CAVES & KARST
"... karst, a type of landform where sinkholes, sinking streams, and springs are considered normal features and are indicative of the relationship found between the surface and the underground."
— National Park Service
— National Park Service
Caves, Karst & Honeycomb Rocks!
April 20, 2021
For those who come to visit and view our Texas Hill Country and sites in Comal County, geological features abound!
Any walk across an acre in the rise of the Edwards escarpment gives clues to natural drains in the porous substructure limestone. It’s an ancient story for another time.
In more recent geologic time, namely some decades ago, Karen’s Aunt who operated and managed over a thousand acres of Hill Country ranching called out to me, “Frank boy, bring your sons and get in the truck.”
She added that we should bring any pennies I had in change along. Curious, these instructions and preparation, for what was to be a ride through pastures. I did find a penny for each son.
First she took us to a remote well site providing “smelly water” for livestock. We three on the excursion agreed we were glad the well at the ranch house didn’t provide such water!
Then some distance away she had us go to an opening covered by a large rock which we pushed aside for an exposed opening. She instructed each boy some minutes apart to drop his penny in the opening.
Each toss we waited and waited and waited before a splash far away could be heard. Then she asked me to drop a larger stone and after a substantial pause a bigger splash was heard. For a long time after the boys would ask if we could go to the “cave and stream spot.”
In between visits we began to weave imaginary tales about the “under life.” Would that I had taped or written a record of those imaginative promptings the natural phenomena gave us.
It has been so revealing to note the 100+ located caves in Comal County and know the number is still growing as access to private properties allows further identification and documentation.
Of course, noteworthy karst features are even more numerous. What wondrous doors, windows and peepholes to the marvels down under! Additionally, one finds the honeycomb rocks and their sponge-like patterns formed by years of drainage.
This feature is not seen in too many places. Formed as rains bring dry creek beds to life and watersheds become awash with runoffs, precious waters are captured and funneled to the aquifers.
Lest we ignore these wondrous, mysterious features, it becomes so urgent that acres and parcels of open lands in our Hill Country be protected, set aside, preserved and encouraged for conservation as private and public usages get sorted through.
Rapid and accelerating developments eliminate options for future generations. Often these features get sealed and plugged to provide less porous surfaces to be built upon, impeding flows into our essential aquifers below.
Join the efforts to set aside some of these existing acreages long into the future for generations to come, especially in the aquifer recharge and contributory areas.
Explore the efforts of the Comal County Conservation Alliance (www.comalconservation.org) and our many partners.
In Comal County we have two spectacular cave properties with public access. Natural Bridge Caverns has a story of discovery, continued exploration and imaginative public access with a passion for conservation. The Cave Without a Name provides a chamber with acoustical gifts for concerts and more, including a reach all the way down to the edge of the Edwards Aquifer when permitted.
There are legacy parcels where a few families use caves for fresh food storage! Check out cavetexas.org.
One little curious adventure noting a karst opening or a hint of a cave window can provide an exponential adventure for what can become a lifetime of discovery! Enjoy!
Why divide Texas into karst regions? It aids in understanding the histories of karst areas. It helps us compare and contrast different karst styles and their relationships to regional geology and geomorphology. And it provides insight to the types and extents of caves to be found in each region.
The karst regions described here are delimited on several criteria: geomorphology and geomorphic history, stratigraphy, structure, cave density and types. Obviously, karst requires soluble rocks. Are these thin limestone beds interbedded with sandstone and shale (North Texas) or are they massive gypsum beds (Gypsum Plain)? Are they highly fractured with many joints and faults guiding cave orientations (Balcones Fault Zone) or are fractures less important to cave development (Maverick Basin)? Does the area consist of isolated, high-relief mountains (Block-faulted Ranges) or flat, low-relief plains (Northwest Texas)? Are the caves principally horizontal stream conduits (Lampasas Cut Plain) or vertical shafts which transmit water to humanly inaccessible conduits (Devils River Trend)? Clearly, distinct karst regions in Texas can be defined, as we have done below. We also describe a few areas of pseudokarst deserving notice. The regions and subregions are shown in a linked map of Texas karst and pseudokarst.
