Did you know?
In the 19th century, people
already knew that the Earth
was formed by rocks with
many different characteristics
and components.
It was also known that
temperatures in the Earth’s
interior were so high that
many of these rocks melted
and were thrown out to the
Earth’s surface by volcanoes.
The French author Jules Verne
(1828-1905), in his famous
novel
Journey to the Centre of the Earth,
imagined an expedition to the centre
of the Earth, through the crater of an ancient extinct volcano in Iceland. The
members of the expedition were able to return to the surface because of an
eruption, through the crater of Stromboli, a volcano on the island of the same
name, in the north of Sicily, Italy.
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2. Relief
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1. THE STRUCTURE OF THE EARTH
The Earth
is the planet where we live. It a sphere-shaped and its interior is made
up of
three layers
. From the surface to the centre, these layers are the
crust
, the
mantle
and the
core
.
❚
The crust
is the outer layer of the Earth and consists of the continents, the sea
and ocean floors. The thickness of this layer varies. In some areas (under the
mountains) it is 70 km deep, while in other areas (below the oceans) it is only 10
km deep.
❚
The mantle
is the middle layer, which is between 70 km and 2900 km deep.
Temperatures in this layer are high, which causes rocks to melt. These mantle
rocks that are in a semi-solid state are called
magma
.
❚
The core
is the innermost part of the Earth. The temperatures in the core can
reach more than 1000 ºC. The core is composed of two parts: the inner core and
the outer core.
– The
outer core
surrounds the inner core and extends between 2900 km and
5100 km, where the inner core starts. Due to the extremely high temperatures,
rock in the outer core is molten rock
1
.
– The
inner core
is at the centre of the Earth and extends from 5100 km to
6378 km deep. The inner core is solid. The densest and heaviest rocks are here. It
is composed mainly of iron, with some nickel and other minerals.
As it is not possible to study the Earth’s interior by direct observation, indirect methods
are used, such as the analysis of meteorites and seismic waves from earthquakes.
Still from the film
Journey to the Centre of the Earth
(2008)
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molten:
rock made liquid by heat
