Miss Loulousis

Why are rocks

important to us?

Buildings, Roads,

Bridges, Concrete,

Extract minerals – like

iron (Fe) to make steel,

Toothpaste, Salt,

Sandpaper,

Decorations, Jewelry

BELLRINGER QUESTION:

Are all rocks made

of minerals?

Yes

Minerals Similarities Rocks

Inorganic Made of elements Can be organic

Naturally occurring Solid structure Can be man made

Made of element

compounds

Have crystals Made of mixture of

minerals

Can be formed from

solutions

Can be made of

lava/magma

Minerals vs. Rocks

Types of Rock

Rock – natural material that makes up the solid parts of Earth, made of one or more minerals

Based on the processes that form and change the rocks of Earth’s crust, geologists classify rocks into three major types by the way the rocks form.

Igneous rock Sedimentary rock Metamorphic rock

Magma Formation Magma forms when rock melts

Rock will Melt :

1.) When rock is heated must reach above melting point of minerals

Minerals melting point (temperature) is determined by its chemical composition

2.) When pressure changes A decrease in pressure lowers the melting temperatures of

materials ○ Occurs at mid-ocean ridges

An increase in pressure causes materials to melt at hot spots

3.) Water presence Water lowers the melting point of materials

Properties of Rocks

All rock has physical and chemical

properties that are determined by how

and where the rock is formed

The physical characteristics reflect the

chemical composition of the rock and

the minerals that make up the rock

Rate of rock weathering and breakage is

determined by chemical stability of the

minerals

Bowen’s reaction series

Bowen’s Reaction - minerals crystallize from cooling magma according to their chemical composition and melting point Fractional crystallization: different minerals form at

different times, changing the composition of the cooling magma

first crystals to melt in partial melting will be the first minerals to crystallize out when the magma begins to cool.

Therefore, mafic minerals will crystallize first, followed by felsic minerals.

Partial Melting

Partial melting occurs when only a

portion of a solid rock is melted.

A rock containing several different

minerals will go through partial melting

minerals with lowest melting points will

melt first changing the chemical

composition of the original rock.

Fractional Crystallization When magma cools, the cooling process is the

reverse of the process of partial melting.

Process is reverse of partial melting process

Minerals with higher freezing points crystallize first, removing chemicals from the magma

Crystals that form early are largest longest time to grow

Chemical composition of inner crystal differs from composition of outer parts

Due to magma’s composition change while crystal grows

Fractional Crystallization

Study the two image progressions

and summarize what is happening in

the fractional crystallization and

partial melting. Both processes are

related to magma. Tell your summary

to your diving buddy.

Rock Cycle Objectives

Summarize the steps of the rock cycle

Describe what provides the energy for

the rock cycle

Rock Cycle Song

Why is it important to have a basic

understanding of the rock cycle?

Rocks contain clues about the environment.

Helps us understand the formation of the

earth.

What is the law of conservation of

matter?

Law of conservation of matter states that matter

cannot be created or destroyed.

• The changes that take place in the rock cycle never destroy or create matter.

• The elements are just redistributed in other forms.

What is the rock cycle?

To show how rocks slowly change through

time, scientists have created a model called the

rock cycle.

It illustrates the processes that create and

change rocks.

Rock Cycle Any type of rock (igneous, metamorphic,

sedimentary) can be changed into another of

the three types.

rock cycle the series of processes in which

rock forms, changes from one form to another,

breaks down, and forms again by geological

processes

Geologic forces and processes cause rock to

change from one type to another.

What causes the rock cycle?

Energy

Processes driven by heat from Earth's

interior are responsible for forming both

igneous and metamorphic rocks.

Interior heat of the Earth powers the

rock cycle through a process called

convection

Convection Convection – the movement of matter due to

differences in density that are caused by

temperature variation; can result in the transfer of

energy as heat

What causes the rock cycle?

The energy from the sun

Weathering and the movement of

weathered materials are external

processes powered by energy from the

sun.

