Earth was created some 4.5 billion years ago from a mass of iron-rich,
rocky debris orbiting the Sun. The rocks smashed into the young
planet as meteorites, and were welded together by heat generated
from the energy of impact. The bombardment eventually
generated so much heat that the whole planet melted. The
heavy iron then sank towards the centre to become Earth’s
core, while the lighter rocks formed the mantle and crust.Planet Earth
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EARTH’S STRUCTURE
The planet is layered like a peach.
Earth’s rocky crust forms its thin skin,
while the hot, mobile rock of the
mantle is like the peach’s juicy flesh.
At the heart of the planet lies its
metallic core, like the hard stone
at the centre of a peach.Mountains
pushed up where
oceanic crust is
dragged beneath
continents(^1) INNER CORE
The inner core is a heavy ball of solid
iron and nickel. It is heated by nuclear
reactions within Earth to 4,700°C
(8,500°F), but the intense pressure at
the core prevents it from melting.
(^2) OUTER CORE
The solid inner core is surrounded
by a fluid mass of molten iron, nickel,
and sulfur. Swirling currents in
the molten metal of the outer core
generate Earth’s magnetic field.
(^3) LOWER MANTLE
The rocky mantle is 2,900 km
(1,800 miles) deep, and is heated to
3,500°C (6,300°F) at its base. Intense
pressure stops it melting, but rising
heat keeps the hot rock moving slowly.
(^4) UPPER MANTLE
The upper mantle is heated to almost
1,000°C (1,800°F). Where movement in
the mantle cracks the cool, brittle crust,
reduced pressure makes the hot mantle
rock melt and erupt from volcanoes.
(^5) OCEANIC CRUST
The crust between the continents is less
than 11 km (7 miles) thick. It is made of
heavy rock that erupts from the hot
mantle at mid-ocean ridges to form the
bedrock of the ocean floors.
(^6) CONTINENTAL CRUST
The lightest of Earth’s rocks form vast
slabs that “float” on the heavy mantle
like huge rocky rafts. Up to 70 km
(45 miles) thick, they rise above sea
level to form the continents we live on.
Plumes of heat rise
through the mantle,
pushing the plates
of the crust apart
The cool, rocky crust
forms only a tiny fraction
of Earth’s vast mass
The crust is fused to the
top of the upper mantle,
which is in constant motion
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