Soils alld Soil Formation

SoilsalldSoilFormation
Melhdnrl nd drmi.aL \rcatlienngoI rdimed .nd il,. prccxntiDs5ol,d
odu.c rrBDhh ltd.k bla d ), rlt Ims
d.ricd 'nnc'irL coverinsmtr.h or rhe [rnh s land sudacc(Fis. 5 13)
ccolosisls'cler 1oih! lfp{ tu{ ddcE olrc8oLlh.shirh conrri6 h.ll' dii'
cml ind ory.ni! natnd. s soil.s
insonhnd (o!trnirhudn no,c plcntilul),mrysellbc thc diodv3ltrtrbhor
all naiumlreson($ Peolle lv.r!{hcrc dcpc.do' IcrliLc5oik ro {rrpod
pLanisrowth
rnd providelire{u{l
soilsdifferdependins
oi th.N.dhcring p.o.cses.locrld;n!!i. condi
tions.and preexiiinsodefi,k ihx
.omplexand oflendirrhuhio dassify.rv. s l hBr disotrsrr'. rxdos thrl
vc lliake a bnel bok d thelyltsor\oik ihathcLpp.odnccrhefdotlswe ad
lnlluenc*o. Soilrormation
c.hL,d,mdc. 1.0ogi!pliv.lcschoon. and
Pridrlvaie"a/ A !ril\ Dfcnr nrtrial r ihe bedtulk.r {dLmcnt hom
{hi.h the so devcloN
bothrhc 'trticnr rrhne$ dr th! '.strlti',3soilxnd thc.motrd or nrl J]'o
dred (hs. 5 re). For e\rfrrl., soiLsroDi',s from brt:lrir heJrtk diff.i
rron rho\. romiDgbom
markcdlyi'i(m,Nsniotr J,d Fic ol dereLopmcn{
.1'=_
'fr"sih
rfi
im$b^e (disLtroL) iid
ferdraco!hsr0ir
1liritu yrn Nd!
The relationsl p belweer patnt nalerial and soil developbdl
clearly demondrated on J.v! rnd Bomeo, two teicnboing Indonesi
idard; vith the sane dimle. The DaE i naterials lo. Jaw's soils.re lo
Irsh, ndri.nlrich volenic dh dep.sib, *hereas tbe paHt mtldars
Boneot soils stuirt of .ueros
sEnitic botholitbs, gabboi. intdio
lolcstum
on lavs rddshe rP po.itivFi
md mde're flows Oogors
poiasim,
mgresis, {d calcim-i! il5 soils, *h
nhienF+u.n
as
Bomeo,lacling l'€h sh deposlB,hd sis depleredoI rutnenb fta il
DoDuldtionddsiter re0sd thei dr.fr.licalv ditreMl pil fstility and
r a'alpmdu(!iv.-y lsvs ha app'otmte vi160rnabibntsp.r.oum kj
neter dd Bomeoabout2 innabitnt! persqurE kilomelet.
amout ol p*cipilttion it ulerien.et dd
cliimr' An oEs s djnat-lhe
c.
pre€iling lenpsab'*ontrob
the rale of cheniol wslndilg..d
dftntlv &e Ele oI soil lomalion in lhe ata Climite .lso Egdates
sroqd oJ ve..u!on ano $P sbudanreof mnmorEannd tharcdhb
aO, ond o, r. rb. oo(ess of dnsolu 'on, hydrolyis rdd oxid.ti
Chemial f,eath.rins and soil torutim aE n6t Fpid in wm, moisl
hrtes. dd slovet in cold or dry climrA
I'r"zrnr
ropognpbyrcleE ro rhepblqelle' ua ol d l.tdi€pe, !
or slop$, a-d Lbeshapeol 1!
as mounur'. "-d vruevs,the i*pm\
innuen.eslhe alolabiliry oI waterrnd otberwe.th
{oms. Topogmphy
For *ndq
st$p slopes
facton- and lhe mte of $il a.Mulaton
emi's
d then
EinJall .nd snomelt b no* awty swifdy; lidle {a!er
Denelftle the str'fae, and therelore litde or no $il developsthe€ a a
o .hm.ar res|nenng.Aty soil bd doe. fo- on JeeDslope u atr
rmnsDoneddornrlore belore it can a.clmuhte to a sienilicantdep
and Eadily i'6lt!
conv;Mt, in level, 6wlyirs ars w.ter a(udat6
tle g@ud, e.lEndg the prosPds 60rchenicol vathering and son de
tilm',llEe'lEddI|dd*'pcons
GidbeG.
