3- WEATHERINo OF GRANITE

A) CHARACTERISTTCS OF GRANITE

i) llinerol Composition

;l Comprises quqrtz, feldspor, rnico, hornblende ond other minerols

+ the presence of orthoclose feldspor, which is less resistoni, enobles ii 1o beweatheted eosily

ii) Physicol Properties

"l' Rock type: fntrusive igneous rock (plutonic rock)

i Texture: cocrse groined

,{ colouri consist of grey, white, block ond pink minerql grqins

,tl Crystqlline rock\

+ 6reot physicol strength (Hqrd) : due lo the compoct nature of interlockingcrystqls

Fi}r/"e 22. /v\inerol composition of gronite

+ Pock Structure

. Fresh grdnite (neuly forned). non-porous ond highly imPermeoble

. Frdclured granife.' hon-porous but permeoble due to joints

. Extensive poiiern of joints, formed both on cooling ond due to Pressuteteleose

. Verlicoljoints intersecting ot right ongles with horizontol joints fo formpseudo - bedding phnd

. This results in on overoll 'orlhogonol' joint sirucfure.

. Sometimes, sheet joints / rodiqljoinls. often curvilineor in form; developpqrollel to the morgins of lorge gronitic mqsses. Grqnite formed undervery gteot pressure in the eorth's crust undergoes exponsion os theoverlying strotq ore groduolly striPped off by denudotionol processes.

Such pressure release iends to produce cuNe sheets of rock runningporollel to the surfqce of the gronilic mqsses.

B) WEATHERING PROCEssEs AFFECTING oRANITE

- 6ronite is susceptible to

. Chenicdl sealhering - hydrolysis, oxidotion ond hydroiion

. Physicdl wedtheing - freeze thaw weathering, insolqtion weothering, soltcryslol growth ond ptessure release

. Refer to weolhering notes

i)Deep Weothering in the TroPics

'L Ropid chemicol weothering (moinly hydrolysis) to o depth of up to 60m.

+ Result: deep layers of weothered moteriol (or sqp\olite).

+ Thickness of the weolhered mqntle: 30 to 6Om (Refer to Strqkhov'sdrogrom).

* Fdctorc Promolirg Deep Weatheing in the tropics:

Clinate! High prevoiling lemperotures

reoction, for e.9. hydrolysis is

rise in lemperoture;> High precipifdtion - ovoilobility of woter for chemicol processes.

Vegetation> Protects soil from roinwcsh erosion but releoses lorge mosses of

vegetql motter - production of orgonic ocids - focilitote rockdecoy.! E.g. the qnnuol releose of orgonic mciter from tropicql roanforests is

10 - 20 times thot from coniferous forests.

Long periods of fectohic stabilifv) For e.g.lqrge ports of lhe oncient Africon londlnoss hos experienced

little uplift over long periods of geologic time.

Qnt How for deep con deep weofhering occur?

+ Basal Surfdce of l4eothering

. Oflen lhe wedtl\eted loyer (weolhering montle) hcs o very cleorly

defined bose wiih o shorp chonge from highly weathered io complefely

unweothered rock.

. This boundory or sutface thot sePqrotes oltered (decomposed ordisintegroted) rock fron fresh, unweolhered rock is referred to os thebasal surface of weothering (BSt1/) or wea,fhering front.Il morks lhedownword litnit to deep weothering.

. The depth of fhe BSW below ground level depends on o number offqctors, nomely, the climote ol the oreo,, the tYpe of porent rock (its

minerol composifion ond the presence of joints/bedding plones qnd ofherIines of weokness), ond time.

. Where the rock hos o complex ond deep system of joints, weothering willproceed ropidly and the BSW will be highly irregulor ond found otgreoter depth below ground level.

fovouring ropid rotes of chenicolspeeded up 2 + times for every looC

FiE)re 23- Bosol surfoce of weothering

ii) Ruxton qnd Berry (1957): l,lodel of DeeP Weothering of Grqnite in

Tropicol Areos

4 Bosed on observqtions of octuol weqthering horizons in Hong Kong.

The groduol decomposilion of gronite from the surfoce downwords willproduce 4 zones, eoch 'older" or "nore odvonced" thon the o^e 5eneoth it.

