Transcript Chapter 1

Chapter 1
Plate
Tectonics
Chapter 1 Earth’s Interior Key
Terms:
• GeologistScientist that study the forces that make
and shape Earth.
• GeologyThe study of planet Earth.
• Seismic WaveA vibration traveling through Earth
carrying the energy released during an
earthquake.
• PressureThe amount of force pushing on an area.
Chapter 1 Key Terms:
• CrustLayer of rock that forms Earth’s outer
surface.
• BasaltA dark, dense igneous rock found in the
oceanic crust.
• GraniteUsually a light colored rock found on Earth’s
continental crust.
• MantleThe layer of hot solid material between the
crust and the core.
Chapter 1 Key Terms:
• LithosphereA rigid layer made up of upper part of the
mantle and the crust.
• AsthenosphereSoft layer of the mantle on which the
lithosphere floats.
• Outer CoreLayer of molten iron and nickel that
surrounds the inner core.
• Inner CoreSolid iron and nickel in the center of the
earth.
Objective:
The students will
determine methods
used by geologists to
explore the interior
of the earth.
Finding direct Evidence
• Geologists study the processes that create
Earth’s features and search for clues
about Earth’s history.
• Scientists cannot travel inside the Earth
to explore it. So scientists must learn
about Earth’s interior, or inside, in other
ways.
• Scientists use drills to get rock samples
from inside Earth. The rock samples help
scientists learn what conditions were like
inside the earth when rocks formed.
Finding Indirect Evidence
• Geologists study how seismic waves travel
through Earth. Seismic waves are waves
made by earthquakes.
• Seismic waves show that Earth is made up
much like an onion.
• How?
• It has layers.
(Like an ogre)
A Journey to the Center of the Earth
• Earth has three main layers. The CRUST is the
outside layer, the MANTLE is the middle layer.
The CORE is the inside layer.
Temperature
• Temperature increases from crust to the core.
It is very hot inside Earth. One reason it is so
hot is that some substances inside Earth give
off energy.
Pressure
• Pressure also increases from the crust to the
core. Pressure is caused by a force pressing on
an area. There is great pressure inside Earth
because of all the rock pressing down from
above.
Objective:
The students will
diagram and describe
the layers of the
earth.
Parts of the Earth
The Crust
• The crust is a layer of rock that forms
Earth’s outer skin. The crust is Earth’s
thinnest layer. It is only 5 to 70
kilometers thick.
• The crust that makes up the ocean floors
is called the oceanic crust. Oceanic crust
is made mostly of a rock called basalt.
• The crust that makes up the continents is
called continental crust. Continental crust
is made mostly of a rock called granite.
• Continental crust is thicker than oceanic
crust.
The Mantle
• The mantle is the layer below the crust.
The mantle is Earth’s thickest layer. The
mantle has three parts.
• The top layer of the mantle, along with
the crust, is the lithosphere. The top
layer of the mantle is hard rock.
• The middle layer of the mantle is the
asthenosphere. The middle layer is soft
rock, like hot road tar.
• The bottom layer of the mantle is called
the lower mantle. It is also hard rock.
The Core
• The core is Earth’s inside layer. The core
has two layers: the outer core and the
inner core.
• The outer core is made of liquid metal.
The liquid metal flows in currents. The
currents make Earth act like a giant
magnet, with north and south poles that
attract iron.
• The inner core is made of solid metal.
The inner core is solid because it is under
so much pressure.
Parts of the Earth
• Crust-Mantle
• Crust-Mantle-Core
Ticket Out
Identify the interior parts of the
Earth.
Brain Pop- Earth's Structure
Interior Ticket Out
Section 2 Convection Currents
and the Mantle Key Terms:
• Heat TransferThe movement of energy from a warmer
object to a cooler one.
• RadiationThe transfer of energy through empty
space.
• ConductionHeat transferred by direct contact of
particles of matter.
Section 2 Key Terms
• ConvectionHeat transfer by the movement of heated
fluid.
• DensityHow much mass there is in a volume of a
substance.
• Convection CurrentThe flow that transfers heat from one
part of a fluid to another.