@;*droachemk,l"-b.dds*oirrchnops
d.dowihill)soGkdd 'o
vererafor Vesciarion
.oDtibutesoqrd. ndlle.ro soitsrnd produ..smudi
ol flr o:3nd co, irNolvedin ch.micrLscaihc.ins
r.dion soitsdevetop
ins or prairicgnshiJ5, for erample,rc.civchrsc qu,ulies of drs.ni! mai
d trDmrhc dcmy of .xr.trsic subsurfacc
Pl.nB ilso conhibutcH ions lLd herpqedher soits.Thc H ions,
{cxkly 4u!h!d ro plantrootL,cple.. rho hige no5irrve
ionsGuch*.al
cium,li.t!.!n,m, and sodiun)in lcldspar nd orhe.n,rerals,hydroLyzirs
rhei' i o diymincml! Thiscx.haigclielp.developrheso qhileprovdins
rhe0Ldnlrrlirh ionsthd arc nuririonrllyhenetilhtroibem Gndto ut {Fig
5.21).fteseio.\are rclumcdto rh. soitshenLhcpla'rsdieandde.omposc.
be.onidsiva :ble IDr tl[ ncxrBcnearni of plints. lll the planc arc b3r
vc{.d berorerheydie,ho*cvcr, rbcsci.is rr oerh.nenrll-rtmored bom
ihr soil As a re{'lr, .onlinuous13rDins.vctrlurLlvdepleres
I soili supplyol
.al.iur. sodtumrnd potasiu ionsjn thedbe.omesneles3ry1Dsupp1.
mcnrrbese*ith Ddtrrxlof synlheri.fen rss and 3[ov a tauos p.nod ta
pflnd du iDcwhi.rilhe sojlisnot ramcd)to ld rheiois re.ronuhle.l
. o
i t
al
r.l
1!
ri,e soilsmly 6esrnro dcvclop{
cnvmnncDb.blr rirv req6e rho
n irjd d po|I ,csro; r*;1he.rdos m $ir rormrtrn snc cqsr, a rand
ncesovera lonspercd ol tmeuourd.Dn
hin a thickef,DDfc{cr devdopedso rb.' a younserlandQpe.
How.rc..
bes6e oibfl lxcron arno{ slwry\ vlry (n5nrem6ty.i ihnkfl soi E nol
Tr'e erfe.is of {eathe ng rrc grs,resr.1 a soir\ surlace,vhere ther is diEd
cxposurc
to the{eatherinscnvnonheit.
Belowthes!rfa.e,di:tinq wcdurF
ins zonesdevelop w hin a soil as strbran.es lre di$olred fron rhe upp6
layen or rhesoilandlEnspofredro lo*crlcvcls in lolurionorassolidfEe,
menbsuspendcd
in infilrlalingvarer.Thse hanspofred
subianceserctho
conmonly prccipibied or depsned in the lower soi! laycF. Ttus. iho lpper
pai oI a dcvclopingsoil toses$ne oI i6 onsinal marnab, whilc tha rover
par sainsne, .ompoienls.E.ch dnljnd wcaihcriq zonc k cllred a .oit
bonzon. soil sienrisls h.ve identilied dozensoI horizon rypes. Anong th.
mo$ comnon are th. o, A, E, B, and c ho'izons. whi.h are rolnd virrua[tr
r rhere are other ho zons as ucl. vhict
ircnment.]|e verticl sumGsionor3ofl
honzonsin a sivcn locaiion, ihe lo.atidn\ soil prolile (Fig.s 22), k a prcdud
or rhc local soil.fomins conditions.DiffcEnt lo.dliiies v.ry in rhe ryTesoI
honzons.nd then deprhand dqree or developmenr,and thus havc diffeled
frsnd i2
soirpror cs.G)Th. turuE! of a rrrii hmre€E zoic
d c hdDoN(s{ rxo O)
r h - u p p c ,D o ,i o . o r J ! o p o t . , o - . , r . o
hdo A J dEnonzo
Irr O I o's" ,-"' LorTon
sisrsm.iily oI orsanic mrter, su.h as re.osnizablefibcB of planr nafe.