Model implies thot over tine, the uppermost zones will grow ot the exPense

of lhe lowermost zones ond ihqi the whole weqthering loyer will evenluqlly

become highly rotted residual debris

It olso ossurnes thot there is o downword limit to deeP weothering (bos?rl

surfoce of weothering) coused eiiher by permonent solurotion of the rock orthe disqppeoronce of joinls

{

+ Actuol weothering profiles in the tropics hove been shown to resemble, otlimes, the Ruxton ond Berry model.

'l For e.9. J W Bornes described rotted gneiss in Ugondq: q progressive

tronsition from surfoce soil, through highly weothered rock ond moderotelyweqthered rock, to porliolly weatheted rock ond fresh rock qt o depth of49fit.

4 Zone 1

. Uppermost zone of "residuol debris"

. Structureless moss of cloy minerols such qs kqolinite ond quortz Sqnd

. Vory ih ihickness fron l to 25m

. Results from protrocted (prolonged) ond complete decoy of the groniteover o long period of time.

'L Zone 2

. Less decornposed

. comprises some residuol debris. some'gruss" (q tnoss of ploty frogmenlsproduced by breqkdown of feldspor crystols) dnd q number of'flooting"ond rounded core-stones.

. Peferred to os zone of residuol debris ond gruss togelher with rounded

cote-stones. Occupy up to 50"L of the zone: Moy be up to 60 rn in thickness

,1" Zone 3

. Dominoted by lorge numbers of rectongulor core-stones seporqted fromeqch other by poriiolly decomposed gruss.

. Up to 17 m thick

* Zone 4

. Eose of weqthering prolile

. UP to 30 m thick

. Portiolly weolhered rock, resulting from the initiol Penetrotion ofociduloted wqter ond opening up of joints \

Zone 1il-25m);Residutldebds

loie ? iup b6&i}l RrsiCual

ddds + qruss +

Zono 3 (7"17rn):

Qruss + 16q6

rumber otaedaioular

Zo,re 4 (8ir)ilntialeeiiigoli{irls. solli

b€dtuit

(b):Vy'eath$rd

larer ronsisling olEridr.laldeb s !!1lll

reblively lsrcorcslones

Fi})te 24. Ruxion ond Berry's Model of Deep Weothering Profiles

C) 6RANITE LANDFORM5

+ Different qronite londforms moy evolve under vorying conditions in diffetentenvironmen l5

In lempetote lotitudes, groniie is o highly resistonl rock, forming ploteous

ond uplonds (e.9. Dortmoor, SW Englond)

In tropicol hunid regions, it is prone to ropid chemicdl weqthering whichotfo.ks the feldspor ond mico io give o thick loyer of decomposed rock(regolith).

Becouse of lety active chemical weolhe' mg theidepth of regolith in thehunid fropics is the greotesf in the world; exceeding 30m in some regions.The produci of deep weotherinq is the forrnotion of fors.

i) Exfoliotion Domes

-L Dome-shoped hill with o bore rock surfoce

* Possess curvilinear sheet joints

* Well-developed in mcssive coorse-grcined rocks (gronite) by theprocess of exfoliotion

+ Egs. Sugor Losf Mountoin (Brozil), Holf Dome in Yosemiie NotionqlPork (UsA)

Figure 25. Exfoliotion dome in yosemite Notionol Pork, USA

ii) Boulder Fields / Felsenmeer

+ Occur in oreos where gronife hos 6een weathered into smoller boulders by

frost ocfion ond hove dccumuloted in o low lying oreo.

ol Boulders con olso be tronsported by wqter to resi ot o low lying oreo

Fi})re 26. A boulder field in Conodo weothered by frost oction.

iii) Tofoni

Tofoni ore deep co\ilies or hollows produced by solt crystql growth in thesides of rock ouicrops ond boulders.

occur in rnony krnds of rocks, but ore usuolly found in gronulor or crystollinerocks such os sondstones or gronites

Tcfoni usuolly occur in groups, in coosiol regions or deserts. Individuolhollows ronge in depth and diomeier from a few centimeterc 10 severol

tneters

Formotion storis when wofer brings dissolved minerols to the ioints qnd

other lines of weoknesses of ihe rock. When the wofer evoporotes, -ihe

minerols form crystdls fhof force smoll porticles \o lloke oft the rock. Thehollows ore enlarged by progressive floking of the interior surfoces ond

their grohulor disjnlegrotion. Wihd probobly removes loosenad moteriol frornlhe co'rilies

+

Figure 27 . Huge lofoni in the Nomib Deserf

FiEtrc 28. Groups of srnoll hollows known qs tofoni

iv) Tors

Tors ore mosses of spheroidolly-weothered boulders often ol yonite whichhove the boses an the bedrock ond surrounded by weofhered debris

They are considered relics (remndnts) of fortner londscopes ond resull frbmlong-term differentiol weothering ond erosion of fhe bedrock which, ofterthe removol of the weolhered moteriol, leqds ro lhe emetgence of theresis-ton-f rocks 05 tors.

