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Le relief de la Terre
RELIEF
Rafael AGÚNDEZ BLANCO
IES « Fray Pedro de Urbina »
1. The structure of the Earth
The Earth is divided into layers :
1. The core
2. The mantle
3. The crust
1
2
3
The core, over 6 000 km deep, is
made of iron and nickel. Earth’s
core temperature is estimated at
around 5 000 ºC.
The outer core, is liquid, but the
inner core remains solid because
of the high pressure.
6 000 km
The mantle, over 3 000 km deep, is
divided into two layers:
a) the lower mantle ou
asthenosphere, viscous;
b) the higher mantle, solid.
3 000 km
The higher mantle and the crust, a
thin solid layer (5 km deep), form
the lithosphere.
Lith
osp
he
re
Crust
Higher mantle
30
km
5 k
m
2. Plate tectonics
The lithosphere is broken into
tectonic plates, which ride on the
asthenosphere.
Tectonic plates move because of
asthenosphere movements.
Tectonic movements cause the
collision or divergence of tectonic
plates.
Plate boundaries are commonly
associated with geological events
such as earthquakes and the
creation of topographic features
such as mountains or volcanoes
Continents move at a speed of 10
cm per year because of plates
tectonics.
Continental drift is the movement
of the Earth's continents.
Arthropodes (e.g. trilobites) prosper in the
oceans.
Trilobite
Cambrian 500 m. a.
Ordovician 470 m. a.
The water temperature close to the surface is
40 ºC. One day is equivalent to 21 hours.
Silurien 430 m. a.
Land plants evolve from algae.
Dévonien 370 m. a.
First amphibians evolved from fish.
Carboniferous 300 m. a.
Earth is covered by forests, which produced
large quantities of coal in Europe.
First reptiles developed in response to an
drier climate.
Trias 220 m. a.
Pangaea was the supercontinent that existed
250 million years ago, before the component
continents were separated into their current
configuration.
A warmer and wetter climate allows the
developement of large rainforests. Ice caps
don’t exist.
It was a golden age for dinosaurs.
Jurassic 150 m. a.
Asteroid
Cretaceous 65 m. a.
A massive asteroid impact of 10 km caused
the a mass extinction of animal and plant
species.
Éocène 50 m. a.
Mammals expand after the extinction of the
dinosaurs. Australia separated from
Anctartica. The Himalaya is a result of the
continental collision between the indo-
Asutralian plate and the Eurasian Plate.
In several million years,
Africa will collide with
Europe.
Finally, every continent
will form a new
pangaea.
+50 m. a.
+250 m. a.
3. Landscape transformation
Tectonic
movements
Volcanos Erosion
The collision of tectonic
plates can produce two kinds
of lithosphere deformation
depending on the material
composition:
• Faults (fractures)
• Folds (curved
deformation)
Fold
Fault
The oceanic ridges are submarine
mountain ranges that result from the
divergence of tectonic plates.
Europe America
Oceanic
ridge
Vaults and folds exist from the
microscopi scale at hundreds of
kilometers.
The large vaults and folds result
in orogenics movements, which
are the origin of most of large
kinds of relief.
.
A mountain is a natural elevation of the Earth surface.
A peak is the pointed top of a mountain.
Altitude and steepness are used as criteria for
defining a mountain.
If altitude is considered, the highest mountain is the
Everest. But if steepnees is considered, the highest
mountain is Mauna Kea (Hawai).
10 200 m 8 844 m
Everest Mauna Kea
If the altitude of an elevation is not significant, it
is a hill,
If its steepness is not significant, it is a plateau, a
large flat area of land at high altitude.
Hill Plateau
The biggest landform in the world is the
Tibetan Plateau, called “the roof of the
world”.
It is four times the size of France and
has an average elevation of 4 500 m.
A mountain range is a long
and narrow succesion of
mountains.
A massif is a compact group
of mountains.
Massif
A fault might cause an earthquake, a sudden
movement of the Earth’s surface.
