Inner Space Cavern (Also known as Laubach Cave) is a

karst cave Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant r ...

located in

Georgetown, Texas Georgetown is a city in Texas and the county seat of Williamson County, Texas, United States. The population was 67,176 at the 2020 census. It is 30 miles (48 km) north of Austin. Founded in 1875 from four existing colleges, the oldest of ...

. The cavern was formed by

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...

passing through Edwards

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms wh ...

. The cavern is estimated to be around 20-25 million years old but were only open to the surface since the late

Pleistocene The Pleistocene ( , often referred to as the '' Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed ...

period 14,000–45,000 years ago.

Geology

Speleogenesis

Inner Space Cavern lies within limestone and dolomite rocks of the

Edwards Group The Edwards Group is a geologic group in Texas. It preserves fossils dating back to the Cretaceous period. A stratigraphic column at the Mount Bonnell Fault location starts with the Lower Cretaceous Trinity Group overlain by the Edwards Grou ...

formed during the

Cretaceous period The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

. Following the formation of the

Balcones Fault The Balcones Fault or Balcones Fault Zone is an area of largely normal faulting Edwards Aquifer in the U.S. state of Texas that runs roughly from the southwest part of the state near Del Rio to the north-central region near Dallas along ...

, a series of vertical fractures through the Edwards Formations allowed ground water to freely move through the limestone marking the beginning of the cavern's formation. As water from the surface became ground water,

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...

(CO₂) was picked up from the atmosphere and from decaying organic matter, creating carbonic acid (H₂CO₃), which would react with and dissolve the limestone rocks creating voids. Over millions of years these voids grew leaving behind large rooms and passages.

Fossil Record

There were several large openings to the caverns during the

Ice Age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gre ...

, an evidence of several skeletons of prehistoric Ice-Age animals including a baby

mammoth A mammoth is any species of the extinct elephantid genus ''Mammuthus'', one of the many genera that make up the order of trunked mammals called proboscideans. The various species of mammoth were commonly equipped with long, curved tusks and ...

giant sloth Ground sloths are a diverse group of extinct sloths in the mammalian superorder Xenarthra. The term is used to refer to all extinct sloths because of the large size of the earliest forms discovered, compared to existing tree sloths. The Caribb ...

and the

saber-toothed tiger ''Smilodon'' is a genus of the extinct machairodont subfamily of the felids. It is one of the most famous prehistoric mammals and the best known saber-toothed cat. Although commonly known as the saber-toothed tiger, it was not closely related ...

have been found in the cavern; many were trapped in the cavern after they fell through the opening, unable to escape, and others drowned in thick,

quicksand Quicksand is a colloid consisting of fine granular material (such as sand, silt or clay) and water. It forms in saturated loose sand when the sand is suddenly agitated. When water in the sand cannot escape, it creates a liquefied soil that los ...

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

sinkhole A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The term is sometimes used to refer to doline, enclosed depressions that are locally also known as ''vrtače'' and shakeholes, and to openi ...

s have been found, including the prehistoric entrance to the cavern. All natural entrances closed approximately 14,000 years ago.

Discovery

Inner Space Cavern was discovered by the Texas Highway Department drilling team in the spring 1963 during the construction of an overpass for

Interstate 35 Interstate 35 (I-35) is a major Interstate Highway in the central United States. As with most primary Interstates that end in a five, it is a major cross-country, north–south route. It stretches from Laredo, Texas, near the Mexican border ...

. The cavern was mapped for the first time by the Texas Speleological Association in 1963; since then, several miles of the cavern's passage have been surveyed, with many sections of the cavern remaining unexplored, due to filled-in areas being blocked.

Time as a Tourist Attraction

The cavern was opened to the public in 1966. Three different levels of tours are available, ranging from a basic walking guided tour to an advanced wild cave

spelunking Caving – also known as spelunking in the United States and Canada and potholing in the United Kingdom and Ireland – is the recreational pastime of exploring wild cave systems (as distinguished from show caves). In contrast, speleology is ...

tour, 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. Apart from the main entrance, which was created by dynamite blasts, a vertical borehole, located in the Inner Cathedral Room, serves as an emergency entryway/exit and a means for ventilating the cavern.

References

External links

*
Inner Space Cavern
official website * *Map: {{Coord, 30, 36, 28, N, 97, 41, 16, W, format=dms, display=inline,title, type:landmark_region:US-TX Caves of Texas Georgetown, Texas Landforms of Williamson County, Texas Limestone caves Show caves in the United States Texas Hill Country Tourist attractions in Williamson County, Texas