Modelling of the land relief

MODELLING OF THE LAND RELIEF

The structure of the Earth

3 parts:-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

GEOLOGICAL AGENTS

-Wind-Glaciers

-Wild waters (streams, torrential fluvial)

-Fluvial waters (rivers)-Groundwater

-Sea

Modelling of the relief phase:

1.METEORISATION

2. EROSION

3. TRANSPORT

4. SEDIMENTATION

SEDIMENTARY PROCESS

1.METEORISATION

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?

3. TRANSPORT

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

Fungi rock

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

AEOLIC ABRASION

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: ERGAnd 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.

Fungi rock

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.

-Deflation-Aeolic abrasion

AEOLIC TRANSPORT: the particles carried by the wind are transported:

-A desert of stone: REG.-A desert of dunes: ERG.

-Individual Dunes.-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

- Stream

- Torrent

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:

-Bad-lands-Fairy chimneys

TRANSPORT OF WILD WATERS: it´s very variable. It depends on the intensity of water.

-Alluvial plainsCONO DE DEYECCIÓN (in Spanish language)

• Rivers

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)

-Bad-Land (landscape)-Fairy chimneys (landscape)

FLUVIAL TRANSPORT: the particles carried by the water are transported:

-Alluvial plains-Fluvial terraces

-Deltas-Estuary

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.

Meanders

Alluvial plain

Delta

Estuary

IES TORREÓN DEL ALCÁZARMARTA SÁNCHEZ REINO

SCIENCE