Speleo-What?

by	Jeff Miller, Ph.D.

Have you ever been in a cave? The most beautiful caves are solution caves, because they oftentimes have cool-looking formations called speleothems (SPEE-lee-oh-thims). Stalagmites and stalactites are probably the most well-known, but cave bacon, cave pearls, flow stone, columns, and soda straws are also amazing speleothems. These formations are called secondary features, because they form after the cave itself forms.

How do speleothems form? As rain drops to the ground and seeps down towards a cave, it picks up carbon dioxide from decaying plants and turns into carbonic acid. When it reaches the limestone above a cave, it dissolves some of it and picks up calcite from the limestone. When the liquid reaches the cave air, it releases its carbon dioxide gas (like fizz coming from a soda can when you open it). The calcite “sticks” to the cave as the carbon dioxide is released and as the water drips to the base of the cave. As this process happens, the calcite gradually builds up, forming speleothems.

	Stalagmites are speleothems that grow upward from the floor of a cave as calcite is deposited there from drops of the liquid.
	Stalactites are speleothems that hang (tight) from the ceiling of a cave as calcite is left behind before the droplet falls to the floor of the cave.
	Soda straws are a type of stalactite. As a droplet hovers on the ceiling before dropping, its calcite gathers along the edges of the droplet, making a ring. When the water then drops, a calcite ring is left. If it continues to grow, it becomes a hollow tube—like a straw—that hangs from the ceiling. If the hole in the bottom of the tube ever gets clogged, the straw will begin turning into a normal stalactite.
	Columns form when a stalagmite grows as a stalactite grows directly above it. Eventually, if they continue to grow, they will join, forming a column.
	Cave bacon is a formation that looks like a curtain of bacon when light shines through it. It forms as droplets run in a line along a hanging surface, instead of dropping straight to the ground. Calcite builds up on the line, forming what looks like drapery.
	Flow stone forms when droplets run down walls or large objects, making speleothems that look like calcite waterfalls.
	Cave pearls look like…pearls. Sometimes droplets land directly on a piece of something on the floor of a cave. Calcite begins to build up the substance, and the continued droplets “polish” it, making it smooth and, oftentimes, spherical—like a ball.

Old Earth geologists argue that some speleothems are so large that it would have taken tens of thousands of years or longer for them to form. As usual, old Earth geologists typically make such claims because they are assuming uniformitarianism is true: the belief that whatever processes and rates we see happening today in geology have always happened that same way throughout time. The problem is,  uniformitarianism does not fit the actual evidence when we study speleothem growth. Many factors play a role in how fast speleothems grow, including the amount of rain at the surface, the surface air temperature, the drip rate and concentration, and the level of carbon dioxide in the soil. In the years immediately following the Flood, during the Ice Age, there would have been much more rain (faster drip rate), much higher levels of carbon dioxide in the soil from dead plants and animals (leading to more calcite in droplets), and lower temperatures (leading to wider stalagmites).

Cave tour guides will typically give an estimate of how fast speleothems grow—very slowly. The average growth of flowstone per year today, for example, is said to be 0.01 inches. Nearly every tour guide in my travels, however, highlighted that they give low growth rates like that, but they have observed much higher speleothem growth rates in their own caves. Tour guides for Squire Boone Caverns in Mauckport, IN, for example, showed me a stairwell leading down to the cave that was built in 1973: 46 years ago. At 0.01 inches of growth per year, there should have been about one half of an inch of flowstone in the stairwell. Instead, flowstone covered much of the 73-step stairwell, and it was 2-3 inches thick in several places. The size of speleothems is not a problem for the young Earth position that the Bible teaches.

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