External dynamics

Autora: Marta GarcíaT.

WEATHERINGWeathering takes place as rocks are

broken down into progressively smaller pieces by the effects of atmospheric agents (water, ice, wind) and living beings.

These pieces do not move to a new location, they simply break down.


There are three types of weathering:

Chemical Weathering: is the descomposition of rocks through chemical reactions that change its mineral composition. It is caused by water, mainly.

For example: Oxidation.


Mechanical Weathering: it takes place when rocks are broken down without any change in its chemical nature. The rocks are essentially torn apart by physical forces (of water, wind or living things).

For ex: Freeze-thaw weathering: when water in rocks freezes, it expands, breaking down materials.


Biological Weathering: it is caused by living organisms.

http://www.uky.edu/AS/Geology/howell/goodies/elearning/module07swf.swf




AGENTS THAT SHAPE LANDSCAPEThe agents that shape landscape are water, wind, ice, gravity and ocean movements. They are responsible for these geological processes:

1. Erosion: it moves small pieces of weathering rocks to another place.

2. Transportation: it moves the eroded roch material.

3. Deposition: rock materials are deposited. It occurs when the transporting agent looses energy.


Which geological process…?



Wind may erode, transport and deposit rock materials. It is only effective in dry regions with not much vegetation. It erodes in two ways:

- Deflation: wind picks up small particles and leaves bigger ones. This produces the Desert Pavement.


http://upload.wikimedia.org/wikipedia/en/c/c7/Desert_Pavement_Mojave_2000.jpg

Abrasion: Small particles carried by the wind erode the rocks. The results are Mushroom-shaped Rocks and Arches.


The wind can create landforms when it deposits its sediments. These forms are called Dunes.

Large areas of Dunes are called Ergs.



Glaciers are masses of moving ice.We can find them in alpine and polar

regions.The move from high areas to low areas by

the force of gravity.

http://www.youtube.com/watch?v=qm43zJz6SWI&feature=related


Glaciars erode landscape creating:

Striations: grooves in the bedrock.Galcial Valleys: U-shaped valleys.


Glacial Cirques: rounded depressions where snows accumulate.

http://www.brainpop.com/science/earthsystem/glaciers/


Ice forms Glacial Tongues which carry and deposite rock material.



Main glacial deposits are called Moraines (ridges of material).



Rivers are masses of current water.They erode, transport and deposit

material. The predominant process on each course depends on the velocity of water:


In the upper course, rivers flow fast. Erosion and transportation are the dominant processes, creating:

V – shaped Valleys (narrow and deep). Waterfalls. Gorges.


In the middle course the velocity decreases and transportation is dominant.

Valleys are wade.Water forms deep bends called Meanders.

http://www.wwnorton.com/college/geo/egeo/animations/ch14.htm


In the lower course rivers are slow and deposition is dominant. Here is the river’s mouth.

If deposited material is pushed into the sea, a Delta will be formed.

http://www.brainpop.com/science/earthsystem/rivers/


Estuaries and Marshes are coastal areas where fresh water and salt water meet. They have a very special biodiversity because of the their particular salt content.

http://iessuel.org/ccnn/flash/cuenca.swfAutora: Marta GarcíaT.


Karst LandscapesThey are landscapes produced by the

dissolving action of water on soluble rocks (carbonate).

Water dissolves carbonates creating geological structures on and under the ground surface.

CaCO3 + CO2 + H2O 2 (HCO3)- + Ca2+

When water drips inside caves, the dissolved calcium carbonate forms deposits.


http://esp.brainpop.com/category_45/subcategory_445/subjects_3922/preview.weml



Find a definition for each termLarge underground cavities.Depressions produced by the

collapse of underground cavities.

Natural resurgence of groundwater.

Deposits which grow downward from the cave ceiling.

Horizontal galery.Deposits which grow upward

from the cave floor.Vertical galery.

SpringStalactiteDolineCaveStalagmiteTunnelShaft





There are three types of water motion in oceans that model coastal areas:

1. Waves: are mainly caused by the wind. They erode, transport and deposit materials.2. Tides: caused by the gravitational atraction of the Moon and the Sun. They transport materials.

3. Currents: caused by differences of temperature. They transport materials.

http://www.brainpop.com/science/earthsystem/tides/


Erosion Landforms:

Bays

http://www.brainpop.com/science/earthsystem/oceancurrents/


Cliffs.Archs.Stacks



Deposition Landforms:

Beaches.Spits.Sandbars.



Sedimentary rocks are usually formed through these three processes:

1. Sedimentation: layers of sediments (pieces of rocks) are deposited.

2. Compaction: sediments on top compresses sediments at the bottom. Water is squeezed out from between the sediments, but the dissolved salts stay.

3. Cementation: These salts form a sort of glue that cements the pieces of rock together.



Education

External dynamics