A Karst Giant
The first time I saw Tom Aley, not surprisingly, was at a water conference. He ambled up to the podium—tall and lanky, with a high-domed forehead where he sometimes rested his palm while thinking. He leaned into the podium and in soft but authoritative tones asked his listeners to expand their minds; to think three-dimensionally about the land—not only about topographic variations on the land surface, but also about spatial variations in the subsurface, hidden below. Not long into the talk, he held up his hands and asked us to imagine a milk jug. I remember wondering how this could possibly tie in with his discussion about karst topography.
At the time, there was a lot of subsurface dye tracing going on in the Ozarks. As a karst hydrologist, Tom did much of this work, often at the behest of people opposed to the siting of potentially polluting facilities like landfills or sewage lagoons. Tom’s tracing studies often indicated dye went from a single injection point, such as a sinkhole, to several springs or wells, sometimes in opposite directions from the injection point. Resource agency personnel occasionally expressed doubt about the veracity of these traces. Tom however, after decades of perfecting his tracing techniques, was confident of his results. He had also become very good at public speaking—using simple conceptual models like milk jugs to explain complicated subterranean flow networks.
Imagine a milk jug full of water, Tom suggested. Now, punch holes at different levels on all sides of the jug. Water will squirt out in all directions. But as the water level in the jug drops, holes higher on the jug will quit flowing. The lowest holes will flow the longest, until the water level drops below them. Karst groundwater systems are a lot like that, Tom explained. At higher groundwater levels, as after a heavy rain, water comes out at more holes, or springs, higher in the landscape. As levels drop, only the lowest holes (springs) will continue to flow, often from points on opposite sides of the conceptual milk jug. To the audience, the lesson was clear. Investigators must take into consideration differing groundwater levels if they hope to get a full and complete picture of karst flow networks.
Tom’s first dye tracing experience was with the U.S. Forest Service in the 1960s. Over the ensuing decades, he perfected his methodology, using not only fluorescent dyes but also optical brighteners (fabric dyes) and clubmoss spores. In the mid-1960s, he pursued a new passion. He wanted a place to study caves and educate visitors about karst, so he bought a cave deep in the Ozarks. Here, at the Ozark Underground Laboratory (OUL), Tom and his wife, Cathy, performed peer-reviewed research on caves, springs, karst hydrology, and cave ecosystems. Tom’s consulting work, which supported OUL, would take him to the Caribbean, Australia, Asia, and North and South America—any place where questions arose about subterranean flows and potential groundwater impacts.
Tom developed a burning curiosity about the natural world at an early age. Until the 7th grade, he lived in rural Ohio, at the “margins of Appalachia,” where he roamed the nearby fields and woods—experiences, he claimed, “critically important” to his future career. At age fifteen, he had visions of becoming a forester, especially after reading Aldo Leopold’s Sand County Almanac. Fascinated by caves, he eagerly devoured Kunsky’s 1954 book, Homes of Primeval Man: Wandering the Caves of Czechoslovakia. Tom’s first cave experience was Mark Twain Cave at Hannibal, where, on the way, he got to steer a steam-powered paddleboat.
Tom’s dad worked for a firm out of Pittsburgh, and job relocations would take the family to Washington and Virginia. The magnificent forests of Washington reinforced Tom’s desire to become a forester. After high school, he applied to the Forestry School at the University of California, Berkeley, reasoning that California had lots of forests so needed lots of foresters. He got accepted, and while in school joined a hiking club where he went caving as well as hiking. The friendships he formed there would last a lifetime.
While in school at Berkeley, Tom visited many caves in the western U.S., including the Grand Canyon. In 1959, he explored the Grand Canyon cave conveying Cheyava Falls, a spring derived from rain and snowmelt seeping downward from the karst of the Kaibab Plateau, 2,000 feet above, pouring from the sheer-faced Redwall Limestone. The experience was particularly thrilling for Tom, as he had to descend 80 feet on a cable ladder from a high ledge down to the cave entrance.
Tom finished school at Berkeley and married Phyllis Tate in 1963. The next year, he went to work as Chief Hydrologist for a consulting firm in Los Angeles. The pay was good, but his heart really wasn’t in that line of work—measuring flows for adjudication of water rights. An idea kept bubbling up in his brain—running an underground research center. There were government-funded underground labs in France and China, but none in the U.S. He envisioned researchers coming to his lab, bringing their research grants with them—funds that would support his laboratory administration and overhead.
In Tom’s mind, the cave he purchased needed to meet specific criteria. He wanted to own most of the land over it; he wanted a cave with as much biological diversity as possible; and it needed to be large enough to host educational tours. For nearly a year he searched for the perfect cave. He liked New Mexico, but couldn’t find what he wanted there. After visiting caves in Wyoming, he decided he didn’t want a cave anywhere there was “deep snow in May.” He spent nine months looking for caves in the Ozarks, sending post cards to real estate companies saying he was interested in property with a cave on it.
In 1965, with the assistance of an Ozark real estate agent, Tom bought 125 acres overlying Bear Cave in southern Taney County, near the Arkansas line. The property was largely overgrazed, eroded pasture lands and cutover forests, but he only had to pay $7,725 for the whole parcel, just over $60 an acre. He closed on the deal on April Fool’s Day, 1965. Tom suggested the joke was on him, but despite that, he never regretted the purchase.
Tom didn’t own the cave entrance at first, so in 1966 he drilled and blasted a vertical entrance into a cave passage below, making sure it had proper airlocks so cave humidity and air flow wouldn’t be adversely affected. He renamed the cave Tumbling Creek Cave because, he said, there were already too many “bear caves” in the region. This underground space would become the Ozark Underground Laboratory, a sophisticated research facility still functioning today—the unique lab that an NPR story would proclaim as “known around the world.”
Not long after buying the cave, Tom unexpectedly found work as a hydrologist with the Forest Service in Missouri. He had called at the Forest Service office in Springfield hoping to get a forester position. Luckily for him, the Service needed to fill thirteen hydrologist positions on National Forests across the eastern U.S—a job for which Tom, to the pleasant surprise of the Forest Service Supervisor, was already eminently suited.
