WeatheringWeatheringand and Soil Soil

FormationFormation

What is weathering?What is weathering?

Weathering is the process by Weathering is the process by which rocks are broken down.which rocks are broken down.– This can be either:This can be either:

Physical Physical ChemicalChemical

Physical a.k.a. MechanicalPhysical a.k.a. Mechanical Mechanical weatheringMechanical weathering is the is the

breakdown of rock into smaller breakdown of rock into smaller pieces by a physical means.pieces by a physical means.

For example:For example:– WindWind– WaterWater– GravityGravity– IceIce– PlantsPlants

Ice WedgingIce Wedging Water seeps into Water seeps into

cracks in rock. cracks in rock. Then, when it Then, when it freezes it expands. freezes it expands. This causes the This causes the cracks to enlarge.cracks to enlarge.

Ice WedgingIce Wedging

1. Water seeps into cracks in rocks.

2. The water freezes (ice expands). This causes the cracks to get larger.

3. The cracks get so large that the rock breaks apart.

AbrasionAbrasion

The weathering of rocks due to them The weathering of rocks due to them rubbing against other rocks or rubbing against other rocks or particals.particals.

Wind, Water, GravityWind, Water, Gravity These are These are

all ways all ways that that abrasion abrasion occurs.occurs.

PlantsPlants Some plants can Some plants can

easily break easily break through rocks.through rocks.

AnimalsAnimals

Burrowing animals such as rats, Burrowing animals such as rats, earthworms, ants, coyotes, and earthworms, ants, coyotes, and rabbits cause a lot of weathering.rabbits cause a lot of weathering.

Chemical WeatheringChemical Weathering

Chemical weatheringChemical weathering is the process is the process by which a rock is broken down as a by which a rock is broken down as a result of a chemical reaction.result of a chemical reaction.

WaterWater Water is the main ingredient in Water is the main ingredient in

chemical weathering. chemical weathering. It may take thousands of years, but It may take thousands of years, but

water can even break down granite.water can even break down granite.

See the difference?

1908 1968

Acid PrecipitationAcid Precipitation Acid precipitationAcid precipitation

is any rain, sleet, is any rain, sleet, or snow that or snow that contains large contains large amounts of acid.amounts of acid.

All precipitation is All precipitation is naturally acidic, naturally acidic, however, acid however, acid precipitation precipitation contains more contains more than normal.than normal.

Acid can also be found in Acid can also be found in groundwater or in the air.groundwater or in the air.

Oxidation is the chemical reaction Oxidation is the chemical reaction that occurs when elements react that occurs when elements react with oxygen.with oxygen.

Weathering ReviewWeathering Review1.1. Give three ways that living organisms can Give three ways that living organisms can

weather rocks.weather rocks.

2.2. How does ice wedging occur?How does ice wedging occur?

3.3. Give an example of how water can Give an example of how water can weather rocks mechanically (physically).weather rocks mechanically (physically).

4.4. Give an example of how water can Give an example of how water can weather rocks chemically.weather rocks chemically.

5.5. How does gravity help weather rocksHow does gravity help weather rocks??

Rates Rates of of

WeatheringWeathering

Rates of WeatheringRates of Weathering

Hard rocks weather slower than soft Hard rocks weather slower than soft rocks.rocks.

This is also called This is also called differential differential weatheringweathering..

Devils Tower in WyomingDevils Tower in Wyoming

What Happened?What Happened? Long ago, magma cooled in the Long ago, magma cooled in the

center of a volcano to form igneous center of a volcano to form igneous rock.rock.

Over time, the outer rock, softer rock Over time, the outer rock, softer rock weathered away leaving only the weathered away leaving only the harder inner rock.harder inner rock.

Devils TowerDevils Tower

Surface AreaSurface Area

Because weathering occurs on the Because weathering occurs on the surface of rocks, the more surface surface of rocks, the more surface area exposed to weather the faster a area exposed to weather the faster a rock will weather.rock will weather.

Warm UpWarm Up1.1. Explain how climate affects the rate Explain how climate affects the rate

of chemical weathering.of chemical weathering.

2. Explain how climate affects the rate 2. Explain how climate affects the rate of mechanical weathering.of mechanical weathering.

3. Describe how parent rock is used in 3. Describe how parent rock is used in the formation of soil.the formation of soil.

Climate affects weathering.Climate affects weathering.

Climate is average weather condition Climate is average weather condition in an area.in an area.

