layers of-earth
TRANSCRIPT
Layers of the EarthCrust
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 crust- oxygen, 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 4000-5000º 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