Tom and Phyllis were stationed in Winona in a small, drafty house, with only a fireplace for heat. The fireplace was defective, sending smoke into the house—a house so cold in winter they had to buy a refrigerator to keep things from freezing, Tom joked. The Aleys spent their weekends driving to the cave, building the new entrance and cave trail with the help of their real estate agent, Deb Walley, who had become a trusted friend. They soon discovered that the cave met one of their main criteria—it had a very diverse fauna, with 129 species now documented, “more than any cave west of the Mississippi,” Tom said, proudly.
Tom’s hydrologist position with the Forest Service was largely a blank slate, upon which he would, in his words, “design his own career.” The Service had designated the Hurricane Creek Watershed as a “barometer watershed,” the “type example” for studying forest management effects on water quality in a karst region. Tom quickly discovered there was one obvious thing missing from Hurricane Creek—water. When he first visited, the creek flowed only in its lower few miles, just above its confluence with the Eleven-Point River. Streams in non-karst areas with watersheds the size of Hurricane Creek’s, 113 square miles, would normally have flow from headwaters to mouth, but not Hurricane Creek. Tom realized his major task would be to determine where all that “missing” water went.
He found places where water in Hurricane Creek conspicuously slurped into the ground, called losing points, or swallow holes. He planned to do dye tracing from these points to determine where the lost water surfaced. Did it come up further downstream on the Eleven-Point River, or somewhere else? He suspected that at least some of the lost water showed up at Big Spring on the Current River, to the northeast.
First, he had to work out his dye tracing techniques. In the early 1960s, there was little technical information available to help him. One report described tracing work done by the United States Geological Survey in 1906. He found information from Europe, where groundwater tracing had been going on for decades, suggesting his trace attempt at Hurricane Creek would probably require over 700 pounds of dye. He worried that using that much dye might turn the whole county green. Besides, he didn’t even know where he could get his hands on that much dye.
To perfect his techniques, Tom decided to work first with short traces and small amounts of dye. Much of the dye tracing to date had been “visual,” meaning dyes coming through the groundwater system would color the receiving spring bright green or red, depending on the kind of dye. Tom figured out he could use very small amounts of dye and concentrate it in charcoal packets, referred to as “bugs,” placed in water flow at receptor points such as springs. He didn’t have instruments to detect the low levels of dye washed free, or eluted, from the charcoal packets, so he turned to Jerry Vineyard of the Missouri Geological Survey to do those laboratory analyses.
When he felt comfortable with his methods, he took on bigger projects like the lost flow of Hurricane Creek. As he suspected, even though Hurricane Creek was a tributary of the Eleven-Point, the dye didn’t go there at all, but instead crossed under creeks in the Eleven-Point watershed, traveling at least 17 miles to reappear at Big Spring in the Current River Watershed. In effect, the Current River “stole” water from the Eleven Point through Big Spring. This revelation was big news, and not just for Tom’s bosses at the Forest Service. A headline in the New York Times blared “Forest Service Discovers Source of Big Spring.”
Tom did many more traces from the Eleven-Point watershed to Big Spring. The longest was from the Middle Fork of the Eleven-Point River, 39.5 miles. This turned out to be one of the longest traces ever recorded, anywhere. The subsurface flow was rapid, with dye covering the 39.5-mile straight-line distance in 13 days, or about 3 miles per day—very fast for groundwater, especially when you consider the fact that the water, and its dye, almost certainly didn’t travel in a straight line.
Eventually, Tom left the Forest Service to concentrate on running the OUL and on pursuing his karst consulting work. He found a very able partner and fellow researcher in Cathy Keith, first employee of the OUL, who he married in 1975. With her strong background in biology, Cathy “jumped into” the work of the OUL, especially the study of cave fauna.
In those early years, the consulting work was touch and go; feast or famine. But Tom and Cathy were able to expand their ownership in the recharge area of Tumbling Creek Cave whenever opportunities presented themselves. It was a financial struggle, but Tom suggested they got “a lot of experience buying land at inconvenient times.” They also built a beautiful, rustic house near the cave in 1976 and in the late 1990s, finally bought 263 acres of land including the cave’s natural entrance in Bear Cave Hollow. They focused on buying land in the recharge area with “problems,” often sinkhole dumps, finding 22 of these dumps within the cave’s nine-square-mile recharge area. Since much of Tom’s income came from consulting work—often determining if landfills threatened groundwater—and much of his money went toward buying land with sinkhole dumps, he joked that he “worked at dumps to make money to buy dumps.”
Tumbling Creek Cave, the Aleys soon discovered, contained a tiny white snail—blind, without even the vestiges of eyes. The Tumbling Creek Cavesnail became listed as an endangered species, found nowhere else in the world. In the 1970s, the Aleys saw thousands of them in the cave. But as time went on, their numbers declined, dramatically. The Missouri Department of Conservation (MDC) and U.S. Fish and Wildlife Service (USFWS) intervened in efforts to save the snail from extinction, with Tom and Cathy as enthusiastic, supportive landowners. MDC and USFWS “own” the responsibility for the cave snails, Tom said, but “Cathy and I own the habitat. It’s an obvious partnership of opportunity.”
Funding from the USFWS and other agencies went toward protecting snail habitat, both above and below ground. Much of the work in the recharge area involved re-vegetating eroded gullies and riparian areas along losing streams. In total, over 75,000 trees were planted. Over two miles of eroded gullies were re-vegetated. 140 acres of native grasses were established, along with 50 acres of glade habitat and 15 acres of savannah. With funding assistance from the USDA Farm Services Agency, six miles of fence were built to keep cattle out of planting areas. Through a grant from the USFWS, septic tanks in the recharge area were pumped.
Tom, a deep thinker, always looked for partnerships; for win-wins. One memorable success involved the Mark Twain School, not far from the cave. Over the years, the tiny rural school had struggled to stay open. When it came to light the school’s sewage lagoon leaked into karst groundwater, and the expense of fixing it presented an insurmountable obstacle for the school system, Tom came to the rescue with a grant from the USFWS. With additional funding from the LAD Foundation and private-public partnerships, a new wastewater system was completed at the school in 2006. Tom was especially proud of the headline appearing in the Taney County Times: “Mark Twain School Saves Endangered Species.”
