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THE EARTH´S STRUCTURE
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• The Geosphere: Crust, Mantle and Core
• The dynamics of the geosphere:
Convection currents
• The lithosphere:
• Submerged relief:
Continental platform:
Continental shelf: Talud continental
Abyssal plain: Llanura abisal
Oceanic ridge: Dorsal oceánica
Oceanic trench: Fosa oceánica
the Earth’s spheres
The geosphere
• Of all the Earth’s spheres, the geosphere occupies the greatest
volume. It is almost perfectly sphere-shaped.
• It is divided into a number of layers:
Crust: This is the thinnest layer of the
geosphere. The hydrosphere, the biosphere
and the atmosphere are located on this
layer.
Mantle: The thickest layer, the mantle is
made of malleable rocks and some molten
materials.
Core: This is the innermost and hottest
layer of the geosphere. It consists of the
outer core, which is molten, and the inner
core, which is solid.
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The dynamics of the geosphere
The dynamics of the geosphere
• The Earth’s internal heat, called geothermal energy, increases with depth, driving
the inner dynamics of the geosphere.
• The movements of the rocks in the mantle are convection currents.
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1
The intense heat of the
deep mantle makes the
rocks less dense, causing
them to rise towards the
surface.
As the rocks move
towards the surface,
they cool down and their
density increases,
causing them to sink
back to the deeper
zones, where they heat
up and consequently rise
again.
The lithosphere and lithospheric plates
What is the lithosphere?
• The lithosphere is formed by the Earth’s crust and the upper part of the mantle
(made up of hard rocks).
• Its thickness varies, from 70 km under the oceans up to 200 km in the
continents.
• There are two types of lithosphere: the continental lithosphere and the oceanic
lithosphere.
Oceanic
lithosphere
Continental
lithosphere
Crust
Lithosphere
Hard
mantle
Submerged relief
Continental platforms
• Continental platforms are extensions of continents submerged in the ocean.
• They are usually quite flat but get deeper the further into the sea they are.
• The platform ends in a steep slope called the continental shelf.
Continental
platform
Continental shelf
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Submerged relief
Abyssal plains
• These are large plains located at great depths (normally at depths of
more than 3,000 metres). They make up the largest part of the ocean floor.
• Submerged mountains and volcanoes can be found here. They are
sometimes so high that they form islands.
Volcanic island
Abyssal plain
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Submerged relief
Ridges
• These are large underwater mountain ranges that are thousands of
kilometres long. They cut through the abyssal plains. They can be so high that
they emerge from the water and create islands, as is the case of Iceland.
• Ridges have a fissure down their middle, called a rift.
Rift
Ridge
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Submerged relief
Trenches
• These are very deep, narrow, long depressions.
• The largest trenches are more than 10 kilometres deep and hundreds of
kilometres long.
Trench
The lithosphere and lithospheric plates
Lithospheric plates
• The lithosphere is not one continuous surface: it is divided into a number of pieces,
called lithospheric plates, or tectonic plates.
• Plate boundaries can be easily identified because they coincide with notable features
of the lithosphere like oceanic ridges, oceanic trenches and large mountain ranges.
North American
plate
Eurasian plate
Philippine
plate
Juan de
Fuca plate
Arabian
plate
Cocos
plate
Pacific
plate
Nazca
plate
Scotia
plate
South American
plate
Pacific
plate
African plate
Indo-Australian plate
Antarctic plate
Do you remember the following
features of the lithosphere?
• Oceanic ridge: …………… oceánica
• Oceanic trench: …………… oceánica