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

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 0 o C, or 32 o F

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 WEAHTERING

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 and DOLOMITE

What rocks commonly used in buildings and monuments will also be affected by acid in the environment?

Answer: LIMESTONE, DOLOSTONE, AND MARBLE

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.

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What are some Factors which can affect the Rate of Weathering?

Rate of weathering is affected by Climate - temp and H 2 O Rock Composition Surface Area Topography - slope

What climate conditions are best for chemical weathering?

Answer: HOT and 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 and Composition

What will a relationship graph describing how the rate of weathering is affected by the surface area of a material look like?

Hint:

SURFACE AREA  WEATHERING 