i - ' +. weernenrNc oF LrMEsroNE l

Limeslone is obundoni on Eorth thof mony londscopes ore composed of it.These oreas ore quite susceptible to chenicol weotheting, creoling korsticlondforms (Figure 42).

Figwe 42- 6lobol dislribution of limesione

A) CHARACTERI5TIC5 OF LIAAE5TONE

i) Minerol Composifion

re9rons

+ Comprases moinly of colcium cqrbonote (40-98%)

ii) Physicol Properties

+ Rock fype: sedimeniory rock formed orgonicolly fromqnd skeletons of smqll morine orgonisms loid down in

seas

shell frogmentsshollow lokes of

Colour: white lo lighl grey (pure voriefi€s);ddrker in lone.

inpure limestones are commonly

Texturer fine-groined

Corboniferous limestone: non-crystolline rock; some types of limestone qre

c.ystalline

+

ond korsf

* Hordness: vories between soft cholk to the hord Corboniferous ond dolomitelimeslohe.

+ Rock Structure: non-porous bui highly permeqble (well-jointed)

. exfensive system of joints ond bedding plones formed during lithification

iii) Types of limestone

+ Limestone vqries with. Age ond compoction. Formotion. Structure

,iL The three rnost commonly found lihestone ore:

. Corboniferous lineslone

'> Hard, grey, crystolline ond well-jointed tyPe of limestone

> Grea| sltehgth,low porosity ond high permeobility> Mossively jointed - hos o distinctive bedding plone ond joint pottern! High permeobility which prevenis much surfoce droinoge olihough

rivers cqn oppeor on the surfqcez It contoins nony fossrls) The rock wos formed on the bed of o wqrm cleor seo ond qdds to the

evidence ihoi ihe Brilish isles once loy in wormer lotitudes> It hos developed its own unique londscope, known os korst.> Korst feotures sre well-developed on Cqrboniferous limestone

. Jurassic (oolitic) linestone

> It contoiru 'ooliths' or groins of cqlcqreous moteriol deposited in q

concentric wqy qround o nucleus such os q sond porticle> Its scenery is sinilor to thot typicol of cholk

. Cretaceous chdlk

> This is o pure, soft ond well-jointed limesto4e> rt is dssomed to be the remoins of smoll morine orgonisms which lived

in cleor, shollow secs

B) WEATHERINo PROCE5SE5 AFFECTING LIME5TONE

,l' Chenical ueothering is doninont process offecting limestone regions in boththe hunid tropjcs ond temperote regions.

d Solufion ond carbonation ore the moin types of chemicol weothetingprocesses thot ore responsible for the formation of lamestone londforms.especiqlly in the humid tropics where conditions ore highly conducive.

+ Cdrbonalion and Solution. Atmospheric corbon dioxide dissolves in roinwqter, forms weok ocid

colled cqrbonic qcid which chemicdlly qttocks limestone.. Coz being olso obundont in soils mokes soil woten ocidic os well.. CoCOt (colcite) + HrCO3 (corbonic ocid) o Co (colcium) +2HCOs (colcium

bicatbonate) - reversible process. Cqlcium bicorbonote is highly soluble ond dissolves by solution. As the woter is rich in colciun bicorbonoie, 2 things con occur:

> The evdporoiion of woter increoses the concentrqtion of colciumbicorbonote until il becornes soturoted

> Re-precipitqtion of colcium corbonqte to form cove deposits occurswhen corbon dioxide escopes inlo ihe cove's air, rerersing thecorbonotjon process.

+ Foclors thdt control the dnounl dnd tate of linestone solution. The ornount of cqrbon dioxide in the oimosphere, soil ond groundwofer. The omouht of woier in conioct wiih limestone. Wqter Temperoture - corbon dioxide is more soluble ot low temperotures. The turbulence oI the wotet. The presence of dense vegetotion - orgqnic qcids

. rhe presence of leod, iron sulphides, sodium or potdssium in the woter

'$ Affer long-continued solution hos operoied on linestone rock, some omountsof insoluble moieriols remgin irs o residue in the form of o deep reddish-brown cloy overlying limestone bedrock known ss lerd tosa. The reddishhue is due ro the presence of iron hydroxides. It is moinly found in thehumid tqopics or in oreos where conditions were wetter thon ot present.

