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44 Cards in this Set
- Front
- Back
Soil Depth
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Volume of soil available to roots
Affects nutrients, moisture, anchorage, aeration Also called effective root depth |
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Limitations of extremely shallow or deep soil
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Shallow soil is poorer at supplying nutrients, water, anchorage
Deep soil course may drain to quickly of water |
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Five soil forming factors
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Climate
Organisms Relief Parent Materials Time |
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Soil =
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Function (Cl, O, R, P,T)
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Father of Pedology
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Dochuchaer
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Describe how climate effects soil formation
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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. |
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Temperature and moisture factors in climate that effect soil formation
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Average temperature
Total rainfall Distribution of rain and snow throughout the year Temperature range Seasonal changes |
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Climosequence
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Soil formation when all other factors are held constant (O,R,P,T)
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Graph change in depth of soil as move in latitude from artic to tropics (inc temp)
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Shallow in artic
Highly variable in temperate Deep and well formed in tropics |
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Graph rate of clay formation (whethering rate) as precipitation increases
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Slow in low precipe, fast in high precipe
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Graph quantity of soil organic matter as move in latitude from the artic to tropics
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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.
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Soils Association
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Pattern of soils in the landscape due to topography and parent materials
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Absolute and relative time
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Absolute is how long have pedogenic processes been happening.
Relative is how developed is a soil - this more important the absolute |
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Parent materials
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The rocks and minerals that from which soil is formed
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Influences of parent material on a soil
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Texture
Water movement Whethering rate pH Nutrient cycling Horizons Depth of soil |
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Soil texture type lead to by
a) granite b) loess |
Granite - course texture
Loess - fine texture |
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Types of consolidated parent materials (rocks)
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Igneous, Sedimentary, Metamorphic
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Igneous rocks
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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 |
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Sedimentary
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Consolidated sediments formed into new rocks.
Formed by cementation - sandstone or precipitation - limestone |
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Metamorphic rock
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Igneous or sedimentary rocks changed under pressure or heat
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Types of uncosolidated parent materials
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Residual
Transported |
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Residual
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unconsolidated rocks left in place
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Methods of transporting unconsolidated materials
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Gravity
Water Wind Ice |
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Gravity deposits
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Colluvial
rock slides - talus, etc. |
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Water deposits
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Alluvial or Fluvial. Rounded rocks from streams and rivers. Fine textured marine and lacustiran sediments.
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Wind deposits
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Eolian.
Loess - wind born fine sand, silt, and clay. |
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Types of deposits from glaciers
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Moraines
Outwashes Till Drumlins Eskers |
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Moraines
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Moved along in front of a glacier. Mixed up loose material.
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Outwashes
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Material deposited by glacial streams or rivers. Larger rocks from glacier streams, finer from glacier lakes.
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Till
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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.
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Drumlins
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Cigar shaped hills of tills formed when glacier rode up over something. Face the direction the glacier was flowing.
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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. |
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What is the most resistant rock mineral to weathering? Why?
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Quartz
Formed at a lower temperature and pressure |
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Two types of weathering
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Physical and Chemical
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Describe physical weathering
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Mechanical breakdown of rocks without any chemical alteration.
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Basic physical weathering processes
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Exfoliation
Ice Salts Roots Wind |
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What happens in chemical weathering?
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Chemical changes in rocks and minerals occur, soluble ions are released, and new minerals are formed.
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Basic types of chemical weathering
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Dissolution
Hydrolysis Acidolysis Oxidation/reduction Hydration |
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Dissolution
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Soluble ions dissolve in water and are removed from rock. Eg: CaCO3 becomes Ca+2 + C03
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Hydrolysis
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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) |
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Acidolysis
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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) |
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Oxidation/reduction
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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. |
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Hydration
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Inclusion of water into a mineral
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Factors affecting weathering rates
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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. |