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Inside Edition
The Earth’s Interior:
A Hot Topic
A Planet at Rest?
From the surface or from space the
earth appears stable and calm
Except for infrequent violent volcanic
and earthquake activity the earth
hides its volatile nature
The key to understanding this side of
the earth is understanding its interior
A Model of the Earth
Inner Core
Outer Core
Mantle
Crust
Differentiation
Remember how the Earth Formed?
The Nebula Hypothesis
Planetesimals joined together to
form protoplanets which were molten,
at first
Dense materials like iron and nickel
would tend to sink towards the middle
As cooling progressed lighter
materials floated to the surface like
“scum” and formed the crust
This was all completed about 4 billion
years ago
Inner Core
1216km (754 miles) in
radius
Rich in Iron and Nickel
Intense Pressure and
Heat:
37000c (67000 f)
Dense materials sank to
core as earth cooled
Solid
Outer Core
2270km (1410miles) thick
Molten Iron and Nickel
1500ºc
Less pressure than inner core
liquid
Inner and outer core = 1/6
volume, but 1/3 mass
Mantle
2900km (1800miles)
thick
Mainly Fe, Mg, Si, and O
About 1200ºc
Makes up 2/3 of Earth’s
mass
Less pressure than cores,
but still pretty intense
Plasticlike-partially
molten compostion that
can slowly “flow”
Crust
30-40km(19-25miles)
average thickness
Beneath mountains can
reach 43 miles
This thin layer that floats
on denser mantle
Average composition is
basaltic
Solid – Made of Plates
•if you were to imagine the Earth as a soccer ball, the
crust would be about ½millimeter thick.
The Thickness of the Crust Varies:
•This is a contour
map of the
thickness of the
Earth's crust. The
contour interval is
10 km; it also
include sthe 45 km
contour for greater
detail on the
continents.
•Where are the
thickest parts of the
crust?
Rock Solid
Continental Crust
Thickest type of crust;
- can be 43 miles
thick beneath mtns.
Very old rocks, 3.8
billion years old
Lighter granitic
composition
Do You Want Some
Water With That Crust?
Oceanic Crust
Thinnest part of the
crust, 4-7 miles thick
Rocks are relatively
young, only 200
million years old
Dense basaltic
composition
Crust and Mantle
The interaction of the crust and mantle gives
rise to tectonic activity and crustal movement
The crust and mantle are broken down into
three different zones
Lithosphere – cool, rigid upper layer of earth
Asthenosphere – softer layer of the earth under
the lithosphere
Mesosphere – very slowly flowing layer under
the asthenosphere
Lithosphere
Composed of the Crust and upper mantle
Solid – rigid plates made of the lithosphere
Varies from a few to 190 miles thick (62 miles average)
Ocean Water
Continental Crust
Oceanic Crust
Upper Mantle
Lithosphere
Asthenosphere
Very hot, weak zone of the upper mantle
capable of flowing
Temperatures reach 26000F – hot enough to
melt some of the mantle material
This creates a soft layer about 200 miles thick
that the overriding lithosphere “floats” upon
The lithosphere can move independently of the
asthenosphere
So What?
The movement of the lithosphere
created because of the uneven
Why is this
heating of the interior of the
important
to
know?
earth causes many things, like….
Earthquakes
And……
Volcanoes
Coloring the Earth’s Plates:
Color each plate a
different color
•Be sure can still
see the arrows
showing the
direction the
plates are moving
•Answer the
questions
associated with
the map