\

C) LI/$E5TONE LANDFORMS / KARST LANDSCAPES

+ 'Korst' londscqpe refers to limestone s cenety which is formed by Solufion ond

cqrbondtion processes. E.9. in Mommoth Cove region of Kenlucky, Guilin inSouthern Chino, Kros Region in former yugoslovio, Grqnds Causes of Fronce

+ A distinciive karst lopogtdphy (defined os terroin thot is composed ofdistinctive londforms developed on relotively soluble rocks) is chorocferizedby the obsence of surfqce droinoge sysiem, numerous depressions (sinkholes

or dolines) into which streoms disoppeor, clinls ond grykes etc. Below thesurfqce ate subterroneon sireom Systems leoding to Spectoculdr cqverns,stdldctites ond stologmites.

& Conditions lhat enhdnce lhe developnenl of a karst toryrdphy:

. Presence of q mossive bed of lihestone lying ot or neor the surfoceLimestone must be highly jointedLimestone outcrop lies in cn oreo of moderote to qbundont roinfollPresence of on imperrneoble rock loyet beneath the limesione beds so os

fo prevent downword percolotion of groundwofer

oL However, due to .the different climotic conditions of temperote ond hunidtropicql regions, fhe resulfont types of korst londscopes ore different.

nd korko6ifl erences between tto rsi ond temDerote l(orstTropicdl Korsf Temperole Kdrsf

Higher si]rfqce solulion due 1o highersurfoce runoff, which is further oided byIhe ptesef.ce ol dense vege+otion cover ond

bioloqicoloctivity.

Lower sorfoce solution due to lower surfocerunoff. V€gefotion cover is olso less denseos compored.to the humid tropics.

Surfoce korstic lcndforms qre t\oreilnporton+- Cove systehs sre irslolly smoller(excepl for o lew cases)-

Uhd€rgrouhd korstic londforms ore moreimporlont. Cav€ systehs ore usuolly lorgerond welldeveloped.

cohspicr.rous uplqnd f eo+ures include cockpitond tower korst.

cohspaci.rous uplond f€otures include

unconsumed uplonds ond dry volleys. otherdistihctive feotures include sinkholes,dolihes Dolies. .

More rcpid korslic evolution (developmenl oflondforms) due lo hrgh rniensily of solutionond corbonolioh.

Slower rote of korglic evolution du€ tomoderote in+ensity of solulion ond

i) Temperote Kqrst

+ Temperote korst londforms include limestone povement (cl:nts ond grykes)&limestone gorges.

+ 600d exomples ore found in northern Englond, cenfrol ond wesfern Ireldnd

1) Limestone Pavenent

.tr A horizontol or gently inclined bore limesfone surfoce, broken by numerous

smoll scole solutionol feotures coinciding with mcjor joints ond beddingplones

+ Corbonotion ond solution occur in lines of weqknesses to produce clints andgrykes

. Clinls Upstonding ridges or blocks of limesione, bounded by grykes ond

formed by the solutionol deepening of joints

. arykes. deep, enlarged grooves in o limestone povement resulting fromthe solulionol deepening of .ioinfs

Grykes

Figure 43. Limestone povemehi wilh clinfs ond grykes

.L They con be found obove Molhom Cove in Yorkshire ond in Irelond

2) Limeslone Oorges

+ They ore sleep-sided volleys found in dry kqrsf qred e.9. Cheddor 6orge, UK.

'L During the melt woler phose of fhe lqsi ice oge, underground streomseroded vost coverns os huge volumes of wofer troveled through thelimestone.

