Texas boasts over 3000 caves, caverns, and sinkholes. If you live in the state, there is likely one near you. Some of the most famous show caves include Natural Bridge Caverns, Longhorn Caverns, the Caves of Sonora, Cascade Caverns, and Devil’s Sinkhole. Here we use photos a particular cave to explore our topic: the Inner Space Caverns, found in Georgetown, Texas. As a special geological structure, we’ve dedicated this blog post to caves and their origins!
How Caves Are Made
Generally speaking, caves are formed from dissolving limestone. Carbon dioxide from the air we breathe trickles into the ground through rainwater. From there, the weak acid slowly eats the limestone, leaving the remaining cave and speleothems (rock formations).
Although solutional caves, as described above, are the most common type of cave, there are others. Primary caves are formed at the same time as the surrounding rock, such as a lava cave. A littoral cave, or sea cave, form from waves eroding at weak points in cliffs. Corrasional caves, or erosional caves, are similar but formed by streams rather than the sea. Glacier caves are from melting ice flowing within and under glaciers.
History of Inner Space Caverns
Inner Space Caverns was discovered while the Texas Highway Department in the Spring of 1963. As they began to drill a six inch core, their diamond drill bit fell twenty-six feet. The crew then realized they had something in the ground besides rock. The Texas Speleological Society then was granted permission to enter and explore the hole. Each person on the team was lowered down the narrow shaft one at a time. Within several days, seven thousand feet of the solutional cave were surveyed. Three years later, Inner Space Caverns was opened to the public.
'Tites or 'Mites or Flows?
Now, your two most identifiable structures in a cave are stalactites and stalagmites. But what, you may ask, is the difference? Stalactites hang downward from the ceiling. As each drop of water trickles over the formation, it loses the carbon dioxide and deposits a ring of calcite--a mineral made of calcium carbonate. The begin as fragile tubes, as pictured. These beginning tubes are called soda straws, or tubular stalactites. It grows about one centimeter every hundred years. As water accumulates, the deposition increases. The diameter of the stalactite can increase from the width of a drop of water to the size of the barrel, given enough time to grow of course.
A stalagmite starts from the bottom, from where the drip of water the stalactite fell off of. These drips deposit the rest of the calcite before the water continues on its journey. When the two meet, a column forms. A general way amateur spelunkers (cave explorers) remember the difference between the stalactites and stalagmites is stalactites hold tight to the ceiling and stalagmites might one day reach a stalactite to become a column.
The last major cave formation is a flowstone. Different from a stalactite and stalagmite, a flowstone forms from a constant flow of water, rather than a persistent dripping. These structures are usually found on cave floors and along cave walls.
Of course, there are a few types and many more sub-types of speleothems. Most are named after food. Dripstones, a categorical name for stalactites and stalagmites, include soda straws, curly-fries, and fried eggs. Flow stones include cave bacon and waterfalls. Other formations include moonmilk cave popcorn, and scallops. I suppose spelunking can make any explorer hungry.
Preserving Our Caves
Cave environments are delicate. Geological formations, although generally categorized, are unique to the individual caves they are found in. Ecologically speaking, some species of salamanders, bats, spiders, and other creatures are endemic to caves; these species can serve as indicators of the health of an environment. From an anthropological standpoint, caves were commonly used as dwellings and burial places.
All too often people destroy caves. While some may purposefully carve initials or break off formations for keepsakes, others injure the cave unknowingly. The natural oils on our skins contaminate any calcite deposits we touch, terminating the growth at that spot. Water glides across the oil that remains on the stone, unable to leave behind any calcite. The dripstones and flowstones will never grow there again. Indirect ways of damaging caves include disturbing wildlife, littering , removing artifacts, and tampering with entrances.
Caves are a natural resource that allows us to peer into our history, both with unique geological formations and important anthropological artifacts. As a result, caves should be protected to let future generations to enjoy.