ROCKS

Classifying rocks Rocks are made up of two or more

minerals. About 20 minerals make up most of the

earth’s rocks. When studying rocks, geologists

observe the mineral composition, color and texture of the rock.

This rock contains

three minerals.

Rock color A rock’s color can indicate the rock’s

mineral composition. Certain minerals are light in color while other minerals are dark in color.

Granites are usually light Basalts are usually dark

Rock Texture Texture

involves 3 components:

1) Grain size2) Grain shape3) Grain pattern

Fine grained Coarse grained

Rounded grains Jagged grains

Nonbanded banded

Three Groups of Rocks Igneous – form from

the cooling of magma or lava

Sedimentary – form when particles of rocks are pressed & cemented together

Metamorphic – when existing rocks are changed by heat, pressure, or chemical reactions.

This is NOT the correct answer!

How do Igneous Rocks Form?First rocks must melt into Lava/Magma!

Increase in Temperature – rocks melt Decrease in Pressure – hot rock can

remain solid if it is under high pressure deep within the Earth. When hot rock rises to the surface, the pressure goes down and rocks can melt.

Addition of Fluids – when fluids, such as water, mix with rock, the melting temperature of the rock decreases and the rock can melt.

IGNEOUS ROCKS Igneous rocks are

classified according to their origin, texture, and mineral composition.

ORIGIN:Extrusive – formed from

lava that has erupted (outside-”exit”).

Intrusive – formed when magma hardens under the earth’s surface (inside).

Basalt

Granite

Most commonIntrusive rock

Most common Extrusive rock

Types of Magma/Lava Different

compositions of lava or magma determine the types of igneous rocks formed.

Magma that contains sodium, potassium, and aluminum will form light colored called Felsic rocks such as granite.

If the magma is high in iron, magnesium and calcium will form dark colored rocks called Mafic such as basalt.

Extrusive vs. Intrusive Extrusive Rapid cooling Small crystal size;

fine grained Can have a glassy

texture

Intrusive Slow cooling Larger crystals;

coarse grained

Uses of Igneous Rock Igneous rock has

been used for thousands of years for buildings and statues. Granite is the most widely used igneous rock.

Borax Experiment Final Observations

Trace two petri dish circles into your notebook.

Inside one circle draw what you see with the unaided eye.

Inside the second circle, draw what you see with the magnifying glass.

Describe the process we used to create these crystals.

How do these crystals compare with igneous rock creation?

SEDIMENTARY ROCKS Sediments are small bits & pieces of

rocks, shells, sand, bones, or parts of plants.

Can you see the shells?

This is called silt

Sediments can be carriedaway by water to be deposited somewhere else.

From Sediment to Rock

• Particles are carried away by wind or water

• Particles are deposited

• DEPOSITION

Erosion

• Particles are squeezed together by pressure

Compaction

• Particles are glued together as mineral solutions hardenCementatio

n

Steps 1 & 2

Step 3

Step 4

Sedimentary rock formation

Formation under waterThe most noticeable feature of sedimentary rocks

are layers called strata. Stratification is the process in which sedimentary rocks are arranged

in layers.

Three Major Types of Sedimentary Rocks

Clastic•Rock formed by rock fragments that are cemented together;

sometimes visible large fragments, sometimes small, fine fragments

•Two common types are conglomerates, sandstone, breccias

Organic •Rocks formed by the remains of plants/animals that are cemented together.

•Two common types are coal and limestone

Chemical

•Formed when minerals dissolved in water are crystallized when the water evaporates away

•Calcite and Halite can form this way.

CLASTIC SEDIMENTARY ROCKS

These are conglomerates

This is a breccia.Notice the jaggededges.

This is sandstone.The individual fragmentsAre not easily seen.

This is shale, splitseasily into thin sheets.

ORGANIC SEDIMENTARY ROCKS

Limestone – forms in the ocean from shells, corals, calcite skeletons being compacted

Coquina- a special type of limestoneIn which shells can be easily seen

Fossils are found mainlyIn sedimentary rocks.

Coal is one of the most important organic rocks.

The formation of COAL

Coal is made from once living plants & animals.

Limestone is formed from corals, and other sea animals.

These shells and animal remains get crushed and cemented together over time to form limestone.

Limestone formations

These are called pancake

rocks!