An Earthquake’s point at ground level is called
epicenter.
A seismograph is a device which
measures and records the magnitude
(strengh) of an earthquake.
The magnitude is a logarithmic scale,
so an increase of 1 step corresponds
to a 32 times increase in the amount
of energy released.
Magnitude Description Effects Frequency
2 Micro Not felt 8 000 per day
4 Light Shaking of indoor items 6 000 per year
6 Strong Major damage to poorly constructed buildings
120 per year
8 Great Serious damage. 1 per year
A submarine earthquake might cause a tsunami, a
lseries of waves caused by the displacement of a large
volume of water.
The sudden elevation of a fault cause the displacement
of a large volume of water to sea surface.
200 km
This wave cause a raised line of
water not very high (1 m), but
very long (200 km) and
extremely fast (800 km/h).
This makes tsunamis dificult to
detect over deep water.
As the tsunami approaches the
coast, its wavelength and velocity
diminish, but its height grows
enormously: the wave might be
over 30 m.
1,80 m
30 m
The 2004 Indian Ocean
Tsunami killed over 200 000
people.
Before After
A tsunami can change the coast landscape.
A volcano is an opening in the Earth’s crust, which allows
magma, ash and gases to scape from below the surface.
Magma is molten rock that is found beneath the surface
of the Earth.
If the magma reaches the surface, it erupts as lava or
tephra.
Lava is hot liquid rock which comes
out of the earth through a volcano
Pyroclasts or tephra are solid
fragments which are blasted into
the air (ashes, lapilli, volcanic
bombs…)
Lapilli Volcanic bomb
Volcanic cones are structures built by the accumulation
and solidification of lava flows.
A lava dome is a circular mound-shaped structure from
the slow eruption of very viscous lava from a volcano.
Volcanic fissures are fissures through which lava
erupts, usually without any explosive activity.
Volcanic fissures produce often lava fountains.
An underwater volcano
might produce the sudden
formation of an island.
The conduit is the passage through which the magma
travels to the surface.
A crater is a circular depression formed at the top of a
volcano.
Volcanic eruptions cause the formation of an ash cloud
20 km high. Ash clouds can generate lightnings.
Lava flow is a moving outpouring of lava, caused by the
rise of magma to the surface.
A dyke is a vertical infiltration of magma.
A sill is an horizontal infiltration of lava.
A batholite is a large accumulation of magma.
A fumarole is an opening in Earth’s crust which emits
steam and gases.
A geyser is a spring characterized by intermittent
discharge of water ejected turbulently and accompanied
by steam.
A nuée ardente is a fast-moving
currents of hot gas which travels
away from the volcano at speeds
generally as great as 700 km/h.
The gas can reach temperatures of
about 1 000 °C.
In Martinique, a nuée ardente
killed 30 000 people.
A lahar is a type of debris flow composed of pyroclastic
material, rocky debris, and water. The material flows
down from a volcano, typically along a river valley.
Snow is suddenly melted by lava, the
flood can flow 100 km/h, causing
catastrophic destruction in their path.
Lahars can be deadly because of their energy
and speed.
The lahars from the Nevado del Ruiz
eruption in Colombia in 1985 caused
the Armero tragedy, which killed an
estimated 23,000 when the city of
Armero was buried.
A caldera is a cauldron-like volcanic feature usually
formed by the collapse of land following a extremely
violent volcanic eruption.
A collapse is triggered by
the emptying of the magma
chamber beneath the
volcano
An islet (a dome) is often
formed in the center of the
caldera..
The collapse of the volcano results in a large
depression.
The eruption of a caldera in Toba,
70 000 years ago, was the Earth’s
largest eruption.
This event resulted in a global
cooling of atound 15 ºC and 10
years volcanic winter.
Volcanos often form landscapes of remarkable beauty.