Texas karst regions are divided into three main categories based on rock type. The carbonate regions include those areas where caves are almost entirely formed in limestone or dolomite, although a few are in interbedded gypsum. Gypsum area caves are mostly in gypsum, although some caves are in interbedded dolomite. Pseudokarst regions contain caves in rocks that are much less soluble than limestone or that formed by means other than solution. Although isolated pseudo-karst caves occur throughout Texas, only those areas with several caves of similar origin are presented.
Texas caves have developed from a highly diverse range of geologic conditions. Some areas stand out as exceptionally good cave-formers while others are cave-poor. Preliminary attempts to compare the density of caves within the regions outlined in this report demonstrates that this scale does not yield meaningful results. A more detailed analysis is needed. About 10,000 caves, sinkholes, and rock shelters are known in Texas. Surveys for new caves continue in many karst areas, and many caves have been added to the Texas Speleological Survey's database during the past ten years. This work should prove invaluable to better defining and delimiting the karst regions of Texas, and to advancing the conceptual basis of cave development.
Page updated 7/2014. Original page by A. Richard Smith and George Veni.
From the Texas Speleological Survey (TSS) a non-profit corporation established in 1960 to collect, organize, and maintain information on Texas caves and karst
Paleoindians utilized Texas cliffs and rockshelters for "animal kills." As long as 12,400 years ago, Bonfire Shelter near the Rio Grande received animals driven off the cliff. People processed the carcasses in the shelter. Kills of mammoth, bison, and horse occurred several times. In the Archaic Period (9,000-1,000 years ago) many shelters in the Lower Pecos River and Devils River area were inhabited by hunter-gatherers. Fine pictographs may still be seen in Fate Bell Shelter at Seminole Canyon State Historical Park near Comstock. Pit burials, where the dead were dropped into deep sinkholes, also have been documented. Important archeological materials no doubt remain to be found in caves and are protected by law.
The TSS defines a cave as a naturally occurring, humanly enterable cavity in the earth, at least 5 m (15' 6") in traverse length, and where no dimension of the entrance exceeds the length or depth of the cavity. Note: This definition is used by the Texas Speleological Survey to classify karst features, but five meters is not universally accepted. Other states and the Texas Commission on Environmental Quality have different standards.
At least 13,000 caves, sinkholes and springs are known in Texas, distributed in karst regions covering about twenty percent of the state. Karst is a terrain formed by the dissolution of bedrock, and generally is characterized by sinkholes and caves that channel water underground. Texas caves and karst aquifers are important economic, scientific, and recreational resources.
Karst requires soluble rocks, and Texas has many karst regions (see map). The majority of Texas caves occur in the Cretaceous limestones of the Edwards Group, Glen Rose, and Austin Chalk, distributed in the Balcones Fault Zone, the Edwards Plateau, the Stockton Plateau, and the Cibolo Creek and the Guadalupe River basins. In the Llano Region, the Ellenburger Group carbonates (Ordovician age) are intensely cavernous. Permian reef limestones in West Texas contain important caves. Two gypsum karst areas (Permian age) occur north of Van Horn, Culberson County, and in fourteen counties in Northwest Texas. Some unusual caves occur in pseudokarst (false karst), where caves did not form primarily by dissolution in groundwater. Examples of pseudokarst are granite (Enchanted Rock Cave, Llano County), volcanic tuff and conglomerate (Big Bend), sandstone, travertine, shale, caliche, and other materials. Many caves are being degraded, filled, or quarried by humans before their contents can be adequately studied.
Long Caves: At least 137 caves in Texas are longer than 300 m. Honey Creek Cave is the state's longest at 33.3 km long (20.7 miles), and is still being actively explored. The cave is a tributary to the Guadalupe River, extending under Comal and Kendall counties. Powell's Cave System, a complex of three caves in Menard County, is at least 26.1 km long (16.2 miles).