Objective:
The students will
explain how heat is
transferred.
Types of Heat Transfer
• When an object heats up, particles in
the object have more energy and move
faster. This energy can travel, or
transfer, from a warmer object to a
cooler object. This is called heat
transfer.
• There are three types of heat
transfer: radiation, conduction,
and convection.
Radiation
• Radiation is the transfer of energy
through space. For example, sunlight
travels through space by radiation
and warms Earth’s surface. Radiation
also explains why your hands get
warm when you hold them near a fire.
Conduction
• Conduction is the transfer of
heat between objects that are
touching. If you touch a hot
pot, heat travels from the pot
to your hand by conduction.
Convection
• Convection is the transfer of heat
by the movement of particles in
fluids such as water. Moving
particles transfer heat throughout
the fluid.
Types of Heat Transfer
• REMEMBER:
– Radiation transfers heat through the air.
– Conduction transfers heat through solids.
– Convection transfers heat through liquids.
Convection, Radiation, Conduction
Objective:
The students will
identify the cause of
convection currents.
How Can Heat Cause
Motion in a Liquid?
• As you watch the demonstration, think
about the following:
• How do you explain what happened to
the droplets of food coloring?
• Why do you think the second droplet
moved in a way that is different
from the way the first droplet
moved?
Convection in the Earth’s Mantle
• Remember, convection is the transfer of
heat by the movement of particles in
fluids. This movement of particles is
called a convection current.
• A convection current starts when there
are differences in temperature and
density in a fluid. Density is the amount
of mass in a given volume of a substance.
A high-density substance feels heavy for
its size.
What does this mean???
What does this mean?
• Suppose you put a pot of soup on a stove. The
soup at the bottom of the post gets warm
first. Because it is warmer, the soup at the
bottom is less dense than the cooler soup
above it. So the warmer soup rises. At the
same time, the cooler, denser soup sinks to
the bottom of the pot.
• The cooler soup now at the bottom gets
warmer, and the process repeats. A constant
flow of particles begins. Warmer soup keeps
rising, and cooler soup deeps sinking. This
movement of particles transfers heat
throughout the soup.
Convection Currents in Earth
• The heat inside Earth causes convection
currents in the mantle and outer core.
• Convection currents inside Earth are like
convection currents in the pot of soup.
Hot materials at the bottom rise to the
top. Cooler materials at the top sink to
the bottom.
• Convection currents in the mantle move
very slowly. This is because the mantle is
made of solid rock.
Convection Currents in Earth
• Remember, Earth is like a giant magnet
because of currents in the outer core.
Those currents are convection currents.
lithosphere
asthenosphere
mantle
Section 3 Drifting
Continents Key Terms:
• PangaeaThe name of the landmass in the theory
that all the continents were joined at one
time.
• Continental DriftThe idea that the continents slowly moved
over the earth’s surface.
• FossilAny trace of an ancient organism that has
been preserved in rock.
Objective:
The students will
explain the theory of
continental drift.
The Theory of Continental Drift
• Some continents are shaped like puzzle pieces.
For example, the west side of Africa and the
east side of South America look like matching
puzzle pieces.
The Theory of Continental Drift
• Scientist Alfred Wegener (VAY guh ner)
tried to explain why continents are shaped
this way.
• Wegener thought that Earth had one big
continent about 300 million years ago. The
big continent broke into smaller pieces and
formed smaller continents. The continents
slowly drifted apart. Wegener called this
CONTINENTAL DRIFT.
• Wegener named this supercontinent
PANGAEA, meaning “all lands.”
Pangaea
Objective:
The students will
explain evidence of
the theory of
continental drift.
Wegener’s Evidence
• Evidence shows that continental drift
really happened.
• Wegener studied information from three
sources to prove that his theory was
correct. He studied...
1- Landforms
2- Fossils
3- Climate changes
Evidence from Landforms
• Mountains in Africa and South America line up
like they were once part of the same mountain
range.
Evidence from Fossils
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•
Fossils from plants and animals have been
found to support Wegener’s theory. The
plant Glossopteris was found in rock in
Africa, India, Australia, and Antarctica.