The Aleys also formed comfortable, productive partnerships with Grottos, or caving clubs. Jonathan Beard, a noted Missouri caver, remembers his club helping with restoration work in the cave. The caver volunteers hauled out hundreds of buckets of rock and clay left over from building trails in the cave, and erased footprints and scrubbed muddy handprints off speleothems to give the cave a more “natural” look and feel. Tom was always standing by with a dose of his signature humor. Once, while Jon and other cavers were waiting by the bunkhouse, they heard a booming voice rising from the vicinity of Tom’s house: “This is the cave speaking. Please assemble.”
When an industrial solvent, trichloroethylene (TCE), contaminated air inside Fantastic Caverns north of Springfield, Tom was hired to investigate the problem. The TCE had most likely come from an old industrial lagoon, since closed, near the airport. Jon Beard, on behalf of the caving club, helped Tom determine how much air circulated through the cave. From that calculation, they were able to install a vent system to keep TCE levels under the OSHA standards. A sprinkler system on the surface, spraying water that seeped into the subsurface, helped keep cave humidity levels up while ventilation was in progress.
Tom frequently hosted cave tours for Ken Thomson’s speleology class at Missouri State University. Tom loved to educate young students, but he wasn’t above pulling their legs, either. On an earlier exploratory trip with Jerry Vineyard through upper passageways of the cave, they saw ants crawling on the floor and walls. Tom told Jerry the ants showed they were only about thirteen feet from the surface at that point. When the next group of Ken’s students arrived for a field trip, Tom told them that unlike most caves, his wasn’t formed by running water, but by ants—slowly, over the eons, carrying out crumbs, one by one, enlarging the passages. The students just stared at him, mouths agape, until Dr. Thomson burst out laughing.
When he wasn’t working in a cave, or entertaining students, or rehabilitating a recharge area, or a saving a country school, Tom was consulting, largely to buy more land and pay for operating the OUL. Much of this work was focused in the Ozarks. He once conducted a dye trace from a large sinkhole full of trash near Dora, Missouri. Along with trash in the sinkhole, he saw a large pile of crusty black material. When he kicked his boot in it, he realized it was septic tank pumpage. As he drove away, foot out the window, he called the material “by name,” he joked. His dye from the Dora Sink showed up at Hodgson Mill Spring, where a cup hung on the end of a pipe, inviting people to take a drink of “pure” spring water. It was a curious offering to Tom, who spent the better part of his career convincing people that springs in karst country were very often anything but pure.
Tom also conducted a trace from the municipal sewage lagoon at Winona to Big Spring. This trace had been requested by the mayor of Winona, who thought a positive trace would “show the need” for a new sewage system. Tom used the mayor’s request as an example of successful educational efforts about karst. People like the mayor once believed the cold water of Big Spring came from faraway places like the Great Lakes or Rocky Mountains. After learning about karst processes, they now accept that sources are much closer, and admit that actions on their own land could affect the spring’s quality.
Throughout his career, Tom assisted both private individuals and agencies. At the Forest Service’s cave at Blanchard Springs, he investigated runoff from a new parking lot. The builders had placed the parking lot some distance from the cave, and put gravel under it to allow drainage, but were savvy enough to ask Tom to determine if these measures were enough to adequately protect the cave. Tom introduced dye into the surface drain from the parking lot and recovered it from dripping stalactites in the cave. After his investigation, parking lot drains were diverted away from the cave’s recharge area.
Another investigation involved a proposed landfill near Pindall, Arkansas. Tom wasn’t able to access the property directly, so he injected dye into a sinkhole just outside the property boundary. While surface runoff went to a small stream north of the site, groundwater moved in the opposite direction, toward the Buffalo River. He detected his dye at five wells, but 90% of his dye went to Mitch Hill Spring, 4 ½ miles from the landfill site and less than a quarter-mile from the Buffalo. Eventually, the Pindall landfill project was dropped, and personnel at Buffalo National River were grateful. At the time, the community of Pindall was strapped for cash, so Tom and Cathy accepted payment in office furniture from the furniture factory in town.
In a study at a National Forest in Indiana, Tom found that a proposed reservoir, just downstream of a major losing stream segment, would almost certainly not hold water. The Forest Service had requested Tom’s services, even though the proposed dam would be constructed with “small watershed” funding through the Natural Resources Conservation Service (NRCS). After Tom suggested the NRCS had performed an “abysmal” site investigation, the project was canned. He got a letter of commendation from the Forest Service for saving them at least $100,000 on a poorly conceived project. Six months later he got another letter, this one reprimanding him for “comments critical of a sister agency.” With his keen appreciation for bureaucratic irony, Tom framed both letters and hung them on his office wall, side by side.
Tom’s consulting work took him far from the Ozarks. Early in his career, he explored caves in Jamaica, where the U.S. government thought the Russians might be hiding nuclear weapons during the Cuban missile crisis of 1962. Some of his work resulted in major policy shifts. His dye tracing in southeastern Alaska, in the Tongass National Forest, delineated areas with the greatest potential to adversely affect salmon migration and survival. As a result of that work, the Forest Service adopted a new policy, specifying that none of these areas would ever be logged. And Tom testified as an expert witness on many legal cases involving potential groundwater contamination in karst, from deep well waste injection in Oklahoma to herbicide migration in runoff from tobacco fields in Kentucky.
For decades, Tom and Cathy ploughed money from consulting back into OUL and the cave’s recharge area, where the Aleys and Tumbling Creek Foundation now own over 3,500 acres. They also spent time and money studying and protecting the cave itself. Weirs were built in the cave to more accurately measure flows, critical to understanding rates of karst recharge. They built a large gate at the cave’s natural entrance to protect the 80,000 gray bats that roost there in summer. But the problem of a declining population of cave snails was particularly troubling, especially after their numbers failed to bounce back after restoration work in the recharge area. The Aleys began to more fully investigate other potential factors in the snails’ decline.
