Chapter_15 Limestone Environmet

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Chapter 15

Limestone

Environment



Limestone landscape

• A limestone region characterised by sinkholes and

caves is known as karst

• It is formed by the chemical weathering (carbonation

and solution) of limestone rocks

Formation of karst

• When rainwater reacts with carbon dioxide in the air or

in the soil, it forms carbonic acid

• The acid changes the calcium carbonate in limestone tocalcium bicarbonate which dissolves in water

• This rocess results in the formation of karst features

on the surface and beneath it

Chapter 15: Limestone Environment



Importance of understanding karst systems

• !arst landscaes make u about "#$ of the %arth&s

surface

• They are most abundant in troical humid regions but

also occur in temerate, troical, aline and olar

environments

• A 'uarter of the world&s oulation deend on water

sulied from karst areas

• owever, karst systems are vulnerable to groundwater

ollution due to the relatively raid water flow and the

lack of a natural filtration system

• ocal drinking water sulies risk being contaminated

as a result




Limestone pavements

• *lat areas of exosed limestone

• +esemble artificial avements

• omrise large rectangular blocks called clints

searated by long grooves known as grikes

• A result of chemical weathering along the -oints andcracks in the limestone rocks

• The grikes will deeen

and widen over time


A limestone pavement in Malham Cove,

England



Sinkholes

• .eressions in the land surface

• aused by the dissolving of underlying limestone and

the collase of surface material

• A river that flows over a limestone area may disaear

down a sinkhole

• hemical weathering couled with erosion by the river

may enlarge the grikes on the surface until they become

holes, causing the river to disaear into underground

caverns and channels

• The art of the original channel downstream where the

river formerly flowed is called a /dry valley&

• The river returns to the surface at the /resurgence oint&





Sinkholes



Dry valleys

• 0tee1sided valleys that no longer have water flowing

over the surface

• .uring the last ice age, limestone was fro2en to great

deths

• As the climate warmed, melting ice formed rivers that

carved out valleys over the still1fro2en rocks

• When the rocks thawed, the water infiltrated down

through the rocks and the valleys were left with no

surface water, resulting in dry valleys

• 3nderground caves may form below dry valleys

• The caves may collase to form a gorge





• A small deression

formed when one cave

collases is called adoline

• When several dolines

coalesce, they form a

ol-e or uvala

Sinkhole Plain, a limestone

environment near Mammoth

Cave, USA

ater

ta!le



Stalactites and stalagmites

• Water that dris from the roof of a cave contains

calcium carbonate

• When the water dros fall, they leave behind some

calcium carbonate

• The water dros also deosit calcium carbonate on the

floor of the cave

• These deosits accumulate to form stalactites (hanging

from the roof) and stalagmites (on the ground)

• When water flows down the walls and over the floor of

the cave, flowstone or rimstone deosits are formed

• When water dris over the edges of ledges, thin sheets

of deosits called draeries are formed





Stalactites and stalagmites in a cave

Stalagmite

Stalactite

"nderground

pool



#rotecting karst resources in the Cari!!ean

• The aribbean has one of the world&s remier karst

landscaes (which make u more than half of the total

land area of the region)

• About 4#$ of the karst is in the 5reater Antilles

• 6ther significant areas are in the 7ahamas, Anguilla,

Antigua, the ayman Islands, the 8irgin Islands,

5uadeloue, 7arbados, Trinidad and Tobago, and the

9etherlands Antilles

• :ost countries have adoted conservative strategies in

the establishment of arks, reserves and sanctuariesencomassing karst landscaes

• +egionally, there are ";" rotected karst areas,

covering "<=>$ of the total karst





Economic value of karst

1. Agriculture

• 0ome karst regions have rich and highly roductive soils

• The caves may be used for secialised agricultural activities

such as fish breeding, mushroom growing and cheese

roduction

• In 0outheast Asia, limestone caves are an imortant sourceof bird&s nest

2. Industry

• imestone is an imortant raw material for steel1making and

cement

• It is also used to reduce some forms of industrial ollution,

e=g= by removing sulhur dioxide from gases




3. Tourism

• Annually, about ;#

million eoleworldwide visit

limestone caves

• The 5reen 5rotto

aves in ?amaica,

arrison&s ave in7arbados and

5asaree aves in

Trinidad are tourist

attractions

• Tourism is animortant source

of income for the

residents in karst

areas

$arrison%s Cave

&asparee Caves



Scientific value of karst• !arsts are a key source of information on landform evolution and

climate change• The caves contain imortant archaeological and alaeontological

material

• !arsts host various endangered lant and animal secies, both

underground and on the surface

'ecreational value of karst• !arsts offer oortunities for caving, which has become a oular

recreational activity

• This contributes to tourism




(hreats to karst systems

• .rawing of water within karst areas disturbs the

hydrological system

• The water level and the water 'uality are threatened

• :oisture within the cave microclimate is affected

• The lant and animal secies in the caves aresubse'uently affected

• @uarrying for recious minerals such as bauxite

destroys the caves

• .uming of sewage and domestic and industrial wastecan lead to groundwater ollution as there is little

natural filtration in karst regions




Case study: (he )amaican karst landscape *

Cockpit Country

• :ostly located in Trelawny, but sreads through the

neighbouring arishes of 0t %li2abeth and 0t ?ames

• haracterised by a regular series of round1toed

conical hills and its


The landscape of Cockpit

Country



*ormation

• ockit ountry is a massive limestone lateau with an

elevation of about ##m above sea level

• According to one theory, its characteristic toograhy is

the result of heavy troical rain washing through the

fissured lateau over millions of years

• The water dissolved and eroded the fissures andwashed the debris through the sinkholes into the sea

• Another theory ostulates that water moves slowly at the

to of the hills with little erosion

• As the water flowed downhill, it icked u momentumand gathered debris, resulting in a more ronounced

scouring action




*eatures of a karst landscae




Identifying karst features on a topographical map• 3ndulating landscae as indicated by the irregular

contour attern• .ry valleys• .eressions B as indicated by

short hash marks inside circles• .isaearing streams

• 0rings at the foot of steeescarments and lace namesthat begin with /sring& such as/0ringvale&=

• .ee gorges

• *eatures and symbols that reresent 'uarries andcement1making, since limestone is an imortantingredient for cement roduction

• ittle or no surface drainage


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Chapter_15 Limestone Environmet

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