If the fragments are large, like the size of pebbles or

sand, pressure alone can’t make the solid rock form.sand, pressure alone can’t make the solid rock form. When water moves through soil and rock, it picks up When water moves through soil and rock, it picks up

materials released from minerals during weathering.materials released from minerals during weathering. This dissolved mineral solution then moves between This dissolved mineral solution then moves between

the large loose rock sediments and cements them the large loose rock sediments and cements them together.together.

CementationCementation, usually occurs when minerals such as , usually occurs when minerals such as quartz, calcite, and hematite are deposited between quartz, calcite, and hematite are deposited between sediments.sediments.

These minerals act as natural cement and hold These minerals act as natural cement and hold sediments together like glue, and forming detrital sediments together like glue, and forming detrital sedimentary rock. sedimentary rock.

Detrital Sedimentary RockDetrital Sedimentary Rock

Detrital rocksDetrital rocks have a granular texture, kind of like have a granular texture, kind of like granulated sugar. And they are named according to granulated sugar. And they are named according to the shapes and sizes of the sediments that form them.the shapes and sizes of the sediments that form them.

Ex: The Sedimentary rocks, conglomerate and breccia Ex: The Sedimentary rocks, conglomerate and breccia both form from large sediments.both form from large sediments.

If the sediments are rounded, the rock is called If the sediments are rounded, the rock is called conglomerate. If the sediments are sharp then the conglomerate. If the sediments are sharp then the rock is called breccia.rock is called breccia.

The roundness of sediment particles depends on how The roundness of sediment particles depends on how far they have been moved by wind or water.far they have been moved by wind or water.

ConglomerateConglomerate

Materials Found in Sedimentary Materials Found in Sedimentary RocksRocks

H.W. pg 114 ques. 11-20H.W. pg 114 ques. 11-20 The gravel sized sediments in conglomerate and The gravel sized sediments in conglomerate and

breccia are often composed of quartz and feldspar. breccia are often composed of quartz and feldspar. These 2 minerals (quartz, feldspar) can be found in These 2 minerals (quartz, feldspar) can be found in

gneiss, granite, and limestone.gneiss, granite, and limestone. The natural cement that holds the sediments in The natural cement that holds the sediments in

sedimentary rock together are usually quartz and sedimentary rock together are usually quartz and calcite.calcite.

Sandstone if formed from smaller particles than Sandstone if formed from smaller particles than conglomerate and breccia, but they are made from conglomerate and breccia, but they are made from types of quartz and feldspar that are more resistant to types of quartz and feldspar that are more resistant to weathering.weathering.

Chemical Sedimentary RockChemical Sedimentary Rock This is the second type of This is the second type of

sedimentary rock, and it is sedimentary rock, and it is formed when dissolved formed when dissolved minerals come out of minerals come out of solution.solution.

Like our saltwater example, Like our saltwater example, mineral deposits can form mineral deposits can form sediments and rocks when sediments and rocks when sea or lake water sea or lake water evaporates.evaporates.

An example of chemical An example of chemical sedimentary rock is sedimentary rock is gypsum. gypsum.

Chemical sedimentary Chemical sedimentary rocks do not form from rocks do not form from pieces of preexisting rocks.pieces of preexisting rocks.

Chemical Sedimentary RockChemical Sedimentary Rock Limestone- this is composed Limestone- this is composed

mostly of Calcium Carbonate mostly of Calcium Carbonate CaCOCaCO33. And forms when . And forms when

calcium carbonate comes out of calcium carbonate comes out of solution as calcite and its many solution as calcite and its many crystals grow together to form crystals grow together to form limestone.limestone.

Limestone is 50% calcite and is Limestone is 50% calcite and is usually deposited on the bottom usually deposited on the bottom of lakes or shallow seas.of lakes or shallow seas.

A lot of the United States A lot of the United States bedrock is made of limestone. bedrock is made of limestone. And that is due to the fact that And that is due to the fact that seas covered much of the seas covered much of the country for millions of years.country for millions of years.

Chemical Sedimentary RockChemical Sedimentary Rock Rock Salt- When water is Rock Salt- When water is

very rich in dissolved salt , very rich in dissolved salt , it often deposits the mineral it often deposits the mineral halite.halite.

Halite deposits can range in Halite deposits can range in thickness from a few meters thickness from a few meters to more than 400m.to more than 400m.

Companies mine these Companies mine these deposits because it is used deposits because it is used as a very important as a very important resource.resource.

Its used in the making of Its used in the making of glass, paper, soap, and some glass, paper, soap, and some dairy products. Also, its dairy products. Also, its processed and used as table processed and used as table salt.salt.

Organic Sedimentary RockOrganic Sedimentary Rock Rocks that are made of the remains of once-Rocks that are made of the remains of once-

living things are called living things are called organic sedimentary organic sedimentary rocks.rocks.

The most common of this type of this rock The most common of this type of this rock would be fossil rich limestone.would be fossil rich limestone.

The difference between regular limestone and The difference between regular limestone and fossil rich limestone is that fossil rich fossil rich limestone is that fossil rich limestone contains some remnant of once limestone contains some remnant of once living ocean organisms, instead of just calcite.living ocean organisms, instead of just calcite.

Ex: muscles, clams, coral, snails. They have Ex: muscles, clams, coral, snails. They have shells made from calcium carbonate. When shells made from calcium carbonate. When these shells cement together they form fossil these shells cement together they form fossil rich limestone.rich limestone.

Fossil rich limestoneFossil rich limestone

If a rock is completely If a rock is completely made of shell fragments made of shell fragments that you can see, the that you can see, the rock is called coquina. rock is called coquina.

Organic sedimentary rockOrganic sedimentary rock Chalk- is another organic sedimentary rock Chalk- is another organic sedimentary rock

that is made of microscopic shells.that is made of microscopic shells. When you write with naturally occurring chalk When you write with naturally occurring chalk

you a crushing and smearing the calcite-shells you a crushing and smearing the calcite-shells remains of a once living organism.remains of a once living organism.

Coal- is another useful organic sedimentary Coal- is another useful organic sedimentary rock. It forms when dead plants are buried rock. It forms when dead plants are buried under other sediments in swamps.under other sediments in swamps.

Microorganisms feed off of and change these Microorganisms feed off of and change these plant materials, and they are compacted over plant materials, and they are compacted over millions of years to eventually form coal.millions of years to eventually form coal.

H.W. pg 116 questions 1-17H.W. pg 116 questions 1-17Test on chapter 3 in one Test on chapter 3 in one

week!!!!!!!!!!!!!week!!!!!!!!!!!!!

chapter 4- rocks

Business

rock cycle rocks

granitic rock

rock material

andesitic rock

rock fragments

small rock

calledmetamorphic rock

rock layers