A 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.
Formation Process
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.
The 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.
Reader-Submitted Photographs of Caves
Related Topics
You May Also Like
Go Further
Animals
- Cougar travels 1,000 miles in one of longest recorded treksCougar travels 1,000 miles in one of longest recorded treks
- Rare gray whale spotted in the Atlantic—and it's only the beginningRare gray whale spotted in the Atlantic—and it's only the beginning
- Why 'funga' is just as important as flora and faunaWhy 'funga' is just as important as flora and fauna
- Termite fossils prove mating hasn't changed in 38 million yearsTermite fossils prove mating hasn't changed in 38 million years
Environment
- Why the 2024 hurricane season could be especially activeWhy the 2024 hurricane season could be especially active
- Mushroom leather? The future of fashion is closer than you think.Mushroom leather? The future of fashion is closer than you think.
- This deadly fungus is hitchhiking its way across the worldThis deadly fungus is hitchhiking its way across the world
- Why 'funga' is just as important as flora and faunaWhy 'funga' is just as important as flora and fauna
- This exploding mine holds a treasure that may change the worldThis exploding mine holds a treasure that may change the world
History & Culture
- See the story of Jonah and the whale like never beforeSee the story of Jonah and the whale like never before
- This ancient mosaic offers extraordinary insights into the pastThis ancient mosaic offers extraordinary insights into the past
- These are the real dunes that inspired Dune—and you can visit themThese are the real dunes that inspired Dune—and you can visit them
- Meet the only woman privy to the plot to kill Julius CaesarMeet the only woman privy to the plot to kill Julius Caesar
Science
- Women’s bodies are understudied—but that’s starting to changeWomen’s bodies are understudied—but that’s starting to change
- Hundreds of tiny arachnids are likely on your face right nowHundreds of tiny arachnids are likely on your face right now
- What's worse than a hangover? Hangxiety. Here's why it happens.What's worse than a hangover? Hangxiety. Here's why it happens.
Travel
- A taste of West Bengal, from curries to Kolkata street foodA taste of West Bengal, from curries to Kolkata street food
- Discover southeastern Spain's secret coastal regionDiscover southeastern Spain's secret coastal region
- All aboard Norway's slow train under the midnight sunAll aboard Norway's slow train under the midnight sun