+ Sometimes fhe roofs of these coverns con collopse when they cqn't supportihe rock obove then.

.i1". This exposes the "underground streom" through o very steep sided gotge.

GE 1 - LIMES

Figure 44. Developmeni of o linestone 9or9e

'fumyewclq f;arStCrz.s'e .stoulq 2

WEAIHER(NG. ROCI$ AND REL'EF ri-rnTtiirl

cheddar corqe is an excellent exam P le of a n asvmmetric d ry ' solifluction' mass wastinq and ove and iun_ofihelPed remove the

denrded hmestone.

Atthe cnd oflhe perislaci.l phasc, conditions walmed2nd normil

oelmeability returned. 5urface waters sank into the limestone. The

' leddd co,lewr .", d a dryvrll"\,. wth " mdll I Ne emc ainq'lthe basewherethe impeltrleable clayand the Pelmeable limestone

meet. Evidence to supportthistheory includes:

. the intedockinq spu6 on lhe sides ofthe vrllev

. rl,e ordindge a,ed ol ( hPdddr Gorqc bprnq nu' h h ger lhdn lhe

ordr,dqp dpr thdr F"d. ro oLher. 'mdller qorqp\ in t' e rhFdda'

. river erosion still occurrins in the Chedda I reqion aft€r heavv .ains

. the shape ofthe SorSe; which.is narrow at the base and wide at

the top, does not.coffelate with the coll:iPse of a cave svstem

5. ip\ oP

valley. lt .ises to a heiqht o1250 m on the weste.n side of tliet\4endip plateau- ln plan view itresembles a ftreandering stream and

isbordered bya steep north_f.cinq sloPe and a morcgentle south

flcing siope- A number oftheorjes to exPlain iis otigin have beer

suggesled, su.h as the collapse of a cave system and tectonic

catastrcphes. However. it is likely thatcheddarCorqe was fomred by

,Lrrd, " ..red " d nq , old periqla(idl Dhr.e

Drrinq these peiiods winter temperntores fell below fte.zingr rnouah . mn c lpmperrrure\ were cbovc 0'L. tdr)r.q \P ina

snown.lt Howevel the water within the limestone remained.ro.p nrouqno .' hc yedr r.n, du,Fd rhe lim. ro F lo remdrn

.noen."ble. tnLene d"nud"rron louk nidLp ourino lhs Jerod.r I .e/p rhJw wd\ aprd. h"rp"d by lh" numF-ou: e\Po$ d io:nt\

and b"ddino pldnPl. carbonation increased owins to the in.ieared solubiiity ofCo:

with the low temperatures. snowmet caused .iver discha tqes to rise to a levelover 50 tim€s

q,"d e rhln rodry r

uestions:1 Evoluote the fo owinq os o neansof exploinins the evolunon of

: (d) the calkpf af o @w systen(b) n.a h m \ oiat,on n p, n,eoDit:N aq l DT e..

t: ave reosoT far yau aTwq'2 tn Mot ways does the tilt af Ihe bedding planes, os shawn in

Ir- r - I ' . :i.ldi, tlre .roii.pnfile of Ched.lor 6orye? wl1ot

' . '. -i".t cantibute to its dnpe? ::::ffi==::-r.-j.Tffi27

3) Dolines / Sinkholes

"t Dolines ore lorge conicol depressions ih fhe ground formed by the solution orcollopse of linestone.

+ Most rqnge in depih from 10 to 30 feet.

,iL The covernous terroin of Cenlrol Keniucky is morked by over 60 000sinkholes. As solulion processes continue, sinkholes increose in numbers qnd

size

+ Fornotion of dolinest

Carb o nation and so Iu tionF Dolines moy be formed by cqrbonqtion ond solution olong joints in

lirnesione oreds-

> Moss novement processes moy control their shope. Once lhe hollow is

deep enough ond the sides ore sufficiently steep, mqss movement mqy

occur to deepen the hollow unfilon equilibrium slope ongle is reoched.

