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Plate tectonics
What you need to know
Earth can be
divided into
three layers
based on
chemical
composition:
the crust, the
mantle, and
the core.
Earth’s 3 Layers
•The outer
part of the
earth is the
lithosphere
•The
lithosphere
is broken
into sections
called
tectonic
plates
Lithosphere
The Crust
• The outer layer of the
lithosphere is the crust
Tectonic plates
•Beneath the
tectonic plates is a
layer of the earth
known as the
Asthenosphere.
•This layer is made
up of the mantle,
which has the slow
moving rock that
moves the plates.
Asthenosphere
Moving Plates
Because the
plates sit on
top of melted
rock they are
constantly in
motion.
Evidence of Plate Tectonics
• In the late 1800s, Alfred Wegener
proposed his hypothesis of
continental drift.
• According to this hypothesis, the
continents once formed a single
landmass, broke up, and drifted.
Pangaea
• Today, scientists accept that the
continents were once joined.
• About 245 million years ago, the
continents were joined in a
single large landmass called
Pangaea.
• Over millions of years, Pangaea
broke into fragments that
drifted and collided with each
other.
P
A
N
G
E
A
Tectonic plate boundaries
• There are three types of plate
boundaries:
–Convergent boundaries
–Divergent boundaries
–Transform boundaries
• Each type of boundary is
associated with characteristic
landforms.
• Convergent
boundaries
form where two
plates collide.
• Remember
having a
conversation with
someone.
• Creates
mountains and
trenches
Mountains
• Where two
continental
plates collide
the formation
of mountains
occur
• At a divergent
boundary, two
plates move
away from
each other, and
magma forms
new lithosphere
or land. This is
happening at
mid-ocean
ridges.
A boundary at which
two plates move past
each other horizontally
is called a transform
boundary.
At transform
boundaries, the
motion of the two
plates often produces
earthquakes.
EARTHQUAKES
• Earthquake – the shaking of earth’s
surface, caused by the quick release of
stored pressure in rocks.
• The pressure is caused by plates:
1. Pressing against each other
2. Sliding by one another
3. Stretching and pulling from each other.
Earthquakes
• Fault – The break or crack, in Earth’s
surface along which movement has
occurred.
• Earthquakes are also associated with
folding. Folding is when rock layers bend
without breaking.
Subduction
• If two plates collide, subduction can
happen. Subduction is one plate sinks
and melts back into the mantle
• A deep canyon or trench forms where
the plates meet.
• Volcanic mountains can also form at
subduction zones
Oceanic/Continental Subduction
• This also occurs with oceanic and continental
plates. The denser oceanic plate sinks
(SUBDUCTS) below the continental plate,
forming volcanoes.
Magma and Lava
• Magma – is
molten rock that
has not reached
the surface
• Lava - is molten
rock that has
reached the
surface.
Hot Spots
• An area of volcanic activity in the middle
of a tectonic plate is known as a hot spot.
• Hot spots will always be located in the
same area.
• The Hawaiian
Islands are
examples of a
hot spot.
The Ring of Fire
• The area that forms
the outer edge of
the Pacific Ocean is
also called the ring
of fire.
• More than 75% of
volcanoes and
earthquakes take
place in this region.