Terms in this set (54)
The process of soil formation
Geo-Biochemical Weathering Process
What does "equilibrium with its environment" mean when talking about soil being dynamic?
Rock can only disintegrate and soil can only be formed according to its environment.
Where does soil formation begin?
From the Parent Material
What are the two processes of rock weathering?
Define physical weathering of the parent material?
A disintegration of rocks by a physical or mechanical process.
What are the six ways physical weathering breaks down rock?
1. Development of joints
2. Crystal growth
3. Thermal expansion
4. Root wedging
5. Animal activity
6. Frost wedging
Define chemical weathering of parent material?
Minerals that are in rocks react to their new environment to produce new minerals.
What are the two main agents of chemical weathering?
2. Weak acid
What are the five reactions to parent material from chemical weathering?
5. Complete dissolution
What are the five factors of Soil Formation?
How many of the essential elements for plants come from inorganic parent material?
12 of the 16
What are the three types of parent material?
1. Residual (residuum-from the earth's crust)
2. Transported (soft rock-unconsolidated-glacier movement)
3. Cumulose (Organic-preserved by high water table-peat)
What are the three types of residual parent material?
1. Igneous-Granite, basalt or lava
2. Sedimentary-Limestone, sandstone or shale
3. Metamorphic-Marble, quartzite or slate
What is Igneous Parent Material?
It is formed from molten material that has solidified
What is Sedimentary Parent Material?
It is formed from minerals, rocks, organisms and precipitate from the sea to form soft stone.
What is Metamorphic Parent Material?
Either Igneous or sedimentary that have been transformed beneath the surface of the earth by heat, pressure and chemically active liquids.
What are the four ways Parent Material is transported?
What are the three water transporters called.
1. Alluvial - Rivers (Where particles are sorted)
2. Lacustrine - Deposits in lakes from glaciers
3. Marine - Sediment deposited in the ocean by rivers
What are the two wind transporters called?
1. Eolian - Deposits from dust storms at the sand dunes
2. Loess - High silt deposits developed from the last glacier
What are the three ice transporters called?
(This a big factor for parent material in Michigan)
1. Moraine - Build up of sediment in front of glacier (pushed)
2. Till plane - Smooth deposit caused by retreating glacier
3. Outwash plane - sand/gravel deposits on a level plain from from the water flow of rapidly melting ice.
What is the gravity transporter called?
Colluvial - unsorted soil debris at the foot of a slope
What are the four causes of Colluvial Parent Material?
3. Soil creep
What is Cumulose Parent Material?
Partly decomposed plant and animal residue accumulated in shallow water that is preserved because of low levels of oxygen.
What are the four stages of decomposing organic material?
1. Fibric - Beginning stage of decomposition (Fibrous Peat)
2. Folic - Partly decomposed (Leaf mold)
3. Hemic - Half decomposed (Muck)
4. Sapric - Completely decomposed (Rotten muck)
What is the dominating factor acting on the Parent Material?
Climate (Temperature and precipitation)
What is the direct influence physically on the Parent Material from temperature?
Freezing and thawing
What are the two direct influences physically on the Parent Material from precipitation?
What are the three different types of climate that influence vegetation?
1. Humid - Forest
2. Semiarid - Grassland
3. Arid - Desert
What is the necessary annual rainfall needed to classify each type of climate?
1. 30" - Forest (Humid)
2. 10" - 30" - Grassland (Semiarid)
3. < 10" - Desert (Arid)
What are the four ways lots of water speeds up soil formation?
What are the four signs that the soil is lacking water?
1. Slow chemical reaction
2. Light color soil
3. Natural salts are not leached
4. Shallow soil
What is Sodic Soil?
Soil with high salt content
What is Shallow Soil?
Less depth of horizons A and B
How does temperature affect soil formation?
High temps cause decomposition to speed up as low temps cause decomposition to slow down. (Soil forms quicker in Georgia than it does in Michigan)
What are the two direct affects on soil with little rainfall?
1. Shallow soil
2. Accumulation of soluble salts
What are the three direct affects on soil with high rainfall?
1. Acid soil due to intense weathering and leaching.
2. Erosion of soil on slopes.
3. Deposition of soil material downstream.
(Each of these affects are intensified in climates where soil doesn't freeze)
What are the two characteristics of a soil profile taken in a grassy area?
1. Dark A horizon due to the depth of the grass roots.
2. Neutral to alkaline soil due to basic cations being recycled to offset leaching.
What are the five characteristics of a soil profile taken in the forest?
1. Dark A horizon but it will be shallow due to depth of root system.
2. Acidic soil due to leaching of basic cations.
3. Increase in mineral weathering.
4. Adds little organic material each year due to no grass growth and decay.
5. Light colored A2 horizon.
What are the two main micro-organisms and what are their roles?
1. Fungi - Works on dead material.
2. Bacteria - Works on fresh material.
What are the five organisms that retard the development of a soil profile?
How do organisms retard the development of a soil profile?
By constantly mixing the soil, slowing down the movement of material or disrupting the process.
What are the three ways topography can effect soil formation?
1. Moisture and temperature related to the slope orientation.
2. Water movement related to the pitch of the slope.
3. Soil movement due to creeping.
What are the seven characteristics of a steep slope?
1. More water run-off
2. Usually dry
3. Less leaching
4. Reduced plant growth
5. Lower organic material
6. Shallow soil
7. Soil formation is more rapid
What are the four ways soil moves?
1. Mud slides
What four things affect the speed of soil movement?
1. Pitch of the slope
2. Soil texture
3. Rate of water application
4. Amount of water applied
What four things is the length of time for the development of a soil profile dependent on?
1. Parent material
What are the three classifications of soil by time?
What are the six characteristics of young soil?
1. Beginning differentiation of horizon A and B
2. Leaching of soluble salts
3. Slight darkening of the upper soil
4. Unconsolidated soil (Not a strong profile)
5. Not as many horizons as mature soil
6. Very permeable
What are the four characteristics of mature soil?
1. Strong profile development
2. Steady state-Soil production equals soil loss
3. High clay content in B2 horizon
4. Good support for plant growth
What are the three characteristics of old soil?
1. Decline in fertility (Phosphorus and nitrogen)
2. Large amounts of clay in B horizon
3. Low permeability
Where is the only place on earth with old soil?
Why does it appear as though the soil in Michigan is old?
Human factor - Our soil is stripped and sold leaving us with no A horizon.
What are the eleven factors that retard soil formation?
1. Resistant parent material
2. Low rainfall
3. Low relative humidity
4. High lime or sodium carbonate of parent material
5. Excessive sandiness
6. High percent of clay
7. Steep slopes
8. Constant accumulation of soil material by deposition
9. Sever wind or water erosion
10. Large number of burrowing animals
11. People activity - Plowing , Liming, Fertilizing
What are the eleven steps to the process of soil formation?
1.Parent material formation
2. Rainfall occurs
3. Rain adds nitrogen
4. Rain and dew provide moisture for organism growth
5. Nitrogen fixation begins
6. Organic material starts to accumulate
7. Soluble carbonates are leached
8. Clay particles disperse
9. Eluviation occurs
10. Illuviation occurs
11. Continued weathering of the parent material releases plant nutrients
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