Speleothems

Crystal Cave has a variety of speleothems which decorate the passages and rooms. Each forms in its own unique way.

STALACTITES are deposits which hang from the ceiling of a cave, looking like icicles. They begin as a ring of crystals, deposited around a droplet of carbonic acid hanging suspended from the ceiling. Slowly, the Flowstonecrystals build a small tube with the droplets moving through the center. The stalactite, when hollow and only one drop wide, is called a SODA STRAW STALACTITE because of the resemblance to a soda straw. Most soda straws have a short life span. The central tube tends to plug causing the carbonic acid to run in a thin film down the outside of the soda straw. Calcite continues to be deposited but now the deposition is on the outside of the speleothem, causing the soda straw to become larger in diameter; fat and longer, not skinny and longer. Those soda straws that continue to grow as narrow tubes eventually break under their own weight. One of the longest known soda straws is in Kartchner Caverns in Arizona. It is 23 feet long, still growing, and only as wide as a drop of water and hollow.

If the flow of carbonic acid from ceiling of a cave is too rapid for growth of a stalactite or soda straw, the liquid will drop to the floor of the cave where a STALAGMITE will form. Stalagmites tend to be much broader, flatter and more round than stalactites because the drop will disperse when it hits the floor. This spreads the carbonic acid over a much greater area. Often, only a stalagmite will be found because the flow is always too great to allow formation of a stalactite. If both a stalactite and stalagmite form, they will eventually join together to create a COLUMN.

Crystal Cave has many small HELICTITES throughout the cave. Helictites are finger-like growths of calcite that look like clusters of spaghetti, branching and twisting without regard for what is up or down. They are formed by water that seeps into the cave in amounts so small that it moves by capillary forces, rather than by gravity. Water covers the growing helictites in a thin film, depositing most of its dissolved calcite on bulges and outward projections, where carbon dioxide is rapidly lost to the cave air. Any bumps on the original helictite grow in this irregular manner, lengthening into branches. Most helictites have microscopic tubes running through their centers which supply moisture from the bedrock to the growing tips.

CAVE PEARLS are found near several of the small pools in the cave. They form when the calcite is deposited around tiny pebbles or sand grains. If the drop of acid falls from a great distance, the grains may roll around and remain unattached. As they grow, the grains become more rounded until they look just like pearls.

Age of Speleothems

Speleothems have many different ages and grow at different rates. The growth rate depends on several conditions including 1) the temperature both inside and outside the cave, 2) the amount of precipitation, 3) the amount of water moving through the cave (rivers, flooding, etc.), 4) the abundance or lack of plants on the surface and 5) the amount of carbon dioxide available in the soil. All these factors affect the amount of dissolved calcite carried into the cave. Which in turn affects Soda Strawthe growth rate of the speleothems. Some speleothems can be dated by measuring tiny amounts of unstable or radioactive elements present within the calcite. But if the formation is too old (>350,000), there will be too little datable material. Also, to date a speleothem, it is necessary to destroy part of it. This dating is done only when it is absolutely necessary.

The formations in Crystal Cave are relatively young, less than 3,000 years old for the largest. Most of the small speleothems are under 500 years old. Pictures taken just after development of the cave began (1941), show formations in Trails End that have since been broken and regrown. The regrown portion is about 1” long. We can tentatively place a growth rate on our speleothems of about 1.5” per 100 years.

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