The outer core is a 2000 km thick layer also made of nickel and iron. The outer core is not under as much pressure as the inner core. This, along with intense heat, causes the outer core to be fully molten.
GEO DICTIONARY
Static: not moving or changing
The outer core spins around the static inner core, causing the metals to become charged (much like a turbine used to generate electricity). This movement generates the Earth’s magnetic field which protects us from the sun’s harmful radiation.
Oceanic crust Continental crust
Lithosphere Asthenosphere Mantle
Outer core
Inner core
: Fig. 1.2 A closer look at the Earth’s layers
: Fig. 1.2 A closer look at the Earth’s layers.
: Fig. 1.3 Huge convection currents rise from the lower mantle towards the crust. As the semi- molten magma moves laterally (sideways) underneath the lithosphere, friction causes the plates to move.
1.2 The Mantle GEO DICTIONARY
Semi-molten: when magma begins to cool, it becomes thick and pasty
6 EARTH
The mantle is the largest layer in the Earth, making up 75 per cent of its volume. The mantle is made up of layers of rock which are molten close to the core, as it is so hot. Closer to the crust, the rock is semi-molten or solid as it is cooler. The mantle can be divided into three layers: the lower mantle, asthenosphere and lithosphere.
Identifying or labelling the different layers of the Earth is a frequently asked question in the Leaving Certificate exam.
