Soil recap
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Soil Recap. What did you learn by digging through your soil and observing the soil of others ?. What is soil?. Loose, weathered material on Earth’s surface. Made up of: -rock particles -minerals -decayed organic material (humus) (HYOO mus ) -water -air.

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Soil Recap

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Soil recap

Soil Recap


Soil recap

What did you learn by digging through your soil and observing the soil of others?


What is soil

What is soil?

  • Loose, weathered material on Earth’s surface.

  • Made up of:

    -rock particles

    -minerals

    -decayed organic material (humus) (HYOO mus)

    -water

    -air


What does soil texture depend on

What does soil texture depend on?

  • Particle size!

Which particle type

Is the best for plant

Growth?

Loam- Soil that is equal parts clay, sand, and silt


Soil recap

What are soil horizons and

how are they formed?

Horizon:

  • A layer of soil that differs in color and texture from the layers above or below it

  • Topsoil, subsoil and bedrock

  • Check out this animation of how horizons form: Pearson Prentice Hall: Web Codes

  • How do living organisms help the soil’s fertility?

    • Decomposition-page 52


How do scientists classify different types of soil

How do scientists classify different types of soil?

  • They are classified based on climate, plants and soil composition

  • Look at page 51-Which soil type exists where we live? What climate and vegetation types occur in our region?


Why is soil one of earth s most valuable natural resources

Why is soil one of Earth’s most valuable natural resources?

Everything that lives on land, including humans, depends directly or indirectly on soil.

  • What can be done to preserve soil?

    • Contour plowing

    • Conservation plowing

    • Crop rotation


How does weathering occur what is the difference between weathering and erosion

How does weathering

occur?

What is the difference between weathering and erosion?


Weathering vs erosion

Weathering vs. Erosion

  • Weathering and erosion work together…

  • You can’t see weathering – wearing down over rock over time

  • Erosion is a movement of dirt/soil particles by wind, water, ice or gravity


Soil recap

Weatheringis the process by which rock materials are broken down by the action of physical or chemical processes.

  • Mechanical weathering is the breakdown of rock into smaller pieces by physical means

  • Chemical weathering is the process by which rocks break down as a result of chemical reactions. Water, weak acids, and air can cause chemical weathering.


Causes of mechanical weathering

Causes of Mechanical Weathering

Ice Wedging

Water seeps into cracks during warm weather. When temperature drops, the water freezes and expands, causing the ice to push against the sides of the crack. This causes the crack in the rock to widen.

Abrasion

The grinding and wearing away of rock surfaces through mechanical action of other rock or sand pebbles.

  • Wind and water are forces of abrasion


Soil recap

John Ford Point Monument

Also See Fig. 13.7 of the Colorado Plateau

Figure 3.8: Ship Rock Arizona

Volcanic Neck

Fig 5.3

John Ford Point Monument, Arizona.

Ship Rock, New Mexico

Volcanic Neck


Chemical weathering

Chemical Weathering

  • is the process by which rocks break down as a result of chemical reactions.

  • New mineral composition!


Causes of chemical weathering

Causes of Chemical Weathering

Water

Oxygen

CO2

Living Organisms

Acid Rain


Soil recap

H2O

Dissolves minerals in rock


Soil recap

Acid Rain

CO2

Forms carbonic acid, dissolves limestone


Soil recap

Oxidation


Types of mechanical weathering

Types of Mechanical Weathering

LIVING ORGANISMS


Factors that affect rates of weathering

Factors that affectRates of Weathering

  • Joints, fractures and/or porosity increase surface area

  • This can accelerate both mechanical and chemical weathering


More factors that affect rates of weathering

More factors that affectRates of Weathering

  • Type of Rock

    • Hard rocks weather more slowly than softer rocks

    • Limestone vs. granite and permeability

  • Climate

    • Chemical weathering occurs faster in warm, humid climates


Exit slip

Exit slip

  • Give examples of weathering and erosion in nature


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