Transcript The Earth`s Structure

The Earth’s Structure
A Journey to the Center of the Earth
The Interior of the Earth
The Earth’s Layers
 Earth can be divided
into three main layers –
the crust, mantle and
core.
 The layering is due to
differences in density
 Temperature and
pressure in Earth’s
interior increase with
depth
The Crust
 Rocky outer layer of
Earth
 Made up of Silicates
 Two types of Crust

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Continental Crust –
rocks that make up
continents; thickness
between 8 -75 km
Oceanic Crust – rock
that makes up ocean
floor; average
thickness 7 km
The Mantle
 A thick layer of hot
semi-solid dense rock
 Approximately 2850 km
thick
 Composed of mostly
iron, magnesium and
aluminum.
 Makes up about 84% of
Earth’s volume
“Sub Layers” w/n Crust & Mantle
Lithosphere – composed of
the oceanic and continental
crust and the rigid upper
mantle; thin outer shell of
Earth; broken up into “plates”.
Asthenosphere – softer and
weaker rock in the midmantle; can flow slowly when
under pressure
Mesosphere – stronger lower
part of the mantle
The Core
 A large sphere of metal
that occupies Earth’s
center
 Composed mostly of
iron and nickel
 Divided into 2 parts:


Outer core – composed
of liquid metal; 2260 km
thick
Inner core – solid due to
very high pressure; 1220
km thick
How do Scientists study Interior of
Earth?
 Use of Seismic Waves
 2 Types of Seismic Waves: S & P waves

P waves:

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
Travel through solids, liquids and gases
Faster than S waves
S waves

Travel only through solids
 Speed and direction of both waves are
affected by the composition of material they
are traveling through
Shadow Zones
 Locations on Earth’s
surfaces where
neither S or P waves
are detected
 S waves will not travel
through liquid core
 P waves speed and
direction change
causing them to bend