Modelling of the land reliefPresentation Transcript
MODELLING OF THE LAND RELIEF
The structure of the Earth
CRUST (continental and oceanic)
MANTLE (upper mantle and lower mantle)
CORE (outer and inner)
THE CICLE OF ROCKS
What are the names of the rocks which are on the Earth´s surface? SEDIMENTARY ROCKS What structure produces the action of geological agents on sedimentary rocks? THE LANDSCAPE
Wild waters (streams, torrential fluvial)
Fluvial waters (rivers)
Modelling of the relief phase:
Destruction of preexisting rocks by the action from ATMOSPHERIC AGENTS (temperature, rainfall, action of gases), without displacing the fragments. 3 Types of meteorisation: 1. Mechanical o physical meteorisation: it doesn´t change the chemical composition.
2. Chemical meteorisation: structure and components are decomposed. 3. Biological meteorisation: living beings break up the rocks.
2. EROSION 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 …)
4. SEDIMENTATION 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 The soil is not simple accumulation of sediments. It is formed very slowly under the influence of fhese factors:
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 productivity. 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)
GEOLOGICAL AGENTS: WIND
The wind or aeolian processes can produce erosion, transport and sedimentation.
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 stone field : REGS
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.
AEOLIC EROSION: AEOLIC SEDIMENTATION:
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)
INDIVIDUAL DUNES BRANCHAN DUNE PARABOLIC DUNE Moving crescent-shaped dune whose arms extend in the same direction as the wind Moving crescent-shaped dune whose arms extend in the opposite direction to the wind LONGITUDINAL DUNE When the dunes are parallel to the directon of the wind
EXTERNAL AGENT: FLUVIAL PROCESSES
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. - DISADVANTAGES:
- ADVANTAGES: 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 water.
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:
water water FLUVIAL EROSION PRODUCES VALLEYS TOO
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 relief.