These are

located in

Vietnam.

More limestone formations

Many cave formations are

made of limestone.

Here are some hot springs in

limestone.

Chemical Sedimentary Rocks Gypsum and Halite are two of the most

common chemical sedimentary rocks. They can also be minerals! They formed by dissolved chemicals

crystallizing as water evaporates. For this reason they are sometimes

called EVAPORITES.

This is GYPSUM in a cave in New Mexico. Gypsum is Calcium Sulfate. It is usedIn plaster of paris, drywall, and Cement.

This is a chemical form of limestone. It is called TUFA.

Coral Reefs are responsible for much of the limestone on earth. Coral is an animal much like a sea

anenome. They have tentacles and eat plankton. To protect their soft bodies they secrete a hard substance called CALCITE. When they die, these calcite shells remain.

Ancient Coral Reef vs. Living Coral Reef

Great Barrier ReefAustralia

Sedimentary Rock Experiment

1. What are some similarities between the three samples?

2. What are some of the differences?3. Are the grain sizes in the samples

the same?4. How would you describe the shapes

of the grains you observe?

Sedimentary Rock Experiment

Closure1. Draw a cycle, cartoon or some

animation of your understanding of the formation of sedimentary rocks. Color your drawing if time permits.

2. Draw and label the layering of the sediments after they settle.

METAMORPHIC ROCKS Heat (temps between 150-1000 degrees

celcuis) & pressure deep in the earth can change any rock into a metamorphic rock. They can form from igneous, sedimentary and other metamorphic rocks.

Extremely high temps and pressures deep in the earth can actually change a rocks mineral composition.

Stories in Stone - Metamorphic

1. Form 20 red and 20 blue small marble sized spheres.

2. Form the yellow clay into a pancake about the size of your hand.

3. Break the green in half and form 2 pancakes.

Metamorphic Rock Experiment1. Observe and describe the layering in the

piece of the model you just cut off.2. How was your fist similar to what

happens when metamorphic rock is formed?

3. How was your fist different?4. How is the piece of the model you

“metamorphized” different from the piece you cut of that wasn’t “metamorphized”?

5. Describe the metamorphic layers.6. How do metamorphic rocks differ from

igneous or sedimentary rocks?

Two Types (textures) of Metamorphic Rocks

FOLIATEDRocks grains are arranged in parallel bands or layersCommon examples:Slate, gneiss, schist

NONFOLIATEDGrains are arranged randomly.Common examples:Marble, quartzite

Non-foliated Metamorphic Rocks

With pressure, granite becomes gneiss (foliated rock). Igneous rock is changed to a metamorphic rock.

Increasing pressure causes greater foliation

Increasing Pressure

SHALE SLATE SCHIST GNEISS

SEDIMENTARY

ROCK

Index Minerals Some minerals, such as quartz, can form

at many different temperatures. Other minerals, such as garnet, form only

at certain temperatures and pressures. Therefore, rocks that contain minerals

like garnet probably also formed at those temperatures and pressures and are called index minerals.

Index minerals and can indicate the temperature and pressure or depth at which a rock formed.

Two ways rock can go through Metamorphism

Regional metamorphism – high pressures and temperatures cause the rock in a large area to change. It can happen where rock is buried deep below the surface or at convergent boundaries.

Two ways rock can go through Metamorphism

1. Contact metamorphism – rock is heated by nearby magma. The nearer the rock is to the magma, the more changes occur.

USES OF METAMORPHIC ROCK

World’s Largest Marble QuarryTate, GA

Uses of SLATE

Rock Cycle Simulation1. Where did you spend the most time?2. Why is the rock cycle called a cycle?3. Why did everyone not follow the

same path?4. How does a rock become Igneous?

Sedimentary? Metamorphic?5. Where are rocks being born and

transformed today?

Rock Cycle Simulation 5. Where are rocks being born and

transformed today?6. How much of the rock cycle can be

observed? How much must be inferred?7. How are people affected by movement

of Earth material through the rock cycle?

8. If each step of our rock cycle game was 200,000 years, what was the time period represented in the game?

The Rock CycleIt is a series of processesin the earth’s crust, mantleand on the earth’s surfacethat SLOWLY change rocks from one kind toanother.Click on the link for a Rock

Cycle animation