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