Layers of the Earth
Crust
Mantle
Outer Core
Inner Core
Crust
•Avg. thickness- 35 km
•2 kinds
1. Continental
20-90 km thick; known as
sial; contains older rock,
primarily granite; less
dense than oceanic crust
2. Oceanic
5-10 km thick; known as
sima; younger rock,
primarily basalt; more
dense crust
Crust Cont.
•All life exists in the crust of the
Earth.
•Approximately 90 different
elements are found in the crust,
but 5 make up 90% of the crustoxygen, silicon, aluminum,
iron, & calcium
•Sodium, potassium, &
magnesium are the most
common elements in the
remaining 10%
Mantle
Earth’s mantle contains 80% of
Earth’s volume & 67% of Earth’s
mass.
Common elements found in the
mantle are: silicon, oxygen,
aluminum, iron, & magnesium.
The mantle consists of solid rock,
except for the asthenosphere.
Density increases in the mantle as
depth increases
Layers of the Mantle
The mantle is divided into 3
sections.
1. Lithosphere- consists of the
uppermost part of the mantle
(rigid rock) & the crust.
Average thickness is 100 km.
- Moho’s discontinuity- boundary
separating crust from mantle;
discovered in 1909 using
seismic data; found
approximately 30 km from
Earth’s surface
Layers of the Mantle cont.
2. Asthenosphere- 100-250 km
deep; more fluid layer, but not liquid
3. Mesosphere- lowest layer; rigid
rock; 660-2900 km deep
-temperature increases with depth,
as does density
Core
Diameter of the total core is 6960
km = to approximately the diameter
of Mars
The core is 1/6 of Earth’s volume &
1/3 of its total mass
Outer Core
•Approximately 2270 km thick
•Temperature approximately 40005000º Celsius
•Liquid; very dense molten iron &
nickel
•Believed to create Earth’s
magnetic field; similar to the
magnetic field around a magnet
Inner Core
•Temperature is about 5000º Celsius
•Believed to be solid; very dense iron
& nickel
•Remains solid due to immense
pressure (may be 2 million times
stronger than normal pressure
exerted on Earth’s surface);
molecules can not spread out &
become liquid