Weathering forms Sediment

Steps of the Rock Cycle

Step 1

Rock melts

forming magma

due to burial

Burial is when rock

gets pushed deep

into Earth’s crust

Step 2

Magma cools off forming igneous rock -involves crystallization and solidification

Crystallization – formation of minerals that create rock as magma cools (fractional crystallization)

Magma cools because of uplift Uplift is when rock is forced

toward Earth’s surface

Step 3

Igneous rock is

exposed to

weathering

creating sediment

Forms

Sediment

Weathering and Erosion When rock is exposed to air, water, or ice, it breaks

down chemically and physical (mechanical) into small pieces.

Physical involves water, wind, and temperature acting directly on the rock to break it down

Chemical involves acid rain and rust, due to reaction between molecules in atmosphere.

• This process, which breaks rocks into smaller pieces, is called weathering.

• The movement of weathered material is called erosion.

Weather vs. Erosion

Step 4

Sediment is transported by erosion

Sediment is transported to a new location by

wind, gravity, water, ice

Types of sediment includes: gravel, sand, silt,

mud, clay, soil

Step 5 Sediment is deposited (deposition)

the laying down of sediment carried by wind,

water, or ice

Step 6 Sediment goes through

compaction and cementation

Compaction – sediment squeezed together

Cementation – sediment is glued together from mineral precipitates

Lithification – is a term that refers to both compaction and cementation as one process

Step 7

Sedimentary rock

forms

Step 8 Sedimentary rock

goes through burial

and then is exposed to

extreme heat and/or

pressure that leads to

metamorphism

Step 9

Metamorphic rock

forms

It’s a Cycle! Sedimentary and

metamorphic rock can weather and erode to become sediment

Igneous and sedimentary rock can melt and form magma

Igneous rock can undergo heat and pressure to become metamorphic rock

Igneous Rock Objectives

Describe how igneous rock forms

Determine the ways igneous rock is

classified

Identify the families of igneous rock

Igneous rock Igneous: forms when magma, or molten

rock, cools and hardens.

Igneous rocks are classified by:

Where they were formed

Texture/What they are made from

(mineral composition)

1.)Where they Form Igneous rocks are classified according to

where magma or lava cools and hardens

(solidifies).

1. Intrusive igneous rock

cooling and solidification of magma

Beneath earth’s surface

2. Extrusive igneous rock

cooling and solidification of lava

at earth’s surface

Intrusive Igneous Rocks Intrusive igneous rocks can also

be called plutonic.

The word “plutonic” comes from Pluto, the name for the Greek god of the underworld.

They form when magma enters a pocket or chamber underground that is relatively cool and solidifies into crystals

it cools very slowly.

Rock Structures

Intrusive Igneous Rock Structures:

Intrusions: when magma enters other rock

masses underground

Batholiths, Laccoliths, Sills-magma, Dikes

Extrusive Igneous Rocks Also called volcanics

form when magma makes its

way to Earth's surface.

The molten rock erupts or flows

above the surface as lava, and

then cools quickly forming rock.

Are exposed to weathering

and erosion

Examples include basalt,

rhyolite, and andesite.

Rock Structures

Extrusive Igneous Rock Structures:

Extrusions- igneous rock masses that

form on Earth’s surface

Volcanoes, Volcanic necks, Lava flows, Lava

plateaus, Tuffs

2.)Texture/

What they are made of

The texture of igneous rock is determined

by the size of the mineral crystals in the

rock.

The size of the crystals is determined by

the cooling rate of the magma.

Rocks can have a mixture of large and

small mineral crystals called a porphyritic

texture.

Igneous Texture Categories

A. Coarse-Grained Igneous Rock Intrusive igneous rocks cool slowly, they

commonly have large mineral crystals.

Igneous rocks that are composed of large, well-developed mineral grains are described as having a coarse-grained texture.

B. Fine-Grained Igneous Rock Extrusive igneous rocks cool rapidly, they are

commonly composed of small mineral grains.

Igneous rocks that are composed of small crystals are described as having a fine-grained texture.

Intrusive Igneous

Rock Rock

have large, well formed crystals, large enough to see without a microscope.

The more slowly molten rock cools within the Earth, the larger the igneous rocks crystals will be.

Examples of intrusive igneous rocks are granite, gabbro and diorite

Granite Gabbro Diorite

Glassy Igneous Rocks or Volcanic Glass

Pumice (left)

Scoria (bottom left)

Obsidian (bottom)

Note gasses in the lava can

cause fine holes called

vesicles as seen in the pumice

and scoria.