Deep Caves: At least 132 caves are 30 m (99 ft.) deep or deeper. Sorcerer's Cave (Terrell County) is the deepest at 173.7 m deep (570 feet). The largest cave in terms of volume may be Fern Cave (Val Verde County), estimated at about 300,000 cubic meters (10 million cubic ft.).
The scientific resources of Texas caves are many. Hundreds of ancient species, specially adapted to an energy-efficient life in permanent darkness, are scattered through the karst of Central Texas. Cave-adapted salamanders, catfishes, shrimps, isopods, amphipods, snails, spiders, harvestmen, pseudoscorpions, beetles, millipedes, centipedes, and other types have been described. Most of these eyeless "troglobites" occur in the Balcones Fault Zone, where geologic isolation in faulted, river-dissected karst blocks has resulted in an evolutionary history like that of an archipelago. Some of these species are endangered by land development, overuse of groundwater, pollution, and pests such as the red imported fire ant.
Bats are recognized as important but are feared by many nevertheless. A 1917 state law protecting bats was rescinded during a rabies scare in 1957. Several other insectivorous bat species inhabit hundreds of Texas caves, but have been killed or driven out of some caves by vandals. Bat Conservation International moved its headquarters to Austin in 1986 and has been educating the public on the ecological importance of bats.
About twenty-five Texas caves have yielded important fossils of vertebrate animals. Extinct species, such as the scimitar cat, dire wolf, Columbian mammoth, ground sloth, glyptodon, spectacled bear, and flat-headed peccary, denned in, fell in, or were eaten in Texas caves. Radiocarbon dates up to 23,000 years before present have been recorded. Bats have utilized Texas caves for many millennia. The remains of small mammals found in cave soil and flowstone strata have chronicled the climatic shifts in Texas since the ice ages ended about 11,000 years ago. Central Texas was a cool, moist environment until about 3,000 years ago. Burrowing mammals, such as moles and gophers, were common. With the increasing aridity there was a massive loss of soil. A second episode of soil loss was caused by the loss of fire ecology and the overgrazing by domestic animals that continues to this day.
About two dozen Texas caverns harbor a total of about 100 million Mexican free-tailed bats from April to November every year. These migratory bats consume 6,000 to 18,000 metric tons of insects annually in Texas. The largest known mammal colony in the world is the colony of 20 million or more Mexican freetails in Bracken Bat Cave, Comal County.
Early scientific work in Texas caves began in 1896 with the description of the Texas blind salamander Eurycea rathbuni from an artesian well at San Marcos.
Important bat guano caves were documented in 1901; the caves had been sources of nitrates for gunpowder but became fertilizer mines for citrus and vegetable farms. Serious speleology in Texas began with the 1948 publication of The Caves of Texas by the National Speleological Society (NSS). Caving groups (grottos) formed in the 1950s and systematic documentation of the state's caves began, first by the grottos and the Texas Cave Survey, then by the Texas Speleological Survey (TSS), founded in 1960. NSS conventions were held in Texas in 1964, 1978, and 1994; the 2009 NSS Convention was held in Kerrville in conjunction with the 15th International Congress of Speleology.
Today's Texas Speleological Association (a regional division of the NSS) includes eleven grottos in major cities. Caves are conserved and managed by the Texas Cave Management Association, The Nature Conservancy, Texas Parks & Wildlife Department, Bat Conservation International, and many private landowners. The State Caverns Protection Act protects caves from vandalism and destruction. Another statute protects landowners from liability for injuries to cave visitors, unless they have paid for access to the cave.
The Edwards Aquifer, which extends from Brackettville to north of Austin along the margin of the Edwards Plateau, is a karst aquifer that supplies drinking water to 1.5 million people in the San Antonio area. As increased pumping begins to exceed natural recharge and aquifer levels decline, several rare species that live in the aquifer are increasingly threatened, and maintaining water supplies to human populations is becoming an economic and social issue of major importance.The Comal and San Marcos rivers, which originate from large karst springs, are important in maintaining the Guadalupe River ecosystem all the way to the San Antonio Bay estuary on the Texas coast.