Warm, humid climateWarm, humid climate

Chemical weathering Chemical weathering occurs faster in occurs faster in warmer, wetter warmer, wetter climates.climates.

Like GeorgiaLike Georgia

Water and TemperatureWater and Temperature

More water and lower temperatures More water and lower temperatures affect mechanical weathering.affect mechanical weathering.

If water freezes and thaws often then If water freezes and thaws often then ice wedging occurs more.ice wedging occurs more.

Mountain TopsMountain Tops

Mountain tops weather faster Mountain tops weather faster because they are exposed to more because they are exposed to more wind, rain, and ice.wind, rain, and ice.

From Bedrock From Bedrock to Soilto Soil

What is soil?What is soil?

SoilSoil is a loose mixture of small is a loose mixture of small mineral fragments, organic material, mineral fragments, organic material, water, and air that can support the water, and air that can support the growth of vegetation.growth of vegetation.

All soil is differentAll soil is different

Soil (weathered rock fragments) can Soil (weathered rock fragments) can be made of many different types of be made of many different types of rock. The type of rock that the soil rock. The type of rock that the soil was made from is called was made from is called parent parent rockrock..

Parts of SoilParts of Soil

BedrockBedrock Bedrock is the layer of rock beneath Bedrock is the layer of rock beneath

the soil.the soil. Some soil is made from bedrock, so it Some soil is made from bedrock, so it

remains above the parent rock.remains above the parent rock.

HumusHumus

HumusHumus is the dark, organic material is the dark, organic material in soil that is formed from decayed in soil that is formed from decayed remains of plants and animals.remains of plants and animals.

Soil HorizonsSoil Horizons

Soil is usually layered with humus-Soil is usually layered with humus-rich soil on top, sediment below that, rich soil on top, sediment below that, and bedrock on bottom.and bedrock on bottom.

Soil Soil ConservatioConservatio

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Soil ConservationSoil Conservation

Soil ConservationSoil Conservation is a method to is a method to maintain the fertility of soil by maintain the fertility of soil by preventing erosion and the loss of preventing erosion and the loss of nutrients.nutrients.

Importance of soilImportance of soil Soil provides nutrients to plant life.Soil provides nutrients to plant life. If the soil losses these nutrients then If the soil losses these nutrients then

the plants will not grow. the plants will not grow. All animals get energy from plants.All animals get energy from plants.

– How can unhealthy soil effect us?How can unhealthy soil effect us?

Housing and WaterHousing and Water Soil is also important to providing Soil is also important to providing

shelter for animals that live in soil.shelter for animals that live in soil. It also stores water for plants and It also stores water for plants and

animals, and helps prevent flooding.animals, and helps prevent flooding.

Can you tell which is grown in Can you tell which is grown in healthy soil?healthy soil?

Land DegradationLand Degradation When soil is overused it loses its When soil is overused it loses its

nutrients.nutrients.– This can happen from poor farming This can happen from poor farming

techniques or overgrazing.techniques or overgrazing. Plants can’t grow in infertile soil. Plants can’t grow in infertile soil. Without plants and moisture the soil Without plants and moisture the soil

can be washed or blown away.can be washed or blown away.

ErosionErosion ErosionErosion is the process by which wind, is the process by which wind,

water, or gravity transport soil and water, or gravity transport soil and sediment from one location to another.sediment from one location to another.

This happens when land is left This happens when land is left unprotected.unprotected.

This happened in south Georgia long This happened in south Georgia long ago. The result was Providence ago. The result was Providence Canyon.Canyon.

What was once cotton fields is now a What was once cotton fields is now a 150 ft. deep canyon.150 ft. deep canyon.

Providence CanyonProvidence Canyon

Providence CanyonProvidence Canyon

Providence CanyonProvidence Canyon

Providence CanyonProvidence Canyon

Providence CanyonProvidence Canyon

Soil ConservationSoil Conservation

There are many ways that farmers There are many ways that farmers help prevent erosion.help prevent erosion.

– Contour plowingContour plowing– TerracingTerracing– No-till farmingNo-till farming– Cover cropsCover crops– Crop rotationCrop rotation

Contour PlowingContour Plowing

TerracingTerracing

No-till farmingNo-till farming

Cover cropsCover crops

Cover crops are crops such as soy Cover crops are crops such as soy beans and peanuts that help restore beans and peanuts that help restore important nutrients to the soil.important nutrients to the soil.

Crop rotationCrop rotation

Rotating crops from one year to the Rotating crops from one year to the next.next.