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Layers of the Earth
The Earth’s Interior
Most scientists agree that soon after
Earth’s formation, Earth was a large ball of
molten (melted) rock. As time passed, the
molten materials cooled, hardened, and
separated into layers.
Composition
(What it is made of)
• Crust
• Mantle
• Core
The Crust
• Thin, outer layer that
covers the planet
• 8 - 32 km thick
• 2 types of crust
– Oceanic (very dense,
made of basalt)
– Continental (less
dense, made of
granite)
Oceanic and Continental Crust
The Mantle
• Middle layer
• Very thick layer
(2900 km thick)
• Made of silicon,
oxygen, iron,
magnesium
- solid that has the
ability to flow =
plasticity
The Core
•
•
•
•
Central part of the planet
Made of iron and nickel
1/3 of the earth’s mass
Very hot
- inner core = solid
- outer core = liquid
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
Do scientists travel to the inside of
Earth to learn about the layers?
• High temperatures and tremendous
pressure in the Earth’s interior would
make traveling there and remaining alive
impossible.
• Even the deepest oil wells are only a few
kilometers deep, and the diameter of the
Earth is 12,756 km.
So, how do we know about the layers?
The study of behaviors of seismic waves
has allowed geologists to piece together
information about the parts of Earth that
man has never seen directly.
When earthquakes occur,
vibrations are sent out
through the Earth. These
vibrations are called
seismic waves.
Seismic Waves
• Seismic waves can travel along the surface of the
Earth or through its interior.
• The waves speed up, slow down, or stop
depending on the type of material (medium) that
they are passing through.
For example:
S-waves are a type of seismic wave that can't go
through liquid. Therefore, scientists know that the
part of the Earth that S-waves can't penetrate is
made up of liquid.
The Inner Core
The deepest layer in Earth is
the inner core. It is located at
the center of Earth because it
contains the densest material of
all of Earth’s layers. The inner
core is solid and mostly
composed of the element iron
(Fe). Its extremely hot
temperature is estimated at
6,000 °C. This layer is
approximately 1,250 km thick.
The Outer Core
The outer core is less dense than
the inner core and, therefore, is
located around the inner core. The
temperatures range from 4,000 °C
to 5,000 °C. The outer core is
approximately 2,200 kilometers
thick and is a combination of
mostly liquid iron (Fe) and nickel
(Ni).
The Mantle and Asthenosphere
The mantle is located outside the outer
core. This layer is mostly made of iron
(Fe) and magnesium (Mg) and has a
thickness of approximately 2,900
kilometers. The upper mantle’s high
temperatures of 2,800–3,200 °C can
melt rocks. The upper part of the mantle
is called the asthenosphere. The
asthenosphere is a solid that flows like
a liquid. This physical property is called
plasticity. Scientists believe that the
lithosphere and the crust are able to
move slowly over the top of the mantle
and asthenosphere.
The Crust and Lithosphere
The layer around the asthenosphere is
known as the lithosphere. The
lithosphere is the coolest, thinnest layer.
This layer is made mostly of the
elements oxygen (O2) and silicon (Si).
Continental crust is thicker than oceanic
crust. The crust is broken into many
large pieces called tectonic plates.
Scientists believe these plates “float”
and move around very slowly on the
semiliquid asthenosphere.
Layers of the Earth Model
1. What doesthe
marble represent?
Why?
2. What do the 2
playdoh layers
represent? Why?
3. What does the
aluminum foil
represent? Why?