Transcript Inside the Earth

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.