•Glassy Igneous Rocks cool so rapidly, that atoms don’t have enough time to get together, bond and form crystals. To cool this quickly the rocks MUST be extrusive.

•Has small amount of gasses

Rock Families

What minerals are in rock is determined

by chemical composition of the

magma from which the rock forms

3 Families

Felsic

Mafic

Intermediate

2b.) Igneous Rock Composition

Families

1.) Felsic

rich in feldspars and silica

light in color

Examples: granite, rhyolite, obsidian, pumice

2.) Mafic

rich in magnesium and iron

dark in color

Examples: basalt and gabbro

Stop and Think

Applying Ideas An unidentified, light-

colored igneous rock is made up of

potassium feldspar and quartz. To what

family of igneous rocks does the rock

belong? Explain your answer.

Sedimentary Rock Objectives

Describe how sedimentary rock forms

Define sediment

Understand how sedimentary rock

provides clues about past history or

Earth’s environment and life forms

Garden of the Gods, Colorado

Sedimentary Rock

About 70-75% of all the rocks on Earth

are sedimentary rocks

Found at top 10miles of Earth’s crust

The composition of a sedimentary rock

depends upon the composition of the

sediments from which it formed.

What is sediment? Sediments are loose materials such as rock

fragments, minerals, and organic material that results from natural processes including the physical breakdown of rocks that have been moved by wind, water, ice, or gravity.

Sediments come from already-existing rocks that are weathered and eroded.

Sedimentary rock forms when sediments are pressed (compaction) and cemented together (when minerals form from solutions)

Stratification or Bedding

• Sedimentary rocks often form as layers of

stacked rocks(stratification).

• Stratified layers, or beds, vary in thickness and composition.

The older layers are on the bottom because they were deposited first.

Sometimes, forces within Earth overturn layers of rock, and the oldest are no longer on the bottom.

GRADED BEDDING

Medium-coarse sandy

lithounit (cross stratified)

Fine gravelly lithounit

Laminated layers of fine silt and clay Cross-stratified sst.

Paleo-flow from right to

left

Sedimentary Rock Formation

Sedimentary formation: form when rocks, mineral crystals, and organic matter have been broken into fragments, called sediments, and are compressed and cemented together. Sediment forms from weathering

Sediment is transported by wind, water, ice, or gravity to new location

Sediment is deposited

Sediment is compacted

Sediment is cemented

○ Compaction and cementation together can be called Lithification

Formation Processes

Compaction: volume (space) and

porosity of a sediment is decreased by

the weight of overlying sediments

The bottom sediment layers are undergoing

burial

Cementation: minerals precipitate from

water filling pore spaces between

sediment grains and bind (cement) the

sediment into rock

Classification

1. process of formation

2. composition of the rocks

three types of sedimentary rocks—chemical, organic, and clastic (dentritis)

classes subclassify based on the shape, size, and composition of the sediments that form the rocks

1.Chemical sedimentary Rock

Made from dissolved minerals in the water that formed into crystals (minerals precipitate from a solution or settle out of water) When water evaporates, the minerals

that were dissolved in the water are left behind.

Rocks that form through evaporation

are called evaporites Gypsum and halite.

2.Organic Sedimentary Rock

Rock that forms from the remains of plants or animals

Coal and some limestones are examples of organic rocks.

Organic limestones form when marine organisms, such as coral, clams, oysters, and plankton, remove the chemical components of the minerals calcite and aragonite from sea water.

The organisms make their shells from these minerals, and when the organisms die, their shells settle to the bottom of the ocean, accumulate, and are compacted to form limestone.

Formation of Limestone- an

organic sedimentary rock

3.Clastic Sedimentary Rock

Rock that forms when fragments of preexisting rocks are compacted or cemented together

Clastic sedimentary rocks are classified by the size and shape of the sediments they contain. A. Conglomerate: contains large, rounded pieces B. Breccia: contains large, angular pieces C. Sandstone: composed of sand-sized grains D. Shale: composed of clay-sized particles

Clastic Sediment Characteristics

Physical characteristics of sediments are determined by the way sediments were transported before deposited.

Both distance moved and method of movement determines the characteristics of sediment

Sediments are transported by four main agents: water, ice, wind, and the effects of gravity.

