Saikat Nandy, Soil Formation & Structure

1. ADAMAS INSTITUTE OFADAMAS INSTITUTE OF
TECHNOLOGYTECHNOLOGY
Saikat NandySaikat Nandy
CE(B) – 2CE(B) – 2ndnd
YearYear
Roll NO. - 107Roll NO. - 107

2. Formation & Structure of SoilFormation & Structure of Soil

3. Soil FormationSoil Formation

4. Types of rockTypes of rock
Magma:Magma: molten rockmolten rock
IgneousIgneous :: cold, solid magmacold, solid magma
Sedimentary:Sedimentary: materials deposited frommaterials deposited from
suspension or precipitated from solutionsuspension or precipitated from solution
Metamorphic:Metamorphic: rocks changed by heatrocks changed by heat
and pressureand pressure

5. The Rock CycleThe Rock Cycle

6. RegolithRegolith
 RegolithRegolith
 Unconsolidated debris from the breakdownUnconsolidated debris from the breakdown
of solid rockof solid rock
 May have formed from the rock it now liesMay have formed from the rock it now lies
on top ofon top of
 Or been transported from somewhere elseOr been transported from somewhere else
 Varies in thicknessVaries in thickness

7. ParentParent
MaterialMaterial
 Upper layers of regolith haveUpper layers of regolith have
been altered more thanbeen altered more than
deeper layersdeeper layers
 Deeper layers are most likeDeeper layers are most like
the original regoliththe original regolith
 This original regolith is theThis original regolith is the
soil parent materialsoil parent material
MoraineMoraine
 An accumulation of earth,An accumulation of earth,
usually with stones, carried andusually with stones, carried and
deposited by a glacierdeposited by a glacier
 heterogeneousheterogeneous
 unsorted and unstratifiedunsorted and unstratified

8. Morainal parent materialMorainal parent material

9. Fluvial depositsFluvial deposits
Deposited by flowing waterDeposited by flowing water
Includes glaciofluvialIncludes glaciofluvial
Gravel, sand, and/or siltsGravel, sand, and/or silts
Rounded grains, sorted and stratifiedRounded grains, sorted and stratified

10. Fluvial parent materialFluvial parent material

11. Lacustrine depositsLacustrine deposits
 Deposited in lakesDeposited in lakes
 StratifiedStratified
 SortedSorted
 Absence of stones - usuallyAbsence of stones - usually

12. Lacustrine parent materialLacustrine parent material

13. Eolian depositsEolian deposits
Transported and deposited by windTransported and deposited by wind
Medium to fine sized sandMedium to fine sized sand
Medium to fine sized siltMedium to fine sized silt
or both sand and siltor both sand and silt
SortedSorted

14. Eolian parent materialEolian parent material

15. ColluviumColluvium
Moved by gravityMoved by gravity
Heterogeneous mix of sizesHeterogeneous mix of sizes
UnsortedUnsorted
UnstratifiedUnstratified
Rock fallRock fall

16. Colluvium parent materialColluvium parent material

17. Residual parent materialResidual parent material
Formed from rockFormed from rock
Weathered in placeWeathered in place
Not transportedNot transported
Parent material in CanadaParent material in Canada
 During Ice Ages, Canada was coveredDuring Ice Ages, Canada was covered
by ice.by ice.
 The ice scraped off most of the surfaceThe ice scraped off most of the surface
and moved materials aroundand moved materials around
 When the ice left, soil formation startedWhen the ice left, soil formation started
all over againall over again

18. The Laurentide Ice Sheet CoverThe Laurentide Ice Sheet Cover
Godfrey 1993Godfrey 1993

19. Glaciers and parent materialGlaciers and parent material
 Ground moraineGround moraine
 Glacial till (Also called till)Glacial till (Also called till)
 End moraineEnd moraine
 Recessional moraineRecessional moraine
 Lateral moraineLateral moraine
Glaciers and parent materialGlaciers and parent material
 KettleKettle
 EskerEsker
 KameKame
 Outwash plainOutwash plain
 Braided streamBraided stream
 DrumlinDrumlin

