The answer turns out to be
almost as interesting as the
views themselves. For the
limestone cliffs -- made famous
the world over by the James
Bond film The Man with the
Golden Gun -- are karst
formations, meaning they are
sculpted by chemistry rather
than just erosion.
Specifically, a rock formation is
said to be karst if more of its
material is lost as a result of its
being dissolved rather than its
being eroded by the elements,
according to Dean Smart, a
cave consultant with the Royal
Forestry Department (RFD).
Most limestone formations are
karst, and most karst formations
are limestone, but there also
karst formations made of
gypsum, rocksalt and even
quartzite and sandstone, says
Smart. So karst is really an
environmental term more than a
geological term -- the result of a
complex relationship between
water, vegetation, soil, rock and
the atmosphere.
Limestone mountains are of
course the remnants of dead
sea animals, packed together
under great pressure.
Limestone is mostly made up of
calcium carbonate, which
dissolves in water, but not very
easily -- unless the water is
acidic.
As it happens, much of the
water found in nature is
(slightly) acidic. Rainfall picks
up small amounts of carbon
dioxide in the atmosphere, and
larger amounts when it hits the
ground and mixes with decaying
matter in the soil, forming
carbonic acid.
Limestone dissolves very nicely
in acidic water, around 15 times
faster than in normal water.
That's why you see so many
small pits (known as ''karren'')
and pinnacles in the rock on
limestone mountains. On a
larger scale, limestone
formations often feature towers
and ''dolines'' -- enclosed
depressions, rather like valleys
with one or both ends enclosed.
Another common feature found
on limestone towers by the sea
(for instance, in Phang Nga
Bay) are the indentations found
at the base of the cliffs. These
are not the result of battering by
the waves, explains Smart, nor
are they strictly caused by rock
dissolving into the sea, since
seawater is already saturated
with limestone.
Rather, the indentation is a
result of the mixing of fresh
(rain) water and seawater.
''When they form a mixture of
about 97 per cent seawater,
which often occurs as rain runs
down the cliffs and meets the
sea, it becomes very
aggressive, dissolving away the
base of the towers,'' says
Smart. ''And the salts in the
seawater enhance the process,
acting like a catalyst.''
What about caves, which seem
so abundant in limestone
towers? Limestone actually is
not very porous, but it does
have many cracks, he explains.
Caves are formed as water
runs into these cracks,
constantly eating away at the
rock and widening the channels
until they intersect.
The weird chemistry of
limestone karst formations
creates other strange features,
such as the rocky, seemingly
wind-blown protuberances often
found at the mouths of caves.
These are known as
''eucladioliths'' and are formed
because algae tends to grow on
the side of stalactites which
face the light. As the algae
absorbs carbon dioxide from
water dripping down the
stalactite, the water
compensates by depositing
calcium, and so the eucladiolith
grows out toward the light --
almost like living rock.
The labyrinthine nature of most
limestone formations also
makes karst management tricky,
Smart warns. Dams and roads
are particularly destructive.
''Dams in karst areas cost about
50 per cent more than in other
areas because there is lots of
leakage [through subterranean
channels],'' he says. ''For the
Khao Laem Dam in
Kanchanaburi, they had to build
a concrete curtain inside the
mountain to block the leaks. The
Nam Theun II Dam in Laos is
also in a limestone karst area.
''Karst hydrology is also very
fragile. It's virtually impossible
to know which streams produce
which springs, so construction
work -- on the Yadana pipeline,
for instance -- could divert some
channels, causing some
streams to completely dry up.''