Chapter 6 Flashcards
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
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)
What does soil support?
supports all plants and animals one earth
The availability of soil controls what?
number of people earth can hold
-This is because we grow food in the soil
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)
Look at the pyrmaid things of clay
alalalal
What are the Five factors in soil development
Climate
Organic Activity
Relief of ground surface
Parent Materals
Time
First factor in the Five factors in soil development(Explain)
Climate: Temperature, rainfall, wind
Second factor in the Five factors in soil development(Explain)
Organic Activity- Action of bacteria(animal) and plants
Third factor in the Five factors in soil development(Explain)
Relief of ground surface(Structure of surface)
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
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)
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
What are the two major types of Weathering
Physical disintegration
Chemical decomposition
Physical(Mechanical) Weathering What happens?
Big rock-> small pieces by agents of physical weathering
What are the Physical(Mechanical) Weathering agents
Tempurtare
Water
Pressure
Organic Activity
First Physical(Mechanical) Weathering agents
Tempurtare: Rocks adjust to new temperature by breaking up
-Thermal Expansion/Contraction
(Look at picture)
Second Physical(Mechanical) Weathering agents
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
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
Organic Activity
Human beings
Insects, worms, burrowing animals
Roots of plants
Chemical weathering
the erosion or disintegration of rocks, building materials, etc., caused by chemical reactions
Agents of Chemical Weathering
Hydrations
Oxidation
Solution
First Agents of Chemical Weathering
Rock + water
-Forms hydrated minerals-> chemical break down(like salt)
Second Agents of Chemical Weathering
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
