Inner Space Cavern is a Karst

Karst topography

Karst topography is a geologic formation shaped by the dissolution of a layer or layers of soluble bedrock, usually carbonate rock such as limestone or dolomite, but has also been documented for weathering resistant rocks like quartzite given the right conditions.Due to subterranean drainage, there...

 cave

Cave

A cave or cavern is a natural underground space large enough for a human to enter. The term applies to natural cavities some part of which is in total darkness. The word cave also includes smaller spaces like rock shelters, sea caves, and grottos.Speleology is the science of exploration and study...

 located in Georgetown, Texas

Georgetown, Texas

Georgetown is a city and also the county seat of Williamson County, Texas, United States with a population of 47,400 at the 2010 census. Southwestern University, founded in 1840, is the oldest university in Texas and is located in Georgetown, about 1/2 mile east of the historic square...

. The cave was discovered by the Texas Highway Department

Texas Department of Transportation

The Texas Department of Transportation is a governmental agency in the U.S. state of Texas. Its stated mission is to "work cooperatively to provide safe, effective and efficient movement of people and goods" throughout the state...

 in 1963 during the construction of Interstate 35

Interstate 35

Interstate 35 is a north–south Interstate Highway in the central United States. I-35 stretches from Laredo, Texas, on the U.S.-Mexico border to Duluth, Minnesota, at Minnesota Highway 61 and 26th Avenue East. Many interstates used to have splits or spurs indicated with suffixed letters , but I-35...

. There were several large openings to the caverns during the Ice Age

Ice age

An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...

, and several skeletons of prehistoric Ice-Age animals have been found in the caverns; many were trapped in the cave after they fell through the opening, unable to escape, and others drowned in thick, quicksand

Quicksand

Quicksand is a colloid hydrogel consisting of fine granular matter , clay, and water.Water circulation underground can focus in an area with the optimal mixture of fine sands and other materials such as clay. The water moves up and then down slowly in a convection-like manner throughout a column...

-like mud at the bottom of watering holes. Some filled-in sinkhole

Sinkhole

A sinkhole, also known as a sink, shake hole, swallow hole, swallet, doline or cenote, is a natural depression or hole in the Earth's surface caused by karst processes — the chemical dissolution of carbonate rocks or suffosion processes for example in sandstone...

s have been found, including the prehistoric entrance to the caverns. Several miles of cave passage have been surveyed, with many sections of the cave remaining unexplored, due to filled-in areas blocking passage.

The caverns were carved by water

Water

Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 passing through Edwards limestone

Limestone

Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

. The caverns are estimated to be 90–100 million years old but were only open to the surface since the late Pleistocene

Pleistocene

The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

 period 20,000–45,000 years ago, evidenced by finds of mammoth

Mammoth

A mammoth is any species of the extinct genus Mammuthus. These proboscideans are members of Elephantidae, the family of elephants and mammoths, and close relatives of modern elephants. They were often equipped with long curved tusks and, in northern species, a covering of long hair...

 and sabre-toothed cat

Smilodon

Smilodon , often called a saber-toothed cat or saber-toothed tiger, is an extinct genus of machairodonts. This saber-toothed cat was endemic to North America and South America, living from near the beginning through the very end of the Pleistocene epoch .-Etymology:The nickname "saber-tooth" refers...

 bone

Bone

Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...

s. All natural entrances closed approximately 14,000 years ago.

The cave was opened to the public in 1966. Visitors enter via cable car

Cable railway

A cable railway is a steeply graded railway that uses a cable or rope to haul trains.-Introduction:...

 which is lowered into the cave. Three different levels of tours are available, ranging from a basic guided tour to guided spelunking

Caving

Caving—also occasionally known as spelunking in the United States and potholing in the United Kingdom—is the recreational pastime of exploring wild cave systems...

, with over 1.2 miles of passage being open to the public. However, non-public passages are well-guarded and independent exploration is not allowed. The only known entrance to the caverns today is the one into which the cable car is lowered, which was created by dynamite

Dynamite

Dynamite is an explosive material based on nitroglycerin, initially using diatomaceous earth , or another absorbent substance such as powdered shells, clay, sawdust, or wood pulp. Dynamites using organic materials such as sawdust are less stable and such use has been generally discontinued...

blasts.

Inner Space Caverns is the first cave to place felony charges on a visitor for damaging the cave's formations.

External links

• Inner Space Cavern official website

• Cavern Photos by Alexander Muse