Collapse of cave ceilinqs} If ihe oreo o6ove qn individuql cove collopses due to continued

solutionol weothering on fhe roof, o doline is dlso formed.

Figurc 45. Cylindricol doline, fhe entronce to Dunnore Cove, Irelond.Sortcei htlpi / / www.showcoves.comlenglish/exploin,/ Karst/Doline.hirnl

Coilapse Doline Solution Doline

SubsidenceDoline

SubjacentCollapse

Alluvial StreamsinkDoline

,//- - -\ \\, i/: ::, \\ \ rr/,'r'-a,, ', '.\' l'/ / /',<-t{.

\\\\ryK\\r

Figute 46. Types of dolines forrned by different processes

4) Swallow holes and disdpped ng slreant

+ Where surfqce streons disoppeor flowing into on underground chonnel, iheploces of descent ore colled swollow holes

il This moy occur (t q foult or mosfer joint thot is persistently widened overtime, perhqps by o surfoce river, creoting o funnel-shoped opening leodinginfo o subterroneon droinoge system.

;l Woien cuts downword inlo soluble limestone ot o junction between limesloneond impermeoble rock like cloy

\,{ some disoppeoring streoms noy eventuolly return to the surfoce os

resutgent strednswhen the linestone is underloin by impermeoble rock.

+

5) Caves

;l When streoms coniinue io flow underground (subtetdnedn streans) in slimestone oteos, caves ore forned.

* Coves ore conduits for the underground tronsmission of woter, corved out bythe radter itself through solulion ond corbonotion

'{t Most coverns ore developed of or just below the woter ioble in the zone olSoturotion.

Woter firsi enters the ground vio sinkholes or individuol fissures. Once

underground, wqter noy be confined olong o concentroted poth of leostresistonce, often olong extensive joints ond horizontol bedding plones

The infilirqiing wqter qlso uses joints or foults to trovel deeper into the rock.Through time, the dissolving process slowly creqtes covities ond groduollyenlorges them into coverns. Dissolved moteriols ore eventuolly dischdrged intoStTeoms.

When the woier toble (i.€. lhe lppermost surfcce of grolndwater zone dividing

soturated rock froh lnsdfuroted rock) for o cove tegion dedeoses owihg 1o ropiddowncutiing of the streom, ihese coverns (seen in the photogroph l>elow) wereleft dry

FiE)te 47. Enlrdnce to d cdve

\

6) speleolhens

+ speleofhens. smoll-scole formotions found in o cove thoi is composed ofminerol deposits

"l The rofe qt which speleothems forrn depends upon the omount ond roie ofwatet enteting the cove, the omouni of ocidity ohd minerols in the wotet,ond the temperoture ond humidity conditions when the woter enters thecove.

* Stalactites. ttolagnites. colunns

. stalactites: icicle-shoped rninerol deposits growing down from the ceilingol o cave

. sfaldgnites: minerol deposits growing up from the floor of o cove

. Colunns: Formed when stoloctites ond stologmites unife eventuqlly

How ore stoloctiies ond stoloqmites formed?They ore formed when colcium corbonole crystols ore re-precipitoted. The

colciie dissolved into the wdter is precipitoted out ogoin when the wofer is

stotionqry.Eqch succeeding drop odds more colcium cqrbonote so thot eventuolly o cone-

shdped projection is built from the ceiling or floor.

* Othet featutes

. Drip curtain: Thin, verficol sheel of rock fprmed by woter percolqtingfron o frocture in lhe roof

. Flowstone: Formed os the colcium corbonote solufion slowly trickles down

cove wolls or floors. Il storts qs o thin covet of colcite on the wolls qnd

floors of the cove. O\er long periods of time, loyers ore qdded. When

flowstone is formed ocross q streom due to obstructions to woteroutflow, o rinsfone don is formed.

. Helictit$: Twig-like structures whose centro\tubes qre so norrow tholwoter cdn only pass through vio copillory qction. I-l con form ot ony pointin d cove.

