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Transcript
Inside the Earth
Composition (What it is made of)
• Crust
• Mantle
• Core
Physical Structure of the Earth
(5 Layers)
• Lithosphere- rigid outer layer (crust)
• Asthenosphere- solid rock that flows
slowly (like hot asphalt)
• Mesosphere- middle layer
• Outer Core- liquid layer
• Inner Core- solid, very dense
The Crust
• Outer layer
• 5-100 km thick
• 2 types of crust
– Oceanic (very dense,
made of basalt)
– Continental (less
dense, made of
granite)
2 Types of Plates
• Ocean plates - plates below
the oceans
• Continental plates - plates
below the continents
Oceanic and Continental Crust
The Mantle
• Middle layer
• Very thick layer
The Core
• Made mostly of iron
• 1/3 of the earth’s mass
• Very hot
Earth’s Layers
• How are the earth’s
layers similar to an
egg?
• Shell=crust
• Egg white=mantle
• Yolk=core
Physical Structure of the Earth
(5 Layers)
• Lithosphere- rigid
outer layer (crust)
• Asthenosphere- solid
rock that flows slowly
(like hot asphalt)
• Mesosphere- middle
layer
• Outer Core- liquid
layer
• Inner Core- solid, very
dense
What is the Lithosphere?
• The crust and part of the upper
mantle = lithosphere
–100 km thick
–Less dense than the material
below it so it “floats”
What is the Asthenoshere?
• The plastic layer below the
lithosphere = asthenosphere
• The plates of the lithosphere
float on the asthenosphere
Tectonic Plates
• Earth’s crust is broken into about 19
pieces
• These plates move on top of the
asthenosphere
Theory of Plate Tectonics
Plate Tectonics
Plate Boundaries
Causes of Plate Tectonics
Plate Tectonics
What is Plate Tectonics
• The Earth’s crust and upper
mantle are broken into
sections called plates
• Plates move around on top of
the mantle like rafts
Questions...
• What is the theory of plate
tectonics?
• What is the lithosphere?
• What is the asthenosphere?
• What is the connection between
the two?
• What are the two types of plates?
Plate Boundaries
Types
• Divergent
– Rifting
• Convergent
– Sub-duction
• Transform Fault Boundaries –
(Sliding)
Divergent Boundaries
• Boundary between two plates
that are moving apart or rifting

• RIFTING causes SEAFLOOR
SPREADING
Divergent Plate Movement: Seafloor
Spreading
• the movement of two oceanic plates away
from each other (at a divergent plate
boundary), which results in the formation
of new oceanic crust (from magma that
comes from within the Earth's mantle)
along a a mid-ocean ridge.
• Ocean floor spreading was first suggested
by Harry Hess and Robert Dietz in the
1960's.
Features of Divergent
Boundaries
• Mid-ocean ridges
• rift valleys
• fissure volcanoes
Convergent Boundaries
• Boundaries between two
plates that are colliding
 
• There are 3 types…
Type 1
• Ocean plate colliding with a
less dense continental plate
• Subduction Zone: where the
less dense plate slides under
the more dense plate
• VOLCANOES occur at
subduction zones
Andes Mountains,
South America
Type 2
• Ocean plate colliding with
another ocean plate
• The less dense plate slides
under the more dense plate
creating a subduction zone
called a TRENCH
• Two Oceanic Plates - When two oceanic
plates collide, one may be pushed under
the other and magma from the mantle
rises, forming volcanoes in the vicinity
•Two Oceanic Plates - When two oceanic plates
collide, one may be pushed under the other and
magma from the mantle rises, forming volcanoes
in the vicinity
Aleutian Islands, Alaska
Type 3
• A continental plate colliding
with another continental plate
• Have Collision Zones:
–a place where folded and thrust
faulted mountains form.
• Two Continental Plates - When two
continental plates collide, mountain ranges
are created as the colliding crust is
compressed and pushed upwards.
Transform Fault Boundaries
• Boundary between two plates
that are sliding past each other
• EARTHQUAKES along faults
• When two plates move sideways against
each other (at a transform plate
boundary), there is a tremendous amount
of friction which makes the movement
jerky.
• The plates slip, then stick as the friction
and pressure build up to incredible levels.
When the pressure is released suddenly,
and the plates suddenly jerk apart, this is
an earthquake.
San Andreas Fault, CA
Questions...
• What are the types of
boundaries?
• What direction do plates go for
each?
• Which boundary has a subduction
zone…what occurs at a
subduction zone?
Causes of Plate
Tectonics
Convection Currents
• Hot magma in the Earth
moves toward the surface,
cools, then sinks again.
• Creating convection currents
beneath the plates that cause
the plates to move.
Questions...
• What causes plates to move?
• How is a convection current
formed?