The seeds would be to large to have been
carried to the continents as they are
today.
Evidence from Climate
•
•
•
•
Other evidence shows that continents’
climates have changed. This could
happen if continents had drifted.
Tropical plant fossils found on an ice
covered island north of Norway.
Deep scratches in rock show possible
continental glaciers in Africa.
Wegener's theory was Earth’s climate
has not changed, but the position of the
continents has.
Scientists Reject Wegener’s Theory
•
•
Wegener could not explain what causes
continental drift. So most other
scientists of his time thought he was
WRONG! New evidence????
Wegener used his idea of continental
drift to explain how mountains form.
Wegener thought mountains form because
drifting continents bump into each to
other. When this happens, edges of the
continents crumple. The crumpled edges
form mountains.
Section 4 Sea Floor
Spreading Key Terms:
• Mid-Ocean RidgeThe longest chain of mountains in the
world.
• SonarA device that bounces sound waves off
underwater objects then records the
echoes of the sound waves.
• Sea-Floor SpreadingThe process of molten material being
added to the oceanic crust.
Section 4 Key Terms:
• Deep-Ocean TrenchA deep valley along the ocean floor
through which oceanic crust slowly sinks
towards the mantle.
• SubductionThe process by which the oceanic crust
sinks beneath a deep ocean trench and
back into the mantle at a convergent plate
boundary.
Objective:
The students will
describe the process of
sea-floor spreading.
Mid-Ocean Ridges
• Since the mid-1900s, scientists have used sonar to
study the ocean floor. Sonar is a device that bounces
sound waves off underwater objects. The longer it
takes the sound to bounce back, the farther away the
objects are.
Mid-Ocean Ridges
• Using sonar, scientists found long
mountain ranges on the ocean floors.
Scientists call the mountain ranges midocean ridges. Mid-ocean ridges run
through the middle of oceans.
• In a few places, mid-ocean ridges poke
above the surface and form islands.
Iceland is the top of a mid-ocean ridge
in the North Atlantic Ocean.
Mid-Ocean Ridges
What is Sea-Floor Spreading?
• Sea-floor spreading is a process that slowly
adds new rock to the ocean floor. Scientist
Harry Hess came up with the idea of seafloor spreading in 1960.
• Here is how sea-floor spreading works. In
the center of the mid-ocean ridge, melted
rock pushes up through cracks in the
ocean floor. The melted rock pushes older,
solid rock away from both sides of the
ridge. The melted rock cools and forms
new solid rock at the center of the ridge.
What is Sea-Floor Spreading?
• This process keeps repeating. Slowly, the ocean floor
is pushed farther and farther away from both sides of
the mid-ocean ridge. At the same time, new rock
keeps adding to the ocean floor in the center of the
ridge.
Sea Floor Spreading
(4 min.)
Objective:
The students will
describe and provide
evidence of the process
of sea-floor spreading.
Evidence for Sea-Floor Spreading
• In the 1960s, scientists tried
to find evidence of sea-floor
spreading. They found
evidence from three sources.
The three evidences are
evidence from molten material,
magnetic stripes, and drilling
samples.
Evidence from Molten Material
• Scientists used a submarine to
get rocks from a mid-ocean ridge.
They found rocks shaped like
toothpaste squeezed from a tube.
This could only be caused by
molten (melted) material from lava
that has hardened quickly along
cracks of the mid ocean ridge.
Evidence from Magnetic Stripes
• Scientists also found evidence
from magnetic stripes. Strips of
rock on the ocean floor showed
that there had been the reversal
of Earth’s magnetic poles.
• These Magnetic Stripes (2 min.) move
away from the mid ocean ridge.
Evidence from Drilling Samples
• Scientists used a drill to get
rocks from below the ocean
floor. Rocks closest to the midocean ridge were the newest.
Rocks farthest from the midocean ridge were the oldest.
• Deep Sea Drilling Project
(3 min.)
Objective:
The students will
describe the process of
subduction.