Texas caves abound with natural delights. Seven show caves are open to the public: Cascade Caverns and Cave Without A Name (both near Boerne), Caverns of Sonora (Sonora), Inner Space Cavern (Georgetown), Longhorn Cavern (Burnet), Natural Bridge Caverns (New Braunfels), and Wonder Cave (San Marcos). Caverns of Sonora is considered by many experts to be the most beautiful cave in the world. The other show caves offer an amazing variety of beautiful speleothems (mineral formations), fossils, and history. Wild Caving tours are now offered at Colorado Bend State Park, Kickapoo Caverns State Natural Area, West Cave (a botanical preserve and travertine cave near Austin), and at some of the show caves in the state.
SUGGESTIONS FOR FURTHER READING
The Caves and Karst of Texas. Elliott, W.R., and G. Veni (eds.). 1994. 1994 Convention Guidebook. National Speleological Society, Huntsville, Alabama. 342 pp. + viii + 13 maps. (TSS publication available through the TSS; chapters on Texas karst biology, geology, hydrology, archeology, and paleontology can be downloaded from this page).
An Introduction to the Caves of Texas. Ronald G. Fieseler, James Jasek, and Mimi Jasek. 1978. NSS Convention Guide, 1978, 117 pp. (TSS publication available through the TSS.)
Living With Karst: A Fragile Foundation. Veni, George, Harvey DuChene, Nicholas C. Crawford, Christopher G. Groves, George N. Huppert, Ernst H. Kastning, [Jr.], Rick Olson, and Betty J. Wheeler. 2001. American Geological Institute, Alexandria, Virginia, Environmental Awareness Series 4, 64 pp. + 1 pl. (Available through the TSS.)
Texas Caves. Pittman, Blair. 1999. Louise Lindsley Merrick Natural History Environmental Series No. 31, Texas A&M University Press, 122 pp. (Available through the TSS.)
50 Years of Texas Caving. Kunath, Carl E. 2007. San Angelo, Texas: A&K Enterprises, 526 pp. (available from the TSS). (Available through the Carl Kunath.)
Visit Caves Close To Home
In March of 1960, Orion Knox Jr., Preston Knodell, Al Brandt and Joe Cantu, four college students from St. Mary's University in San Antonio, obtained permission to explore the area that is now Natural Bridge Caverns. The students were convinced that large underground passages existed under the amazing 60-foot limestone bridge. On their fourth expedition, Orion felt a cool draft from a rubble-filled crawlway. Such air currents often indicate the presence of additional rooms or passages.
The explorers made their way carefully climbing and crawling through two miles of vast cavern passage. After making this amazing discovery, they returned to the surface to tell the landowners. The discoverers knew immediately what an astonishing find they had made and the land owners decided to develop the first 1/2 mile, the most spectacular part of the caverns, for the enjoyment of guests from around the world. That first 1/2 mile is now the Discovery Tour. Natural Bridge Caverns Discovery Tour was developed with two main goals in mind: preservation of the caverns' environment and comfort of its guests. The result is one of the world premier show caverns, and one of the most popular attractions in Texas.
formed the different limestone layers. Geologists give different names to the various layers, and visitors to Natural Bridge Caverns will find the Glen Rose and the Kainer (Edwards) layers. The Glen Rose, as the oldest rock layer, contains the lowermost chambers, while the Kainer forms the Natural Bridge.