20. Formation and deposition ofFormation and deposition of
glacial materialsglacial materials

21. Edmonton region during finalEdmonton region during final
stages of deglaciationstages of deglaciation (Godfrey, 1998)(Godfrey, 1998)

22. Surface geology of the EdmontonSurface geology of the Edmonton
regionregion

23. Soil Structure
Soil may be a loose assemblage of individual and
random particles, or consist of distinctly structured
aggregates of distinctive size and shape; the
particular arrangement of which is called soil
structure.
Most methods of measurement are indirect, and
measure various properties that are dependent or at
the least influenced by specific structural properties;
e.g., total porosity, pore size distribution, liquid
retention/transmission, and infiltration.

24. Soils may be non-structured (e.g., single grain or
massive) or consist of naturally formed units known
as peds or aggregates.
The initial stage in the formation of soil structure is
the process of flocculation.
Individual colloids typically exhibit a net
negative charge which results in an electrostatic
repulsion.

25. Reduction of the forces of electrostatic repulsion
allows the particles to come closer together.
Flocculation
This process allows other forces of attraction to
become more dominant. The formation of these
“flocs” in suspension represents the early stages of
aggregation.

26. As this process continues, the flocs
become larger and larger forming the
more refined structural units.
On their own, these units are pretty fragile and
the process is easily reversed. But in the
presence of natural or artificial binding become
more strongly cemented together forming stable
soil aggregates.
These binding agents may be:
Inorganic – Fe & Al oxides, carbonates,
amorphous gels and sols; or
Organic – polysaccharides, hemicellulose,
and other natural or manufactured organic
polymers.

27. The arrangement or organization of individual soil
particles (soil separates) into a specific
configuration is called “soil structure”. Soil
structure is developed over a geologic time frame, is
(or can be) naturally fragile, and is affected by
changes in climate, vegetation, biological activity,
and anthropogenic manipulation.
Soil structure influences the mechanical properties
of soil such as stability, porosity and compaction, as
well as plant growth, hydrologic function, and
erosion.

28. There are three broad categories of soil
structure; single grained, massive, and
aggregated.
When particles are entirely unattached the
structure is completely loose and such soils are
labeled single grained. When packed into large
cohesive blocks the structure is called massive.
Neither have any visible structural
characteristics.
Between these two extremes particles are
present as aggregates or peds.

29. The observable shapes of soil structure in the
field are classified as:
Platy: Horizontally layered, thin, flat aggregates
similar to wafers.
Spherical: Rounded aggregates generally < 2.0
cm in diameter that are often found in loose
condition called “granules or crumbs”.
Blocky: Cube-like blocks, sometimes angular
with well-defined sharp faces or sub-angular
with rounded faces up to 10cm in size.
Columnar or Prismatic: Vertically oriented pillars
up to 15cm in diameter.

30. Platy and spherical soil structure is common to the
surface soil horizons, blocky and columnar/prismatic
are associated with the deeper subsurface soil
horizons

31.  Non-StructuredNon-Structured
– Single GrainSingle Grain
– MassiveMassive
 StructuredStructured
– Platy: horizontal &Platy: horizontal &
flatflat
– SphericalSpherical
(Grannular): rounded(Grannular): rounded
and <2.0 cmand <2.0 cm
– Blocky: cubes up toBlocky: cubes up to
10 cm that are10 cm that are
angular (sharpangular (sharp
edges) or subangularedges) or subangular
(rounded)(rounded)
– PrismaticPrismatic
(Columnar): longer(Columnar): longer
than wide, often 6than wide, often 6
sided, sharp orsided, sharp or
rounded, < 15 cmrounded, < 15 cm

32. Aggregate size distribution also influences the
pore size distribution.
Macropores: Inter-aggregate cavities that
influence infiltration, drainage, and aeration.
Micropores: Intra-aggregate capillaries
important to water and solute retention.
Mesopore: Inbetween.

33. Thank You.