One of these was an invasive crayfish, the gapped ringed crayfish, a species native to Missouri but rare or absent from Tumbling Creek cave until 1968, although reported before that time from 71 caves in Missouri and Arkansas. Studies in these caves showed that small snails were “clearly on this crayfish’s menu.” Tom discovered that where he had established weirs, cavefish were largely unable to pass upstream. But some slipped by. By 2020, Tom and his helpers had removed about 6,000 crayfish from the cave.
From these experiences, Tom and Cathy learned of other factors, external to the cave, exerting untoward effects on the cave ecosystem. One was Bull Shoals Reservoir, just a few miles away. When the lake is at flood pool, it inundates all but two of the springs that drain Tumbling Creek Cave, changing groundwater gradients. The decrease in groundwater velocity as the cave stream reaches the flooded lake causes silty water to deposit sediment in karst conduits, smothering federally-designated “critical habitat” for cave snails. Further, infiltrating lake water allowed invasion by gapped ringed crayfish into cave snail habitat.
It was one of those conundrums that so often surround the protection of endangered species. One federal agency, the U.S. Fish and Wildlife Service, charged with protecting cave snails and their habitat, might advocate actions diametrically opposed to the those of another federal agency, like the U.S. Army Corps of Engineers (USCOE), which regulates the levels of reservoirs like Bull Shoals. Part of the regulatory agenda of USCOE is to provide flows below Bull Shoals dam sustaining trout fishing in the White River. Tom, concerned about protecting the snails, said USCOE, by ignoring damages to critical cave habitat, had “traded the survival of an endangered species for more satisfied trout fishermen and the resorts they visit.” The Corps and the Fish and Wildlife Service ultimately provided funding for Tom to build crayfish barriers on springs near the lake and in the cave stream, which has helped to slow the invasion.
Tom has never been afraid of controversy. He always landed on the side of protecting the resource, whether it was the quality of springs or the survival of endangered species. While giving expert testimony, he saw lawyers representing their clients—sometimes people concerned about a proposed landfill, for example, or a company planning to build something. Tom was fond of saying he was “speaking for the land,” because, he said, the land had no attorney to represent it. On the board of the James River Basin Partnership, whose letterhead listed board members representing cities, counties, or agencies, Tom always represented “The River.”
Tom was proudest of his accomplishment in getting people to think three-dimensionally about the land—understanding that the earth is not an infinite filter, but has a delicate subterranean ecosystem vulnerable to our activities on the surface. He had a great knack for reading his audiences, learned partly from his days on the road playing folk music. This allowed him to impart wisdom in a quiet, patient way, bringing his listeners along on an intellectual journey into the hidden blackness beneath their feet. This led to real and substantial progress, in Tom’s estimation, as when the mayor of Winona asked for his help in determining where water from his town’s leaky lagoon went.
Tom understood and appreciated the idea of “property rights.” As a major landowner in the Ozarks, he couldn’t help but see the fundamental application of this principle among his neighbors. But he saw his rights differently than most of them. Instead of worrying about and fighting trespass, he invited the public in to his property, hoping they would come to understand what he was doing there, and why it was important. His most precious property right, he said, was the “right to clean water flowing into, or underneath, my land.”
Throughout his long professional career, Tom maintained that razer wit, the dry humor that to many associates and friends became his trademark. One of my favorite stories involves a man who owned a gas station and asked Tom to investigate his well because it had gasoline in it. The man didn’t have a lot of money, so Tom took partial payment in the repair of his old truck. Tom’s cursory investigation revealed that the station’s buried gas tanks had, in fact, polluted the shallow well. Tom told the man the well wasn’t that good, so he needed a new one, anyway, adding, “I’m sorry I couldn’t be of more help.” You can imagine the old man’s head nodding as he thought about this. “Well,” he finally said, “I’m sorry I couldn’t be more help with your truck. You need a new one anyway.”
Tom Aley fashioned a remarkable career in a subterranean world few of us really understand, and rarely appreciate. His mind was like a vast, complex karst ecosystem, with myriad connections linking land and water, landowners and agencies, educators and students. We are all better off because Tom sided with the resources—the land and water and their biota—because in so doing, he positioned himself on our side. Think of how many bad ideas never came to fruition because Tom was looking out for the land, the water, and for us. Think of how much cleaner our groundwater is because he spent a lifetime down there, in the caves, in the hills, traveling the globe, defending our planet’s precious natural resources at every turn.
Tom was a giant in the world of karst science. His search for hidden truths has guided us in making many important decisions about the land—what we do, where we do it, and why we should or shouldn’t do it. He was a dedicated scientist, but also a good friend—always listening to what someone had to say. He might not agree with them and would let them know, gently, usually in jest, when he didn’t. But he was respectful of people in the same way he respected the land, and its inherent rights. The world is surely a better place for having Tom to speak on its behalf. Far too few people know that in doing this, he also protected us.
Perhaps one of Tom’s most impressive accomplishments was his ability to plan beyond himself, ensuring that the land, the cave, and the snails are protected into the future. Well before his passing, he recognized that a new generation of karst defenders would be needed. He and Cathy modified their estate plan to make sure their land, business, and assets would be left to the foundation. In 2020, Tom recruited (poached, as he liked to call it) his successors to replace himself and Cathy as they neared the end of their very impressive careers.
Dave Woods, a fisheries biologist with the Missouri Department of Conservation, had been working as the Tumbling Creek Cavesnail state recovery leader for about a decade when Tom asked him if he knew anyone who might be interested in heading up the foundation. Tom was a bit surprised when Dave said, “sure, let’s talk.” Two weeks later, Dave was the new Executive Director of the foundation and senior scientist at the OUL.
Shortly afterwards, Tom hired Trevor Osorno to direct the consulting practice part of OUL. Trevor, a promising young hydrogeologist, had been visiting the OUL with his professor and foundation board member Rick Devlin for years. Together, Dave and Trevor, a new generation of karst giants, along with the exceptional staff assembled by Tom and Cathy, are continuing the Aley legacy of protecting karst resources while stewarding the OUL and the Tumbling Creek Cave Foundation into the future.