reemssilh life, containinc
2 lnllion bacrcris,
400 nillion fun8l 50 nili
,l8ae, and rhousands
ol irsectsin a sinslckilosram(2.2 polndt. Th
or8,nimsconiriburc
o:r co} andorsanka.idsto rhedevelodnssoil.
r$$
drcud 6e o, a. od E hod,is,
The A honzon .ouisrs minly ol inorganicninenl malter nixed with
hlrrJ, a dark-coloied,carban.richsubstance
derivedfrom deconpdsed
o4anic rutna1 tun the O hoizon. The rhiclne$ of the A hoizon depends
upon dr quantity ol deconposedve8etationin.oaonted into the soilr In a
' - o p i i s l - v i - o n m r n 'q r h l - ! h \ e 8 e u r o n . ' . o b \ o u \ A h o 1 / o - 3 .
dewlop in as lidle as a few hundredyeas i! an environmeni-hcrc vescra
tion b spase,it nay |rke everal thoLsd yss.
The E horizon k a lipht.coloredzone belov the A horizonljrh litde or
no oigrnic ftltedal. Ils light color res'ljt lron dissolutionand removalof lhs
iron ind allminlm conpounds i! rie upper fe* mercn of rwolirh. The E
dands for sla,iaAb4 rhe rhcss b
soil horizon:Fresh{ater.onrainin8 org.nicallypBdmed co, perolates
doMvard t6n the surlrce, dissolvingsolnbleinols'ic soil conponent and
tdnspodingthen .lon8with fines
'Ihe
B horizon, which lies below fie
naterialsdissolved
or tmtuportednechanicallyfron the trpperhonzons.
Tiis is s zonc oI /tu,i,iion, rhe addition ro a lower 3oil horizon ol nate als
rdov.d and lransponedby sater fbn upperhonzom (Fis. 5.23). Theie are
a lariety of B'holizon types,cldsilied a(ordins to rhen piedoninant .omple, hasa hi8h .oncentrationol.dded
humnq s Bo horizon hs a high concmhrion of oxides.
In dd rnd scmi and ar6, {here sudacewater quickly evrpoEig, a
disrinctarbonaie rich nonzon is lo€red v hin or belo* the B honzon st be
depth to whirh unu'l ninlal penetats. Tnn qli.te layer n fomed when
qlcilF qlbomte in ihc upperlaye6 oI soil ind
bief heavyr.ins dGsolve
hnspon it downvardj ,s the v!t$ r,pidly €wpoEts, $c s onateprecip.
natei toming a narkedly while lry.r in rho soil (Fig. 5 24) In pafricularly
and regions,hundredsor tho6ands or ysn may be requned b precipit.te
enough@lciun c,6omie ro fom a well developedlayer of oli.he.
The O, A, E, and B ho.izonshcar lidle Eemblance to the onginal p.r
ent materi.l. The C horizon, however,dc love* zonc of sisrilicanr weather
ins, consnboI paientnatenll that h,s beenpdially weatheEdbut $ill
rtains nost ot ilr onginrl .ptearan@. ft my show sism of ondation hm
penetaringdxygei.;.h goundmrer, or it may be completely
unoxidized
lhe C horizon is very ihin shcrc rherc hasbem ljitle chemi.alre,theiing
for ebnple, in , desefr but can be as much as 100 meres (330 feet) lhick
where chenical veatnering is drcnsivc, snch as in the wam, wet lropis.
Below rhe c horizon lie ualtered pareni natcdal.