Subduction at Deep-Ocean Trenches
• Sea-floor spreading makes the ocean floor
get wider. New rock keeps forming at midocean ridges. Old rock keeps getting pushed
farther and farther away from both sides of the
ridges.
• After million of years, old rock reaches
underwater canyons, called deep-ocean
trenches. At a deep-ocean trench, the rocky
crust of the ocean floor bends downward and
sinks into the mantle. This process is called
subduction. Subduction occurs because the
more dense oceanic crust sinks beneath the
less dense continental crust.
Subduction at Deep-Ocean Trenches
• Sea-floor spreading and subduction work together.
They keep the ocean floors moving like conveyor belts
in an airport. As new rock is added to the ocean
floors, old rock disappears. Overall, the size of the
ocean floors does not change very much.
Subduction at Earth’s Oceans
Pacific Ocean
• If a deep ocean trench swallows more
oceanic crust than the mid-ocean ridge
produces, the width of the ocean will
shrink.
Atlantic Ocean
• The Atlantic has only a few short
trenches, which causes the ocean floor to
spread.
• The spreading floor causes the continent
of North America to move.
Section 5 Plate Tectonics
Key Terms:
• PlateA section of the lithosphere that slowly
moves over the asthenosphere, carrying
pieces of oceanic and continental crust.
• Scientific TheoryA well tested concept that explains a wide
range of observations.
• Plate TectonicsThe theory that pieces of the Earth’s
lithosphere are in constant motion driven
by the convection currents in the mantle.
Section 5 Key Terms:
• FaultBreaks in the Earth’s crust where rocks have
slipped past each other.
• Transform BoundaryWhere plates move in opposite directions.
• Divergent BoundaryPlace where two plates move apart.
• Rift ValleyA deep valley that forms when two plates move
apart.
• Convergent BoundaryPlace where two plates come together.
Objective:
The students will
explain the theory of
plate tectonics.
Hot Plates
• As you watch the demonstration, think
about the following questions:
– What happens to the sponges as the
water heats up?
– What can you infer is causing the
changes you observe?
– What material represents the mantle in
this activity? What represents Earth’s
crust?
– What would happen if we added several
more candles under the pan?
A Theory of Plate Motion
• Earth’s lithosphere is broken into many
jagged pieces. The surface is like the shell of
a hard-boiled egg that has been dropped.
The pieces of Earth’s surface are called plates.
Plates carry continents, ocean floors, or both.
• The theory of plate tectonics (tek TAHN iks)
says that Earth’s plates move because of
convection currents in the mantle. Currents in
the mantle carry plates on Earth’s surface,
like currents in water carry boats on a river.
A Theory of Plate Motion
• Plates can meet in three different
ways. Plates may pull apart, push
together, or slide past each other.
Wherever plates meet, you usually
find volcanoes, mountain ranges, or
deep-ocean trenches.
Objective:
The students will
Identify various types
of plate boundaries.
Plate Boundaries
• A plate boundary is where two
plates meet. Faults form along
plate boundaries. A fault is a
break in earth’s crust where
blocks of rock have slipped
past each other.
Plate Boundaries
Divergent Boundaries
• Where two plates move apart, the boundary
is called a divergent boundary. A divergent
boundary between an oceanic plate and a
continental plate forms a mid-ocean ridge.
A divergent boundary between two
continental plates forms a deep-valley called
a rift valley.
Plate Boundaries
Convergent Boundaries
• Where two plates push together, the boundary is
called a convergent boundary. A convergent
boundary between an oceanic plate and a
continental plate or two oceanic plates forms a
deep-ocean trench. A convergent boundary
between two continental plates forms a
mountain range.
• More dense plates slide under less dense
plates. (Subduction)
• Plates of equal density causes the crust to
crumple into mountain ranges.
Notice the Converging and Diverging plates.
Plate Boundaries
Transform Boundaries
• Where two plates slide
past each other in
opposite directions, the
plate boundary is called a
transform boundary. At
a transform
boundary,
earthquakes may
occur.
