test 1 - soils Flashcards
What does a soil form from
the underlying parent material
Name the three soil profiles
A horizon
B horizon
C horizon
List main elements of the three soil profiles
A horizon - zone of leaching, mostly organic matter. Clay and immobile soluble minerals leached down(elluviated) in to B horizon
B horizon - zone of accumulation, leached minerals from A re-precipitate here. This is a concentration of material leached out from A. usually more clay here
C horizon - parent material
What are the typical soil colors and what do they mean
Black/brown = organic matter (A horizon) Yellow/red = ferric Fe (re-precipitated in B horizon) Gray/white = re-precipitated sio2 and caco3
Why do some soils have better texture
they have a higher percentage of sand, silt, and clay
What are the two main factors of well developed soil
climate and time
Define CLORPT
controls on soils
climate organic matter topography parent material time
What is the dominate control on soil at the regional scale
climate
What are the Pedogenic regimes
Podzolization
Laterization
Calcification
What is Podzolization
A pedogenic regime:
Removal of iron ions from A to B horizon
Occurs in humid temperate climates, forest vegetation areas
Has acidic soils
End products are resistance primary minerals (quartz), Fe & Al hydrates, clays
What is Laterization
A pedogenic regime:
Occurs in areas with high precipitation - TROPICS
Intense leaching; even silica
Organic accumulation is inhibited; very thin A layers
Ancient soils; brick red
Fe & Al compounds left over from leaching
What is Calcification
A pedogenic regime:
Occurs in warm and dry environments
Precipitation is insufficient to drive soil water down to water table
Ions mobilized to B and re-precipitate there; think - cemented colluvium
What is used to determine or infer soil age
Its relative thickness and maturity
What is the problem with inferring soil age
The complications presented by polygenic soil-form factors with time; think differing pedogenic regimes; and that soil formation is usually episodic - cannot assume constant formation over time
What are paleosols
Soils formed on a past landscape / ancient soils