Until reenrly, North America was dasified by $il $ienthrs as r No soil
continc : Tne eaiem haf {as coveredby redrfer (ron $e Lrrin rcot ped
Ior 'toil," al for aluninun, and "fe" for non), and rhe wcicm half by
,edoc,k (ped, plus tal" for the caliche lryes typhal ol the arid we$)
Ped3lleB ae rclatively fdile, hisbly dlgrnic, non- and llunjnum nch soils
lomed in hunid renpemte enviro
thin, orgaiic.podr soik w h high co
As wc havc seen,however,the omplex inteEcrion ol Frenr mtnal,
climare,toposkphy,vesebtidn,and tine .a6e localsoil developnentto
vary in signilicant*ays. Modem soil .l'sificriion (Table5-1) atteopt
srsrer piectuionrhrn rhe old two{oih sydcm. Ior very pr..hol is.sonsr
Dishnd soil typeshavespecilicphysjcaland chenicalchamdei$ie thai
allect our 6es for them. Accumtesoil ',l3sification influencesdecisionsdbour
TFiq|[email protected]
T|rbk'd!lk'highlyqsoicAhol'on:
&hi!h allow{ds roiir rDt Ezdiry);
sE$s
ve{ 6ish day @doti $r +dnk, Gpon dryrq)
ard $eLL Gpor rdr4) {iln nonuc vadaroE
sorld.sis.arionsou.trtrcDi drsifi.aiion {hcnr ,3mcssD s a(ordi,rgr:
rl!..r'.r,ror (thc,oor'cnt c dcri'!:
trom dr) is.soil tlnthasnorvcr.!pc,i.D..dsisnif,Grthonzondev.lorn!d. .nd may be : rc.cn( IloDdd.ponr or lrcsh roL.inicash A rcrr,
t\!hi!h (cnJsro c4and r.fh.iIv) .onrxinsdav minsaLitha( s!ell Nh.:
no(ened rnd sh.inkwhendricd vcdLJoL!
u, mdemme moi nnrciur
ch|pb''wea$e'i4lreBrcddoM0l30[rs
'anlAngk.|wdlme|!dcanbodi.'<howing'h.
j dqre$ ol dumbiliw €xhib €d by difiedr soil i}?6. ftc
rl! prcducb d 'hi! wqdend
. iho4. he 8€!nrj0{4ly
wficn r
of cne
Exhede ueatheins in bopiel arear produ.es o*db (ndned loi their
hEh conHtmtion of insolubb non oxid6) or llt:rorr (lor then rldmare, or
nos advan.ed,dcsftc ol soil developnent).In ultisoh, even the ordinanly
insolnblc quftz hs bccn disslvcd away, lsvins only rhc no$ insoluble
elemob, suchas ircn and alunilum. (Oxidized ircn makesthe$ sojlsdark
red.) Wnen th6e soils dry our, rhey are *ro4 endgh to 3ene s building
slones, and ar connonly used to build dvellings and other sttucruresin
tmpi$l resions(Fig. 5 25); sdob3 h a nne gnined soil mirlure tadirionally
ued as a buildins nate al in the Ane.ican Sourhwst and Mexno. oxnoL
"nd ulr)o ! ,ie dephreoo rhenpohsium.d[ iLn. )oditr. s-d zgnrsiu.onrent,nd ae poor pospecis lor agii.lltlre. Rrking cmps with signifisnt
nutiiional veiuc in sojlssuchas ihee, conpccd pmdominantlyof imoluble
imn and ,lnminum, re'tuiresedvanccdagri.ulbnl rechnolqy and inrensive
ue ol fefriljzes. TlE cops ol lhe l@pi6 themtorc rend to be 6e so.€lled
''csh cops' qitn poornlhitionll vllue, slch as@tree,iobamo,sugar.ane,
paln oil, and cac@(the pnne ingredientin chocolale).mile someot !s mly
subsiston thar diet, the nos .Bdoltuhlly 6etul soib .re genelally those
th.t havewealneredle$ and ret.in sone bmelicirl nutnenG
Prr.@/r somctines pmvioBly huned soilsaB Mcovded rhat have chamcteriiic diffcrdr Imm rhose oI orhe. soils in rheir resions, su8seiin8 thar
they lomed under differenl in p!frictrlar, rcicnt<onditions
Buied soils
that predarenodern soil fornation are c,lled p,leosoh ( old soils ).