Plate Boundaries
•
•
•
•
Plate movement.html
Plate Boundaries. Notebook
BrainPop- Plate Tectonics
Discovery Education Video
Chapter 2
Earthquakes
Section 1 Earth’s Crust in Motion
Key Terms:
• EarthquakeThe shaking and trembling as a result of
rock moving beneath earth’s surface.
• StressA force that acts on rock that changes its
shape or volume.
• ShearingStress that pushes a mass of rock in two
opposite directions.
Section 1 Key Terms:
• TensionPulls on the crust causing it to be
thinner in the middle.
• CompressionSqueezes rock until it folds or
breaks.
• FaultA break in Earth’s crust where slabs
of rock slip past each other.
Objective:
The students will
describe how stress
forces affect rock.
Earth’s Crust in Motion
Types of Stress
• When Earth’s plates move, rocks are
pushed and pulled. The pushes and
pulls are called stress.
• Stress adds energy to rocks. Rocks
keep storing the energy until they
cannot stand any more stress. Then
the rocks break or change shape.
How do rocks change???
Earth’s Crust in Motion
Types of Stress
Tension
• Tension is stress that pulls and
stretches rocks. Tension makes rocks
thinner in the middle. Tension
happens when two plates move apart.
Earth’s Crust in Motion
Types of Stress
What does Tension look like?
Earth’s Crust in Motion
Types of Stress
Compression
• Compression is stress that squeezes
rocks. Compression makes rocks fold
or break. Compression happens when
two plates push together.
Earth’s Crust in Motion
Types of Stress
What does compression look like?
Earth’s Crust in Motion
Types of Stress
Shearing
• Shearing is stress that pushes rocks in
opposite directions. Shearing makes rocks
break, slip apart, or change shape.
Shearing happens when two plates slip past
each other in opposite directions.
Earth’s Crust in Motion
Types of Stress
What does shearing look like?
Earth’s Crust in Motion
Types of Faults
• A fault is a break in Earth’s crust
where rocks are under stress.
• There are three different types of
faults: normal faults, reverse
faults, and strike-slip faults. Each
type is caused by a different kind
of stress on rocks.
Earth’s Crust in Motion
Normal Faults
• A normal fault happens when tension pulls rocks
apart. In a normal fault, the hanging wall slips
down and becomes lower than the footwall.
Earth’s Crust in Motion
The Hayward Fault in Oakland, California
is a normal fault.
Earth’s Crust in Motion
Reverse Faults
• A reverse fault happens when compression pushes
rocks together. In a reverse fault, the hanging
wall slides up and becomes higher than the
footwall.
Earth’s Crust in Motion
The New Madrid fault that spans the
Mississippi River is a reverse fault.
Earth’s Crust in Motion
Strike-Slip Faults
• A strike-slip fault happens when shearing pushes
rocks in opposite directions. In a strike-slip
fault, two blocks of rock move past each other,
but neither block moves up or down.
Earth’s Crust in Motion
The San Andreas fault in California is a
strike-slip fault.
Section 2 Measuring Earthquakes
Key Terms:
• FocusThe point under the Earth’s surface where
rock breaks, triggering an earthquake.
• EpicenterThe point on the surface directly above
the focus.
• Seismic wavesVibrations traveling through the Earth
carrying energy released by an
earthquake.
Section 2 Key Terms:
• SeismographA device that records ground movements caused
by seismic waves as they move through Earth.
• Mercalli scaleA scale that rates earthquakes based on their
intensity and how much damage they cause.
• Richter scaleA scale that rates seismic waves as measured by a
particular type of seismograph. This scale rates
the size of seismic waves.
• Moment magnitude scaleA scale that rates earthquakes by estimating the
total amount of energy released by an earthquake.
Objective:
The students will
identify types of
seismic waves and
describe how they
travel through Earth.
How does stress affect
Earth’s crust?
•
•
•
Be sure to wear your safety goggles!!!
Listen to my directions carefully.
With your partner, discuss the
following:
– What happened to the wood in each
situation?
– How is the wood like the earth’s crust?
– What might eventually happen as the forces of
plate movement bend the crust?
