Structure of the Earth

The Earth is made up of 4 different layers.  They each have unique characteristics as described below.  The diagram shows where each layer is located.

Image courtesy of the BBC


The crust is the thinnest layer of the Earth and is the layer we live on.  It is made up of a variety of rocks and can reach up to 70km thick in places.  The crust itself is divided into large chunks called tectonic plates.  There are around 7 large and 12 small plates, which ‘float’ on top of the mantle beneath them.  The plates themselves are made up of 2 different types of crust, continental crust under the land and oceanic crust under the sea.  Continental crust is thick (25-70km) and light because it is made of rocks with a low density.  Oceanic crust is thin (6-11km) and heavy because it is made of rocks (mostly volcanic rocks) that have a high density.  The oceanic crust covers 2/3 of the Earth’s surface.


The mantle is the thickest layer of the Earth at 2,900km thick.  It makes up nearly 80% of the volume of the Earth.  The mantle itself is divided into 2 layers, the upper and lower mantles and the heat within these layers drives convection currents.  The upper mantle is semisolid rock called magma that flows slowly due to convection currents.  It is less than 1,000°C in temperature.  The lower mantle is kept solid due to pressure and is between 1,000-3,500°C.  If you had to describe the mantle as a whole, it is classed as a liquid.

Outer Core

The outer core is made of liquid iron and nickel and is between 3,500-4,000°C.  As the liquid metal swirls around, it induces a current that generates the Earth’s magnetic field.  Heat from the core powers the convection currents in the mantle.  It is 2,900km thick.

Inner Core

The inner core is the hottest part of the Earth reaching temperatures between 4,000-4,700°C, which are as hot as the surface of the sun.  It is made of solid iron and nickel that are under so much pressure they cannot melt.  It is 1,200km thick and heavy radioactive elements within the core generate the intense heat as they decay.