PLATE TECTONICS

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PLATE TECTONICS

• Why the Earth is Like It Is

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Earth Layers

• Earth is made up of 5
• layers
• Inner Core
• Outer Core
• Mantle
• Asthenosphere (Lower and middle mantle)
• Lithosphere (Upper mantle and crust)

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The crust is thin, varying from a few tens of
kilometers thick beneath the continents to less
than 10 km thick beneath the many of the oceans.
The crust and upper mantle together constitute
the lithosphere, which is typically 50-100 km
thick and is broken into large plates. The plates
sit onthe asthenosphere.
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Plate tectonics is the theory that Earth's outer
layer is made up of plates, which have moved
throughout Earth's history. The theory explains
the how and why behind mountains, volcanoes, and
earthquakes.
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Continental Drift

• Continental Drift Alfred Wegener's theory that
  all continents were once connected in a single,
  large landmass (called Pangaea) that broke apart
  about 200 million years ago and drifted slowly to
  their current positions.

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What Did The Earth Look Like In The Past?
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What evidence do we have that the continents have
moved?

• Fossil Clues
• Fossils of similar plants and animals have been
  found on continents that are now very far apart,
  but were perhaps once joined together.
• Climate clues
• Evidence of glaciers can be found on land that is
  now tropical, because that land was once located
  in a colder region of our planet.
• Rock Clues
• Similar rock structures can be found on
  continents that are now far apart, again
  suggesting that they could have once been joined.
  Rocks found in the eastern US are similar to
  those found in western Europe.

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Major Tectonic Plates
Tectonic Plates World Map (link)
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Do land features continue to change?
Are the continents still moving?

• The earths tectonic plates continue to gradually
  move even today. The plates interact. Where one
  plate meets another, is called a boundary.
• Divergent Boundary between two plates that are
  moving apart.
• Convergent Boundary between two plates that are
  pushing together.
• Transform (Strike-slip) Boundary between two
  plates that are sliding past one another.
• Subduction Zone The area where one plate pushes
  down under another. Volcanoes are often created
  by this.

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How do we know?

• Hot Spots
• (Hawaii,
• Yellowstone)

Volcanoes and Earthquakes Ring of Fire very
active region of subduction
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Why Do Plates Move?
Plates are pushed and pulled over the surface
of the Earth due to unbalanced forces.
When convection currents reach the surface,
plates are pushed apart
As the plates move away from each other, part of
them are pulled into the Earths mantle
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Convection Currents

• The mantle "flows" because of convection
  currents. Convection currents are caused by the
  very hot material at the deepest part of the
  mantle rising, then cooling and sinking again
  --repeating this cycle over and over.

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Plates Move Toward Each OtherThis is called
Convergent Boundary these are destructive
boundaries since they deform the plates
Continent/Continent
Ocean/Continent
Ocean/Ocean
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Convergence creates mountains

• Most volcanoes (but not all) form along
  Convergent boundaries, as one plate is pushed
  under another and the old crust melts.
• As two plates rub against one another, a number
  of small and large earthquakes could occur near
  convergent boundaries.

http//geology.com/nsta/convergent-plate-boundarie
s.shtml
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Convergence Moving Together
Trenches
Mountains
Structural Mountains
Volcanic Mountains
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Plates Move Away From Each OtherThis is called
Divergence these are constructive boundaries
since they produce new land
Africa and Arabia
North America and Eurasia
Mid-Atlantic Ridge
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Divergent Boundaries
http//geology.com/nsta/divergent-plate-boundaries
.shtml

• Most often takes place at ocean ridges.
• As the two sides of the crust move away from each
  other, magma wells up from the Earth's interior.
• It then solidifies into rock as it is cooled by
  the sea, creating new ocean floor. Causes some
  volcanoes and earthquakes to form.

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The ridges are zones of intense volcanic
activity. In addition to forming at the bottom of
oceans, these divergent boundaries can also form
on continents. When this happens, a line of
volcanoes emerges.
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Divergence Moving Apart
Rift Valley if the land is above water
Sea Floor Spreading when the land is below water
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The San Andreas Fault is undoubtedly the most
famous transform boundary in the world. To the
west of the fault is the Pacific plate, which is
moving northwest. To the east is the North
American Plate which is moving southeast.
http//geology.com/nsta/transform-plate-boundaries
.shtml

• Plates Move Side By SideThis is called Transform
  Boundary Transform boundaries neither create
  nor consume crust. Rather, two plates move
  against each other, building up tension, then
  releasing the tension in a sudden and often
  violent jerk. This sudden jerk creates an
  earthquake.

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San Andreas Fault

• Is a continental transform fault that runs a
  length of roughly 1,300 km (800 miles) through
  California.

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Review clip(click on the link above)
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As two continental plates move toward each other,
what landforms would you expect to see?

1. Volcanoes
2. Cliffs
3. New Land
4. Mountains

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As two continental plates move toward each other,
what landforms would you expect to see?

• Volcanoes
• Incorrect
• These form at edges of plates or over hot spots

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As two continental plates move toward each other,
what landforms would you expect to see?

• Cliffs
• Incorrect
• These are erosional landforms or minor uplift
  areas

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As two continental plates move toward each other,
what landforms would you expect to see?

• New Land
• Incorrect
• Forms when plates move apart

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As two continental plates move toward each other,
what landforms would you expect to see?

• Mountains correct -
• because 2 continental masses will push into each
  other and crumple the edges to form mountains

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Where would you find the newest land on Earth?

1. In areas of continental convergence
2. In areas where two ocean plates come together
3. In areas where plates are moving apart
4. In areas where two plates are sliding past each
   other

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Where would you find the newest land on Earth?

• In areas of continental convergence
• Incorrect
• Mountains would form here from existing land.

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Where would you find the newest land on Earth?

• In areas where two ocean plates come together
• Incorrect
• You would find trenches in this area.

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Where would you find the newest land on Earth?

• In areas where two plates are sliding past each
  other
• Incorrect
• You would find land movement but not new land
  being formed

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Where would you find the newest land on Earth?

• In areas where plates are moving apart
• Correct
• When plates move apart it is due to magma
  reaching the surface. When magma cools new land
  is formed.