Modelling of the relief phase:
Destruction of preexisting rocks by the action from ATMOSPHERIC
AGENTS (temperature, rainfall, action of gases), without displacing
3 Types of meteorisation:
1. Mechanical o physical meteorisation: it doesn´t change the
2. Chemical meteorisation: structure and components are decomposed.
3. Biological meteorisation: living beings break up the rocks.
Destruction of preexisting rocks by the action from GEOLOGICAL
AGENTS which move the fragments towards other different place.
What are the differences between
Meteorisation and Erosion?
The transport of rock fragments from the place which produce the
meteorisation and erosion to other different.
This transport depend on:
-Size of fragment rocks.
-Force of external agent (wind, water …)
It´s a process of accumulation of rock fragments transported.
- This acumulation forms SEDIMENTS.
- When sediments are compacted form SEDIMENTARY ROCKS.
Explain what conditioning factors ( or
atmospheric agents ) influence in the action of
the external agents in the next pictures
The soil is not simple accumulation of
It is formed very slowly under the influence of
MOTHER ROCK: the original matter
over which soils are formed.
Sometimes is originated by the
compactation of sediments (gravel ,
sand or clay), and it gives to the soil
several mineral components.
The different composition of
materials and the accumulation of
substances form different layers
known as HORIZONS.
HUMUS: is decomposed organic
matter that comes from the
remains of animals and plants,
Humus give to the soil a huge
LIVING BEINGS: the animals of
the soil (worms, for example) and
the roots of plants help to mix the
materials to air it.
CLIMATE: temperature and rainfall
for example, produce alteration of
rocks (by leaching, for example)
• The wind or aeolian processes can
produce erosion, transport and
• The action of wind is very active in HOT
and COLD arid zones.
• There are two kinds of erosive action:
DEFLATION: is the normal process of
erosion by the wind, that is, the selective
movement of particles which fall on the
ground and it forms different landscapes.
A desert formed by dunes: ERG
And the thinnest particles can travel long distances and when the
wind loses its force the particles fall down in humid zones and
it forms LOESS.
Its the origin of the mud and clay
AEOLIC ABRASION: is the wearing
away of rocks caused by the repeated
impact of the particles carried by the wind.
-By traction: when the particles are carried without
losing contact with the Earth´s surface.
- By saltation: when they are lifted slightly and they
touch the Earth´s surface from time to time.
-By suspension: when small particles are in the air
without touching the Earth for a long time.
AEOLIC TRANSPORT: the particles carried by the wind are transported:
-A desert of stone: REG.
-A desert of dunes: ERG.
-Loess deposit: it is the origin of clay and mud. LIMOS (de poco grano, entre
arenas finas y arcillas, es transportado por viento y agua. También zonas
inundadas sedimenta y da mucha fertilidad a los suelos)
dune whose arms extend
in the same direction as
dune whose arms extend
in the opposite direction to
When the dunes are parallel
to the directon of the wind
A. WILD WATERS
Surface waters from rainfall that flow with no
fixed course. When the water flow through small
channels are known as streams.
The action of these geological agents is especially important in steep
hillsides which are unprotected by a layer of vegetation.
This erosion is very important because these geological factors can wear
away the soil and it produces a lost of productivity.
This erosion produce nice landscapes:
-BADLANDS: are abrupt areas where there are “V” shapes of
varying depths. Badlands is formed by the rainfall that wear away the
soft rocks but not the hard rocks, and by channels of streams which
produce erosion too (CÁRCAVAS)
-FAIRY CHIMNEYS: are conical shapes in the rocks where the
upper part is composed by harder rocks than rocks located down.
They are produced by a strong rainfall, surface waters and the wind.
(CHIMENEAS DE HADAS)
EROSION OF WILD WATERS: this erosive capacity of the water depends on
the effect of friction caused by sediments, the geological characteristics of the
land ( such as steep slope ) and how long that wild waters are in land.
Produce landscapes such as:
SEDIMENTATION OF WILD WATERS: the most common forms are:
TRANSPORT OF WILD WATERS: it´s very variable. It depends on the
intensity of water.
CONO DE DEYECCIÓN (in Spanish language)
B. FLUVIAL WATERS
Surface waters that flow with fixed course
The high, medium, and low courses of a river produce erosion, transport
and sedimentation in any point along the river´s course.
The erosion, transport and sedimentation depend on the speed of the
FLUVIAL EROSION: this erosive capacity of the water depends on the speed
of the water, the effect of friction caused by the sediments and the geological
characteristics of the land ( such as steep slope ).
FLUVIAL SEDIMENTATION: the most common forms are:
-By dilution in the water.
-Floating on the surface.
-Suspended in water.
-Jumping and rolling.
-The own course of the river
-Waterfalls (factor of erosion and landscape)
-Meanders (factor of erosion and landscape)
-Fairy chimneys (landscape)
FLUVIAL TRANSPORT: the particles carried by the water are transported:
MEANDER: curves in the middle of the
river that erod on the concave edge.
DELTA: accumulations of sediments
that appear in some river. It occurs in
shallow, calm waters.
ESTUARY: accumulations of
sediments that appear in
some river, but its
influenced by the force of
the sea (the sea goes
towards the land and the
sediments are dispersed)
FLUVIAL TERRACES: are layers of river
deposits situated at higher level than
the actual river bed.
ALLUVIAL PLAINS: smooth land where extensive
deposits of materials are deposited by decrease of
the river or stream speed after crossing a steep