Transcript inner core

The Structure of the Earth and
Plate Tectonics
Lesson Objectives
This lesson will teach you everything you need to know
about the Structure of the Earth and Plate Tectonics. By
the end of this lesson you will be able to…
1.
2.
Name and describe Earth’s main layers.
Name and describe three types of plate boundaries
Instructions
• Complete this lesson on your own and at your own pace.
• Use the navigational buttons along the bottom to move
throughout the lesson.
• Take notes as you go.The objectives (on the previous
page) will be assessed by practice quizzes and on our
Chapter Test.
• After linking to a website, simply close your browser
window to return to this lesson.
• Have a pencil & paper handy.
• Have fun!
Structure of the Earth
Mantle
• The Earth is
made up of 4
main layers:
– Inner Core
– Outer Core
– Mantle
– Crust
Outer core
Inner core
Crust
Structure of the Earth
Working from the center of the Earth out we have:
The inner core is a primarily solid sphere about 1220 km
in radius situated at Earth's center.
Based on the abundance of chemical elements in the
solar system, their physical properties, and other chemical
constraints regarding the remainder of Earth's volume, the
inner core is believed to be composed primarily of a
nickel-iron alloy, with small amounts of some unknown
elements.
Structure of the Earth
Working from the center of the Earth out we have:
The liquid outer core is 2300 km thick and like the inner
core composed of a nickel-iron alloy (but with less iron
than the solid inner core).
Iseismic and other geophysical evidence indicates that the
outer core is so hot that the metals are in a liquid
state.
Structure of the Earth
Working from the center of the Earth out we have:
The mantle is approximately 2,900 km thick and comprises
70% of Earth's volume.
This is the largest layer!!
In the mantle, temperatures range between 500-900
degrees Celsius at the upper boundary with the crust to over
4,000 degrees Celsius at the boundary with the core.
The Crust
This is where we live!
The Earth’s crust is made of:
Continental Crust
& Oceanic Crust
The Crust
Continental Crust
Continental crust forms the
land (the continents, as the
name suggests) that we see
today.
Continental crust averages about 35 km thick. Under some
mountain chains, crustal thickness is approximately twice that
thickness (about 70 km thick).
Continental crust is less dense and therefore more buoyant than
oceanic crust
Continental crust contains some of the oldest rocks on Earth.
The Crust
Oceanic Crust
As the name already suggests, this crust is below the oceans.
Compared to continental crust, Oceanic crust is thin (6-11 km).
It is more dense than continental crust and therefore when the
two types of crust meet, oceanic crust will sink underneath
continental crust.
The rocks of the oceanic crust are very young compared with
most of the rocks of the continental crust. They are not older than
200 million years.
Checkup Quiz:
Review song/video of the layers
Move forward when you are
ready to test yourself on the
knowledge you gained!
Checkup Quiz:
Which layer is the rigid outer layer of the Earth?
Outer core
Asthenosphere
Inner core
Crust
Mantle
Structure of the Earth
Mantle
• The Earth is
made up of 4
main layers:
– Inner Core
– Outer Core
– Mantle
– Crust
Outer core
Inner core
Crust
Which layer is the rigid
outer layer of the Earth?
Crust
Checkup Quiz:
Which layer of the earth is made of
mostly solid metals?
Outer core
Asthenosphere
Inner core
Mantle
Lithosphere
Structure of the EarthVideo
Which layer of the earth is
made of mostly solid
metals?
Inner core
Checkup Quiz:
Which layer of the earth is made of
mostly liquid metals?
Outer core
Asthenosphere
Inner core
Mantle
Lithosphere
Structure of the EarthVideo
Which layer of the earth is
made of mostly solid
metals?
Outer core
Checkup Quiz:
Which layer labeled as #5?
Asthenosphere
Outer core
Inner core
Lithosphere
Mantle
Hint: use the scale on the right of the figure!
Structure of the Earth
Mantle
• The Earth is
made up of 4
main layers:
– Inner Core
– Outer Core
– Mantle
– Crust
Outer core
Inner core
Crust
Which layer labeled as #5?
What is Plate Tectonics?
• If you look at a map of the world, you may notice that some of the
continents could fit together like pieces of a puzzle.
Plate Tectonics
• The Earth’s crust is divided into 12 major
plates which are moved in various directions.
• This plate motion causes them to collide, pull
apart, or scrape against each other.
• Each type of interaction causes a
characteristic set of Earth structures or
“tectonic” features.
• The word, tectonic, refers to the deformation of
the crust as a consequence of plate
interaction.
World Plates
What are tectonic plates made of?
• Plates are
made of rigid
lithosphere.
The lithosphere is
made up of the
crust and the upper
part of the mantle.
What are tectonic plates made of?
• Take a look at
both labels for
lithosphere.
The lithosphere is
made up of either
type of crust and
the upper part of
the mantle.
What lies beneath the tectonic plates?
• Below the
lithosphere
(which makes
up the tectonic
plates) is the
asthenosphere.
Plate Movement
• “Plates” of lithosphere are moved around by
the underlying hot mantle convection cells
Plate Movement
only need the first :35 sec.