+ They ore usuqlly less thon 30m in heighf

.L Upper ports of iors often comprise detoched ond rouhded corestones, withdiometers ronging from 3m lo 8m

+ The cuboidol sfruclure of grdnite is well-displcyed when the tors oreexposed onto the eorth's surfoce.

+ Although fors ore found widely ond ore not res-tTicted lo gronitic rocks, therocky tors of Dortmoon in soufh-west Englond, ore the besf known

d

Figure 29. Hound Tor, Dortnoor

Formdtion of Tors

,iL The formstion of tors hqs generoted much debote omong geomorphologists.

Vorious hypotheses h@te 6een proposed io exploin the formolion of Jors. Acommon feoture omong the hypotheses is thol tors ore formed in oreos ofwidely spoced joinfing ond thetefote ore more resistqnt to weothering ond

erosion thon surrounding oreos with closely spoced joints.

+ The nore widely accepted theory of tor formotion is thoi of deepweothering theory (in which weqthering fook ploce subsurfoce/underground).

Linton's Theory of Tor Formdlion

'4 Linton (1955), who worked on the Dortmoor Tors, proposed o two-stogemodel thdt involves o prolonged period of deep chemicol weothering duringihe worm cnd humid Pliocene Period.

',.L Feldspor is lhe leost resistont minerol to the chemicql weathering process ofhydrolysis while quqrlz is the most resistont minerol. Deep chemicolweotherihg of feldspor is most octive in worm ond humid conditions,especially in grqnite with well-developed joini systems ollowing gteotetpermeobilify.

'l The moin processd involved in deep chernicol weotheting of gronite include

hydrolysis qnd solution which occur when ociduloted roinwoter penelrqteolong joints into the body of the gronitic moss. fn hydrolysis, the hydrogenions in wqter reoct direcfly with feldspor to form kqolinite.

{' The joints ollow the reody penetrotion of woter ond increqse the sub-surfoce oreq of the rock for physicol ond chemicol ottock.

+ The pottern of the orthogonol joints delermines the pqttern of the tor tholis formed. The widening of moderotely-spoced ond widely-spoced joints willresult in ihe formotion of rectongulor blocks or corestones.

;! The corestones becqme smoother qnd rounder over titne when chemicolprocesses selectively ottcck the edges of the rectongulor blocks, resulting in

spheroidol weothering qs grqnite is mcde up of minerols of vorying

resistonce. \

'* This prodlces q fine regolith (sond ond cloy) in closely spoced joints ond

corestones in noderotely /widely loinled rock.

Ih ternperote oreos, this is followed by the removol of the r€golath bysolifluction which is the process whereby moisture-lqden soil flowsdownslope, during the periglociol Pleistocene Period ond the.iors will be

exposed.

fn tropicql oreqs, fhe finer regolilh will be removed ond eroded during o

period when vegetolion is less dense due lo lower precipitotion, exposing iheunweothered blocks of gronite tors.

For tors 1o be formed, the rote of erosionol stripping must be foster thon'fhe weof herinq process.

Figure 30.

Tors in the hopics1

joi.ls

Figure 31.

The fornoiion of tors (D. L. Lihton)

C oselv sooced pinrs 2 Widely sp;ced ioinLs

nrore decp yvearhered q€alhered essdeeply

Cl0s6ly

iointe

Forhotioh of lors in the

Overlhousands ol y€rrs werlherinq\ and ri\re6 reiroved he brolen roclr

Tors slood tL.ll

t.opics

c0rusloner emBrgiag

j0inling

\i/earhcring pef slratl ng

!lon9 joinlt

The formofion of tors in the sub-humid tropics

Figure 33. Formotion of Tors

WEATHERINC. ROCKS AND RIIIIF EiIMiF.f!

-Sepwinar 2

Linton (19s5) arsued that the well developed jointinq system (of

irrequla. spacins)was chemlcilly weathered. This occurted undeihumid conditions during wanrr, wet periods in the Tetiary era.