Visitors to the caverns walk through different layers of limestone, a sedimentary rock. Geologists theorize that during the Cretaceous period, a warm, shallow sea covered much of Texas. Sediments and dead marine organisms collected on the ocean floor, compacted and
Perhaps around 20 million years ago, a number of faults formed in Texas due to settling of the coastal regions. These movements created an extensive series of faults known as the Balcones Fault Zone. The eroded face of the Balcones Escarpment marks both the fault zone and the beginning of the Texas Hill Country. In addition to creating the faults, the tectonic stresses also created joints, or cracks in the rock. Underground water moving along the joints eventually carved the passages at Natural Bridge Caverns, one of the main sources of San Antonio fun.
NATURAL BRIDGE CAVERNS IS CELEBRATING THE 2021 INTERNATIONAL YEAR OF CAVES AND KARST
You may be thinking; what is karst? Why do caves matter? Hold on to your hats! 2021 is the International Year of Caves and Karst. Over the course of the year, Natural Bridge Caverns along with other industry partners will be supplying you with all the fun and astonishing facts. We are planning partnerships, presentations, fun events, contests, experiments and much much more. Our goal in 2021 will be to promote exploration, understanding and protection of our caves and karst landscapes.
Bracken Cave contains the largest single-species bat colony in the world, with an estimated 20 million Tadarida brasiliensis, or Mexican free-tailed bats. The nearly 1,500-acre preserve ensures human encroachment and artificial lighting remain away from the bats’ roosting site. The preserve also protects important recharge zone for the Edwards Aquifer which supplies 90 percent of San Antonio’s water supply and critical nesting habitat for the endangered migratory Golden-cheeked warbler. We conduct evening guided tours to watch the hours-long dramatic departure of millions of bats.
Karst areas are among the world's most diverse, fascinating, resource-rich, yet problematic terrains. They contain the largest springs and most productive groundwater supplies on Earth. They provide unique subsurface habitat to rare animals, and their caves preserve fragile prehistoric material for millennia. They are also the landscapes most vulnerable to environmental impacts. Their groundwater is the most easily polluted. Water in their wells and springs can dramatically and rapidly fluctuate in response to surface events. Sinkholes located miles away from rivers can flood homes and businesses. Following storms, droughts, and changes in land use, new sinkholes can form suddenly, collapsing to swallow buildings, roads, and pastures.
TESPA and WVWA Join Together: For the Love of Karst!
TESPA and WVWA Join Together: For the Love of Karst!
The Trinity Edwards Springs Association (TESPA) and Wimberley Valley Watershed Association (WVWA) have once again joined forces for an educational campaign to celebrate and raise awareness about the unique, fragile landscape beneath our feet – our karst and caves.
Our campaign theme jingles in with a lesson, “The water flows, through rocks and holes….” answered by the campaign name, “Deep in the Karst of Texas” — for a campaign logo that virtually sings.
“We’re excited to announce our two organizations are working together again on our shared missions—preserving and protecting our natural resources,” said Patrick Cox PhD, executive director of TESPA. “The Permian Highway Pipeline which came barreling through the Hill Country last year taught us two things, 1) karst and pipelines don’t mix, and 2) many who live in the Hill Country and drink water from our karst aquifers are not yet familiar with the term ‘karst’. So, we aim to fix that.”
What is Karst? Karst is a landscape where the bedrock has been dissolved by rainwater to form sinkholes, sinking streams, caves, springs and other characteristic features, like holes in rocks. Karst is formed when water dissolves or erodes soluble rock such as limestone, dolomite or gypsum
creating underground drainage systems where surface water and groundwater systems are linked. Texas has more than 15,000 documented caves, sinkholes and springs, and more than two million Texans rely on groundwater stored in karst aquifers as their sole water supply.
“TESPA and WVWA saw immediately that the International Year of Karst and Caves was a natural fit in 2021 to highlight the sources for our water supply,” added David Baker, executive director of WVWA. “We want not only to teach what karst is, but also show why it deserves our love and investment. Humans are the beneficiaries of this remarkable landscape with springs that many have considered sacred and transformative, but we are also its greatest threat. Education and experience of karst in all its forms gives us tools to be better stewards.”
