Earth Layers

• The Earth is divided into four main layers.

*Inner Core*Outer Core*Mantle *Crust

The Earth’s Crust• The crust is the thinnest layer on Earth, 5 km to 100 km

• There are two types of crust

•Oceanic crust – made mostly of the igneous rock basalt. Found under the ocean. Relatively thin, 5 km to 7 km. Contains more iron than the Continental crust, therefore is more dense.

•Continental crust – made mostly of granite. Found under the continents. Relatively thick, up to 100 km.

Special parts of the Crust

• Lithosphere• Crust is the upper part of the lithosphere.• Broken up into large plates.• The uppermost part of the mantle is also

part of the Lithosphere• Asthenosphere

• Upper part of mantle, below lithosphere • 130 – 160 km thick• Cooler part of the mantle that the

lithosphere plates slide on top of.

The Earth’s Mantle• Located directly above the outer core

• Starts below the crust

• Is the largest layer

• 80% of the Earth’s volume & 68% of Earth’s mass

The Earth’s Mantle• Composed of more iron than the crust.

• Density, pressure, and temperature all increase the deeper you go in the mantle

• Temperature ranges from 870 C – 2200 C

Special layers of the mantle

• Lithosphere – crust plus the upper, solid part of the mantle. Forms plates.

• Asthenosphere – just under the lithosphere. Slow moving “Silly putty” layer on which the lithospheric plates slide. (Solid rock that flows very slowly.)

The Earth’s Core

The Earth’s Core• Composed of the inner and outer

core• Both are made of iron and nickel

The Earth’s Outer CoreThe Outer Core - Liquid• Surrounds the inner core

• Temperature ranges from 2200 C – 5000 C near inner core

• Molten (liquid) iron and nickel

The Earth’s Inner CoreThe Inner Core - Solid• Temperature reaches 5000 C

• Solid iron and nickel • Usually both would be liquid but are solid in

the core because of the incredible pressure

• The solid core is the source of Earth’s magnetic field

Magnetosphere• The inner core and outer cores do not

turn at the same speed as the rest of the earth.

• Causes a generator effect which produces a magnetic field.

• It protects us from some of the sun’s harmful radiation.

•What does the inside of the Earth look like?

•How do scientists know that there is a solid inner core?

Determining the composition of the Earth

• Scientists cannot see the interior of the planet, or drill to the core, so they use seismic waves to determine the composition of the layers.

• Seismic waves: are vibrations that are produced when an earthquake happens.

• Seismic waves travel at different speed depending on the composition and density of material. Measuring these waves tells us what is in the Earth’s layers, and how the materials change.

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What do you know about these layers?