Decomposition was most rapid alonq joint planes. Whe.e thedistance betweea the joint plares wrs argest, masses of qtanite

.emained relatively unweatheted and formed. essentially,

embryonictD6- 5ubseq u€n! denudrt'on, perhaps under Pe.iqlaci: I

.onditions, removed the residue of weatherinq, leavi.q th€

! nweath.red blocks as to15 (Fiqure 2.22).

(r ) D€ep .h emi.a I werth ering to llow.d by etrip pin I

An altemrtive theory prcposed by Palmcrand Nielson (1962) also

relates tor formation to the varied spdcing ofjoints within theqr.nite. They believe that frost action under periglacial conditions

was the dominant procesr. this led to the removal ofthe mo.eclosely iointed po.tions ofthe rock. The evidence lendstosupPotitheir idea, !s the amount of kaolin in thejoinis is limited; so too is

the amount ofrounding that ha! occurcd- Both ofthese features

are expected to be dominant if chemica I weathering were the mainprocess in operation. Palmerand Neikon sugqestthat intense frostshati:ering followed by solifluction, .emoved the finer material and

leftthe tors stinding (Fiqure 2-23).

(b)

(.) Fron.cfi on d!rinq peiqlacial periodr

Tols are a qood Nmple ofequiffnality. This means that diffetentprocesses.an produce the samc end result- Thus it is hiqhly

debatable whether tors arc formed by chemical weathednq or

mechanical weathering, or a €ombination ofthe two- Whatis clear

however. is th.t the joints and beddinq planes, and the qrctri

strength and resist:nce ofthe rocks have dcteniined the dist.ibution oftou on the landscape.

strm'nit Frostactioninwelt jojntcdtor rrcas loosensblo.ks

41

The Formation of Torson the Dartmoor Granite- an outlineThe processes resulting in the formationof the Da.tmoor tors started about 280m:llion years ago as the granite foftingDa{mooa cooled and solidified from moltenrock at a temperature of 90O - 1000'C. Theminerals which make up granite crystallisedas closely interlocking g.ains forming thehard rock,

Granite is foamed of ihree main minerals:Quaatz - appearing in the granite astranslucenl. slightly greyish looking grains;Feldspar - white grains. sometimes stainedyellow:sh or pink (in parts of the granitefeldspar forms large white crystals); andEiotite - dark brown glistening flakes.

The setting of the initialpattern

The sti{l hot but solid granite continued tocool. Contraction caused the formation ofjoints (open fractures) usually near vertical,in the graalte. :]ot water moving lhroughthespjoinrs com-nonly led Io lheir becominglined or filled by minerals sLrch as quartz ora black mineral called tourmaline or both. Theorientation of thejoint pattern was controlledby pressure in the earth's crust. The_joint .

pattern was accentlrated and modified byactual movements along fractures called fau:ts.

The unroofing of theg.an;te

The cover of rocks above the granite, mainlyslate and sandstoae, which was 2 3 km thick,was worn away qulckly, and the fragmentsof granite and .elated rocks can be foundamong the New Red Sandstone rocks ofDevon today-

The removal of ihe pressurc of the overlyingrock allowed the granite to expand upwards

sr{6lcI&&i ! [i{:A Level - Geology & Geography

starting thc formation of horizontaljoints.Thesejoints tend to follow the shape of thesurrounding lancj. They are usually horizontalon hill top tors and may be inclined on valley'side tors.

F KaolinisationKaolinisation is one of the importaniprocesses Ieading to the breakdown of thesolid granite. it is caused by the circulationof water that has been heated within tlx)granite- The feldspar minerals comprisingsome 30-40o% of the granite are decomposcdlorming rho wh,re clay. kaolin. fho m riurarea of kaolinisation is aroLrnd Lee Mooron the southern edge of the granite, butmany smaller areas of kaolinisation occur.WhitewonFs for example.3km SSE ofPrincetown, as the name suggests, ,s an areawhere the granite is more or less kaolinised.This process also affccted joints and faults o!rsmaller areas of granite, across the moor. Thisstarted the process of shaping thc tors as thesurrounding gra.lite was softened andweakened in placcs. The kaolinisation processprobably continued for a considerable lengthof time as heat continued to be generated inthe granite by its natu.al radioactivity.

