1. Earth’s Interior (What’s down there below us?)

2. There are 4 main layers inside Earth

3. How THICK are the layers?
(entire Earth is ~ 8000 miles wide)
Crust: oceanic crust miles thick
continental crust miles thick
Mantle: about
1700 miles thick
(2/3 of Earth’s mass)
Outer core: about
1400 miles thick
Inner core: about
1500 miles thick

4. How HOT are the layers?
Crust: 0oC at surface  400oC where it contacts mantle
Mantle: ~500oC to
~3700oC deeper down
Outer core: ~4000oC
Inner core: ~7000oC
(hotter than the surface
of the sun!!)

5. What are the layers made of?
Crust: Rock
Mantle: Dense rock
Outer core:
Liquid metal (iron) !!
Inner core:
Solid metal
(mostly iron)

6. Of course, it’s not quite that simple:
The “lithosphere” is the crust + part of the upper mantle.
It is made of rock and is brittle. The “plates” of the earth’s
crust make up the lithosphere.
Below the lithosphere
is a softer layer called
the “asthenosphere”.
In the asthenosphere,
The rock is near it’s
melting point, and
flows very slowly, kind
of like asphalt or tar.

7. Why the partly melted asthenosphere??
This graph shows why there is a layer of soft, partially melted rock (the ASTHENOSPHERE) in the top part of the mantle of the earth.
From 100 to 200 km ( miles) below the surface, the temperatures are above the melting point of the rock - even at the very high pressure at this depth.
MELTING
POINT OF
ROCK
(yellow)
ACTUAL
TEMP
(green)
This layer - the ASTHENOSPHERE - is what the plates of the crust
“float on” and explains why they can move around.

8. Finally – a very cool map showing thickness of earth’s crust (in km)
Continental crust
is thick.
Oceanic crust
is thinner