The 3 main layers
The crust is the Earth’s outermost and thinnest layer (approximately 5km thick under oceans and 30 kilometres thick under the continents).
The thickest section of the Earth is the mantle at approximately 2,900 kilometres. It is made up of semi-molten rock, called magma.
The core is the innermost part of the Earth and is composed mostly of iron.
Click on each layer name below the diagram to find out more.
The crust is the hard and rigid outer layer of the Earth.
The oceanic crust
The oceanic crust is the thinnest part of the crust and underlines the oceans. It is composed of dense rocks, such as basalt, typically low in silica and high in ferromanganese minerals.
The continental crust
The continental crust is the thicker part of the crust and is much less dense. It forms the continents and is composed of rocks such as granite, typically high in silica and high in aluminium.
The mantle is the widest layer and is approximately 2,900 kilometres thick, composed of dense rocks very low in silica, for example peridotite. The Earth's crust is divided into huge, constantly moving plates, which float on this layer. The mantle is comprised mostly of silicate rocks. This rocky shell surrounds the hot core of the Earth. It is divided into sections based upon the results of seismology.
The upper mantle
The rock in the solid part of the upper mantle is hard. In comparison, the lower-most part of the upper mantle is composed of semi-liquid, molten rock and is known as the asthenosphere. This has a thickness of 200 kilometres. The lithospheric plates slide over the top of this.
The lower mantle
Little is known about this layer
The core is at the centre of the Earth and is divided into two parts: the outer and the inner core.
The outer core
This part of the core is comprised of molten iron and nickel and is liquid. It is about 2,300 kilometres thick and extremely hot, approximately 6000°C
The inner core
The inner core is composed of iron and nickel. The pressure on this layer is so great that it remains solid in spite of its extremely high temperatures. It is about 1,200 kilometres in diameter and spins at a different speed to the rest of the planet (possibly caused by the Earth's magnetic field).
The lithosphere is the solid outer part of the Earth. It is comprised of the Earth's crust and the solid part of the upper mantle. it is divided into tectonic plates and is always moving, but very slowly. The extreme heat from the upper mantle helps this movement.
The movement at the tectonic plates can create earthquakes and volcanoes.
It is thought that at one time there was only one land mass, called Pangaea; as the plates moved apart it caused this landmass to break into continents. The cycle of continents coming together and moving apart, forming ocean basins, is termed the Wilson cycle.
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