How Caves Are Made
Pictures Courtesy of Carlsbad Caverns National Park
Caves are found around the world and in a variety of settings, from cold alpine environments to warm tropical rain forests, and are formed through a variety of natural processes.
Acidic Rainwater is one of the biggest components to the cave making process.
Cave formation begins when rainwater absorbs carbon dioxide as it falls through the atmosphere. Rainwater must have carbon dioxide to become acidic and chemically react to the limestone bedrock.
Rainwater is absorbed by the soil into the ground. As the water cascades through the soil it absorbs more carbon dioxide that is being produced by plants that are dead.
In this case this changes the ground water to a weaker form of carbonic acid. As it travels down through the ground it approaches solid rock. When the rock is limestone or dolomite caves can form.
The water reacts chemically with limestone and slowly a space will form. As the space becomes larger the water begins to flow and forms an underground stream.
As it flows it erodes and washes away rock and sand. This is what makes a cave larger. Finally over hundreds of thousands of years or even millions of years a cave is formed.
Formations
For every drop of water that enters and falls in a cave a formation is found. Nature creates cave formations such as stalagmites or stalactites very slowly. It may take as much as one hundred fifty years to form an inch of material.
These speleothems (cave formations) take the form of icicles, trees, statues, or the delicate design of lacy flowers. The colors of these structures depend on the mixture of calcite, manganese, iron oxide and limonite trapped in the solution.
- A white, cream to yellowish and even dark brown is due to the presence of limonite that is dissolved from the overlaying rocks.
- A red and orange hue comes from dissolved iron mixing with water to form iron oxide.
- The blue is derived from manganese.
- "Cave onyx" is made up of a variety of calcite. It has a banded, rich brown appearance.
- White is almost pure calcite.
Stalactites are the formations that form on the ceilings of caves and look like icicles. They begin their life as a single drop of water infused with carbon dioxide, calcium carbonate, and calcite.
The water drop is squeezed from between the rocks and drops to the floor leaving behind a minute deposit of the dissolved calcite in the shape of a ring.
Stalagmites are the formations found on the floor of caves. They reach upward to touch its parent, the stalactite.
Columns are formed when the stalactite and the stalagmite continue to build and grow. When the two join, they form a single pillar or column reaching from the floor to the ceiling.
Helictites are a mystery to scientists. These formations defy nature, and gravity. Scientists can only speculate as to why these feathery, crystal like formations are so turned and twisted.
Rimstone pools are dams of rich mineral deposits that hold back water in caves that does not evaporate. Any sort of disturbance of these pools results in collections of calcite around the rim, which are called
Stalagmite ridges with horizontal crests. These crests act like small dams that hold back the pools of water. Continued growth of these rimstone pools tends to reinforce the cave against collapse.
These are just some of the delicate cave formations that make up this science fiction like world. If their beauty is to be preserved a visitor must careful.