Erosion moves sediment particles and alters

the sediment shape

Sorting Sediment

When currents of air or water separate sediments according to size it’s called sorting.

If well-sorted, all of the grains are roughly the same size and shape

If poorly sorted consists of many different sized grains

The sorting of a sediment is the result of changes in the speed of the air or water that is moving the sediment. Faster-moving currents can carry larger particles

than slower-moving currents can.

Degree of roundness helps in knowing the

distance of transportation (method of

erosion)

•Angular clasts- short distance transport from the source

•Rounded clasts- long distance transport

Angularity of Sediment

Providing Environmental Clues

Grain Size - Power of Transport Medium

Grading - Often Due to Floods

Rounding

Sorting

Cross-bedding - Wind, Wave or Current Action

Ripple marks

Mud cracks

Color And Chemistry Red Beds - Often Terrestrial

Black Shale - Oxygen Poor, Often Deep Water

Evaporites – Arid Climates

Ripple marks

Mud cracks

Foot

prints

Biogenic structures

Contain Fossils

Fossils are the remains of organisms that are preserved in rock. As sediments pile up remains are buried Hard parts of remains may be preserved Even hard parts can dissolve, but

impression is left behind

Fossils

Salt Water - Corals, Echinoderms

Fresh Water - Insects, Amphibians

Terrestrial - Leaves, Land Animals

Metamorphic Rock Objectives

Describe the process of metamorphism.

Explain the difference between regional

and contact metamorphism.

Distinguish between foliated and

nonfoliated metamorphic rocks, and give

an example of each.

What is a metamorphic rock?

The term "metamorphic" means "to change form."

Any rock (igneous, sedimentary, or metamorphic) can become a metamorphic rock.

If rocks are buried deep in the Earth at high temperatures and pressures, they form new minerals and textures all without melting.

If melting occurs, magma is formed, starting the rock cycle all over again.

Metamorphic Rock

Metamorphic rock: forms when existing

rock is altered by changes in

temperature, pressure, or chemical

processes.

Metamorphism: process by which heat,

pressure, or chemical processes change

rock

Usually forms deep within Earth’s crust

During Metamorphism

heat, pressure, and hot fluids cause

some minerals to change into other

minerals.

Minerals may also change in size or

shape, or they may separate into

parallel bands that give the rock a

layered appearance.

Indicators of Condition

The type of rock that forms because of

metamorphism can indicate the

conditions under which the original rock

changed.

Conditions that Indicators suggest:

The composition of the rock being

metamorphosed

the amount and direction of pressure

presence or absence of certain fluids

2 Types of Metamorphism

1.contact metamorphism -a change in

the texture, structure, or chemical composition of a rock due to contact with magma or something hot

2.regional metamorphism a change in

the texture, structure, or chemical composition of a rock due mainly to pressure over a large area generally are a result of tectonic forces The rocks are “squished” Most metamorphic rocks form this way

Classification

Primarily classified by texture

Foliated rock

Nonfoliated rock

Chemical composition also helps

classify

The end!

already-

existing rocks

that are

weathered and

eroded

forms when sediments

are pressed and

cemented together, or

when minerals form

from solutions

Detrital Chemical Organic

Broken

fragments of

other rocks

weathering

erosion

compactio

n

cementatio

n

Dissolved minerals come

out of solution

limeston

e

Halite

Made of the

remains of

once living

things

chalk coal

To change

form Other rocks

are exposed to

high heat &

pressure

Foliated Non-Foliated

Flattened &

pushed into

parallel layers

slate

shale

gneiss

layers

Quartzite

marble

Anthracit

e coal

when

molten rock

cools and

solidifies

Magma

(below)

Lava

(above)

Intrusiv

e

magm

a

slowly

large

Granite,

gabbro, diorite

Extrusive

Lava

Slowly

Small or

not visible

Pumice,

obsidian,

basalt

Crystal size

Physical &

chemical

properties

granitic

andesiti

c

basaltic

Rich in Fe & Mg

poor in SiO2

Dense & dark

colored

Ocean floor &

Hawaii

High SiO2

Low Fe & Mg

Light colored,

less dense

On the

continents

b/t basaltic &

granitic

Grey,

medium

Pacific

Rim