Plate Movement
Continental drift is the
movement of the Earth's
continents relative to each
other. The hypothesis that
continents 'drift' was first put
forward by Abraham Ortelius in
1596 and was fully developed
by Alfred Wegener in 1912.
Exercise 1: Wegener
Try to logically piece the continents together so that they form a giant
supercontinent. Use the handout in class to use to cut out and paste.
On the back, explain your reasoning on the evidence.
What happens at tectonic
plate boundaries?
Three types of plate boundary
• Divergent
• Convergent
• Transform
Divergent Boundaries
• Spreading ridges
– As plates move apart new material is erupted to
fill the gap
In plate tectonics, a divergent boundary is a linear feature that
exists between two tectonic plates that are moving away from
each other. These areas can form in the middle of continents or on
the ocean floor.
As the plates pull apart, hot molten material can rise up this
newly formed pathway to the surface - causing volcanic
activity.
Where a divergent boundary
forms on a continent it is called
a RIFT or CONTINENTAL RIFT,
e.g. African Rift Valley.
Where a divergent boundary
forms under the ocean it is
called an OCEAN RIDGE
Age of Oceanic Crust
Ocean Ridges: This map shows the age of the oceanic crust. The
red coloring shows the youngest ages, whilst the dark blue shows
the oldest ages (around 200 million years old).
Where are the Ocean
Ridges located?
Answer:
Divergent boundaries
Courtesy of www.ngdc.noaa.gov
Iceland: An example of continental rifting
• Iceland has a divergent
plate boundary running
through its middle
Convergent Boundaries
• There are three styles of convergent
plate boundaries
– Continent-continent collision
– Continent-oceanic crust collision
– Ocean-ocean collision
Continent-Continent Collision
• Forms mountains, e.g. European Alps, Himalayas
Continent-Continent Collision
Himalayas
Continent-Oceanic Crust Collision
• Called SUBDUCTION
Continent-Oceanic Crust Collision
At a convergent boundary where continental crust pushes
against oceanic crust, the oceanic crust which is thinner and more
dense than the continental crust, sinks below the continental
crust.
The oceanic crust descends into the mantle at a rate of
centimeters per year
Subduction is a way of recycling the oceanic crust. Eventually
the subducting slab sinks down into the mantle to be recycled. It is
for this reason that the oceanic crust is much younger than the
continental crust which is not recycled.
Subduction
• Oceanic lithosphere
subducts underneath the
continental lithosphere
• Oceanic lithosphere heats
and dehydrates as it
subsides
• The melt rises forming
volcanism
• E.g. The Andes
Ocean-Ocean Plate Collision
• When two oceanic plates collide, one runs over the
other which causes it to sink into the mantle forming
a subduction zone.
• The subducting plate is bent downward to form a very
deep depression in the ocean floor called a trench.
• The worlds deepest parts of the ocean are found
along trenches.
– E.g. The Mariana Trench is 11 km deep!
Ocean-Ocean Plate Collision
The subducting plate is bent
downward to form a very deep
depression in the ocean floor
called a trench.
Transform Boundaries
• Where plates slide past each other
Above: View of the San Andreas
transform fault
This map summarizes all the known plate boundaries on Earth, showing
whether they are divergent, convergent or transform boundaries
Checkup Quiz :
Plate Boundary Rap
Move forward when you are
ready to test yourself on the
knowledge you gained!
Checkup Quiz:
Movement of two plates often results a rift valley
is which type of boundary .
Divergent
Convergent
Transform
Movement of two plates
often results a rift valley
is which type of
boundary .
Divergent
Checkup Quiz:
Movement of two plates often results in
mountains is which type of boundary .
Divergent
Convergent
Transform
Movement of two plates often
results in mountains is which
type of boundary .
Convergent
Checkup Quiz:
Movement of two plates toward each other is
which type of boundary .
Divergent
Convergent
Transform
Movement of two plates
toward each other is
which type of boundary
.
Convergent
Checkup Quiz:
Using what you know about the rock cycle,
movement of two plates causing igneous rock is
which type of boundary .
Divergent
Convergent
Transform
Remember: Igneous rock is
formed through the cooling and
solidification of magma or lava.
“NEW” rock
Using what you know about the
rock cycle, movement of two plates
causing igneous rock is which type
of boundary .
Divergent
Checkup Quiz:
Using what you know about the rock cycle,
movement of two plates causing metamorphic
rock is which type of boundary .
Divergent
Convergent
Transform
Metamorphic rocks arise from the transformation of
existing rock types, in a process called metamorphism,
which means "change in form". The original rock is
subjected to heat and pressure, (temperatures greater than
150 to 200 °C and pressures of 1500 bars)
Movement of two plates
often results a rift valley
is which type of
boundary .
Convergent
Checkup Quiz:
Scientists think continental plates move because
of circulating liquid rock below the plates.
True
False
Scientists DO think continental
plates move because of
circulating liquid rock below the
plates.
Plate Tectonics Summary
How are you doing?
Are you able to describe all of the following?
1.Name Earth’s main layers.
2.Name and describe three types of plate boundaries.
1.If so, you are ready to move to the next slide!
2.If not click on the area you need help with!
Plate Tectonics:
Well done! Only one thing left to do:
Turn in your printed Wegener activity with
your explanation of the evidence on the back.