Morning Glory Pool (United States) Giants Causeway (United Kingdom) Champagne Pool (New Zealand)
Dallol (Ethiopia)
Dallol (Ethiopia)
Dallol (Ethiopia)
Erosion is the process of
weathering and transport of solids
in the natural environment.
Coastal erosion
River erosion
Wind erosion
Kars erosion
Ice erosion
Coastal erosion is the
weathering and transport of
solids by oceans
A bay is an area of water mostly surrounded by
land.
A large bay may be called a gulf.
Gulf Bay
An island is any piece of land that is surrounded by
water.
Very small islands are called islets or keys.
Island Islet
An atoll is an island of coral that encircles a body of
shallow sea water or lagoon partially or completely.
Atolls are in tropical waters.
A beach is a landform along the shoreline of an
ocean, sea or lake
The color of sand depends on the composition: the
white sands contain coral and shell fragments; the
black sands have a volcanic origin.
White sands Black sands Pebbles Beachrock
A sandbar is a linear landform extending into a body of
water, typically composed of sand or small pebbles.
A spit is a type of sandbar that
connects to land and extends into
the sea.
A lagoon is a body of sea water
separated from the sea by a bar.
A tombolo is a landform in which
an island is attached to the
mainland by a sandbar.
Spit Tombolo
Lagoon
A cliff is a vertical landform due
to the processes of erosion.
Cliffs are common on coasts and
in mountainous areas,
A natural arch is a landform with
an opening underneath. It may
become in a needle.
Albufera (Valencia)
Etretat cliffs
Tombolo
River erosion is the weathering
and transport of solids by rivers
A river is a natural watercourse flowing toward an
ocean, a lake, a sea, or another river.
A tributary or affluent is a river which flows into a main
river.
The longest rivers in the world are the Nile (6 718 km),
and the Amazon (6 500 km).
However, the Amazon is by far the largest river
because it has the largest flooded basin in the world,
(350 000 km2). It is approximately one-fifth of the
world's total river flow.
Nile
Amazon
Rivers flow downhill from river
source through the river bed.
A lake is a body of water of
considerable size that is
surrounded by land.
It is larger and deeper than a pond.
A waterfall is a place where
flowing water rapidly drops in
elevation as it flows over a
steep region or a cliff.
Niagara Falls (52 m)
A canyon or gorge is a deep valley
between cliffs often carved by a river.
The Grand Canyon in Arizona is 446 km
long, up to 29 km wide and attains a
depth of 1 830 m.
A meander is a curve of a river.
It is formed when the moving water
in a river erodes the outer banks
and widens its valley.
The mouth is the place where a river flows
into the sea.
An estuary is the wide part of a river at the
place where it joins the sea.
A delta is a low land formed at the mouth of
a river, often shaped like a triangle.
Estuaire Delta
A ria is a drowned river valley that results
of sea level changes.
Colorado Canyon
Black Canyon
Glen Canyon
Meandering river
Angel Falls (Venezuela)
Niagara Falls
Havasu Falls
Iguazu Falls
Iguazu Falls
Iguazu Falls
Wind erosion is the weathering
and transport of solids by rivers.
Wind erosion is very important in deserts because
of the lack of vegetation.
A desert pavement or reg is a desert surface that is
covered with pebbles. An erg (also sand sea) is a large
area of desert covered with sand.
Reg Erg
A dune is a hill of sand built by aeolian processes
in the ergs.
A barchan dune is an arc-shaped sand ridge.
Wind
direction
Barchans
Riples are structures with a
sinusoidal profile.
Yardangs are rocky structures
carved from bedrock by the wind
abrasion.
Ripples
Yardangs
Examples of wind erosion
Utah (United States)
Examples of wind erosion
Atacama (Bolivia)
Las Gredas (Murcia)
Examples of wind erosion
Examples of wind erosion
Urulu (Australia)
Man-Pupu-Nyor (Russia)
Examples of wind erosion
Lençois Maranheses (Brazil)
Examples of wind erosion
Examples of wind erosion
Lençois Maranheses (Brazil)
Karst erosion is a landscape
shaped by the dissolution of
limestone.