Measuring Earthquakes
An earthquake is the shaking that
results when rocks move inside
Earth. An earthquake is caused by
stress along a fault. Stress
increases until the rocks break
and release stored energy.
Measuring Earthquakes
The place where
rocks break and
cause an
earthquake is
called a focus.
The point on the
surface directly
above the focus
is called the
epicenter.
Measuring Earthquakes
Seismic Waves
Earthquakes cause waves, called
seismic waves, to travel through
Earth. Seismic waves carry the
energy released by the rocks.
•Seismic waves carry the energy of an earthquake
away from the focus, through Earth’s interior, in
all directions
Seismic Waves
• There are three kinds of
seismic waves: P waves, S
waves, and surface waves.
• P waves (primary waves)
move rocks back and
forth, like a wave passing
through a spring toy when
you push the coils. They
compress and expand the
ground. P waves are the
fastest seismic waves.
Seismic Waves
• S waves (secondary
waves) move rocks up
and down, like a wave
passing through a rope
when you flick it.
They vibrate side to
side as well as up and
down. S waves travel
more slowly than P
waves but do more
damage.
Seismic Waves
• Surface waves are both P waves and S
waves that travel along Earth’s surface.
Surface waves are the slowest waves, but
they also do a lot of damage.
Can you label the seismic waves in
this diagram?
BrainPop-Earthquakes
Objective:
The students will
identify the scales
used to measure
earthquakes.
Measuring Earthquakes
Measuring
Earthquakes
• The Mercalli scale is
based on the amount
of damage an
earthquake does.
For example, a weak
earthquake only
rattles the dishes. A
strong earthquake
can destroy
buildings.
Measuring Earthquakes
• The Richter scale is based on the size
of the seismic waves. A stronger
earthquake makes bigger seismic
waves. An instrument called a
seismograph measures the size of
seismic waves.
Measuring Earthquakes
• The moment magnitude scale is based on the
amount of energy an earthquake releases. The
amount of energy is based on many things,
including the size of the seismic waves.
• Moment magnitude is the measurement and term
generally preferred by scientists and
seismologists to the Richter scale because
moment magnitude is more precise.
Comparison of Richter Scale and Moment Magnitude Scale
Earthquake
Richter Scale
Moment Magnitude Scale
New Madrid, MO, 1812
8.7
8.1
San Francisco, CA, 1906
8.3
7.7
Prince William, AK, 1964
8.4
9.2
Northridge, CA, 1994
6.4
6.7
Measuring Earthquakes
Let’s see these scales
in action at the US
Geological Survey
(USGS).
Objective:
The students will
locate the
epicenter of an
earthquake.
Measuring Earthquakes
Locating the epicenter
• The epicenter is the point on the surface
that lies directly above an earthquake’s
focus. Scientists use P waves and S
waves to
find an
earthquake’s
epicenter.
Measuring Earthquakes
Locating the epicenter
• P waves travel faster than S waves. So P
waves arrive at a seismograph sooner than
S waves. The longer it takes for S waves to
reach the seismograph after the P waves
have arrived, the farther away the
epicenter is.
Earthquake
Arrival of P
Arrival of S
wave
wave
Earthquake A
1 min. 20 sec.
2 min. 55 sec.
Earthquake B
1 min. 40 sec.
2 min. 30 sec.
Measuring Earthquakes
Locating the epicenter
• To find the exact location of the epicenter,
you need seismographs in three different
places. You can draw a circle around each
seismograph to show how far the
epicenter is from the seismograph. The
point where all three circles cross is the
epicenter.
Objective:
The students will
locate the
epicenter of an
earthquake.
Measuring Earthquakes
Recent Earthquake Activity
Let’s explore some earthquakes that
have occurred recently.
US Geological Survey website
Why did these earthquakes occur in
these locations?
Let’s find out!
Measuring Earthquakes
Locating the epicenter
Time to complete the
“Locating The Epicenter of
an Earthquake” Lab.
Let’s look at the directions
first.
Now let’s do one together.
Measuring Earthquakes
Locating the epicenter
There are additional ways to
find the epicenter of an
earthquake when you a
provided with different
data.
Let’s find out how!