Download Chapters 5 and 6

Chapters 5 and 6
Igneous, Sedimentary, and Metamorphic Rocks..
Question of the Day.
How are Igneous Rocks
formed?
Learning Targets
 1). You will be able to explain how igneous rocks are formed.
 2). You will understand how scientists classify igneous rocks; the difference
between intrusive and extrusive igneous rocks.
Cartoon
Chapter 5: Igneous Rocks
WHAT IS AN IGNEOUS ROCK?
 Igneous Rocks: rocks that are
formed from the crystallization of
magma or lava
 Magma = the molten rock found
within the Earth’s crust.
 Lava = the molten rock that flows
out onto Earth’s surface.
Question of the Day.
How can Igneous Rocks look
so different from each other?
Learning Targets
 1). You will understand how scientists classify igneous rocks.
 2). You will practice classifying igneous rocks based upon composition as
well as crystal size.
Cartoon
Group Challenge
 In your lab groups, I want you to separate these igneous rocks into 2 groups.
 Take some time and carefully look at each rock for subtle similarities and
differences.
 Question For Thought…
 1). What different types of magma may have formed these rocks?
Igneous Rocks
TYPES OF IGNEOUS ROCKS
 Extrusive Rocks = fine-grained
igneous rocks that cool quickly on
Earth’s surface.
 Intrusive Rocks = course-grained
igneous rocks that cool slowly
beneath Earth’s surface.
 Granite is the most common intrusive
igneous rock
WHAT’S THE DIFFERENCE
Igneous Rocks
COMPOSITION OF MAGMA
 Magma is often a slushy mix of
molten rock, gases, and mineral
crystals
 The elements found in magma are
the same major elements found in
Earth’s crust.
 Silica (SiO2) is the most abundant
and has the greatest effect on
magma characteristics
 There are 3 types of Magma
1.
Basaltic
2.
Rhyolitic
3.
Andesitic
Question of the Day.
How do the liquids we tested
in lab resemble the different
types of magma?
Three Types of Magma
1. Basaltic = 45-55% Silica (SiO2)
a. high in Fe, Mg, Ca, low in K, Na
b. Low Viscosity = Easier for this type of magma to flow
c. Gas can more easily escape = Less Violent Eruptions
2. Andesitic = 55-65% Silica (SiO2)
a. intermediate. in Fe, Mg, Ca, Na, K
b. Intermediate Viscosity = Intermediate Rate of magma flow
3. Rhyolitic magma = 65-75% Silica (SiO2)
a. low in Fe, Mg, Ca, high in K, Na
b. High Viscosity = More Difficult for this type of magma to flow.
c. Gas has a very hard time escaping = Very Violent Eruptions

Types of Magma
Basaltic Magma
 Made from minerals including olivine, pyroxene, and plagioclase.
 Basalt is erupted at temperatures between 1100 to 1250° C.
 Basalt is the most common rock type in the Earth's crust (the outer 10 to 50 km).
In fact, most of the ocean floor is made of basalt.
 Huge outpourings of lava called "flood basalts" are found on many continents.
The Columbia River basalts, erupted 15 to 17 million years ago, cover most of
southeastern Washington and regions of adjacent Oregon and Idaho.
 Basaltic magma is commonly produced by direct melting of the Earth's mantle,
the region of the Earth below the outer crust. On continents, the mantle begins
at depths of 30 to 50 km.
Types of Magma
Andesitic Magma

Andesite is a gray to black volcanic rock

Andesites contain the minerals pyroxene and sometimes olivine.

Andesite magma commonly erupts from strato-volcanoes as thick lava flows, some
reaching several km in length.

Andesite magma can also generate strong explosive eruptions to form pyroclastic flows
and surges and enormous eruption columns.

Andesites erupt at temperatures between 900 and 1100° C.

The word andesite is derived from the Andes Mountains, located along the western edge
of South America, where andesite rock is common.

Andesite was the main rock type erupted during the great Krakatau eruption of 1883.

