Parent Material and Soil Formation

Created byJim Ippolito

&Mike Hanna

College of Agricultural SciencesColorado State University

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Type of Parent Material: Colluvium Mode of Transportation: GravityDegree of Sorting by Particle Size: Low

Additional Information: The term colluvium classifies parent material transported by gravity. Colluvium is made up of aheterogeneous mixture of boulders, rocks, pebbles, and soil from upslope areas. Thus the degree of particle sorting is low.

Background Photo Source: Jim Ippolito; Northern boundary of Rocky Mountain National Park, Colorado

Colluvium Photo:Source: http://pubs.usgs.gov/of/2002/of02-437/gallery.htm

Background Photo Source: Jim Ippolito; Northern boundary of Rocky Mountain National Park, Colorado

Type of Parent Material: Glacial TillMode of Transportation: IceDegree of Sorting by Particle Size: Low

Additional Information: Parent material transported by ice is called glacial till. This parent material is found where glaciers have deposited material, such as in terminal or lateral moraines. Ice is a poor sorter of particles, and thus glacial till contains everything from the smallest clay-sized fraction to rocks, pebbles, and boulders.

terminal moraine

Glacial Till Photo Source: Peter Fletcher http://www.nesoil.com/images/newport.htm

Soil developed from volcanic ejecta.Soil Profile Source: http://soils.usda.gov/technical/classification/orders/andisols.html

Type of Parent Material: TephraMode of Transportation: WindDegree of Sorting by Particle Size: High

Additional Information: Parent material transported via volcanic ejecta is calledtephra. The mode of transportation iswind. Wind is a good sorter of particles.Larger particles tend to bounce on the Earth’s surface while smaller particles aretransported greater distances.

Background Photo Source: http://hvo.wr.usgs.gov/volcanoes/haleakala/1koolau_large.jpg

Type of Parent Material: Loess or Aeolian Mode of Transportation: WindDegree of Sorting by Particle Size: High

Additional Information: Parent material transported by wind is called loess or aeolian. Wind is a good sorter of particles. Larger particles tend to bounce on the Earth’s surface while smaller particles are transported greater distances. Background Photo Source: http://www.nps.gov/grsa

Aeolian Photo:Source: Dr. Paul McDaniel;

http://soils.ag.uidaho.edu/soilorders/entisols_06.htm

Soil developed from alluvium.Source: http://www.mo15.nrcs.usda.gov/features/gallery/houlka.html

Type of Parent Material: AlluviumMode of Transportation: WaterDegree of Sorting by Particle Size: High

Additional Information: Parent material transported by flowing water (streams, rivers) is called alluvium. Water is a good sorter of soil particles. Larger particles (i.e. sands) settle out of water first, and smaller particles (i.e. clays) settle out of water last. Thus, you tend to find sand-sized particles closer to the water source and clay-sized particles further away.

Lacustrine Deposit Profile Source: NRCS staff,

http://houzi.org/lacustrine.html

Type of Parent Material: Lacustrine Mode of Transportation: LakeDegree of Sorting by Particle Size: High

Additional Information: The term lacustrine classifies parent material transported by alake. Water is acting on the parent material and thus there is a high degree of particle sorting.

Type of Parent Material: Marine Mode of Transportation: OceanDegree of Sorting by Particle Size: High

Additional Information: The term “marine” classifies parent material transported by oceans. Water is acting on the parent material and thus there is a high degree of particle sorting.

Soil Profile Source: http://www.mo15.nrcs.usda.gov/features/gallery/ocilla.html

Type of Parent Material: Residual or Residuum. Mode of Transportation: In place; none.Degree of Sorting by Particle Size: Low

Additional Information: The terms residual or residuum classify parent material formed in place (i.e. non-transported). The degree of sorting is low because no other factors have influenced soil movement.

Soil Profile Source: http://www.mo14.nc.nrcs.usda.gov/features/goldston.html