SOIL ORIGIN .ppt

Soil science

1. SOIL ORIGIN AND NATURE,
FORMATION OF SOILS

2. •Soildevelopsfromparentmaterialbytheprocessesofsoilformation
•Theprocessofformationsoilfromthehardrock(eg.granite)aredividedintotwo
stages
–Rockweathering
–Soilformation
•Themineralmatterinheritedformrocksarereferredtoassoilparentmaterial

3. •Theprincipleparentmaterialsoforganicsoilsareformedduetodecomposingof
plantmaterials
•Themostimportantpropertiesofparent’smaterialsaretextureandmineral
composition

4. •Rocks-formedbythecoolingofamoltonmasscalledmagma
•Themostcommonigneousrocksarebasaltandgranite
•Basaltrock-mostcommonlavarockwhichistheprinciplehardrockunderlying
theoceanbasins
•Basaltrockduetoweatheringproducesalargepercentageofclayandless
percentageofstone

5. •Graniterock-weatherstocoarsegrainedrockstoproducemuchsandiersoil
•Graniteusuallyproducesadeepersoilthanbasalt
•Igneousrocks–source-10%oftheearthsoilarea
•Theremaining90%ofthelandareahasamantleofsedimentaryormetamorphic
rocks

6. SEDIMENTARYROCKS
•Areformedbythecementationofironofmaterialsdepositedbywind,water,ice
orgravity
•Cementationisbyiron,aluminum,silicon,CaCO
3etc)
•Sedimentaryrocksareshale,limestone,quartzstonesetc

7. METAMORPHICROCKS
•Areformedunderheatandpressure
•Sandstonecanchangetoquartzite,shaletoslateandlimestonetomarble

8. SOILFORMATION
•Weathering-responsiblefortheformationoftheregolithandinturnthesoil
•Weathering-combinationofdestructionandsynthesis
•Simultaneouslyrockfragmentsandthemineralsthereinareattachedby
weatheringforces
•Thesechangesareaccompaniedbyacontinueddecreaseinparticlesizeandby
releaseofsolubleconstituents.

9. PROCESSOFWEATHERING
•Mechanicaldisintegration
•Chemicaldecomposition
I.Mechanical
a.Temperature:differentialexpansionsofminerals,frostbetionandexfoliation.
b.Erosionanddeposition–bywatericewind
c.Plantandanimalinfluences

10. II.Chemical
a.Hydrolysis
b.Hydration
c.Carbonationandrelatedacidicprocesses
d.Oxidation
e.Solution

11. MECHANICALFORCESOFWEATHERING
Temperature
•Suddenorwidevariationsoftemperatureinfluencethedisintegrationofrocks
•Warmingandcoolingprocessareeffectiveindisintegrationofparentmaterials

12. •Freezingofwater
Itwidensthecracksanddislodgesrockstofragments
•Water
Waterhasatremendouscuttingpowerinthevalleysofrivers
•Ice
Iceisanerosiveandtransportingagencywhichdisintegratesrocks
•Wind
Windalwayshadbeenimportanttransportingagentforduststorms
•Plants
Mossesandlichensproducesorganicmaterials-helpindisintegrationandthegrowth
ofrootsintherockscrevicesandthusdisintegrationofrock

13. CHEMICALPROCESSOFWEATHERING–DECOMPOSITION
•Hydrolysis
Itisadecompositionreactionespeciallyincaseoffeldspars&mica
•Hydration
ItistheprocessesofattachmentofH
+
andOH
-
ionstothecompounds
2Fe
2O
3+3H
2O 2Fe
2O
3H
2O
Hematite(red) Limonite(Yellow)

14. •Carbonation
Hydrogenion,carbonicacid,HNO
3,H2SO
4
CaCO
3+H
2CO
3 Ca(HCO
3)
2
CalciteCarbonicAcid SolubleBicarbonate
•Oxidation
Fe
++
Fe
+++
4FeO+O
2 2Fe
2O
3
FerrousOxide Hematite

15. Solution
Dissolved CO
2 andH
+
ions
Fig. : How various kinds of parent’s material are formed transported & deposited

16. SOILPARENTMATERIALSORWEATHEREDSOILS
–Residualparentmaterial
–Alluvialdebris
–Alluvialstreamdeposits
–Marinesediments
–Lacustrine
–Glacial
–Eolian(Sandsize)siltsize-Transportedbywind

17. FACTORSINFLUENCINGSOILFORMATION
•Climaticcondition-particularlytemperatureandprecipitation
•Livingorganism -especiallynativevegetation
•Natureofparentmaterial–Texture&structureofsoil
•Chemical&mineralogicalcompositionofsoil
•Topographyofthearea
•Timeofsoilformation

18. SOILPROFILE
•Horizontaldistributionofsoillayersarecalledsoilhorizons
•Theverticalsequenceofsoilhorizonsaretermedassoilprofile
•Soilformingprocessesaregroupedunderfourheads-O,A,BandC
Consolidatedbedrock.

19. •OGroup:Theorganichorizonswhichlieabovethemineralsoil
•Agroup:Themineralhorizonswhichareatornearthesurfacecharacterizedby
maximumleaching
•BGroup:Thelayerinwhichdepositionfromaboveorevenbelow
•Itistheregionofmaximumaccumulationofmaterialssuchasoxidesofironand
aluminumandsilicateclays
•Thesematerialsmayhavewasheddownwardfromthesurfacelayersortheyhave
formedintheBhorizon
•Inthearidregioncalciumcarbonateandcalciumsulphatemaybeaccumulated

20. •A&Bhorizontogetheriscalledthesolum
•C-Horizon:Itistheunconsolidatedmaterialunderlyingthesolution.Least
weatheredaccumulationofCa,Mgcarbonate,cementation,sometimeshighbulk
densityfragipans
•R-Horizon:Consolidatedbedrock.Itmayormaynotbeliketheparentrockfrom
whichthesolutionisformed