Structure of the Earth

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The structure of the Earth is as shown below:

The Crust:

The crust is the outer layer of the earth. It is thin (5-70 km thick), and the rocks in the crust are the least dense and are rich in silicon, oxygen and aluminium. Continental crust = granite, while oceanic crust = basalt.

The Mantle:

The mantle is the widest section of the Earth. It has a thickness of 2,900 km. Most of the mantle is semi-molten. The mantle is largely comprised of peridotite. The mantle has a temperature gradient, with high temperatures closer to the core. Rocks in the upper mantle are cool and brittle, while rocks in the lower mantle are hot and plastic.

The Outer Core:

The outer core is the layer surrounding the inner core. It is a liquid layer, which generates a magnetic field. It is made up of iron and sulfur. It is extremely hot, with temperatures of 4,400 to 6,100 degrees celcius.

The Inner Core:

The inner core is in the centre and is the hottest part of the Earth. It is solid and made up of iron with temperatures of 6-7000 degrees c, caused by radioactive decay of material.

There are two types of crust - oceanic and continental.

The Mohorovijic discontinuity is the separation between the crust and upper mantle

The crust and the rigid upper part of the mantle are collectively known as the lithosphere

The lower semi-molten section of the mantle is known as the asthenosphere - here convection currents are responsible for the movement of tectonic plates

Continental Crust:

Thickness : 30-70km

Age: over 1,500 million years old

Carries land

Less dense

Mostly granite

Oceanic Crust:

Thickness: 6-10 km

Age: less than 200 million years old

More dense

Found under oceans

Mainly basalt

Heat rising and falling in the mantle creates convection currents.