Caves Underground Chambers
Photograph by Raymond K. GehmanA veil of darkness cloaks the natural beauty of caves. Some are
found in cliffs at the edge of the coastline, chipped away by the
relentless pounding of waves. Others form where a lava tube's outer
surface cools and hardens and the inside of the molten rock drains away.
Caves even form in glaciers where meltwater carves tunnels at the
beginning of its journey to the sea.
But most caves form in karst
a type of landscape made of limestone, dolomite, and gypsum rocks that
slowly dissolve in the presence of water with a slightly acidic tinge.
Rain mixes with carbon dioxide in the atmosphere as it falls to the
ground and then picks up more of the gas as it seeps into the soil. The
combination is a weak acidic solution that dissolves calcite, the main
mineral of karst rocks.The acidic water percolates down into the
Earth through cracks and fractures and creates a network of passages
like an underground plumbing system. The passages widen as more water
seeps down, allowing even more water to flow through them. Eventually,
some of the passages become large enough to earn the distinction of
cave. Most of these solutional caves require more than 100,000 years to widen large enough to hold a human.
found in cliffs at the edge of the coastline, chipped away by the
relentless pounding of waves. Others form where a lava tube's outer
surface cools and hardens and the inside of the molten rock drains away.
Caves even form in glaciers where meltwater carves tunnels at the
beginning of its journey to the sea.
But most caves form in karst
a type of landscape made of limestone, dolomite, and gypsum rocks that
slowly dissolve in the presence of water with a slightly acidic tinge.
Rain mixes with carbon dioxide in the atmosphere as it falls to the
ground and then picks up more of the gas as it seeps into the soil. The
combination is a weak acidic solution that dissolves calcite, the main
mineral of karst rocks.The acidic water percolates down into the
Earth through cracks and fractures and creates a network of passages
like an underground plumbing system. The passages widen as more water
seeps down, allowing even more water to flow through them. Eventually,
some of the passages become large enough to earn the distinction of
cave. Most of these solutional caves require more than 100,000 years to widen large enough to hold a human.
water courses down through the Earth until it reaches the zone where
the rocks are completely saturated with water. Here, masses of water
continually slosh to and fro, explaining why many caverns lay nearly
horizontal.
Fanciful Features
Hidden in the darkness of caves, rock formations called speleothems
droop from the ceilings like icicles, emerge from the floor like
mushrooms, and cover the sides like sheets of a waterfall. Speleothems
form as the carbon dioxide in the acidic water escapes in the airiness
of the cave and the dissolved calcite hardens once again.
The icicle-shaped formations are called stalactites and form as water drips from the cave roof. Stalagmites
grow up from the floor, usually from the water that drips off the end
of stalactites. Columns form where stalactites and stalagmites join.
Sheets of calcite growths on cave walls and floor are called flowstones. Other stalactites take the form of draperies and soda straws. Twisty shapes called helictites warp in all directions from the ceiling, walls, and floor.
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