Sources:
Tom Aley, personal interview, Jan. 9, 2009
Tom Aley, Bear Cave Hollow: Stories of Caves and Karst, Journal of the Missouri Speleological Survey, Vol. 65, 2022
Jonathan Beard, personal interview, Feb. 14, 2026
Dave Woods, personal interview, Jan. 13, 2026
At the time, there was a lot of subsurface dye tracing going on in the Ozarks. As a karst hydrologist, Tom did much of this work, often at the behest of people opposed to the siting of potentially polluting facilities like landfills or sewage lagoons. Tom’s tracing studies often indicated dye went from a single injection point, such as a sinkhole, to several springs or wells, sometimes in opposite directions from the injection point. Resource agency personnel occasionally expressed doubt about the veracity of these traces. Tom however, after decades of perfecting his tracing techniques, was confident of his results. He had also become very good at public speaking—using simple conceptual models like milk jugs to explain complicated subterranean flow networks.
Imagine a milk jug full of water, Tom suggested. Now, punch holes at different levels on all sides of the jug. Water will squirt out in all directions. But as the water level in the jug drops, holes higher on the jug will quit flowing. The lowest holes will flow the longest, until the water level drops below them. Karst groundwater systems are a lot like that, Tom explained. At higher groundwater levels, as after a heavy rain, water comes out at more holes, or springs, higher in the landscape. As levels drop, only the lowest holes (springs) will continue to flow, often from points on opposite sides of the conceptual milk jug. To the audience, the lesson was clear. Investigators must take into consideration differing groundwater levels if they hope to get a full and complete picture of karst flow networks.
Tom’s first dye tracing experience was with the U.S. Forest Service in the 1960s. Over the ensuing decades, he perfected his methodology, using not only fluorescent dyes but also optical brighteners (fabric dyes) and clubmoss spores. In the mid-1960s, he pursued a new passion. He wanted a place to study caves and educate visitors about karst, so he bought a cave deep in the Ozarks. Here, at the Ozark Underground Laboratory (OUL), Tom and his wife, Cathy, performed peer-reviewed research on caves, springs, karst hydrology, and cave ecosystems. Tom’s consulting work, which supported OUL, would take him to the Caribbean, Australia, Asia, and North and South America—any place where questions arose about subterranean flows and potential groundwater impacts.
Tom developed a burning curiosity about the natural world at an early age. Until the 7th grade, he lived in rural Ohio, at the “margins of Appalachia,” where he roamed the nearby fields and woods—experiences, he claimed, “critically important” to his future career. At age fifteen, he had visions of becoming a forester, especially after reading Aldo Leopold’s Sand County Almanac. Fascinated by caves, he eagerly devoured Kunsky’s 1954 book, Homes of Primeval Man: Wandering the Caves of Czechoslovakia. Tom’s first cave experience was Mark Twain Cave at Hannibal, where, on the way, he got to steer a steam-powered paddleboat.
Tom’s dad worked for a firm out of Pittsburgh, and job relocations would take the family to Washington and Virginia. The magnificent forests of Washington reinforced Tom’s desire to become a forester. After high school, he applied to the Forestry School at the University of California, Berkeley, reasoning that California had lots of forests so needed lots of foresters. He got accepted, and while in school joined a hiking club where he went caving as well as hiking. The friendships he formed there would last a lifetime.
While in school at Berkeley, Tom visited many caves in the western U.S., including the Grand Canyon. In 1959, he explored the Grand Canyon cave conveying Cheyava Falls, a spring derived from rain and snowmelt seeping downward from the karst of the Kaibab Plateau, 2,000 feet above, pouring from the sheer-faced Redwall Limestone. The experience was particularly thrilling for Tom, as he had to descend 80 feet on a cable ladder from a high ledge down to the cave entrance.
Tom finished school at Berkeley and married Phyllis Tate in 1963. The next year, he went to work as Chief Hydrologist for a consulting firm in Los Angeles. The pay was good, but his heart really wasn’t in that line of work—measuring flows for adjudication of water rights. An idea kept bubbling up in his brain—running an underground research center. There were government-funded underground labs in France and China, but none in the U.S. He envisioned researchers coming to his lab, bringing their research grants with them—funds that would support his laboratory administration and overhead.
In Tom’s mind, the cave he purchased needed to meet specific criteria. He wanted to own most of the land over it; he wanted a cave with as much biological diversity as possible; and it needed to be large enough to host educational tours. For nearly a year he searched for the perfect cave. He liked New Mexico, but couldn’t find what he wanted there. After visiting caves in Wyoming, he decided he didn’t want a cave anywhere there was “deep snow in May.” He spent nine months looking for caves in the Ozarks, sending post cards to real estate companies saying he was interested in property with a cave on it.
In 1965, with the assistance of an Ozark real estate agent, Tom bought 125 acres overlying Bear Cave in southern Taney County, near the Arkansas line. The property was largely overgrazed, eroded pasture lands and cutover forests, but he only had to pay $7,725 for the whole parcel, just over $60 an acre. He closed on the deal on April Fool’s Day, 1965. Tom suggested the joke was on him, but despite that, he never regretted the purchase.
Tom didn’t own the cave entrance at first, so in 1966 he drilled and blasted a vertical entrance into a cave passage below, making sure it had proper airlocks so cave humidity and air flow wouldn’t be adversely affected. He renamed the cave Tumbling Creek Cave because, he said, there were already too many “bear caves” in the region. This underground space would become the Ozark Underground Laboratory, a sophisticated research facility still functioning today—the unique lab that an NPR story would proclaim as “known around the world.”
Not long after buying the cave, Tom unexpectedly found work as a hydrologist with the Forest Service in Missouri. He had called at the Forest Service office in Springfield hoping to get a forester position. Luckily for him, the Service needed to fill thirteen hydrologist positions on National Forests across the eastern U.S—a job for which Tom, to the pleasant surprise of the Forest Service Supervisor, was already eminently suited.
