Page 232 - Big Ideas Year 10 sciPAD 2025

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232 SCIPAD - BIG IDEAS - BOOK 2
EARTH SYSTEMS
Inside the Earth
The Earth is made up of four distinct layers. The outermost layer of Earth is called the crust. It is the
thinnest layer (between 0-60 km thick). The crust is the solid rock layer upon which we live. There
are two different types of crust: continental crust, which carries land, and oceanic crust, which lies
under the oceans. Continental crust is thicker than oceanic crust.
The mantle is the thickest section of the Earth. It sits underneath the crust and continues downwards
for a further 2 900 km. The mantle is made up of molten rock called magma. The temperature of
the mantle varies between 500-900°C near the boundary with the crust, to over 4 000°C near the
boundary with the core.
The outer core is the layer surrounding the inner core. It is approximately 3 000 km below the Earth’s
surface. It is thought that the outer core is liquid, made up of molten iron and nickel. It is extremely
hot, with temperatures ranging between 4 000°C and 5 000°C. Because the Earth rotates, the
outer core spins around the inner core and it is thought that this causes Earth’s magnetic field.
The inner core is in the centre and is the hottest part of the Earth. It is solid and made up of iron and
nickel at temperatures of up to 5 500°C. With its immense heat energy, the inner core is considered
the engine room of the Earth.
1. Use the information above to identify the various layers of the Earth and summarise the key
points about each layer.
2. Identify the layer which is the:
Hottest: Coldest:
Thickest: Thinnest:
3. Define the term ‘molten’. 

4. Outline the differences between the two types of crust.