Types of Magma
Rhyolitic Magma
 Low temperature eruptions (750–850ºC)
 High gas content
 Very explosive
 Erupt from Caldera Volcanoes
Igneous Rocks
ORIGINS OF MAGMA
 In lab, most rocks must be heated
to temps around 800 – 1200
degrees Celsius before they melt
 In nature these temps are found in the
upper mantle and lower crust
PARTIAL MELTING
 Not all minerals have the same
melting points

Because of this not all parts of the rock
melt at the same time
 This explains why magma is often a
slushy mix of crystals and molten rock
 Partial Melting = when some
minerals melt at low temps and
other minerals remain solid
Igneous Rocks
CLASSIFYING IGNEOUS ROCKS
 Mineral Composition
 There are 3 main groups of igneous
rocks
1). Felsic

Light-colored

Have high silica contents
2). Mafic

Dark-colored

Lower silica contents and are rich in iron
and magnesium
3). Intermediate
UNIQUE FEATURES
 Porphyritic Texture = large, well
formed crystals surrounded by
finer-grained crystals.
 Indicates a complex cooling history
where a slowly cooling magma
suddenly began cooling rapidly
Group Challenge
 In your lab groups, I want you to separate these igneous rocks into 3 groups
based upon color.
 Group 1: Light Colored Rocks = Felsic
 Group 2: Medium Color = Intermediate
 Group 3: Dark Colored Rocks = Mafic
Question of the Day.
What are the 2 ways
scientists tell igneous rocks
apart?
Learning Targets
 1). You will practice classifying igneous rocks based upon composition as
well as crystal size.
 You will understand some uses of igneous rocks.
Group Challenge
 In your lab groups, I want you to visit each station around the room which
will give you some practice identifying characteristics of igneous rocks.
 You will have approximately 3 minutes at each station to answer the
question inside the box.
 EVERYONE from your group must write down the answer.
Let’s See What You Remember
1). Compare and Contrast:
Extrusive and Intrusive Igneous
Rocks.
2). Explain how the color of
igneous rocks can help us
determine what they are made of.
Learning Targets
 1). You will understand some uses of igneous rocks.
 2). You will understand how sedimentary rocks are formed.
Igneous Rocks
ORIGINS OF MAGMA
 In lab, most rocks must be heated
to temps around 800 – 1200
degrees Celsius before they melt
 In nature these temps are found in the
upper mantle and lower crust
PARTIAL MELTING
 Not all minerals have the same
melting points

Because of this not all parts of the rock
melt at the same time
 This explains why magma is often a
slushy mix of crystals and molten rock
 Partial Melting = when some
minerals melt at low temps and
other minerals remain solid
Igneous Rocks
 Igneous Rocks as Resources
 They are useful for building materials because of their strength and resistance to
weathering (granite)
Memory Clue
 To show your understanding of igneous rocks and there characteristics,
complete memory clues for vocab 1-8.
 Cross out ultra-mafic
Cartoon
Sedimentary Rocks
FORMATION OF SEDIMENTARY ROCKS
 Sediments = pieces of solid material
that have been deposited on Earth’s
surface by wind, water, ice, gravity, or
chemical precipitation
 When these sediments get
“cemented” together, they form
sedimentary rocks

Occurs from weathering and erosion
 Classified into two groups based on
how they form.
1.
Clastic
2.
Chemical
Clastic Sedimentary Rocks
Clastic sedimentary rock = formed as
bits of weathered rock become
cemented together.



All kinds of rock are subject to weathering
Many different minerals can make up this
group of rocks.
Clays and quartz are the most common.
Classification of Clastic sedimentary
rocks is done according to the size of
the sediments that make up the rock.

The table contains the major groups of
Clastic sedimentary rocks with their
characteristics
Clastic Sedimentary Rocks
Name of Rock
Sediment Type
Texture
Conglomerate
gravel - rounded
fragments
course
over 2 mm
Breccia
gravel - angular
fragments
course
over 2 mm
Sandstone
sand
medium
1/16 to 2mm
Siltstone
mud
fine
1/256 to 1/16 mm
Shale
mud
very fine
less than 1/256 mm
Chemical Sedimentary Rocks
Chemical Sedimentary Rocks
 Chemical sedimentary rocks = form
from dissolved minerals that are
precipitated or separated from water.


This happens most frequently when water
evaporates leaving the minerals behind.
You can see this process taking place in
your own home. The white deposits that
form around the faucets in your bathroom
or kitchen are from minerals left behind as
water evaporates.
 The table contains the major groups
of chemical sedimentary rocks with
some of their characteristics:
Name of Rock
Composition
Texture
Crystalline
Limestone
Calcite - CaCo3
corse to fine Crystalline
Fossiliferous
Limestone
Calcite - CaCo3
visible fragments of shells
Chalk
Calcite - CaCo3
microscopic shells and clay
Chert
Quartz - SiO2
very fine crystalline
Gypsum
Gypsum - CaSO42H2O
fine to course crystalline
Rock Salt
Halite - NaCl
fine to course crystalline
Bituinous Coal
Organic Matter
fine
Sedimentary Rocks


Weathering = the process where the
Earth’s crust is continually getting worn
away by a set of physical and chemical
processes.

