Chapter 6 Flashcards by Chantal Batista

Soil Definition? How is it formed?

Loose material one earth’s surface
-One of the most valuable resources(sedimentary rocks)
-Formed from sufficient weathering to support plant life

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Soil results from what? What kind of event is this?

results from weathering of rock fragments on earth’s surface
(This happens because earth’s surface is more cooler than inside the earth)(Whatever is happening on the surface is a low temperature event)

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What does soil support?

supports all plants and animals one earth

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The availability of soil controls what?

number of people earth can hold
-This is because we grow food in the soil

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Soil means different things to different people. Name people and what soil means to them

Farmer: Earth material rich or poor in humus & minerals (for plant food)
-Engineer: Loose material for constructing structures (houses, bridges etc.)
without first blasting
-Geologist: Weathered material (rock and mineral grains)

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Look at the pyrmaid things of clay

alalalal

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What are the Five factors in soil development

Climate
Organic Activity
Relief of ground surface
Parent Materals
Time

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First factor in the Five factors in soil development(Explain)

Climate: Temperature, rainfall, wind

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Second factor in the Five factors in soil development(Explain)

Organic Activity- Action of bacteria(animal) and plants

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Third factor in the Five factors in soil development(Explain)

Relief of ground surface(Structure of surface)

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Fourth factor in the Five factors in soil development(Explain)

Parent Material
Parent material is the underlying geological material (generally bedrock)
Soils typically inherit a great deal of structure and minerals from their parent material

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Five factor in the Five factors in soil development(Explain)

Time
Since soil development
Shirt-term=immature soil
Long Term=mature soil
(quailty of soil)

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Definition of Weathering?Why is it different from erosion?

Process by which rocks and minerals break down near earth surface
(Different from erosion= removal and transportation of weatherd/unweathered materials by gravity wind and water

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What are the two major types of Weathering

Physical disintegration
Chemical decomposition

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Physical(Mechanical) Weathering What happens?

Big rock-> small pieces by agents of physical weathering

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What are the Physical(Mechanical) Weathering agents

Tempurtare
Water
Pressure
Organic Activity

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First Physical(Mechanical) Weathering agents

Tempurtare: Rocks adjust to new temperature by breaking up
-Thermal Expansion/Contraction
(Look at picture)

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Second Physical(Mechanical) Weathering agents

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Water= freezes and expands-> froaast wedging
Water gets into the cracks, crevices and pores of the rocks and then it freezes and expands and breaks the rocks

Third Physical(Mechanical) Weathering agents

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Pressure: From expansion of H20 or due to loading
Water seeps into cracks in the rocks and freezes and expands which breaks the rocks. The expanding puts alot of pressure on the surrounding rock and acts like a wedge, making cracks wider.
If you put alot of pressure on rocks they will break eventually

FouTH Physical(Mechanical) Weathering agents

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Organic Activity
Human beings
Insects, worms, burrowing animals
Roots of plants

Chemical weathering

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the erosion or disintegration of rocks, building materials, etc., caused by chemical reactions

Agents of Chemical Weathering

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Hydrations
Oxidation
Solution

First Agents of Chemical Weathering

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Rock + water
-Forms hydrated minerals-> chemical break down(like salt)

Second Agents of Chemical Weathering

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Rocks +Oxygen
-Forms oxides-> mostly iron oxides(rust)

Third Agents of Chemical Weathering

Rocks + Carbon Diozxide(H2O) -h2O+ CO2=> H2CO3(Carbonic Acid) -H2CO3 can wear off cementing materials of rocks Solution forms or cuases large openings of rock

Rate Of Weathering are controlled by

Factors in the Environment: Surface Area Climate Nature of Materials

Explain first Rate Of Weathering

Factors in the Environment: -Environment must change -More intense change = faster weathering

Explain second Rate Of Weathering

Surface Area - More surface area, faster weathering

Explain third Rate Of Weathering

Climate: (T, P, Wind) -More intense changes in climatic factors = faster weathering - More physical weathering in dry areas

Explain fourth Rate Of Weathering

Nature of Materials: -Minerals in parent materials are formed under different conditions of T, P - Stability of rock depends on parent material *Note that weathering occurs at surface i.e., low T & P - Content of parent materials also determines rate of Weathering

Sequence of Stability of minerals to weathering:

Quartz(most stable, lowest T) quartz is highly resistant to the types of weathering that occur at Earth's surface. rthoclase feldspar -Amphibole -Pyroxene -Olivine (least stable, crystallizes at highest T)

Soil can form from what rocks? when young and old

Can form from different rock types When young (immature soils), reflect composition of parent rock Given enough time (mature soils), reflect climate rather than parent material

SOIL PROFILE

-Soils are best described using profiles a vertical section of the soil that depicts all of its horizons. -Product of soil forming processes

Soil Classification based on what? What are the Three?

Based on Genetic Origin or Zonal Location Or Physical characteristics

First Soil Classification Agents and its two sub

Genetic -Residual weathered rock that remains in the same place(On parent rock) -Transported Moved from origin

Second Soil Classification Agents

Zonal: Based on 4 main zones where found: -Laterites (tropics & subtropics) - Pedocals (arid regions) -Pedalfer (temperate regions) -Tundra soils (Polar regions)

Third Soil Classification Agents

Physical characteristics : The US Comprehensive Soil Classification -they include: depth, moisture, temperature, texture

Soil Problems: Erosion

Soils take 1000s and millions of years to form -Yet lost continuously through erosion - by winds, running water, etc

Soil is removed by different types of erosion: Name them.

-Sheet erosion: Removal of soil in sheets or layers - Rill erosion: Removal in streamlets -Gully Erosion: Soil is saturated by melting snow, then flows away in gullies -Wind Erosion: Strong winds cause “Dust storm” – resulting in soil erosion

Mitigation for Erosion

Soil conservation method are used: e.g., crop rotation, contour plowing, planting of grass during fallow seasons

Soil Problem: Expansive Soils

Expansive Soils those with excessive swelling clay minerals -When they expand, they exer pressure on foundation of houses, bridges and etc which cause failure in these structures

Migration for Expansive Soils

-Remove soils -Mix with non expansive soils -Reduce soil moisture, e.g., by pumping H2O -Reinforce foundations

Soil Problems: SETTLEMENT

- Weak soils may settle - Settlement may be uniform OR uneven -Mitigation: -Using different approaches

Chapter 6 Flashcards

(43 cards)