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The Core
Approximately the size of Mars
Starts about 2900km down
Centre is 6350 km down
The most dense part of the planet
Made up of rocks rich in iron and nickel
Core temperature over 6000oC
Outer core is semi-molten/liquid (only part of the planet which is!)
Inner core is solid
The Mantle
Separated from the core by the Gutenburg discontinuity
Largely composed of silicate rocks rich in iron and magnesium
Upper mantle (close to the crust) is rigid and together with the crust forms the lithosphere
Most of the mantle (asthenosphere) acts like it is semi-motlen.
Temperatures near the core reach 5000oC
High temperatures near the core are believed to be responsible for the generation of convection
currents.
The Crust
Thinnest, coolest and least dense layer.
Rocks are rich in silicon, oxygen, aluminium, potassium and sodium
Separated from the mantle by the Mohorovijic (Moho) discontinuity.
Varies in thickness from 5 to 70 km
Two types of crust: oceanic and continental
Oceanic crust is mainly made up of basalt (dense, dark volcanic rock)
Relatively thin (5 to 10 km) and young.
Continental crust is composed of a wide variety of igneous, metamorphic and sedimentary rocks.
Less dense and lighter than the oceanic crust.
Can be as thick as 70 km beneath the Earth's mountain ranges
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Lithosphere – consists of the crust and the rigid upper section of the mantle, approximately 8090km thick. Divided into seven large plates and a number of smaller ones.
Asthenosphere – the semi-molten mass below the lithosphere on which the plates float and move.
Beneath the asthenosphere is the rest of the mantle, which is completely solid.
Continental crust
Oceanic crust
Thickness
30-70km
6-10km
Age
Over 1500 million years
Less than 200 million
years
Density
2.6 g/cm3 (Lighter)
3.0 g/cm3 (Heavier)
Composition
Mainly granite; silicon,
aluminium and oxygen.
Mainly basalt; silicon,
magnesium and oxygen.