Cave Formation: How Solution Caves Form

A Gateway to Another World

A Fascination With Caves

Humans have long been fascinated with caves and wherever they discover them, have sought out to explore these underground chambers and uncover their secrets.

Dissolution of soluble materials is a natural process that leads to cave formation around the world, giving humans a window on mysterious subterranean processes in intriguing karst environments.

It seems hard to believe that vast cave systems exist underground. Gaining an understanding of how caves actually form sheds light on what at first seems a somewhat mysterious process.

Some Caves Form Through Wave Action

What Forces Shape Formation of Caves?

The earth is in a constant state of flux and different forces contribute to cave formation, such as wave and volcanic action, glacial action or geological movement; however, many caves form in soluble rock, such as chalk, dolomite and gypsum, limestone, marble and salt. Caves that form out of soluble materials are called solution caves.

The largest caves, in fact, are formed in limestone, which dissolves through the action of both rainwater and groundwater charged with carbonic acid and other naturally occurring organic acids. This produces an environment scientists call karst, characterized by underground drainage systems.

Rainwater (containing carbon dioxide) trickles down through the soil layer to limestone beds. It picks up even more carbon dioxide as it works its way through the soil, which is rich in carbon dioxide by means of decaying organic matter. By a natural chemical process, the water and carbon dioxide form carbonic acid, which is a weak acid solution.

As this acidic water passes through hairline fractures and crevices in the ground and comes into contact with soluble minerals, rock, or more commonly, limestone bedrock, it dissolves these materials. Wherever the water runs, dissolution takes place, and as time passes, the cracks widen and form paths and eventually, a network of passageways.

A Process of Dissolution That Creates an Underground Labyrinth

Baatara Gorge
Baatara Gorge | Source

Formation of a Cave at Water Table

Solution cave formation takes place at the water table. The water works its way downwards to where the ground is saturated. Once there, water collects and soon, channels begin to form. Because these channels increasingly hold more water, this contributes to a faster rate of dissolution of surrounding soluble materials.

As this process continues, crevices form and over time, widen. The water continues it's action underground and as centuries pass, openings form, then tunnels, then caves. As this process continues, actual cave systems develop. If the water table drops, the active area of cave formation shows a corresponding drop.

Solution caves eventually become large enough for humans to enter. Some of these caves are mammoth in size, with numerous chambers and cave galleries, which offer opportunities for exploration by cavers.

Mammoth Cave in Central Kentucky stretches for approximately 405 miles.

Mammoth Cave Entrance

Entrance to Kentucky's Mammoth Cave.
Entrance to Kentucky's Mammoth Cave. | Source

Mammoth Cave

Caves Used for Shelter and Habitation

Solution caves have been used for centuries by both animals and humans, not only as temporary places to "hole up" but even as places to take up permanent residence.

A cave offered shelter out of the elements and animals frequented them and still do to take refuge from blazing sun or to escape rain and snow. Caves offered a spot to hide and a place to sleep.

It wasn't much different for humans. Natural forces had already done much of the building work already and primitive humans made use of caves, not only to shelter in but in some cases to live in. Large arches and caves were also used to build dwellings in. And In some places, monasteries and temples were built into cave openings.

Caves have been used historically to stash items and in modern times, with their relatively constant temperature, to store cheese and wine.

Caves Offer a Cool Place Out of the Heat

A Cave Offers Shelter Out of the Cold

Used by Hunter-Gatherers

Caves as Permanent Dwellings

Mesa Verde - dwellings built inside of cave.
Mesa Verde - dwellings built inside of cave.

A Remarkable Display

Limestone caves are a type of solutional cave and are more likely to contain a remarkable display of formations that form ghostly spires and huge rippling sheets that resemble strips of bacon. The same water that dissolves the calcite in limestone can deposit the calcite in other areas, creating cave formations known as speleothems. Cavers who explore limestone caves are treated to soda straws, stalagmites, stalactites, draperies, boxwork formations and more, in varying hues and shades.

In some cases, oil-eating microorganisms have produced hydrogen sulfide that rises up and mixes with ground water producing sulfuric acid. This sulfuric acid dissolves the limestone and forms caves.

An Amazing Underground World

Caves Appeal to Modern Adventurers

Modern-day cavers enjoy testing their skills and strengths and explore caves and caverns all over the world. Caving can be a challenging and exhilarating experience, with so much below the surface.

Made for Exploring

An Adventure

No doubt about it, whether it's a cave found along a seashore, a cave discovered in the desert, or a cave in a mountainous karst environment, caves hold intrigue and mystery and beg exploration.

Sources:

  1. Ford, D, Trevor, Limestones and Caves of Whales, Cambridge University Press, June 2, 2011
  2. Silvestru, Emil, The Cave Book, Master Books, April 30, 2008
  3. Waltham Tony, Great Caves of the World, Firefly Books, October 10, 2008
  4. Palmer, Arthur N., Cave Geology, CAVE BOOKS, July 1, 2007
  5. Davis, R.V., Limestone Caves, Dalesman Publishing Co Ltd, July 1978

Further Reading:

Burnham, Robert, Caves, Cliffs and Canyons, Discovery Communications

© 2013 Athlyn Green

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Comments 1 comment

DDE profile image

DDE 3 years ago from Dubrovnik, Croatia

When I see a cave I ma always curious about what its like on the inside so mysterious Most interesting facts here about cave formation..

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