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Plate Tectonics
The Plate Tectonic Theory
The plate tectonic
theory states that the
crust of the Earth is
broken into several
large sections known
It is theorized that
these plates are
dynamic and move
continually. The
interaction between
plates produces
changes on Earth’s
surface such as,
volcanoes,
mountains, and
earthquakes.
NOTE-- Divergent Boundaries are in blue,
Convergent Boundaries are in Red.
Why do the crustal plates move?
Tectonic Plates of the World
“Which tectonic
plate is located at
20˚N, 160˚W?”
“What type of
boundary is the
Mid-Atlantic
Ridge?”
RT = Pg. 5
Divergent Plate
Boundary
As the plates
diverge, magma and
lava are forced
upward due to
convection in the
asthenosphere.
The molten rock will
cool to form new
crust.
When a divergent plate boundary occurs under an ocean, it is
also referred to as
Soon thereafter,
new magma will be
forced upward and
will force the new
crust to split and
diverge as well.
Divergent Plate
Boundary
When a divergent plate boundary occurs
under a continent, it is also referred to as
rift valley.
Dynamic activity
associated with a
divergent plate
boundary
includes:
Convergent Plate
Boundary
A convergent plate boundary is where two
plates converge or collide with one
another. Convergent plate boundaries can
take place in three ways:
OCEANIC-OCEANIC CRUST
CONVERGENCE
CONTINENTAL-CONTINENTAL CRUST
CONVERGENCE
OCEANIC-CONTINENTAL CRUST
CONVERGENCE
OCEANIC-CONTINENTAL CRUST
CONVERGENCE
CONTINENTAL-CONTINENTAL CRUST
CONVERGENCE
OCEANIC-OCEANIC CRUST
CONVERGENCE
Convergent Plate Boundary:
SUBDUCTION ZONE
OCEANIC-CONTINENTAL CRUST
CONVERGENCE
CONTINENTAL-CONTINENTAL CRUST
CONVERGENCE
When two plates converge, the
denser of the two plates will
move and sink under the less
dense plate.
A subduction zone is an area of
tremendous heat, pressure, and
dynamic activity. Many features
are associated with convergent
plate boundaries including:
OCEANIC-OCEANIC CRUST
CONVERGENCE
Transform Plate
Boundary
Dynamic activity
associated with a
transform plate
boundary
includes:
San Andreas Fault, California: Transform
plate boundary between the North
American Plate and Pacific Plate
Evidence to Support the
Plate Tectonic Theory
Appearance of Continents
Evidence to Support the
Plate Tectonic Theory
Landmass Features/Fossil Record
Evidence to Support the
Plate Tectonic Theory
Age and Heat Index of Ocean Rock
In a divergent plate boundary, molten rock
rises to the surface and cools to become
new crust.
This newly formed crust is continually
being replaced by new molten rock.
Older crust diverges and is forced to move
away from the area where new molten
rock will form into new crust.
This image is taken of the Mid-Atlantic Ridge –
a divergent plate boundary.
Each color represents rocks of similar age.
Evidence to Support the
Plate Tectonic Theory
Magnetic Polarity
Earth’s magnetic field has reversed its
polarity many times in Earth’s history.
Currently magnetic north is close to
Earth’s North Pole. Yet, in the past,
magnetic north was close to Earth’s
South Pole.
The nature and frequency of these
reversals of magnetic polarity are not
fully understood.
When molten rock cools at the site of
divergence, the minerals within the
molten rock begin to crystallize. Many
minerals found within igneous rock are
magnetic. These minerals will align
themselves in the direction of magnetic
north.
If there is a reversal in magnetic polarity
the minerals with igneous rock will align
in an opposite pattern.
These patterns suggest some plates are
moving away from one another.