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44 Cards in this Set

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Soil Depth
Volume of soil available to roots
Affects nutrients, moisture, anchorage, aeration
Also called effective root depth
Limitations of extremely shallow or deep soil
Shallow soil is poorer at supplying nutrients, water, anchorage

Deep soil course may drain to quickly of water
Five soil forming factors
Climate
Organisms
Relief
Parent Materials
Time
Soil =
Function (Cl, O, R, P,T)
Father of Pedology
Dochuchaer
Describe how climate effects soil formation
Mostly from temperature and moisture influencing the rates of formation.

Temp increases the rate of biochemical reactions, while both temp and moisture effect soil organisms.
Temperature and moisture factors in climate that effect soil formation
Average temperature
Total rainfall
Distribution of rain and snow throughout the year
Temperature range
Seasonal changes
Climosequence
Soil formation when all other factors are held constant (O,R,P,T)
Graph change in depth of soil as move in latitude from artic to tropics (inc temp)
Shallow in artic
Highly variable in temperate
Deep and well formed in tropics
Graph rate of clay formation (whethering rate) as precipitation increases
Slow in low precipe, fast in high precipe
Graph quantity of soil organic matter as move in latitude from the artic to tropics
Low productivity and low decomposition (low water for orgs, cold) in artic so little soil organic matter. High productivity but high decomposition in tropics), so low soil organic matter. Temperate zones high soil organic matter.
Soils Association
Pattern of soils in the landscape due to topography and parent materials
Absolute and relative time
Absolute is how long have pedogenic processes been happening.

Relative is how developed is a soil - this more important the absolute
Parent materials
The rocks and minerals that from which soil is formed
Influences of parent material on a soil
Texture
Water movement
Whethering rate
pH
Nutrient cycling
Horizons
Depth of soil
Soil texture type lead to by
a) granite
b) loess
Granite - course texture
Loess - fine texture
Types of consolidated parent materials (rocks)
Igneous, Sedimentary, Metamorphic
Igneous rocks
Formed from magma
Cooled slowly beneath the surface - intrusive rocks with big crystals like granite.
Cooled quickly at surface - extrusive with small crystals like basalt
Sedimentary
Consolidated sediments formed into new rocks.
Formed by cementation - sandstone or precipitation - limestone
Metamorphic rock
Igneous or sedimentary rocks changed under pressure or heat
Types of uncosolidated parent materials
Residual
Transported
Residual
unconsolidated rocks left in place
Methods of transporting unconsolidated materials
Gravity
Water
Wind
Ice
Gravity deposits
Colluvial
rock slides - talus, etc.
Water deposits
Alluvial or Fluvial. Rounded rocks from streams and rivers. Fine textured marine and lacustiran sediments.
Wind deposits
Eolian.
Loess - wind born fine sand, silt, and clay.
Types of deposits from glaciers
Moraines
Outwashes
Till
Drumlins
Eskers
Moraines
Moved along in front of a glacier. Mixed up loose material.
Outwashes
Material deposited by glacial streams or rivers. Larger rocks from glacier streams, finer from glacier lakes.
Till
Unsorted rocks carried by the ice. Basal till is from rocks carried and compacted under the ice. Ablation till is from rocks carried in the ice and dropped when glacier recedes. Not compacted.
Drumlins
Cigar shaped hills of tills formed when glacier rode up over something. Face the direction the glacier was flowing.
Rocks become soil because of?

Why does it occur?
Weathering

Because rocks are formed in a different environment and are not stable at the surface of the earth.
What is the most resistant rock mineral to weathering? Why?
Quartz

Formed at a lower temperature and pressure
Two types of weathering
Physical and Chemical
Describe physical weathering
Mechanical breakdown of rocks without any chemical alteration.
Basic physical weathering processes
Exfoliation
Ice
Salts
Roots
Wind
What happens in chemical weathering?
Chemical changes in rocks and minerals occur, soluble ions are released, and new minerals are formed.
Basic types of chemical weathering
Dissolution
Hydrolysis
Acidolysis
Oxidation/reduction
Hydration
Dissolution
Soluble ions dissolve in water and are removed from rock. Eg: CaCO3 becomes Ca+2 + C03
Hydrolysis
Decomposition of rock or mmineral by inclusion of h+ or OH- into a mineral - requires lots of water.

Eg: KAlSi3O8 + H2O = HAlSi3O8 (new mineral solid) + K+ + OH- (in solution)
Acidolysis
Similar to Hydrolysis except H+ ion comes from a source other than dissassociation of water, i.e. from and acid (organic, carbonic, nitric)

KAlSi3O8 + H2CO3 (carbon acid) = HAlSi3O8 + K+ + HCO3- (bicarbonate)
Oxidation/reduction
Transfer of an electron. Important for minerals with Fe
Fe+3(orange) = Fe+2 (gray) and vice versa. When in Fe+3 form, tends to become removed from rock.
Hydration
Inclusion of water into a mineral
Factors affecting weathering rates
Environmental - percipitation, temperature, vegetation (which releases organic acids)

Chemical - solubility of minerals

Physical - surface area influenced by particle size, porosity, cementing and crystal size and unconsolidated parent material.