Download Plate Tectonics

Plate Tectonics
By Ms. Neumann & Mrs. Fraser
The Movement of Earth
• Earth’s Layers:
• Crust
• Mantle
• Core
Earth’s Layers
• Crust
– Lithosphere
(outermost, but does
have some mantle
rock) layer that is the
tectonic plates
Earth’s Layers
• Mantle
– Asthenosphere
(solid, soft layer that
moves slowly) layer
that the tectonic
plates move on
– Mesosphere (solid
lower part of mantle)
Earth’s Layers
• Core
– Outer core (liquid
iron and nickel)
– Inner core (solid iron
and nickel)
Earth’s Plates
• Pangaea- Supercontinent that once
existed on Earth around 245 million years
ago…
Plate Movement
•
Continental Drift
– Lithosphere (tectonic plates) is divided into
plates that slide around on top of the slowly
moving asthenosphere.
– It occurred after the break-up of Pangaea,
and since then the continents have drifted
apart
Theory of Continental Drift
–
–
–
Alfred Wegener (early 1900’s) was the first
to discuss the theory of Pangaea and
continental drift.
Theory of Pangaea- claimed that the
continents had formed a single land mass
which has split apart over time.
Wegner was not the first to suggest this
theory, but he was the first to present
information from several fields.
Alfred Wegener’s Theory
• Continental Drift Theory – Was that all of
the continents were once joined together, but
over time have drifted apart.,
• Pangea – name of the supercontinent that
contained all land on Earth
• His theory was very controversial. It was
disproved at the time since Wegener could
not explain how the continents were drifting
apart.
Proof of Continental Drift
• Evidence of Wegner’s theory:
– Similar glacier deposits in South America and
Africa, and fossil findings
– The outlines of the continents fit with each other.
– Mountain ranges line up between Africa and
South America.
Continental Drift over time
How does continental drift work?
–
Plates compress or pull apart from each
other
• Plates collide = convergent boundary
• Plates separate = divergent boundary
• Plates slide past one another
horizontally = transform boundary
• Subduction zone = one plate slides under
another
Convergent Boundary
• Plates collide while moving towards each
other
Converging...They Crash!
And they’re both Continental Plates
• When both are continental plates, the plates
push against each other, creating mountain
ranges.
Subduction Zone
• When a oceanic plate slides under a
continental plate.
Subduction Zones
• Cause: oceanic
trenches, and can
cause volcanoes to
form due to the
oceanic plate
melting and creating
pressure under the
continental plate.
Divergent Boundary
• Plates separate (pull apart)
They’re Pulling Apart!
• When plates pull away from
one another they form: sea
floor spreading, mid- oceanic
ridges or rift valleys
Thingvellir, the spreading zone in Iceland between the North American (left
side) and Eurasian (right side) tectonic plates. January 2003.
Sea Floor Spreading Theory
• Harry Hess formulated the idea of sea
floor spreading in 1962.
• Sea Floor Spreading Theory- idea that
the seafloor moves and carries the
continents with it.
• Caused by divergent boundaries moving
apart and allowing the liquid like
asthenosphere to move upward and cool
creating new oceanic crust.
Transform Boundary
• Plates slide past one another horizontally
Transform Boundary- Plates
sliding past one another
Transform Boundary
• These areas are likely
to cause earthquakes,
and volcanic action,
and fault lines.
For example: Here, the San
Andreas Fault lies on the boundary
between two tectonic plates, the
north American Plate and the Pacific
Plate. The two plates are sliding
past each other at a rate of 5 to 6
centimeters each year. This fault
frequently plagues California with
earthquakes.
Review… Which is what??
DIVERGENT
CONVERGENT
TRANSFORM
Force moving Plate tectonics:
CONVECTION CURRENTS
Convection Currents
• Convection currents, in the mantle, are what
causes the movement of tectonic plates.
• As the extremely hot molten material from
the mantle rises toward the crust, it cools
enough to become denser and sink back into
the hotter area of the mantle.
• The process repeats (cycles) continually.
Rock Layers in the Earth
• Nicolas Steno -was a Danish anatomist and
geologist in 1636-1686
• Law of Superposition – says that rock
layers on the bottom of sedimentary rock
are older than the layers on top.
• That means fossils found in lower layers of
rock are older than fossils found closer to
the surface.
Rock Layers (strata)
• Which layer of rock
would be the
oldest?
• A – Closer to the
center of the Earthbottom layer
• Which layer of the
rock would be the
youngest?
• F – closer to the
top (surface)
Rock Layering…
•James Hutton (1729-1797) -Scottish
Chemist and Geologist
• The law of cross-cutting – That if there is a faulty or
other body of rock that cuts through another rock, then it
must be younger in age than the rock through which it
cuts into or displaces
Law of Cross- Cutting
• Would Rock D be
older or younger than
rock A and rock B??
• Younger because it is
the rock that CUTS
into the rock below!
Fold – bends in the earth’s
crust due to stress
•
Folded Mountains – made when rock is squeezed
together and pushed upward
•
Appalachian Mountains ranging from Quebec to Alabama,
Rocky Mountains ranging from British Columbia to New
Mexico
Fault – broken rock layers,
resulting from stress
•
•
These mainly occur around transform
boundaries
They are due to stress from tectonic plate
movement.
Ring Of Fire
• 90% of the world's earthquakes and 89% of the
world's largest earthquakes occur along the Ring
of Fire in the Pacific Ocean from California
around to India – Caused by subduction
zones.
Whiteboard Practice
•
•
•
•
•
Name the 3 layers of the Earth.
Crust, Mantle, Core
What is the top layer of the mantle called?
Asthenosphere
What is the layer that is the tectonic plates
called?
• Lithosphere
Whiteboard Practice
• What is the landmass called that was composed
of all the current continents before they drifted
apart?
• Pangaea
• Name the scientist who came up with the theory
of continental drift?
• Alfred Wegener
• Name proof that Wegener used for his theory of
continental drift.
• Fossil’s findings on different continents, Noticed
the continents appear like ‘puzzle pieces’,
glacier deposits
Whiteboard Practice
• What do Convergent Boundaries create
when it’s two continental plates?
• Mountains!
• What do Convergent Boundaries create
when its an oceanic and continental plate?
• Subduction Zone
• What type of boundary created mid-oceanic
ridges?
• Divergent
Whiteboard Practice
• What type of boundary causes
earthquakes and volcanic activity?
• Transform
• What does a subduction zone cause?
• Oceanic trenches and can help form
volcanoes
• What causes tectonic plates to move?
• Convection Currents
Whiteboard Practice
• What theory involves a divergent boundary
under the ocean creating new oceanic
crust?
• Sea Floor Spreading
• What law says that rock found in lower
levels of the Earth are older than rock
found towards the surface?
• Law of Superposition
Whiteboard Practice
• Name the scientist who came up with the
Law of Superposition.
• Nicolas Steno
• According to the Law of Cross-cutting,
which rock layer below would be the
youngest?
• Layer D
Whiteboard Practice
• What type of rock is made due to bends in
the Earth’s crust from stress?
• Folded Rocks
• What type of rock is made due to breaks in
the Earth’s crust caused from stress?
• Faulted Rocks
• What is the areas called where the
majority of the world’s earthquakes and
volcanoes occur?
• Ring of Fire
• END OF SLIDES
• MAKE SURE TO STUDY!!