Deep weathering of thegranite

A considerable lcngth ol time eLapsed beforethe next major tor forming process occLrrred.Some 60 - 30 mllllon ycars ago the granitestood above sea levei but the climate wassubt.opical (hol and at times wet), as the areathat is now Britain was nearer lhe equator lnsuch condit ons water containing acids fromrottinq plants is very rcactlve and the minerals,aga n mainly the feldspa.s of granite, wereattacked and weakened. The more stablemineral quartz was much less affected. Theweathering mainly took place along the lines ofthejoints through which water moved. Wherejoints were closely spaced the indlvidual mineralgrains of the granite becamc more or less

completely scparated to a considerable depth.

p ff'r" lce Age, the final phase

In cold conditions r ocks arc not affected byclrem , dl w.aLh, r'rq procas,o. LLrt maiormechanica{ forces can take effect. Of thesethe most impo.lent is the expansion offreezing watet The deeply weathcredgranjte was forccd apart and broken upinto blocks by be ng subjected Lo frequentfreezing and thawing during the cold periodsof the lc(} Age, between 2 mlllion to 10,000years ago. The fo.ce of gravity was alsoimportant, movinq the loose materialdownh r lhis rnovorn.n. ,,rlled 'oliflui:on(soii flow), was aidcd by the ground belowthe surface beinq permanenlly frozen. ln thesummer the sLrrface layers thawed to producea wet mush of debais which could slide andflow downhill over the frozen subsoil. Evenlarge blocks and boulders were moved in thisprocess, as much as a kilometre in some partsof the Moor The result is the boulder fieldsor clitter surroLlnding the ton and the coverof qravelly, broken'up granite, called gaowaniocally and Head by geologists. The flnalresult was ihe removal of the weatheredand loose material l"rom around cores ofrelatively unaltered granite.

The results of all these eventsare Dartmoor Tors

Dartmoor then and now

Approximately 30 million years ago

How Dattmoor might havc looked between30-60 million ycars ago. Densely coveredwnh ltpps and v?geL3tion. lhe undqlyinqgranite is becoming deeply weatherecl byacidic water penetrating bctween thejoints.Thc shape of a tor is being formed in thFIess altered granite.

The same scene at the present day. Theeffects of the lce Age have strippcd awaythe weathercd debris leaving clittersurrounding the bare granite of the tor.

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Dandoor National Park Auth.'ily or the vL/or.l wrd. ircb<hitt,rwwv, danmoornpa !ov !k-

fhis publicztion may ]'c photocopi.d fottducational putposes.

Produced wah.hc support ofthe Devon RIGS Group,lLe Action lot Wildlifa rh. Dartmoor aiodiversity PDject

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0a{Jnoor tl.tiotral Prrk Aunrorjly,P.rkc, Bov.y Trn.ey, Ncur'ton Abbol,lrnvo. lOr3 slQ 1a|1016261a32093

e mril: edd..tionsdadrnoornp. oov uk

v) fnselbergs

.tr 6ermon word meoning'aslond mounloin'.

+ Ate steep sided isolqted hills stonding prominenlly high obove surroundingplqins /pedimenf

* Are usuolly found in lhe seosonolly hLrmid or semi orid tropics

.L The noture of lhe joihls determihes ihe shope of the inselberg thof isforned. The shope of the inselberg is determined by the bosol surfoce ofweothering (BSW) which is influenced by the jointing potterns.

"l If the BSW is q series of domicol rises qnd bosins, the inselbery formed willbe o domed inselberg. If the BSW is irregulor, o blocky inselberg will be

formed.

inselberg severol

Figure 35. A dorned inselberg in Nigeriq

Types of fnselbergs

* Domed inselberg (bornhardt)

. Hos o rounded summit profile qnd mossive curvilineor sheet joints

. Smooth convex profile leoding down fo steep-sided or overhonging wqlls

. They rise obove neqr-level ploins, their sides ore qlmost verticol withunbroken, 5mooth rock-fqces qnd curved summits (-tops).

. They include the high symmetricol dome, osymnetricol dome ond low whole-

bocked dome cqlled 'ruwore'.. Domed inselbergs ore chorocterized by massive sheet joints neor lhe

surfoce of the dome.. The sheef joints develop os q result of pressure releose.. On the summii of the dome, rock sheels moy split qwqy. once delached,

individuql sheets qre themselves broken olong curved ond rodiol froctures.. There is q shdrp chqnge of grodieni belweEn the sides of the inselberg ond

the plqin. This shqrp chonge of grodient is cqlled the knick.

