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EARTH SCIENCE

GROUP 1Ms. Jaziel Grace M. Addun

Ms. Melissa F. Abayon

BEED-I

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 WEATHERING

 Weathering is the breaking down of rocks,

soils and minerals as well as artificial

materials through contact with the Earth'satmosphere, biota and waters. Weathering 

occurs in situ , or "with no movement", and

thus should not be confused with erosion, which involves the movement of rocks and

minerals by agents such as water, ice, wind,

and gravity.

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 physical weathering  involves the

breakdown of rocks and soilsthrough direct contact with

atmospheric conditions, such as

heat,  water, ice and pressure. The

second classification,

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Physical weathering can occur due

to temperature, pressure, frost etc.

For example, cracks exploited by

 physical weathering will increase

the surface area exposed tochemical action. Furthermore, the

chemical action of minerals incracks can aid the disintegration

 process.

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Physical weathering  is theclass of processes that causesthe disintegration of rocks

 without chemical change. The

primary process in physical weathering is abrasion 

.However, chemical andphysical weathering often go

hand in hand.

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chemical weathering  involves the

direct effect of atmospheric chemicals

or biologically produced chemicals(also known as biological weathering )

in the breakdown of rocks, soils andminerals .As with many other

geological processes the distinction

between weathering and related

processes is diffuse.

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 The materials left over after the rock 

breaks down combined with organicmaterial creates soil. The mineral

content of the soil is determined by the parent material, thus a soil

derived from a single rock type can

often be deficient in one or more

minerals for good fertility ,

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Chemical Weathering

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 while a soil weathered from a mix

of rock types (as in glacial, aeolian or alluvial sediments) often makes

more fertile soil. In addition many of Earth's landforms and

landscapes are the result of  weathering processes combined

 with erosion and re-deposition.

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 weathering

(sometimes called Insolation  weathering

results from expansion orcontraction of 

rock, caused by temperaturechanges.

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Thermal stress weatheringcomprises two main types,

thermal shock and thermalfatigue. Thermal stress

 weathering is an importantmechanism in deserts, where

there is a large diurnal temperature range, hot in the day

and cold at night.

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The repeated heating and cooling 

exerts stress on the outer layersof rocks, which can cause their

outer layers to peel off in thinsheets. Although temperaturechanges are the principal driver,moisture can enhance thermal

expansion in rock .

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Forest fires and range fires are

also known to cause significant weathering of rocks and

boulders exposed along theground surface. Intense,

localized heat can rapidly expand a boulder.

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  A rock in Abisko, Sweden fractured

along existing joints possibly by frost

 weathering or thermal stress.

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Frost weathering, frost wedging, ice wedging  or

cryofracturing  is the collectivename for several processes

 where ice is present.

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 These processes include frost

shattering, frost-wedging and

freeze-thaw weathering..

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 This type of weathering is

common in mountain areas

 where the temperature is

around the freezing point of 

water.

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Freeze induced weathering

action occurs mainly inenvironments where there is a

lot of moisture, andtemperatures frequently

fluctuate above and below 

freezing point, especially in

alpine and periglacial areas.

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 An example of rocks susceptible to frost

action is chalk , which has many porespaces for the growth of ice crystals. This

 process can be seen in Dartmoor where it

results in the formation of tors. When

 water that has entered the joints freezes,

the ice formed strains the walls of the

joints and causes the joints to deepen

and widen

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 When the ice thaws, water can flow 

further into the rock. Repeatedfreeze-thaw cycles weaken the rocks

 which, over time, break up along

the joints into angular pieces. The

angular rock fragments gather at the

foot of the slope to form a talus slope (or scree slope). 

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 The splitting of rocks along

the joints into blocks iscalled block disintegration.

 The blocks of rocks that aredetached are of  various

shapes depending on rock structure.

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In pressure release, also known asunloading, overlying materials

(not necessarily rocks) areremoved (by erosion, or other

 processes), which causesunderlying rocks to expand and

fracture parallel to the surface.

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Often the overlying material is

heavy, and the underlying rocks experience high pressure

under them, for example, amoving glacier. Pressure

release may also causeexfoliation to occur.

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Building weathering 

Buildings made of any stone, brick orconcrete are susceptible to the same

 weathering agents as any exposed

rock surface. Also statues, monumentsand ornamental stonework can be

badly damaged by natural weathering

 processes. This is accelerated in areas

severely affected by acid rain.

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Living organisms maycontribute to mechanical 

 weathering Lichens andmosses grow on essentially

bare rock surfaces and createa more humid chemicalmicroenvironment 

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