Tom and Phyllis were stationed in Winona in a small, drafty house, with only a fireplace for heat. The fireplace was defective, sending smoke into the house—a house so cold in winter they had to buy a refrigerator to keep things from freezing, Tom joked. The Aleys spent their weekends driving to the cave, building the new entrance and cave trail with the help of their real estate agent, Deb Walley, who had become a trusted friend. They soon discovered that the cave met one of their main criteria—it had a very diverse fauna, with 129 species now documented, “more than any cave west of the Mississippi,” Tom said, proudly.
Tom’s hydrologist position with the Forest Service was largely a blank slate, upon which he would, in his words, “design his own career.” The Service had designated the Hurricane Creek Watershed as a “barometer watershed,” the “type example” for studying forest management effects on water quality in a karst region. Tom quickly discovered there was one obvious thing missing from Hurricane Creek—water. When he first visited, the creek flowed only in its lower few miles, just above its confluence with the Eleven-Point River. Streams in non-karst areas with watersheds the size of Hurricane Creek’s, 113 square miles, would normally have flow from headwaters to mouth, but not Hurricane Creek. Tom realized his major task would be to determine where all that “missing” water went.
He found places where water in Hurricane Creek conspicuously slurped into the ground, called losing points, or swallow holes. He planned to do dye tracing from these points to determine where the lost water surfaced. Did it come up further downstream on the Eleven-Point River, or somewhere else? He suspected that at least some of the lost water showed up at Big Spring on the Current River, to the northeast.
First, he had to work out his dye tracing techniques. In the early 1960s, there was little technical information available to help him. One report described tracing work done by the United States Geological Survey in 1906. He found information from Europe, where groundwater tracing had been going on for decades, suggesting his trace attempt at Hurricane Creek would probably require over 700 pounds of dye. He worried that using that much dye might turn the whole county green. Besides, he didn’t even know where he could get his hands on that much dye.
To perfect his techniques, Tom decided to work first with short traces and small amounts of dye. Much of the dye tracing to date had been “visual,” meaning dyes coming through the groundwater system would color the receiving spring bright green or red, depending on the kind of dye. Tom figured out he could use very small amounts of dye and concentrate it in charcoal packets, referred to as “bugs,” placed in water flow at receptor points such as springs. He didn’t have instruments to detect the low levels of dye washed free, or eluted, from the charcoal packets, so he turned to Jerry Vineyard of the Missouri Geological Survey to do those laboratory analyses.
When he felt comfortable with his methods, he took on bigger projects like the lost flow of Hurricane Creek. As he suspected, even though Hurricane Creek was a tributary of the Eleven-Point, the dye didn’t go there at all, but instead crossed under creeks in the Eleven-Point watershed, traveling at least 17 miles to reappear at Big Spring in the Current River Watershed. In effect, the Current River “stole” water from the Eleven Point through Big Spring. This revelation was big news, and not just for Tom’s bosses at the Forest Service. A headline in the New York Times blared “Forest Service Discovers Source of Big Spring.”
Tom did many more traces from the Eleven-Point watershed to Big Spring. The longest was from the Middle Fork of the Eleven-Point River, 39.5 miles. This turned out to be one of the longest traces ever recorded, anywhere. The subsurface flow was rapid, with dye covering the 39.5-mile straight-line distance in 13 days, or about 3 miles per day—very fast for groundwater, especially when you consider the fact that the water, and its dye, almost certainly didn’t travel in a straight line.
Eventually, Tom left the Forest Service to concentrate on running the OUL and on pursuing his karst consulting work. He found a very able partner and fellow researcher in Cathy Keith, first employee of the OUL, who he married in 1975. With her strong background in biology, Cathy “jumped into” the work of the OUL, especially the study of cave fauna.
In those early years, the consulting work was touch and go; feast or famine. But Tom and Cathy were able to expand their ownership in the recharge area of Tumbling Creek Cave whenever opportunities presented themselves. It was a financial struggle, but Tom suggested they got “a lot of experience buying land at inconvenient times.” They also built a beautiful, rustic house near the cave in 1976 and in the late 1990s, finally bought 263 acres of land including the cave’s natural entrance in Bear Cave Hollow. They focused on buying land in the recharge area with “problems,” often sinkhole dumps, finding 22 of these dumps within the cave’s nine-square-mile recharge area. Since much of Tom’s income came from consulting work—often determining if landfills threatened groundwater—and much of his money went toward buying land with sinkhole dumps, he joked that he “worked at dumps to make money to buy dumps.”
Tumbling Creek Cave, the Aleys soon discovered, contained a tiny white snail—blind, without even the vestiges of eyes. The Tumbling Creek Cavesnail became listed as an endangered species, found nowhere else in the world. In the 1970s, the Aleys saw thousands of them in the cave. But as time went on, their numbers declined, dramatically. The Missouri Department of Conservation (MDC) and U.S. Fish and Wildlife Service (USFWS) intervened in efforts to save the snail from extinction, with Tom and Cathy as enthusiastic, supportive landowners. MDC and USFWS “own” the responsibility for the cave snails, Tom said, but “Cathy and I own the habitat. It’s an obvious partnership of opportunity.”
Funding from the USFWS and other agencies went toward protecting snail habitat, both above and below ground. Much of the work in the recharge area involved re-vegetating eroded gullies and riparian areas along losing streams. In total, over 75,000 trees were planted. Over two miles of eroded gullies were re-vegetated. 140 acres of native grasses were established, along with 50 acres of glade habitat and 15 acres of savannah. With funding assistance from the USDA Farm Services Agency, six miles of fence were built to keep cattle out of planting areas. Through a grant from the USFWS, septic tanks in the recharge area were pumped.
Tom, a deep thinker, always looked for partnerships; for win-wins. One memorable success involved the Mark Twain School, not far from the cave. Over the years, the tiny rural school had struggled to stay open. When it came to light the school’s sewage lagoon leaked into karst groundwater, and the expense of fixing it presented an insurmountable obstacle for the school system, Tom came to the rescue with a grant from the USFWS. With additional funding from the LAD Foundation and private-public partnerships, a new wastewater system was completed at the school in 2006. Tom was especially proud of the headline appearing in the Taney County Times: “Mark Twain School Saves Endangered Species.”