Chemical Weathering = when minerals in a
rock are dissolved or otherwise chemically
changed.

Physical Weathering = when the minerals
remain chemically unchanged – they just
break off
Erosion = The removal and movement of
surface materials from one spot to
another.
 http://ees.as.uky.edu/educationalmaterials
Types of Mechanical Weathering
1. Frost Wedging
 Water expands when it freezes - an ice cube is about 9% larger than the volume
of the water before it froze.

The expansion of water when it freezes is one of the most effective processes of mechanical
weathering.
 *Wedging: A fracture (crack) in a rock provides ice with a lot of leverage. When
the temperature drops below freezing, the ice exerts force outward on the rock
as it grows.
 *Freeze/thaw: Each freezing may wedge the fracture open just a tiny amount,
so it takes many cycles of freezing and thawing, with water filling the fracture
each time, to break off a piece of rock.
 Most effective in cold, wet climates in which there are many opportunities for
freeze/thaw cycles with water present.

High altitudes (mountain ranges) are particularly prone to such temperature changes
Types of Mechanical Weathering
2. Exfoliation = peeling of layers
 describes sheets of rock peeling off a
bare rock face
 *Rock type: Exfoliation is most
common on rock faces of intrusive
igneous rocks such as granite.
3. Thermal Expansion and
Contraction

Crystals of rock also expand and contract as
they heat and cool


Can loosen grains of a rock enough to cause
weathering.
Most Common in Desert Regions

Temperature may rise and fall as much as 50 deg
Celsius (90 deg Fahrenheit) from day to night

**Fires: Even more pronounced is the fracturing
of rocks that occurs during exposure to forest fires.
Under these conditions, temperatures may rise
briefly by 200 deg C or more, and exposed rock will
expand enough to spall many small pieces off the
rock face. Similarly, campfires can cause enough
thermal expansion for rocks in a campfire ring to
crack loudly, startling any nearby marshmallow
roasters.
Types of Mechanical Weathering
4. Crystal Growth
 Salt crystals growing in rock fractures or in the small pores between
sedimentary grains can cause rocks to loosen up and break. Usually this
happens when salty water gets into the rocks and later evaporation of the
water produces crystallization in the pore or fracture space.
 by pushing the grains apart.
 *Practical Application: For readers who live in cold, snowy climates: be
careful how much salt you use to melt ice on your sidewalks, stairways, and
driveways. Salt crystal growth is one of the biggest causes of road potholes
in the northern United States, and the outdoor stairways leading into many
public buildings are in terrible disrepair due to damage from salt
crystallization.
Mechanical Weathering
5. Tree Roots
 Tree root tips are tiny and penetrate
easily into fine fractures of rocks.
 As the roots grow in diameter, they put
stress on the rock that can cause the
fractures to expand..
 *Where: In terms of climate, this
weathering mechanism can occur
anywhere that sufficient precipitation
exists to sustain tree growth and rocks
are exposed near the surface. Tree root
wedging can also occur invisibly,
beneath a thin layer of soil.
Mechanical Weathering
6. Abrasion
 Rocks breaking or wearing down by
the direct actions of other rocks.
 The rock falling down the cliff as it
tumbles down and breaks into
pieces.
 *Where: Abrasion typically is
strongest in the harshest
environments: cold and wet
(glaciers), high elevations (steep
terrains), arid regions (wind), etc
Mechanical Weathering Assignment
 1). Pick 1 type of mechanical weathering.
 2). Write 4 sentences explaining what it is and how it happens.
 3). Bring in a real picture that shows your weathering in action.
Let’s See What You Remember
1). What is a Sediment?
Cartoon
Chemical Weathering
1.
Dissolution

Dissolution tears mineral grains apart and
carries away the ions (electrically charged
atoms or molecules) in solution.

Example: The salt in the ocean all comes
from chemical reactions of water with
rocks.