Sodd straws: speleothems with o centrol hollow fube thot growdownwords from the cove ceiling or woll- ff is usuolly cylindricol or conicolin form

Cave pearls: Formed os colciun corbonote precipitotes in concentricloyers oround o sond groin or other sond-sazed porticle.

Figure 48. Different types of speleothems in o cove

srnrnc Mrr Es AND s tALAO I t tEssr. elles lra.n ri4n .d, J rJ? i ly'

noy rre cmmd y cacq (Carorc o' araso.te)They a,c Lrsla y ponteCTheyoiten be!f grcwlhasa lode $raw

T.,

Sdagmil6 !ro{ frqr the i oors .i GVeshcy.ye uea y rdnd toppcd

The! a e ffmorrv CaCO,(.acteo aJ.ronre) -

r$

I

I-liFigure 49. Formotion of sioloctiies ond siologmiles

ii) Tropicol Korst

& There ore two mojor londforms ossocioted wifh fropicol korst: cockpit korstand tow€r korst which forms the most specloculor limestone scenery foundin the humid fropics

'l The distinction between cockpit korst ond tower korst is fundqnentql os thehydrologicol ond tecionic conditions ossocioted with each qte quite differcnt

il Coves ond speleoihems (refer lo notes undet tempetate korst) ore olso

found in the humid tropics. Howevet, they ore not os welldeveloped whencompored to those found in tempetote zones.

,* E.g. of tropicol korst londscopes: Chinq (6uilin), Moloysio (Mulu), Loos (Vong

Vieng). Vietnom (Holong Boy), Thoilond

* Tropicat karsl is so distinctive becduse:

. High temperotures ond high roinfoll which increoses rote of chemicolreoctions

. Abundonce of vegetotion which produces corbon dioxide in the soil ond

odds ocidity lhrough chelotion. Less dromotic dnd fewer clirnotic chonges which ollows korsificofion to

proceed withouf interrupiion

+ Developnell of lropical korst con vary due fo:

. Voraqtions in the thickness ond extent of rocks

. Their jointing potiern

. The noture of roinfoll

. fhe presence of vegetotion. Although woter is less oble to dissolve

corbon dioxide in fropicql oreos due to higher temperqtures. thepresence of lqrge amounts of orgonic motter produces lorge quontilies ofcorbon dioxide in the soilwoter.

1) Cockpit korst (Polygonol Korst)

,* Cockpit karsi is o londscope pitted wiih soil-cover6d dePressions withsmooth sides ond cone-like hrlls.

.! Described by Chinese geomotphologists os fenglin (peok foresf)

Chdrdcfeisfi.s of Cockpit Kdrst

.1" 6roups of conicol, hummocky hills seporoted by irregulat, stor-shoped ond

dry depressions (cockpits);! Eoch depression is q doline qnd the residuol hills ore, in effect,lhe di\ide

seporoting the dolrnes

'iL Foirly uniform in height, obout 100-l6Om, with o bose of up to 300m

"t Sieep-sided (20 to 60'). Hord crystqlline limestone (e.9. in 6uizhou) - slopes ore 50 to 60'. Softer limestone (e.9. Jomoico) - slopes qre 20 to 30"

d slopes offen coveredby vegetotion, wiih soils up to 2n deep+ Sides rnqy hove overhongs or tofoni* Al the bose. there noybe o tolus of follen limestone bouldersiL Resultont outlook resembles o kind of "egg box" packing

Figure 50. Cockpit Korst

Disfribution of Cockpil KaBl

,tl Developed in oreos where. there wete g?eoter rotes of tectonic uplift. river downcutting hos been most inlense. limesione hos homogeneous ond regulor bedding

'l cockpit korst is well-developed in Jomoico (CockPit couniry), Puerto Rico,

Cubo, Chino (6uiyong oreo oround 6uizhou), the Philippines (Chocolole Hills)

Fomotion of cockpit karst

;l Thought to originote fron dolines forming on widely-spoced joinis

+ When qn qctive streom network dissects o homogeneous limestone qreo, oregulor sfreqm network ond uniform streom divides result.