Figure 36. Domed Inselberg (Bornhordi)

Figure 37. Ruwore

& Blocky inselbergs

. Developed where rectongulqr or orthogonql jointing is doninoni

. Less common qs compored to doned inselbergs

. Have qn oppeoronce similor to tors.

. The knick is olso aleolure of the blocky inselbErg.

. Stnoll cove-like feotures moy be found qt the knick, produced when

horizontol jointing ollows concenlrolEd chemicol ollock.

Figure 38.A blocky inselberg

Fornotion of fnselberg

Exhumotion hypothesis (2 stdges of Formotion)

Fig 39o. The development of ruwores ond low domes by diffe.e^tial deepw€othering ond subseguent surfoce stripping of the deep wealhered loyer

LANO.SURFACE PRIOR TO DIEP W€ATHEiING

Fuliy d€velopsd dom€resulting lrom one

episodB o, d€sp weath€rinqand exhumaliot

Dome su.tace F.tlydis:ntegr3led by orf olialion

ar|d block weathering

47High dome produced

Figure 39b. The developrnent of high dones in o second phose of weotheringond stripping

Exhumofion hypothesis (2 stoges of Formoiion)

.t Proposed by J D Folconer (1911)

+ Chordcterisiic of seosonolly humid tropics

il' Inselbergs ond their surrounding ploins qre the result of deep weotheringfollowed by removol (or stripping) of the weothered loyer ond scorprelreot ovet geologicol time.

.L fnselbergs originqte qs domicol rises below the ground surfoce which oreloter exposed ot lhe surfoce by the removol of the ovetlying weolheredloyer (or soprolite).

* Deep chemicol weothering during q humid phose (pluviol Period). Chemicol

weothering occurs in zones of closely-spoced joints ond only superficiolly otwidely-spoced join.ts. Therefore, the depth of weothering is unequol fromploce to ploce.

+ At closely-spoced loints, intense deep chemicol weofhering leod to formotionof bosins. At widely spoced joints, domicql rises ore formed.

't The cctuol form on inselberg will foke depends on the spocing of ihe joints,which deterrnines the shope of the bosol surfqce of weothering..

il Widely-spoced joints produce bornhqrdts ond close-spoced joints Producecqstle koppies.

,{ Stripping of the regolifh by surfoce wosh reveols the domicol rise os orull/ore. Successive episodes of stripping reveal more of the bosol surfoce ofweothering ond the inselberg 'grows' in height.

+ Stripping of regolith mqy be facilitoted by:

. Uplift ond streom rejuvenolion (due to o foll in bose level of erosion)..

The renewed energy of the streom will eqsily remove1he weothered

noteriolso thot o new, lower ploin is formed.

. climotic chong'.2 from a wei (pluviol) to qn or(d period (inter-pluviol) \.This reduces the roie of deep chemical weothering, couses fhevegetation to degenerote ond ollows mote effective surfdce wosh lostrip ihe regolith durihg periods of episodic roinfoll ond wei seosons.

'l Thus, o duol process cycle in inselberg formqtion tokes ploce:

. A process of sub-deriol differeniiol weothering;

. Exhunotion by the stripping owoy of the surrounding weothered mqteriol.

{ Differentiol wedthering: weothering is unequol or vories from one ploce toonother in lhe oteo: weolheting will be more intense ot pla.es where tockjoints ore numerous ond closely spoced thon ot ploces where rock joints orefew ond further opart.

* Sub-oeriol uedthe ng: weqthering which tokes ploce below the ground

level.

& one difficulty posed by this hypolhesis is thot fhe qeot height of some

domes (more thon 30 m) connot be exploined by o single episode ofweothering ond stripping.

i! If is likely thot severol episodes of weothering ond stripping produced thevery lotge domes, especiolly if the raie ol weothering of the exposed domes

logged behind thot of the ploins.

vi) Cqstle koppies

"t These rock piles of ongulqr ondjoint-bounded gronite block arc fotmed bythe disinfegrqtion of domed ond blocky inselbergs

+ Due to the presence of rectongulor or sheel joints, domed ond blocky

inselbergs ore subjected to prolonged physicol ond deep chemicol weotheringond collopse, cousing block ond gronulor disintegrotion.

d! These processes result in the formotion of smqll rocky hills r4ith costellotedprofiles, known os costle koppies.

Figure 4Q. Costle Koppies

Figll"e 4l . Cqstle Koppies