Soils NR 200

Unit 2

Formation of Soils From Parent Materials

SOIL FORMING FACTORS

A. Parent Material origins

1)   Igneous rock – ¼ of the earth’s surface solidification of molten rock

     a) Granite - intrusive

                              i. Quartz – weathers to form sand

                              ii. Feldspar biotite – form clays

     b) Basalt - extrusive

2) Sedimentary Rocks – a great majority of the earth’s surface, readily breaks down into soil. Consolidation by silicates and carbonates cementing together.

     a) Limestone - organic marine animal formation

     b) Sandstone

3)   Metamorphic – rock that is heated under pressure and changes-generally resists weathering.

a) Marble

b) Slate

c) Gneiss

d) Talc- which is ground into powder.

e) Graphite- used in pencils and lubricants.

f) Serpentinite

14- Rocky Mountain region all rock types

15- Mostly igneous rocks loess in river basins

16- Great Basin gravels, sands alluvial fans igneous and sedimentary rocks

18. Sierra and Cascade mountains – Igneous

19. Mostly Sedimentary

20. Glacial sediments

21. Great Valley – alluvial fans

B. Climate

1) Heat

2) Water

3) Freezing

C. Biota (Living Organisms)

1) Plants

* Accumulation can form peat bogs, Moss Peat, Herbaceous peat, Woody peat and sedimentary peat

2) Micro-organisms

* Animals turning the soil - pedoturbation

3) Macro-organisms

How organic mater is formed and the accumulation of the material to form peat bogs.

D. Topography

1) Moving soil by water and gravity

2) Low – accumulate salts, if saturated then reduced om degradation

3) Steep areas are never allowed to develop the soil profile as the unconsolidated material leaves the site.

E. Time - allowing for the other factors to affect the soil.

Soil transportation modes. If not transported, Residual

a) Glacial Ice - Moraineb) Wind – Eolianc) Water – Stream –Alluvial Lake - Lacustrine Oceans - Marined) Gravity – Colluvium

A qualifier thapto- indicates the presence of a buried soil or a buried horizon. This would be the case if a soil has a surface mantel of new material that is 50 cm thick or more. The surface mantel is named in the normal way (e.g. as a Regosol, Andosol or Arenosol) and the buried soil would be classified with a prefix qualifier `thapto-`. If the surface mantle is less than 50 cm thick, it is ignored in the soil name but the soil may be marked on the soil map by a phase indicator.

2) Soil Formation processesa)Transformations

i) The physical and chemical changes that occur in the soil

- Degradation of minerals while forming silicate clays

- Degradation of OM and formation of humus and organic acids- Also the changing of aggregates

b) Translocationsi) Movement of materials by water downward when

in abundance and upwards when the absence of surface water.c) Additions

i) OM ii) Fine particles wind deposition

d) Lossi) Leachingii) Erosioniii) OM

3) Soil Profilea)   O- organic layer

i) How is this formed?? ii) Sub classes i and a

b)   A- topsoil – the most productive soil   i) With the addition of the acids from the higher

organic material leaching of the easily soluble compounds calcium, calcite and gypsum will move down into the lower horizons of the profile as far as the water penetration will carry them.

     ii) p -

c)   E – an area where the greatest eluvation (removal of clay, iron and OM) occurs, resistant materials such as quartz, sand and silts remain usually light in color.

d)   B – sub soil or zone of accumulation, illuviation -

usual location of hardpan

i) Where clay and/or silt concentration will increase from transformation of particles weathering and

moving down.

ii) m - cemented zone usually silicates or calcium

iii) g - strong gleying

e)   C – Parent material but broken down but not subject to the soil forming properties as the above solum (A&B) and not massive in structure as R

f)   R- Rock

The subscript notes for each horizon and their meaning.