The Layers of
the Earth
Earth Layers
• The Earth is divided into 4 main layers.
Inner Core
Outer Core
Mantle
Crust
The Crust
 Outermost layer of the Earth
 The Earth’s crust is like the skin of an apple. It is
very thin compared to the other three layers.
 The crust makes up 1% of the Earth and is called the
“rock and mineral” layer.
 The crust of the Earth is broken into many pieces
called plates.
 At the junction of these plates some interesting
things occur!
Plate Tectonics
Volcanoes
Earthquakes
Sea-Floor Spreading
And what type of crust
would you like with your
Earth?
• There are two types of
crust.
– Continental crust
– Oceanic crust
Continental Crust
• Makes up the continents
• Contains light colored
rocks such as granite.
• Floats high on the
mantle
Oceanic Crust
• Makes up the ocean
floor
• Contains the dense
rocks such as basalt
• Thinner than the
continental crust
The Mantle
 The mantle is the layer between the crust
and the outer core.
 The mantle is the largest layer of the
Earth.
 The mantle is made up of MAGMA (hot
molten rock).
 Because of the heating and cooling of liquid
rock, convection currents occur. These
currents force the plates of the crust to
move.
Mantle Zones:
Lithosphere
• Thin, uppermost part of
the mantle and crust;
rigid, brittle rock
• Floats on the
athenosphere, and slides
around very slowly.
• The upper part of the
lithosphere melts rocks,
forming a substance
called magma.
Magma
• Magma (melted rock)
moves like hot oatmeal.
• Uneven heating causes
material in the mantle to
constantly and slowly rise &
fall in convection currents.
• Convection Currents: process
by which hot fluid rises to
the surface, and then sinks
again, like soup being heated
in a saucepan
CONVECTION IN THE MANTLE
CRUST
MANTLE
COOL LIQUID SINKS
HOT LIQUID RISES
OUTER CORE
Mantle Zones:
Asthenosphere
• Hot, weak zone directly
under the lithosphere
• Flows at a very slow
rate like hot asphalt
under a heavy weight
• The movement
(convection currents) of
the asthenosphere is
the reason that the
crustal plates of the
Earth move
Core
• Deep within the Earth is
the core
• The core is made mostly
of nickel & iron
• Twice as dense as the
mantle.
• Main source of heat
that triggers the
convection currents
• The core is made of two
layers
Outer Core
 The outer core of the Earth is a ball of
very hot liquid metal.
 The outer core is made up of mostly iron
and is very dense.
 Because this liquid metal is moving, positive
and negative particles are created and
released that create the Earth’s
MAGNETIC FIELD.
Magnetic Field
Inner Core
 The inner core of the Earth has temperatures
and pressures so great that the metals are
squeezed together and are not able to move.
 Therefore; the inner core is a solid.
 The temperature in the core is nearly as hot
as the surface of the SUN!
Plate Tectonics
• Pieces of the lithosphere that move
around
• Each plate has a name
• Fit together like jigsaw puzzles
• Float on top of mantle similar to ice
cubes in a bowl of water
Continental Drift
Alfred Wegener 1900’s
Continents were once a single
land mass that drifted apart.
Fossils of the same plants and
animals are found on different
continents
Called this supercontinent
Pangea, Greek for “all Earth”
245 Million years ago
Split again – Laurasia &
Gondwana 180 million years
ago
http://members.enchantedlearning.com/subjects/astronomy/planets/earth/Continents.shtml
Evidence of Pangea
Sea Floor Spreading
Sea Floor Spreading
• Mid Ocean Ridges – underwater
mountain chains that run through the
Earth’s Basins
• Magma rises to the
surface and solidifies
and new crust forms
• Older Crust is pushed
farther away from the
ridge
How Plates Move
http://pubs.usgs.gov/gip/dynamic/unanswered.html
Different Types of
Boundaries
http://pubs.usgs.gov/gip/dynamic/understanding.html
Divergent Boundary –
Arabian and African Plates
Divergent Boundary –
Iceland
http://pubs.usgs.gov/gip/dynamic/understanding.html
Divergent Boundary Oceanic
http://www.geology.com
Divergent Boundary Continental
http://www.geology.com
Convergent Boundary – Indian
and Eurasian Plates
Convergent Boundary – Oceanic &
Continental
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Convergent Boundary – Oceanic &
Oceanic
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Convergent Boundaries Continental
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Transform Boundary – San
Andreas Fault
www.geology.com