Transcript Plate Tectonic

Earth’s Layers Review
Which layer of the Earth is
broken into sections that move?
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Core
Lithosphere
Asthenosphere
Continental Crust
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What do the lithospheric plates
float on top of?
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Asthenosphere
Oceanic Crust
Outer Core
Continents
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What causes the lithospheric
plates to move?
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Seismic Waves
Continental Drift
Sea-Floor Spreading
Convection Currents
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Plate Boundaries
Plates
The lithosphere (crust and
upper mantle) is broken
into separate sections
called plates.
Floating Plates
The plates float on top of the asthenosphere
because of convection currents.
The Theory of Plate Tectonics
Pieces of the Earth’s
lithosphere are in constant,
slow motion.
This theory explains the
movement of plates on Earth,
called Plate Tectonics.
The Movement of the Plates
The lithospheric plates move because of convection
currents and the plates meet at boundaries.
Where The Plates Meet
• There are 3 kinds of plate boundaries:
–Transform Boundary
–Divergent Boundary
–Convergent Boundary
Transform Boundary
Sketch of
Boundary
Direction of
Plate Movement
• Plates slide past each other
Description/Feature of
TRANSFORM plate boundary
• Earthquakes are very frequent
• Causes faults (cracks)
Example
San Andreas Fault (California)
Divergent Boundary
Sketch of
Boundary
Direction of
Plate Movement
Two plates move away from each other.
Description/Feature of
DIVERGENT plate boundary
Continental Plates
form a RIFT VALLEY
(deep valley)
Oceanic Plates
form MID-OCEAN RIDGE
Divergent Boundaries
Continental Plate
Examples
Oceanic Plate •
Examples
• Rio Grande Rift (US)
• Great Rift Valley (Africa)
Mid-Atlantic Ridge (Atlantic Ocean)
Convergent Boundary
• At a convergent boundary, two plates come
together, or converge (“collide”)
Sketch of
Boundary
• There are 3 types of
Convergent Boundaries:
Direction of
Plate Movement
– Oceanic crust collides with oceanic crust
– Oceanic crust collides with continental crust
– Continental crust collides with continental crust
When two plates collide, the density of the plates
determines which one comes out on top.
Oceanic crust is more dense than continental crust.
Oceanic vs. Oceanic
When the crust comes together at a trench,
the less dense crust on the plate is on top.
The crust that is more dense dives (“sinks”)
under the other one and returns to the mantle
(this is called subduction).
Oceanic vs. Continental
The plates come together and the oceanic crust
sinks because it is more dense.
 Continental
Oceanic 
Continental vs. Continental
Plates come together and neither sinks.
Mountains are formed.
Example: Himalaya Mountains
Slow Motion…
• The plates move from 1 to 10 centimeters
per year.
• North America and Eurasia move apart
2.5 centimeters per year
this is how fast your fingernails grow-
Plate Movement Review
Which of the following is not a
plate boundary?
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Convergent
Divergent
Persistent
Transform
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Which boundary occurs when
two plates slide past each other?
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Convergent
Transform
Divergent
Oceanic
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Which type of plates collide to
form mountains?
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Oppositional
Continental
Divergent
Oceanic
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Which plate boundary features
the mid-ocean ridge for sea-floor
spreading?
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Continental
Transform
Divergent
Oceanic
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What occurs when oceanic
plates collide?
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Sea-Floor Spreading
Mountain Building
Earthquakes
Subduction
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