+ Concentroted solution occurs olong preferred routes, such os wider ioints,leads to occeleroted weoihering of certoin secfions of ihe limestone,

especiolly during times of high flow, such os during o storn.

4 fntense verticol solution dre to seepage of woter through ioints produces

mohy deep depressions or dolines.

+ Wqter will continue to weother the limestone os for down os the woter toble.

Once the woter toble is reoched, woter will flow loterally rother thqn

verticolly. creoting q flot ploin.

& Enlorgement of the depressions by Solution result in closed depressrons

known os cockpits which will eventuolly isolqte the cone hills.

Figure 51. View of cockpii korst in Jonoico.

Tropica I cockpits

'),j,

60 ,100 m,

-\xz \xA\\\',),W,lr\ll/'.€--\1l

lo e6-

Cockpit

Fl1tte 52. Cockpif korsf ond topogrophicol representotion

2) Tower Karst

'{ Londscope chorocterized by sfeep-sided, isoloted towers of limestonestonding obruptly qbove q flat qlluviol ploin or volley floor

rt- Described by Chinese geomorphologisls os fengcong

Characteristics :

*' Steep-sided hills (greoter qngle ihqn cockpit korst) with pillors qnd

overhongs, known qs m€oles& Sides of mogotes about 60'-90';1, Vdrioble in size+ Height up to 300m& The neor veriical wolls ore often fluted, grooved or honeycombed os o result

of chemicol weolhering{l cavern networks, overhqngs ond solufion notches commonly found ot or hear

ihe bose*li Gently domed summits. Jogged pinnacles moy be found.*l Hills stond obove flqt-floored volleys (poljes); the volleys conioin some

surfoce drqinqge

Figure 53. A nogote

Disttibution of Tover Karct

"l According lo Sweeting, tower korst develops in oreos where:

. tectonic uplift is obsent or negligible

. limesione is in close proxinity io non-limestone rocks

. limestone with strong verticol jointing

. the woter toble lo close to the surfoce

* Tower korst is well developed in South Chino (6uilin), Moloysio (Sorowok),

North Vietnom (e9. Hdlong 8qy), Loos , Cqribbeon, Southern Thqilond(Phongngo Boy)

Condilions thot Favour the Developnenl of Tower Korst in China

,+ Ldrge omounts of roinfoll, over 2000mm per onhum (south Chinq)

+ In ihe norih of Chinq where roinfoll is low, limestone feqfures includeescorpnents ond dry volleys

"! Long periods of slow uplift, esposing brood, gently dipping ploteoux

'l Thick beds of lirnestone. up to 3000m deep, ollowing spectoculor londformsto develop

Fomation of Tower Karsf :

rL In wef monsoonql oreos, rivers will mointdin their flow over limestone, erodethe surfoce ond leove residuol blocks set in o river ploin.

'I Differenf nechanisns moy be responsible for tower kqrst formation indiflerenl oreos:

. Differentiol erosion of rock wiih vorying resistonce

. Differentiql solution qlong lines of weoknesses

. The retreoi of cockpit korst slopes to produce isolqied tower korst

. Loterol erosion

,* Developnent fron Toivet Kotst fron Cockpil Karsl

. Tower kqrsi mqy be formed by on exiension of the processes which formthe cockpit korst when the cockpits reo€h the woter toble viodowncul-fing by rivers ond their floors become permonently wet

. Loterol erosion will occur otihe bose of the vorious hills will eventuollysteepen and isolote them

Figu.e 54. Formqlion of Tower Kdrst

Figure 55. Tower kdrst in Holong Boy, Vietndm

(r) Torver Krrst

Shale

Figure 56. Development of fower korst londscope from sinkholes