Earth’s Layers
- Earth formed approximately 4.5 billion years ago. At this time it consisted almost entirely of molten rock (magma).
- Ever since its formation, Earth has been very slowly cooling down.
- As it cooled, Earth differentiated into layers, with more dense material sinking towards the centre and less dense material moving towards the surface.
- During the first few hundred million years after formation, Earth’s surface became solid and water condensed to form oceans.
- Earth consists of four main layers. Starting from the outside, these are:

Earth’s main layers are the crust, mantle, outer core and inner core.
(Image: Nouval, Adobe Stock)
- Each of Earth’s layers has distinct physical and chemical properties.
- Temperature, pressure and density all increase with depth below Earth’s surface.
- While temperature and pressure increase gradually, there are distinct density differences between Earth’s major layers.

Temperature, pressure and density all increase with depth below Earth’s surface.
(Sources: Karla Panchuk, Wikipedia Commons; Anita Zeidler, ResearchGate; Robert Tenzer, ResearchGate)