The Aleys also formed comfortable, productive partnerships with Grottos, or caving clubs. Jonathan Beard, a noted Missouri caver, remembers his club helping with restoration work in the cave. The caver volunteers hauled out hundreds of buckets of rock and clay left over from building trails in the cave, and erased footprints and scrubbed muddy handprints off speleothems to give the cave a more “natural” look and feel. Tom was always standing by with a dose of his signature humor. Once, while Jon and other cavers were waiting by the bunkhouse, they heard a booming voice rising from the vicinity of Tom’s house: “This is the cave speaking. Please assemble.”
When an industrial solvent, trichloroethylene (TCE), contaminated air inside Fantastic Caverns north of Springfield, Tom was hired to investigate the problem. The TCE had most likely come from an old industrial lagoon, since closed, near the airport. Jon Beard, on behalf of the caving club, helped Tom determine how much air circulated through the cave. From that calculation, they were able to install a vent system to keep TCE levels under the OSHA standards. A sprinkler system on the surface, spraying water that seeped into the subsurface, helped keep cave humidity levels up while ventilation was in progress.
Tom frequently hosted cave tours for Ken Thomson’s speleology class at Missouri State University. Tom loved to educate young students, but he wasn’t above pulling their legs, either. On an earlier exploratory trip with Jerry Vineyard through upper passageways of the cave, they saw ants crawling on the floor and walls. Tom told Jerry the ants showed they were only about thirteen feet from the surface at that point. When the next group of Ken’s students arrived for a field trip, Tom told them that unlike most caves, his wasn’t formed by running water, but by ants—slowly, over the eons, carrying out crumbs, one by one, enlarging the passages. The students just stared at him, mouths agape, until Dr. Thomson burst out laughing.
When he wasn’t working in a cave, or entertaining students, or rehabilitating a recharge area, or a saving a country school, Tom was consulting, largely to buy more land and pay for operating the OUL. Much of this work was focused in the Ozarks. He once conducted a dye trace from a large sinkhole full of trash near Dora, Missouri. Along with trash in the sinkhole, he saw a large pile of crusty black material. When he kicked his boot in it, he realized it was septic tank pumpage. As he drove away, foot out the window, he called the material “by name,” he joked. His dye from the Dora Sink showed up at Hodgson Mill Spring, where a cup hung on the end of a pipe, inviting people to take a drink of “pure” spring water. It was a curious offering to Tom, who spent the better part of his career convincing people that springs in karst country were very often anything but pure.
Tom also conducted a trace from the municipal sewage lagoon at Winona to Big Spring. This trace had been requested by the mayor of Winona, who thought a positive trace would “show the need” for a new sewage system. Tom used the mayor’s request as an example of successful educational efforts about karst. People like the mayor once believed the cold water of Big Spring came from faraway places like the Great Lakes or Rocky Mountains. After learning about karst processes, they now accept that sources are much closer, and admit that actions on their own land could affect the spring’s quality.
Throughout his career, Tom assisted both private individuals and agencies. At the Forest Service’s cave at Blanchard Springs, he investigated runoff from a new parking lot. The builders had placed the parking lot some distance from the cave, and put gravel under it to allow drainage, but were savvy enough to ask Tom to determine if these measures were enough to adequately protect the cave. Tom introduced dye into the surface drain from the parking lot and recovered it from dripping stalactites in the cave. After his investigation, parking lot drains were diverted away from the cave’s recharge area.
Another investigation involved a proposed landfill near Pindall, Arkansas. Tom wasn’t able to access the property directly, so he injected dye into a sinkhole just outside the property boundary. While surface runoff went to a small stream north of the site, groundwater moved in the opposite direction, toward the Buffalo River. He detected his dye at five wells, but 90% of his dye went to Mitch Hill Spring, 4 ½ miles from the landfill site and less than a quarter-mile from the Buffalo. Eventually, the Pindall landfill project was dropped, and personnel at Buffalo National River were grateful. At the time, the community of Pindall was strapped for cash, so Tom and Cathy accepted payment in office furniture from the furniture factory in town.
In a study at a National Forest in Indiana, Tom found that a proposed reservoir, just downstream of a major losing stream segment, would almost certainly not hold water. The Forest Service had requested Tom’s services, even though the proposed dam would be constructed with “small watershed” funding through the Natural Resources Conservation Service (NRCS). After Tom suggested the NRCS had performed an “abysmal” site investigation, the project was canned. He got a letter of commendation from the Forest Service for saving them at least $100,000 on a poorly conceived project. Six months later he got another letter, this one reprimanding him for “comments critical of a sister agency.” With his keen appreciation for bureaucratic irony, Tom framed both letters and hung them on his office wall, side by side.
Tom’s consulting work took him far from the Ozarks. Early in his career, he explored caves in Jamaica, where the U.S. government thought the Russians might be hiding nuclear weapons during the Cuban missile crisis of 1962. Some of his work resulted in major policy shifts. His dye tracing in southeastern Alaska, in the Tongass National Forest, delineated areas with the greatest potential to adversely affect salmon migration and survival. As a result of that work, the Forest Service adopted a new policy, specifying that none of these areas would ever be logged. And Tom testified as an expert witness on many legal cases involving potential groundwater contamination in karst, from deep well waste injection in Oklahoma to herbicide migration in runoff from tobacco fields in Kentucky.
For decades, Tom and Cathy ploughed money from consulting back into OUL and the cave’s recharge area, where the Aleys and Tumbling Creek Foundation now own over 3,500 acres. They also spent time and money studying and protecting the cave itself. Weirs were built in the cave to more accurately measure flows, critical to understanding rates of karst recharge. They built a large gate at the cave’s natural entrance to protect the 80,000 gray bats that roost there in summer. But the problem of a declining population of cave snails was particularly troubling, especially after their numbers failed to bounce back after restoration work in the recharge area. The Aleys began to more fully investigate other potential factors in the snails’ decline.
One of these was an invasive crayfish, the gapped ringed crayfish, a species native to Missouri but rare or absent from Tumbling Creek cave until 1968, although reported before that time from 71 caves in Missouri and Arkansas. Studies in these caves showed that small snails were “clearly on this crayfish’s menu.” Tom discovered that where he had established weirs, cavefish were largely unable to pass upstream. But some slipped by. By 2020, Tom and his helpers had removed about 6,000 crayfish from the cave.