Ennplesinchdealuminln.ichb
zons in connedicut, and deep, hishly weatheredrcsolith in southre.tem
Minneot . All lhesep'esunablyto
ilions rhen p.evailin rhosesreastoday.
sinila.ly, oxisok and ' iso1sindicativeol hoid si-topi.al
or tiopi€l climres have bffi loDd bn ed bena1h tne soik fomiry roday in the *am,
dry dimre of Ausmlia. wtd we find paleosok,ou ahility ro delemine the
climaresunder which they lomed embles s ro identily dinate .hang€sthat
haveoccunedin the seolosicpas.
Weathering
in Extratellestrial
Environments
weathenns as*e know it on Eanh doesnor raketl..e on our eleiial neigb
bor. Lns suspeded,lhis hasbeenconlined hv reenr discoveriesabourrh.
slrlrce conditionsor &e Moon, venus, md M8E.'rrle reasonslor !e dusrE
ol wslherins, how*er, dilrer in ea.h case.
'lhe
Moon has no abosphere; wilhdur ahosphenc waiei, oxygh, c
biologi.al a.lvny, rhea canbe no chmi.al wedhenns. A ne.hani@l {earhering prccss-the impact of nereorit$ and micmnereoriirDrcdlced r!
Moon s regdlith, {hich consisrspnnanly of sh&ttercdbedrock and sla$t
fmsmenls
expelled
tom inpactcmten.Thesharp.dsesor lunarcbre
ti!u.t
5 A roorp'iir relrontheluH su{ec
howevei, even rhe olde$ ones, suggesrrhe absenccor Er{h-like chemi
vsrhc.iry Thus, rhe footpinb lefr in rhe tumr du$ bv the apollo II is
mnb the rnd t,owalk on the Moon_aie hkety ro rbin dteir rreshnes I
nillions ot yeas (ris. 5 26).
vsu\r*
3.u/are rmoemto'ro "oou' 4-+c r900!f)ild un "m
phea conposed almon exdusively of CO,, which kapa heat rdiatins I
the planet'sslrfr.e in a s/eg,lD8z zlic.! High tempemturesnomatty p
morc an incrcded nte of chmical rcaction,but that oI venB k so hiph
tr'F r.h! ptlne.' sL.f"f fte u
qrenr absence
of {ater on venus preventshydroty.n,carbonarionj
I
oxidation, cauile rhe venutian hnd$rpe to appearrenarkabty uvea
eredchemhlny Gis. 5-27).Mechani..l{eathefinson vcnusi as seen
reccnt Edar imagei is probebly dle to themrl expansionerd onmni
enderfoliarion.HEh windsrr rheplaner!surfacenay eisobea facror.
Mr\ ofJlpldr.-oL
.olr'.)"
no( dosely resembleihok on Earth, hrs su'JrcetempeGturesr$ging
-:rftdc ( 22s"F)to 13.c (63.F).Mad d n arnospheFconsishlarcely
co), wirh snalr onounb of nfuogcnandwarervapor Because
ot d,e
xkts 6 i.e, and is senemlly ulaEi
lor chenical readions (althoughil nay pofrore nechanical vearhedns
rro* wedging)!the lack ol heai ,lso redu.es the mre ol chenicat rerctir
d?ry,unwerhercded3sarctedinonyro
thc
d:
bfh
ci|lb'5ws|hgn!}e3re*doM0iFo.k
Thcrcis, houcvcr,clcorelidenceof.henial {eathenngin Mas pst. Tte
cdmsoncolorof rheMaitirn landsare,vhi.h we .!n seeeasilywih, hi8h,
qualily lelescopefron a disl.nceot 73,000,000kilonetes (47,000,000
mil6), is believedto be due to the reddnhnon oxidespmdned by dxidation
of iron-ri.h bedrock,and soil amlyss pe omcd by thc venatilc vikjns lan
der in 1976 conlimed rhe h*h .oncentarion oI imn oxides ar thc planefs
As we hrve seen, various me.hrnical and chemjcalweaihering
pro.e$es cancoivert solid bedro.k to ldose,t nspodabletrasnenb ind dissolved ions. On@ libemted bon their pamnt bedrock,theseImsnenb and
ioc dft IFe to nove under the influenceol such surlaceshapinslorces as
snvity, sheamsand Elacicd,$ind, snd coasblmves T.e pmass thar
tmnspon {eathered mareriel, and rhcir subscqucntdeposirionmd conver
sion to *dimenhry rcck, will be disosed in Chaprer6.