Example: Caves in rock are the result of
dissolution, usually where the mineral
calcite (CaCO3) in limestones has been
dissolved by groundwater.
 *Acids: Most dissolution in chemical
weathering is not performed directly
by the water but rather by acids
contained in natural waters.
Chemical Weathering
2. Oxidation
 Oxidation is rust
 Many minerals contain elements
that can undergo oxidation,
although iron (Fe) is by far the most
common one.
 Many outcrops of iron-rich rock
have reddish stains from "rusting"
due to chemical weathering by
reactions with air.
Learning Targets
 1). You will see the process of weathering in action.
 2). You will understand the differences between chemical and physical
weathering.
Let’s See What You Remember
1). Compare and Contrast
(physical) mechanical and
chemical weathering.
Learning Targets
 1). You will see both processes, chemical and physical (mechanical), of
weathering in action.
 2). You will understand what happens after weathering to sediments to form
sedimentary rocks: processes of deposition and lithification.
 3). You will see how sedimentary rocks are grouped.
Sedimentary Rocks
 Deposition = The process of
weathered sediments settling out
after being moved by erosion.
 Lithification = The process that
transforms sediments into
sedimentary rocks.

Sediments are compacted as they are buried
beneath successive layers of sediment and
cemented by minerals
 Evidence of Past Life

During lithification, parts of organisms are
replaced by minerals and turned into
rocks.

Bedding = The horizontal layering of
sedimentary rocks.
DEPOSITION AND LITHIFICATION
ANIMATION
 http://gomyclass.com/animations2.
html
 http://serc.carleton.edu/NAGTWor
kshops/geomorph/visualizations/er
osion_deposition.html
Cartoon
Let’s See What You Remember
What are the 2 types of
sedimentary rocks?
Sedimentary Rocks
CLASSIFICATION OF SEDIMENTARY ROCKS
 Clastic Sedimentary Rocks
1.
 Most common
 Formed from loose sediments found on
Earth’s crust
 3 types
2.
Coarse-Grained Clastics

Sedimentary rocks consisting of gravel-sized
rock and mineral fragments.

Due to their large mass, these are
transported by high-level flows of water
Medium-Grained Clastics

3.
Sedimentary rocks that contain sand-sized
rock and mineral fragments are mediumgrained
Fine-Grained Clastics

Sedimentary rocks that contain smaller
then sand-sized rock and mineral fragments
are fine-grained
Let’s See What You Remember
What 2 steps come next in the
sedimentary rock cycle after
weathering?
Metamorphic Rocks
CAUSES OF METAMORPHISM
 Metamorphic Rocks = rocks that
change form while remaining
solid.


Pressure and temperature increase with
depth

Temperature and pressure combine to alter
texture, mineralogy, or chemical composition
of a rock without melting it.

The high temps required for this ultimately
are derived from Earth’s internal heat.

The high pressures are generated by pressure
of overlying rocks
Typically occurs at depths between 10 to
30 km where pressure is 6 times greater
and temperature is 800 °C greater than at
the surface of the earth!
Types of Metamorphic Rock
 1. Foliated Metamorphic
Rocks – metamorphic rocks
with visible layers or elongated
grains of minerals
 The minerals in these rocks have
been squeezed into parallel layers
by intense pressure
 2. Non-foliated Metamorphic
Rocks – rocks that do not have
distinct layers or bands
 The majority of these rocks are
formed by extreme heat
 Examples of Metamorphism:
• Granite turns into Gneiss
• Sandstone turns into
Quartzite
• Limestone turns into Marble
• Shale turns into Slate
Metamorphic Rock Cartoon
Rock Cycle
DEFINITION
 The Rock Cycle = The continuous
changing and remaking of rocks.
 http://www.passmyexams.co.uk/G
CSE/physics/rock-cycle.html
EXAMPLES
 Heat and pressure may change an
igneous rock to a metamorphic
rock.
 Metamorphic rocks can change to
other metamorphic rocks, melt and
turn into an igneous rock
 Metamorphic or Igneous rocks may
break into sediments and be
eroded, deposited, and lithified
make a sedimentary rock.
ROCK CYCLE ANIMATION
 http://www.classzone.com/books/
earth_science/terc/content/investi
gations/es0602/es0602page02.cfm
Memory Clue
 To show your understanding of sedimentary and metamorphic rocks,
complete memory clues for vocab 9-17; aka the rest.
Pre-Lab Work
 Title: Rock Cycle in Chocolate Lab
 Purpose 1: You will understand how one rock type can become another.

 Purpose 2: You will understand the processes of each rock type: melting,
crystallization, erosion, weathering, deposition, lithification, and
metamorphism.
Pre-Lab Questions
 1). How do you form igneous rocks?
 2). How do you form sedimentary rocks?
 3). How do you form metamorphic rocks?