From these experiences, Tom and Cathy learned of other factors, external to the cave, exerting untoward effects on the cave ecosystem. One was Bull Shoals Reservoir, just a few miles away. When the lake is at flood pool, it inundates all but two of the springs that drain Tumbling Creek Cave, changing groundwater gradients. The decrease in groundwater velocity as the cave stream reaches the flooded lake causes silty water to deposit sediment in karst conduits, smothering federally-designated “critical habitat” for cave snails. Further, infiltrating lake water allowed invasion by gapped ringed crayfish into cave snail habitat.
It was one of those conundrums that so often surround the protection of endangered species. One federal agency, the U.S. Fish and Wildlife Service, charged with protecting cave snails and their habitat, might advocate actions diametrically opposed to the those of another federal agency, like the U.S. Army Corps of Engineers (USCOE), which regulates the levels of reservoirs like Bull Shoals. Part of the regulatory agenda of USCOE is to provide flows below Bull Shoals dam sustaining trout fishing in the White River. Tom, concerned about protecting the snails, said USCOE, by ignoring damages to critical cave habitat, had “traded the survival of an endangered species for more satisfied trout fishermen and the resorts they visit.” The Corps and the Fish and Wildlife Service ultimately provided funding for Tom to build crayfish barriers on springs near the lake and in the cave stream, which has helped to slow the invasion.
Tom has never been afraid of controversy. He always landed on the side of protecting the resource, whether it was the quality of springs or the survival of endangered species. While giving expert testimony, he saw lawyers representing their clients—sometimes people concerned about a proposed landfill, for example, or a company planning to build something. Tom was fond of saying he was “speaking for the land,” because, he said, the land had no attorney to represent it. On the board of the James River Basin Partnership, whose letterhead listed board members representing cities, counties, or agencies, Tom always represented “The River.”
Tom was proudest of his accomplishment in getting people to think three-dimensionally about the land—understanding that the earth is not an infinite filter, but has a delicate subterranean ecosystem vulnerable to our activities on the surface. He had a great knack for reading his audiences, learned partly from his days on the road playing folk music. This allowed him to impart wisdom in a quiet, patient way, bringing his listeners along on an intellectual journey into the hidden blackness beneath their feet. This led to real and substantial progress, in Tom’s estimation, as when the mayor of Winona asked for his help in determining where water from his town’s leaky lagoon went.
Tom understood and appreciated the idea of “property rights.” As a major landowner in the Ozarks, he couldn’t help but see the fundamental application of this principle among his neighbors. But he saw his rights differently than most of them. Instead of worrying about and fighting trespass, he invited the public in to his property, hoping they would come to understand what he was doing there, and why it was important. His most precious property right, he said, was the “right to clean water flowing into, or underneath, my land.”
Throughout his long professional career, Tom maintained that razer wit, the dry humor that to many associates and friends became his trademark. One of my favorite stories involves a man who owned a gas station and asked Tom to investigate his well because it had gasoline in it. The man didn’t have a lot of money, so Tom took partial payment in the repair of his old truck. Tom’s cursory investigation revealed that the station’s buried gas tanks had, in fact, polluted the shallow well. Tom told the man the well wasn’t that good, so he needed a new one, anyway, adding, “I’m sorry I couldn’t be of more help.” You can imagine the old man’s head nodding as he thought about this. “Well,” he finally said, “I’m sorry I couldn’t be more help with your truck. You need a new one anyway.”
Tom Aley fashioned a remarkable career in a subterranean world few of us really understand, and rarely appreciate. His mind was like a vast, complex karst ecosystem, with myriad connections linking land and water, landowners and agencies, educators and students. We are all better off because Tom sided with the resources—the land and water and their biota—because in so doing, he positioned himself on our side. Think of how many bad ideas never came to fruition because Tom was looking out for the land, the water, and for us. Think of how much cleaner our groundwater is because he spent a lifetime down there, in the caves, in the hills, traveling the globe, defending our planet’s precious natural resources at every turn.
Tom was a giant in the world of karst science. His search for hidden truths has guided us in making many important decisions about the land—what we do, where we do it, and why we should or shouldn’t do it. He was a dedicated scientist, but also a good friend—always listening to what someone had to say. He might not agree with them and would let them know, gently, usually in jest, when he didn’t. But he was respectful of people in the same way he respected the land, and its inherent rights. The world is surely a better place for having Tom to speak on its behalf. Far too few people know that in doing this, he also protected us.
Perhaps one of Tom’s most impressive accomplishments was his ability to plan beyond himself, ensuring that the land, the cave, and the snails are protected into the future. Well before his passing, he recognized that a new generation of karst defenders would be needed. He and Cathy modified their estate plan to make sure their land, business, and assets would be left to the foundation. In 2020, Tom recruited (poached, as he liked to call it) his successors to replace himself and Cathy as they neared the end of their very impressive careers.
Dave Woods, a fisheries biologist with the Missouri Department of Conservation, had been working as the Tumbling Creek Cavesnail state recovery leader for about a decade when Tom asked him if he knew anyone who might be interested in heading up the foundation. Tom was a bit surprised when Dave said, “sure, let’s talk.” Two weeks later, Dave was the new Executive Director of the foundation and senior scientist at the OUL.
Shortly afterwards, Tom hired Trevor Osorno to direct the consulting practice part of OUL. Trevor, a promising young hydrogeologist, had been visiting the OUL with his professor and foundation board member Rick Devlin for years. Together, Dave and Trevor, a new generation of karst giants, along with the exceptional staff assembled by Tom and Cathy, are continuing the Aley legacy of protecting karst resources while stewarding the OUL and the Tumbling Creek Cave Foundation into the future.
Sources:
Tom Aley, personal interview, Jan. 9, 2009
Tom Aley, Bear Cave Hollow: Stories of Caves and Karst, Journal of the Missouri Speleological Survey, Vol. 65, 2022
Jonathan Beard, personal interview, Feb. 14, 2026
Dave Woods, personal interview, Jan. 13, 2026