A doline or sinkhole is a natural depression or hole in
the Earth’s surface.
If the depression is very large and flat, it is called a polje.
Polje
Doline
A limestone pavement is a natural karst landform
consisting of a flat, incised surface of exposed limestone.
Stalactites
A stalactite is a structure that hangs from the ceiling of
limestone caves.
A stalagmite is a structure that rises from the floor of
the cave due to the dripping of calcium carbonate.
Stalagmites
Examples of karst erosion
Tazka (Croatia)
Examples of karst erosion
Witch Finger (United States) Tien Son (Vietnam)
Examples of karst erosion
Ciudad Encantada de Cuenca
Examples of karst erosion
Ciudad Encantada de Cuenca
Examples of karst erosion
Antelope Canyon (United States)
Examples of karst erosion
Chocolate Hills (Philippines)
Examples of karst erosion
Pamukkale (Turkey)
Examples of karst erosion
Pamukkale (Turkey)
Examples of karst erosion
Huanglong (China)
Examples of karst erosion
Blue Hole (New Zealand)
Ice erosion is the weathering
and transport of solids by
glaciers.
A glacier is a large persistent body of ice.
Nowadays glaciers cover a small area of the Earth. However,
20,000 years ago, glacier covered large regions.
During glaciation, water was
taken from the oceans to
form the ice, thus global sea
level dropped by about 110
meters
Nowadays there are two types of glaciers:
1) the indlandsis or ice sheet, masses of glacier
ice that are greater than 50 000 km2 (Antarctica
and Greenland);
2) the alpine glaciers, formed on the crests of
mountains.
Indlandsis Alpine glacier
The indlandsis must be
distinguished from the sea ice,
formed from seawater that
freezes.
Sea ice cyclically freezes and
melts due to the seasons.
An iceberg is a large piece of
ice from freshwater that has
broken off from a glacier and is
floating in open water.
Alpine glaciers form on the crests and
slopes of mountains.
An alpine glacier that fills a valley is
sometimes called a valley glacier.
A cirque is a concave landform
found among mountains as a
result of alpine glaciers. .
A moraine is an accumulation
of glacial debris.
An arête is a thin ridge of rock.
The meeting of three or more arêtes creates pointed
pyramidal peaks, called horns.
A U-shaped valley has steep, straight sides, and a flat
bottom. It is formed when a glacier travels across and
down a slope, carving the valley by the action of
scouring. When the ice recedes, the valley remains.
A glacial lake is a
lake with origins in a
melted glacier.
In Finland, the Ice Age resulted in
a vast quantity of lakes.
In fact, more than 10 percent of
Finland is covered by water.
Coasts having the most pronounced
fjords include the northwest coast of
Europe, the west coast of North
America, the west coast of New
Zealand, and the west coast of South
America and to south-western
Tasmania.
4. Relief representation
A topographic map is a type of map
characterized by large-scale detail and
quantitative representation of relief,
A contour line (also isohypse)
is a curve that joins points of
equal elevation (height).
Contour lines are represented
using numbers (100 m, 200 m,
etc.) or colors (green for
depressions, white for
mountains, etc.).
A topographic profile is a
vertical view of a topographic
map.
Profil topographique
Carte cartographique
A
B
A
B
A
0 m
1 5
00 m
1 0
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5
00 m
500 m
1 0
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1 5
00 m
1 0
00 m
500 m
1 0
00 m
500 m
1 0
00 m
0 m
0 m
1 5
00 m
1 0
00 m
1 5
00 m
0 m
B
500 m
1 000 m
1 500 m
500 m
500 m
A
0 m
1 5
00 m
1 0
00 m
5
00 m
500 m
1 0
00 m
1 5
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1 0
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500 m
1 0
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500 m
1 0
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B
500 m
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1 500 m
500 m
500 m
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