Geology Reference
In-Depth Information
air temperatures by up to 3
◦
C. A party of tourists
in Altamira Cave, Spain, increased air temperature
by 2
◦
C, trebled the carbon dioxide content from
0.4 per cent to 1.2 per cent, and reduced the relative
humidity from 90 per cent to 75 per cent. All these
changes led to widespread flaking of the cave walls,
which affected the prehistoric wall paintings (Gillieson
1996, 242). A prolonged increase in carbon dioxide
levels in caves can upset the equilibria of speleothems
and result in solution, especially in poorly ventilated
caves with low concentrations of the calcium ion in
drip water (Baker and Genty 1998). Other reported
effects of cave tourism include the colonization of green
plants (mainly algae, mosses, and ferns) around con-
tinuous lighting, which is knows as lampenflora, and a
layer of dust on speleothems (lint from clothing, dead
skin cells, fungal spores, insects, and inorganic mate-
rial). The cleaning of cave formations removes the dust
and lampenflora but also damages the speleothems.
A partial solution is to provide plastic mesh walkways
at cave entrances and for tourists to wear protective
clothing. Recreational cavers may also adversely affect
caves (Gillieson 1996, 246-7). They do so by carbide
dumping and the marking of walls; the compaction of
sediments with its concomitant effects on cave hydrol-
ogy and fauna; the erosion of rock surfaces in ladder
and rope grooves and direct lowering by foot traffic; the
introduction of energy sources from mud on clothes
and foot residues; the introduction of faeces and urine;
the widening of entrances and passages by traffic or
by digging; and the performing of cave vandalism and
graffiti. The best way of limiting the impact of cave
users is through education and the development of
minimal-impact codes, which follow cave management
plans drawn up by speleologists, to ensure responsible
conduct (see Glasser and Barber 1995).
Managing karst
Limestone and marble are quarried around the world
and used for cement manufacture, for high-grade build-
ing stones, for agricultural lime, and for abrasives.
Limestone mining
mars karst scenery, causes water
pollution, and produces much dust. Quarrying has
destroyed some British limestone caves and threatens to
destroy others. In southern China, many small quarries
in the Guilin tower karst extract limestone for cement
manufactories and for industrial fluxes. In combination
with vegetation removal and acid rain from coal burning,
the quarrying has scarred many of the karst towers around
Guilin city, which rise from the alluvial plain of the Li
River. It is ironic that much of the cement is used to build
hotels and shops for the tourists coming to see the lime-
stone towers. In central Queensland, Australia, Mount
Etna is a limestone mountain containing forty-six named
caves, many of which are famous for their spectacular
formations. The caves are home to some half a million
insectivorous bats, including the rare ghost bat (
Macro-
derma gigas
). The mining of Mount Etna by the Central
Queensland Cement Company has destroyed or affected
many well-decorated caves. A public outcry led to part of
the mountain being declared a reserve in 1988, although
Karst management
is based on an understanding of
karst geomorphology, hydrology, biology, and ecology.
It has to consider surface and subsurface processes, since
the two are intimately linked. The basic aims of karst
management are to maintain the natural quality and
quantity of water and air movement through the land-
scape, given the prevailing climatic and biotic conditions.
The flux of carbon dioxide from the air, through the soils,
to cave passages is a crucial karst process that must be
addressed in management plans. In particular, the system
that produces high levels of carbon dioxide in soil, which
depends upon plant root respiration, microbial activity,
and a thriving soil invertebrate fauna, needs to be kept
running smoothly.
Many
pollutants
enter cave systems from domestic
and municipal, agricultural, constructional and min-
ing, and industrial sources. In Britain, 1,458 licensed
landfill sites are located on limestone, many of which take
industrial wastes. Material leached from these sites may
travel to contaminate underground streams and springs
for several kilometres. Sewage pollution is also common
in British karst areas (Chapman 1993).
