WEATHERING

Weathering is the process by which rocks on or near

Earth’s surface break down and change

Weathering is different from EROSION, which

is the transport of weathered material from place to place.

PHYSICAL WEATHERING

VIDEO

Weathering that results in the breaking of rock into smaller

pieces (called clasts) without any change in the chemical

composition of the

rocks/minerals is called PHYSICAL

WEATHERING

This type of weathering causes

changes in the SIZE and sometimes the

SHAPE of the weathered material.

Water EXPANDS as it freezes, causing a 9%

increase in volume. If the water is in a crack in the

rock, then this change can exert pressure on the

surrounding rock.

The splitting of rock due to repeated

freezing and thawing of water in the cracks

is called FROST WEDGING.

This process required the temperature to rise and

fall through the FREEZING or MELTING

point of water which is 0oC, or 32oF

Rock at great depth in the Earth is under

extreme PRESSURE caused by the weight of the

overlying rock.

If this rock is removed (by erosion or faulting)

then the WEIGHT on the rock below is

RELEASED allowing the rock to EXPAND

and crack.

Cracks in the rock formed in this way are called JOINTS.

Cracks in the rock can also be

expanded physically by the growth of PLANT ROOTS.

CHEMICAL WEAHTERING

VIDEO

Weathering which results in a change in the mineral or rock’s composition is called

CHEMICAL WEATHERING

These substances are significant agents of chemical weathering.WATER, OXYGEN, CARBON DIOXIDE,

and ACIDS.

What two minerals are easily affected by the presence of acids in the environment?

Answer:CALCITE

andDOLOMITE

What rocks commonly used in buildings and

monuments will also be affected by acid in the

environment?

Answer:LIMESTONE,DOLOSTONE,

ANDMARBLE

As temperature increased the rate

of chemical weathering

INCREASES

Water is called the universal solvent

because it can readily DISSOLVE many substances.

Any reaction of water with other

substances is called HYDROLYSIS.

The chemical combination

OXYGEN with other substances is called oxidation.

Oxidation of metals is commonly referred to as

RUST.

Carbon Dioxide and atmospheric water combine to form a weak acid called

CARBONIC ACID.

What two substances are the major causes of

acid rain and snow?SULFUR DIOXIDE

and

NITROGEN OXIDES

Human beings could greatly reduce the impact of acid rain in the future if we drastically reduce the

need for FOSSIL FUELS

Acids have a pH LESS than neutral

(7), a substance with a pH above 7 is a

BASE.

Next upOur Best Friends

What are some Factors which can affect the Rate of

Weathering?

Rate of weathering is affected by

Climate - temp and H2ORock Composition

Surface AreaTopography - slope

What climate conditions are

best for chemical weathering?

Answer:HOTand

WET

What climate conditions produce the highest rates of

physical weathering?

Answer:COOL

and DRY

(not completely dry)

Lockport experiences both types of weathering

because we have abundant MOISTURE and FLUCTUATING

temperatures.

What two characteristics

will determine a rock’s resistance to weathering?

Answer:Hardness

andComposition

What will a relationship graph describing how

the rate of weathering is affected by the surface area of a material look

like?

Hint:12481632

SURFACE AREA

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AT

HE

RIN

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