.ir .an be bmken doM by ,eathedns, ercsion,or,
, :ombinahonol the No wsthenry is the slow but
. ?rcces {hereby rocks are Bmduallybmken doM
.nncntal factos at thc Eath's sudace.Emsion
! irn mck fiasnens are bansponedand deposfted
:... by novingwater,*ind, or icajbe.a!6e
erosion
r:! !re t-o typesorueltheringrmochani.rl!ealh'
Mechaniqlveathennsmaybeaccomplthed
by: hosr
sedgn'c'tbeexp9donoftrrksii
oacks freezs and expandsislr{ry$al sroMh w hin rcck
cavities,*hich forcesthe cavity walk lanher apanj fiemrl
exTansion
and.onlraction,
theallemate
enlal€€nenr
ond
rhnnkingolrockasit G repealedly
heatedind.ooledj
ncchani..l exloliilion, lhe hadunn8 and renoval or succar
' rtrr srhour chJryrDE
is chemHlomporr oni
afteroveiyinsrockshavccmd.dasayipeneb:tionot
o* ot {ealhenngand.rosioncontnbuleto the
rlrmoil, thelooso,h!8oenledg@lo8icmatenal
, :.nvnareri,llorsedinenrary
rcck.
-
positionol ihc scathcred mcl. Rocksand nincrals bvin8
incrufts rhat are chcnically umbblc at rhc Eanh\ su'face
arc no* succpiiblc to chemi$l seathcring. which chang.s
ment lron which a so developt, .lina!e, ropoglphy (he
physiol reat!res or a trndscapc),legeiation cover,and tme
A developin€
soilconskbot dktinctlayer h3vinsdillerenr
he verticl succesionor
soil horizonsin e givcn locationis the lostiont soil profil..
Mostempente-zone
soilprofiles.oisj{ or ihe iypical
liye6 desisnied(fron rheslrta.edo{n) rheo, A, E, B. rnd
C soilhonzois Cilichcisawhire.
isticofdesenenfionnen$, prcdlcedwhensatcr caryiig
percolales
dnsolved
clciun carbdnate
dosn rron ihesur
produds
acid
and
rhc
art
srned
oll
by
wder.
lace
to
a
loser
soil
hyer
ind
then
evaPoratei
ocudng
In re.en(yea6,soilda$jliqrlon h
Oxidrrjob,rbelc,ctionor ccrtainc
orvgc!, *orks nos cffectvely on iron-nd ro.ks n'ch as
ingly pre.ne as, gnid. ro land.Ns
peridonb.
bsau andultamaft
HydrolFis,thertplacement nd{ dislinguish
len dilterenlordes
ionsin nincrak (paniularlyrheleldspar)
Amenc, for insance,rhereaslheyusedto distiryuish
only
of najor positive
so. P,l.osols,or "old soils,"re bunedhyersol an.ient
with H ionsliom *.ler, trodlcesr
uds ol chemralweihenns,the.l.y ninenls
soilihatmly conrain
eviden.eofe pa* dimatedilferenr
Thente ai {hnh a sivenrolk ormjnerrl ll bechefr. lon tharor loday Forexanplc,a p
na y {cathertddepends
on i vaneryolfadou: climite
nodemsoilin{hatiscliieitly a m
(hot. noni rqions exhib not qedhenng ihr .old or dry
menrney .o.rain r crri.hc laycr, indi.aiins thar a {am add
res,o':)itheachvityoflivingorgaiisn\ lengihof rine
expofd io sealhennsr .tuI the lhe'iic.l sbbility of irs con'
ponenkartheftfrh's5udace.(Miner.Ls
rh.Lcryst.llirear
Wea$enr8hkespleceon orhcrptrnchin ou solar
veryhightcmpflabcs, luchs olivDeandpyroxene!
art
syiem andon rheMoon,altho!3hdiffeiendythanir ocuE
on Eanh.No chemnalweithenngo
srh as'ruert and mica) chcmnal {caihe rins, the mo$
be.auseit hs neirheratmospher (ih!s no O2or co:) nor
p.oduds
norablc
ofvhich arethe cliy minemlsitul several
surt cevate( Ireqlentneieorie im
(he
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