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geo LOGICFoundations in limestone

 The rst curio o karst environments is not their

variety o magnicent and unusual eatures such

as stone outcrops, arches, gorges and caves, but

the presence o carbonate rock such as limestone,

dolomite and marble on the Earth’s surace. This

type o rock did not exist early in the Earth’s history

and rst appeared some 1000 million years ago,

when photosynthesis lowered the acidity o oceans

allowing calcium carbonate to orm.

In New South Wales (NSW) the majority o karst

environments are ormed rom limestone, a

sedimentary rock consisting o the cemented

remains o marine organisms such as corals,

brachiopods, stromatoporoids and crinoids, and/or

ne grained calcite (lime mud), which are all made

rom calcium carbonate (CaCO3).

 This sedimentary material was deposited in the

ocean millions o years ago where it was converted

to limestone and buried under layers o rock. The

liting and aulting o the Earth’s surace exposed the

limestone to the atmosphere, where physical and

chemical weathering resulted in the developmento caves and other karst landorms.

It depends on water

Limestone caves orm in two main ways: rom

surace streams nding their way through cracks in

the ground and orming underground rivers, and

by groundwater rising up through cracks in rocks

under the infuence o heat and pressure, dissolving

out mazes and rounded chambers. Caves in NSW

have ormed rom both o these processes.

3

W at er , and the ma terials  i t d issol ves an

d carries,

d r i v e t he developmen t o f  k ars t en vironm

ents. 

K arst  forming and de velopmen t processes 

Speleothem formation. ©S.Babka

Karst formation and development process. ©M.Inwood 

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 geo LOGIC Karst forming and development processes

Rainwater is responsible or the natural sculpturing

o limestone and many other eatures o caves such

as stalactites. This intricate process begins whenrain alls through the atmosphere and in doing

so, picks up small amounts o carbon dioxide,

which dissolve in the water droplets orming a

weak solution o carbonic acid. As the rain water

continues its journey it makes contact with the

ground, where it travels through the soil prole

picking up urther amounts o carbon dioxide and

other organic acids, increasing its level o acidity and

thereore the ability to dissolve carbonate rock. This

acidic water dissolves outcropping stone resulting

in rich patterns and displays, beore it nds its way

underground through weaknesses in the limestone.

On making its way below the surace, the water

percolates through the various cracks and ssures,

expanding them and creating holes, which over

time, evolve into the great subterranean voids that

are the trademark o karst environments.

Water is also responsible or the array o minerals

and other eatures ound in caves. Chemically

saturated water degasses as it drips, pools, fows and

percolates in the below ground karst environment,

releasing calcium carbonate (that it dissolved during

its travels), which over time, orms into towering

stalagmites, hanging stalactites, straws, columnsand cave pearls to name a ew. These ormations (or

speleothems) may also be ormed rom sediments

comprised o dust, either washed or blown into

caves, guano (bat dung) and various minerals.

Water is the engine o the karst system. It drives

the various chemical and physical processes

that create the karst landscape and provides the

medium or complex biological processes and

interactions to occur.

Published by: Department o Environment and Climate Change NSW59–61 Goulburn Street, PO Box A290, Sydney South 1232

Phone: (02) 9995 5000 (switchboard)Phone: 131 555 (environment inormation and publications requests)Phone: 1300 361 967 (national parks inormation and publications requests)Fax: (02) 9995 5999 TTY: (02) 9211 4723Email: ino@environment.nsw.gov.auWebsite: www.environment.nsw.gov.au

 This material may be reproduced in whole or in part, provided the meaning is unchanged and the source is acknowledged. ISBN 978 1 74122 777 2 DECC 2008/142 May 2008 Printed on environmentally sustainable paper

Roof of Orient Cave, Jenolan. ©J.Lim

Pillar – the joining of stalagmite and stalactite. ©S.Babka

Cathedral structure. ©S.Babka