“Deep in the Karst of Texas” launches now and continues through the end of 2021. Other groups and organizations are invited to join the campaign as “Friends of Karst” and sharing karst information with their own constituencies, linking to the WVWA and TESPA karst webpages, as well as sharing via social media platforms. The Deep in the Karst campaign will also include news stories, multiple informational webinars, a cave tour or two, and a gathering for friends and supporters at a Two-Step for Karst Barn Dance in November.
A Worldwide Celebration!
Two thousand and twenty-one is going to be a celebration year for caves and karst in our National Parks and around the world! Cave week will be especially big in 2021. Caves and related landforms like sinkholes, springs and sinking streams are collectively known as karst. Karst forms in areas worldwide where rocks naturally dissolve, If you live near limestone, marble, gypsum or rock salt you might be in karst. Karst is found throughout the US and is widespread in many eastern states such as Indiana, Missouri, Florida, Kentucky and Tennessee. For the International Year, people are organizing events around the world associated with caves and karst. Activities are expected to include festivals, special cave tours, video showings, social media, blog and web content, class room presentations, commemorative and historical events and much more.
WHY ARE CAVES AND KARST IMPORTANT ALL OVER THE WORLD?
Karst springs and watersheds supply 20% of the world's drinking water and are home to hundreds of rare species of animals. Caves have played a big role in understanding human past as everything from Lucy, our ancient Australopithecine relative to the Dead Sea Scrolls to vast numbers of Mayan artifacts came from inside caves. There are about 150 million tourist visits to caves in more than 100 countries each year. The most popular national park in Europe is Plitvice Lakes. It is a series of beautiful blue and green lakes separated by waterfalls. The falls themselves have lush vegetation. The lakes form due to karst springs that rise to the surface in a canyon. The colors are from the minerals in the karst water newly emerged from underground.
NATIONAL PARKS ARE GREAT PLACES TO CELEBRATE?
Many National Parks feature caves and karst. This includes the longest cave in the world at Mammoth Cave, Kentucky. The second deepest cave in the United States at Lechuguilla Cave in Carlsbad Caverns National Park and thousands of smaller caves in more than 50 parks.
With this many great caves, the National Park Service will also be part of the International Year. Activities will vary park by park and are still in the planning stages. Check in with your local cave park or follow the park(s) on social media to find out what is happening at our National Parks for the International Year of Caves and Karst.
Karst is a type of landscape where the dissolving of the bedrock has created sinkholes, sinking streams, caves, springs, and other characteristic features. Karst is associated with soluble rock types such as limestone, marble, and gypsum. In general, a typical karst landscape forms when much of the water falling on the surface interacts with and enters the subsurface through cracks, fractures, and holes that have been dissolved into the bedrock. After traveling underground, sometimes for long distances, this water is then discharged from springs, many of which are cave entrances.
A sinkhole is a depression or hole formed when the land surface sinks due to underground bedrock dissolution or cave collapse. In developed areas, catastrophic sinkhole collapse can cause significant damage and loss of life.
KARST + WATER
Karst is ideal for storing water as an aquifer and provides vast amounts of clean drinking water to people, plants, and animals. Because of the porous
(Swiss cheese-like) nature of karst, water flows quickly through it and receives little filtration. Therefore, contaminants that enter a karst aquifer are rapidly transported creating water quality problems. About 20% of the United States is underlain by karst landscapes and 40% of groundwater used for drinking comes from karst aquifers. It is imperative for our health and safety to protect karst landscapes.
Karst is a term used to describe the distinctive surface landscapes of cave country, shaped by dissolution of soluble bedrocks such as limestone, dolomite, or gypsum. The surface character of karst results from both surface dissolution of exposed bedrock and dissolution beneath the surface as caves are formed. Voids forming beneath the surface result in slumping or collapse. Streams sink underground and may not reappear until miles away as springs or birthplaces of rivers. Karst landscapes encompass some 10-15% of the earth's land mass and millions of people live in or among karst. Through photos, this page will attempt to convey both the diversity and beauty of the world's karst.