A cave is a hollow or natural passage under or into the earth, especially one with an opening to the surface. Caves have become popular tourism sites due to their natural complexity and beauty, which is often associated with the formation of stalactites and stalagmites.
Caves can be formed in a number of different ways including the chemical breakdown of rocks and through erosion by water or wind. A cave can take anywhere from many years, to a much shorter period of time to form. With the National Speleological Society of America indicating more than 11,000 caves exist in the United States alone, it is easily likely that anywhere up to 100,000 caves may exist in the whole earth.
There are many different types of caves, the most common of which is a cave formed in rock that is soluble, such as limestone limestone. Most limestone caves are said to have formed with the aid of carbonic acid during a process in which CO2 (from the atmosphere and soil) are dissolved in water. Being the single most prominent speculated process of limestone cave formation, this process is considered the single most important aspect of formation of such caves. A few examples of these caves would be the Carlsbad Caverns in New Mexico, Crystal Caves in Ohio, the Devils Lair, the Luray Caverns, the Moaning Caverns, the Hamilton Cave and the Witch's Cave. The earliest forms of development in this type of cave formation is called speleogenesis, or inception. In this process, acidic water will flow through a fracture, or void, causing it to separate, and dissolve, and over time, the adjacent walls with become further and further away from each other, causing the start of what would commonly be known as the cave. Another type of cave is one which will be formed through gasses under the earth's surface seeping up through the rock and dirt and meeting with water from above, forming carbonic acid. from there, the gaseous liquid will continue to make its way upward through the rock, but its new density and acidity allows it to eat away at the rock, forming the beginning of a cave. it is also largely believed that tectonic shifts in the earth's plates as well as earthquakes and floods are key factors in the formation of such caves.  Many of these caves are said to be "solutional caves" due to a large percentage of their creation being due to sulfuric solutions eating away at the rock. Most of these caves are formed in limestone, although there have been reports of these caves having been formed in other rock types such as chalk, dolomite, marble, granite, salt, sandstone, fossilized coral and gypsum. Solutional caves are characterized by their abundance of sinkholes, sinking streams, stalactites, stalagmites, soda straws, helictites (speleotherms that curve away from the vertical forming fragile, angular formations), and draperies.
Lava tubes are formed through volcanic activity and are known as a primary cave (meaning they are formed at the same time as the surrounding rock). The lava flows downhill and the surface cools and solidifies. Because the outer layer of lava will be much cooler than the middle, a sort of "shell" can be formed with the cooler solidified lava on the outside and the much hotter liquid lava flowing on the inside. Once all of the liquid lava from the inside of this shell flows away, a hollow tube like structure would be left, creating a nearly perfectly cylindrical cave. Examples of such caves can be found on the Canary Islands, Hawaii, and many other places. Kazumura Cave near Hilo is a remarkably long and deep lava tube; it is 65.6 km long (40.8 mi).
Another common type of cave is the sea cave. These types of caves are often times formed by the slow erosion of the waves, on a weak area of rock on a coastal line. Most often, the cave will be created under the waterline, due to the currents and wave flows into the rock causing the steady erosion, and removal of weakened rock. In most of the cases where a sea cave is above the water line and open for view from boat or plane, the cave has been exposed because of a shoreline shift, and rise in position. The most common size for a sea cave will be anywhere from 5 to 50 meters in length, but have been known to stretch up to 300 meters in length.
It is also known, that in deserts around the country, and in other areas with heat and heavy to extreme winds, erosional caves can form, due to wind erosion. In a desert type area, where sand and wind are often commonly present, the wind will pick up sand from the ground, and flow into the side of large rock formations, causing a certain kind of sand peppering that erodes weaker areas of rock. Over enough time, these weak rocks will fall away, and the beginnings of a wind cave would make its way into existence.
Rate of formation
All around the world it is easily accepted that over the course of millions of years, through chemical processes, a cave would form. It is said that the common cave is created of millions of years of constant erosion, chemical breakdown, mineral collection and change, and pressure. Although this is one of the more widely accepted processes in which people tend to rely, there are some who believe that caves could in fact have been formed in less than four thousand years. Michael Oard, a young earth creation science expert, explores the possibility of rapid cave formation through sulfuric acid dissolution.  The idea that the dissolution could be formed through carbonic acid, which had fairly weak acidic properties in rock dissolution, was concluded because of the substantial amounts of carbonic acid found as residue on the walls and floors of many limestone caves. Recently, discoveries have been made which have pointed to a different kind of acid, namely sulfuric acid, being responsible for the rock dissolution in caves worldwide. Sulfuric acid, being much more potent in its acidic properties, would have made it possible for caves to form in a much shorter time period than previously thought. This new discovery, leaves open the probability that even very large cave formations could be carved out and formed in a matter of only a few thousand years, rather than millions.
Stalactites and Stalagmites
- Main Article: Stalactite and stalagmite
Stalactites and stalagmites are two types of rock formations typically found in caves. Stalactites hang from the ceiling, much like icicles. Stalagmites grow from the floor. Both are formed when minerals like calcium carbonate precipitate out of dropping water.
The time frame for formation of stalactites and stalagmites is a subject of dispute. According to the uniformitarian model they both take tens of thousands to millions of years to form. According to the creationist model, however, they are able to form much more quickly, and often do.
In Sequoia Caverns, stalactites protected from tourists from 1977-1987 grew 10 inches or 1 inch / year. At this rate they could have grown 300 ft in just 3600 years. The picture at right is of a bat discovered in 1953 in a stalagmite, in Carlsbad Caverns, New Mexico. The stalagmite grew around the bat before it could decay or be eaten. The temperature where this bat is found is just above freezing at a constant 40o F. The water dripping from the stalactite above it is vary salty. This would impede but not prevent decay. Also it would not prevent the bat from being eaten. So this stalagmite still had to form quite rapidly, certainly far less than 5,000 years.
This shows stalactite and stalagmite are forming on the overhang on the wall in a subway tunnel in New York due to calcium carbonate dissolving the concrete.
- Origin of Limestone Caves by Steven A. Austin. Institute for Creation Research, Acts and Facts #79. January, 1980.
- Limestone Caves wikipedia.com
- Formation of the Hamilton Cave West Virginia Arthur Manning. Journal of Creation 21(2)
- Helictite wikipedia, assessed 24 August 2011
- Cave by Wikipedia
- Rapid cave formation by sulfuric acid dissolution Technical Journal: Volume 12, issue 3