Earth's Interior

1. Crust

2. Mantle

3. Core

The layers of the earth based on Chemical Composition

Earth’s Crust

• Outermost layer of the earth

• Thinnest layer (5-7km)

1. Continental Crust

2. Oceanic Crust

The crust can be divided into two types:

Continental Crust

• The thicker and less dense layer of the earth’s crust that is found under the continents (25-70km)

• Composed mainly of granitic rock

• Older than oceanic crust (3.8 billion yrs old)

Oceanic Crust

• The thinner and denser layer of the earth’s crust that is found under the ocean basins (7-10km)

• Composed mainly of basaltic rock

• Younger than continental crust because it is constantly being remade at the mid-ocean ridges

• Age does not exceed 200,000 yrs

Earth’s Mantle

• The layer of hot, solid material beneath the Earth’s crust

• Thickest layer

• 67% of Earth’s total mass

1. Upper Mantle

2. Lower Mantle

The mantle can be divided into:

Upper Mantle

• Relatively rigid

• Contains the asthenosphere, a semi-fluid layer that allows the movement of tectonic plates

Lower Mantle

• Solid

• Contributes to the overall convection and heat transfer within the Earth’s interior

Earth’s Core

• Innermost layer of the Earth

• Mostly metallic iron with small amounts of nickel and contains much less oxygen, silicon, aluminum and magnesium than the mantle

• Densest layer and makes up about 33% of the Earth’s mass

• Outer boundary depth of 2,890 to 5,150km (1790 to 3200 mi) thick

• Made up of molten material and causes the Earth’s magnetic field

Outer Core

• Liquid layer composed mainly of molten, iron and nickel

• 2,300km

Inner Core

• Solid, central part of the earth

• Radius of about 1,220km and is composed of solid iron and nickel

• Hottest part of earth (4,000 to 6,000 degrees)

1. Lithosphere

2. Asthenosphere

3. Mesosphere

4. Outer Core

5. Inner Core

The layers of the earth based on Physical Properties

Lithosphere

• Outermost rigid layer, consists of the crust and rigid upper part of the mantle

• “Rock Sphere”

• 0 to 100km

• Lies above asthenosphere

• Divided into pieces called tectonic plates:

  • Oceanic Plates- thin, dense, made of basalt and form the ocean floor

  • Continental Plates- thick, less dense, made of granite and form the continents

Asthenosphere

• Weak layer of the mantle in which the lithospheric plates float and move freely

• Hot and partially molten

• Approximately 100-350km below the earth’s surface

• “Weak Sphere”

• Both temp and pressure increase with depth

• Effects of temp dominate those of pressure, causing the rock to be in a semi-molten, slowly flowing state

Mesosphere

• Strong, lower part of the mantle

• Rocks move slower than the asthenosphere

• “Middle Sphere”

Andrija Mohorovičić

• Yugoslavian seismologist

• Described how the velocity of seismic waves changes as they travel to the deepest part layer of the Earth. The density of the materials and the kind of materials they made are the factors that affect the velocity of each layer of the Earth.

Moho

The boundary that separates the mantle and crust

Inge Lehmann

• Predicted the existence of the innermost layer in 1936

• Explained that there is another region within the core through seismic reflection

Shadow zones

• Where seismic waves cannot be detected because they are bent or stopped

• Located between 103° to 143° away from the epicenter