Chapter 5: Weathering and Soil DiMarcellaEarth & Space Science I, Level 01 & 02 Notes

CHAPTER 5: WEATHERING AND SOILTable of Contents & Objectives by Section

5.1 Weathering pp 126 - 132

Define mechanical weathering. Explain chemical weathering. Identify the factors that affect the rate of weathering.

5.2 Soil pp 133 - 142

Recognize the major components of soil and list the most important factors in soil formation.

Explain how soils vary with depth. Demonstrate how human activities affect the rate of soil

erosion.

Chapter 5 - Weathering and Soil

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Chapter 5: Weathering and Soil DiMarcellaEarth & Space Science I, Level 01 & 02 Notes

Earth's external processes

Weathering - ________________________________________________

__________________________________________________________.

Erosion – ___________________________________________________

__________________________________________________________.

5.1 - Weathering

Two kinds of weathering

• Mechanical weathering

• Breaking of rocks into smaller pieces, __________ changing the

rock’s ___________ composition.

• Processes of mechanical weathering

• ____________________

• ____________________

• ____________________

• Frost Wedging

Water finds its way into cracks in a rock

As the water freezes it _________ by about 9%

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Objectives• Define mechanical weathering.• Explain chemical weathering.• Identify the factors that affect the rate of weathering.

Chapter 5: Weathering and Soil DiMarcellaEarth & Space Science I, Level 01 & 02 Notes

This pushes rock apart with tremendous force

expanding the cracks and breaking rock into pieces

Frost wedging can result in

_________ - Sections of rock that are wedged loose

may tumble into large piles of rock debris and

typically form at the base of steep, rocky cliffs

Unloading and exfoliation of igneous rocks

o Unloading – large masses of igneous rock are exposed

through ______________ and _______________

o Exfoliation – Slabs of outer rock separate

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Chapter 5: Weathering and Soil DiMarcellaEarth & Space Science I, Level 01 & 02 Notes

Biological Activity

o ___________, _____________, and ___________ can cause

rocks to break apart

Tree roots grow into cracks and expand them

Burrowing animals move rocks to the surface

where weathering is more rapid

Humans accelerate weathering through

deforestation, blasting mines, and creating new

roads

Second type of weathering

• Chemical weathering – transformation of rock into

one or more ______________ compounds

• ______________ – most important agent

• Changes the _______________ of rock

• How it Happens

• Gases dissolve in water creating solutions which ___________

with ____________ in rocks

• Oxygen – causes metallic minerals to ___________

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Chapter 5: Weathering and Soil DiMarcellaEarth & Space Science I, Level 01 & 02 Notes

• CO2 – (from air and decaying organic matter) creates carbonic

acid which reacts with ___________ ( ____________, ___________ )

and other soft minerals/rocks

• Sulfur and Nitrogen – (from ______________________ ) creates

____________________

Rates of Weathering

• Advanced mechanical weathering aids chemical weathering by

_________________________________.

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Chapter 5: Weathering and Soil DiMarcellaEarth & Space Science I, Level 01 & 02 Notes

• Important factors

o _______________

o ___________ and ___________ are the most crucial factors

o Chemical weathering is most effective in areas of

__________ temperatures and abundant _____________.

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Chapter 5: Weathering and Soil DiMarcellaEarth & Space Science I, Level 01 & 02 Notes

5.2 Soil

is a combination of mineral matter, water, and air – that

portion of the regolith (rock and mineral fragments) that supports the

growth of plants

Typical components in a soil that yields good plant growth

Soil texture and structure

• Texture refers to the proportions of different particle sizes

• __________ (large size)

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Objectives• Recognize the major components of soil and list the most

important factors in soil formation.• Explain how soils vary with depth.• Demonstrate how human activities affect the rate of soil erosion.

Chapter 5: Weathering and Soil DiMarcellaEarth & Space Science I, Level 01 & 02 Notes

• __________

• __________ (small size)

• _______________ - (a mixture of all three sizes) is best suited for plant life

Controls of soil formation

• _____________

• _____________ and _____________

• Organisms influence the soil's physical and chemical properties

• Furnish _____________ matter to soil

Soil Profile

• Soil forming processes operate from the surface ______________

• ________________ – zones or layers of soil

• Horizons in temperate regions

O – organic matter

A – organic and mineral matter

E – little organic matter

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Chapter 5: Weathering and Soil DiMarcellaEarth & Space Science I, Level 01 & 02 Notes

B – zone of accumulation

C – partially altered parent material

• _____ and _____ together called topsoil

• O, A, E, and B together called solum, or "true soil"

An idealized soil profile A soil profile showing different

horizons

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Chapter 5: Weathering and Soil DiMarcellaEarth & Space Science I, Level 01 & 02 Notes

Soil erosion

• Recycling of Earth materials

• Natural rates of erosion depend on

• _____________________________

• _____________________________

• _____________________________

• _____________________________

• Human activities that remove natural vegetation accelerate soil

erosion

• ________________

• ________________

• ________________

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Chapter 5: Weathering and Soil DiMarcellaEarth & Space Science I, Level 01 & 02 Notes

• Erosion can be controlled through

• _________________________

• _________________________

• _________________________

• _________________________

End of Chapter 5

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