Geotimes
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Stories from the Underground
Geotimes staff

Every February, Geotimes offers snapshots of a few geoscientists and their careers. This year, we looked deeper to find out about several whose work takes them inside Earth. We focus not only on the paths these adventurous scientists have followed in their lives, but also on the details of their work surroundings — which for this group can reach up to 300 meters below the surface.

Underground town
Indiana Jones and the Dead Sea Scrolls
Adventures in cave exploration


Underground town

Early in the morning, David Leach and two other geologists from the U.S. Geological Survey (USGS) hop into a truck and head into the Ozarks in southeastern Missouri. They wind through hardwood forested hills and alongside emerald streams. Eventually, a small clearing opens up, dotted with a tailings pond, a mill and a small head frame housing a shaft leading down to a lead mine.

Since the discovery of a rich lead district in the Ozarks more than 40 years ago, the Doe Run Company has mined more than 140 million tons of ore that contains lead, zinc and copper — making the company the largest lead producer in North America. The ore lies in a 40-mile-wide strip called the Viburnum Trend that runs beneath the Ozarks. Doe Run has proposed to explore for more lead deposits in the Mark Twain National Forest, south of the current mines. Leach and his crew are here as part of a study to determine how the expanded mining might affect the quality of the region’s surface water and groundwater.

Dennis Murphy, leader for the Doe Run Company Environmental Group, collects a water sample from a discharge along a mine face in the Viburnum Trend. Photo by David Leach.

The geologists don hardhats and safety gear and squeeze into a small metal cage. The door shuts and the elevator slowly descends more than 300 meters into the ground. Their headlamps cast faint patches of light onto the otherwise dark walls of the mine.

When they reach the bottom, the cage doors open, bringing into focus a sight that contrasts starkly with the claustrophobic descent. “It is like a small town — two-million-dollar rock movers and heavy machinery. The walls are painted white; there are lights, refrigerators and pick-up trucks. And all of this huge equipment was brought down the same shaft, piece by piece, and re-welded underground,” Leach says.

An environmental geologist working with the Doe Run Company pulls up to the group in a tractor. The USGS scientists jump on board. A series of interconnected roads takes the team 10 miles along the Viburnum Trend. The tractor dodges trucks loaded with rocks on the surprisingly smooth, gravel roads. They stop at a point where water trickles out of a crack in the wall.

For the past 30 years, Leach has studied the origins of ore deposits like the ones in the Viburnum Trend. Now he finds himself on the opposite end of the equation, investigating not how minerals made it into the deposits but how toxic metals might make it out. He is part of a research team developing a model that uses data on the geochemical and hydrologic properties of local rocks to predict how future mining, in similar sites, could impact the mobilization of toxic metals and other chemicals.

“In many ways, the environmental issues are the inverse of the ore formation processes. Hot waters bring the minerals in and they precipitate by chemical reduction. And to mobilize the minerals, you oxidize them and move them out in water,” Leach says.

Leach and his fellow researchers get out pH and conductivity meters and jot down results characterizing the seeping water. They fill sample bottles. Back in the lab in Denver, Colo., they will analyze the samples for lead, arsenic and other toxic metals.

Mining for lead along the Viburnum Trend requires de-watering: constantly pumping groundwater out from the mine and onto the surface. The groundwater would otherwise fill the mine. That process introduces oxygenated water to rocks that have been sitting in oxygen-poor groundwater. A primary concern is that minerals in the rock will react with the oxygen, lowering the pH of residual groundwater and mobilizing metals contained in the ores. Migration of this tainted groundwater through the highly permeable karst bedrock might contaminate the network of springs and rivers that characterize the Ozarks and provide drinking water to many of Missouri’s citizens.

However, karst is a double-edged sword. Limestone, while permeable, also buffers acidic waters, weakening their acidity. This buffering can prevent mobilization of toxic metals. “The question is: When the oxygenated waters interact with the ores, do you get classic acid mine drainage or is the system effectively buffered by the carbonate rocks?” Leach says.

Through samples from this mine, and samples from more pristine areas, a general picture is evolving. The buffering from the limestone bedrock seems to do a good job limiting the migration of toxic metals in the region, Leach says. Sulfate is another story. It does not react with the limestone; of all the chemicals analyzed to date in the waters in the mining areas, only sulfate can exceed the Environmental Protection Agency’s standards for drinking water.

After 10 minutes of sampling, the geologists hop back onto the tractor, and drive another half hour along the Viburnum Trend. Again, they stop at a site where water comes out of the rock, but this time it is flowing rapidly, as if an open hose is stuck between the rocks. Leach takes notes about the rocks adjacent to the water source while his colleagues continue the sampling, which they have pared down to an efficient set of steps.

In one way or another, Leach has been investigating rocks for most of his life. “I knew from day one that I was interested in geology. I was a mineral collector in elementary school. My neighbor worked in a feldspar mine when I was a kid. Then in high school, I won a science fair and said to myself ‘This is pretty neat.’” Later he earned a science fellowship to Virginia Tech and went on to get a Ph.D. from the University of Missouri at Columbia, studying the origin of lead ore deposits.

His advice to future geologists, especially those interested in adventuring underground, is to get a broad-based training. “Know chemistry, know physics. What has made me successful is not just knowing ore deposits, but also knowing about other areas in science such as environmental geochemistry.”

Greg Peterson


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Indiana Jones and Dead Sea Scrolls

At this time it was that the fight happened at Actium, between Octavius Caesar and Antony in the seventh year of the reign of Herod and then it was also that there was an earthquake in Judea, such a one as had not happened at any other time, and which earthquake brought a great destruction upon the cattle in that country. About ten thousand men also perished by the fall of houses; but the army, which lodges in the field, received no damage by this sad accident.
-Josephus (ca. A.D. 37-100)

Geophysicist Amos Nur views ancient history as a series of earthquakes: the fall of the Mayan civilization, the end of the Bronze Age in the Eastern Mediterranean, level after level of destruction at Troy, Jericho and Megiddo. They all shared a similar, geologically explained fate, says Nur of Stanford University.

Located about a mile from the Dead Sea Transform fault, Jericho was destroyed at least 22 times in history according to archaeological evidence. The Old Testament recounts the story of Joshua’s conquest of Jericho, which would have been around 1250 B.C., but that is only one story in the history of a city 10,000 years old. Nur says that historical and archaeological records show evidence of several earthquakes about every 500 years, including the devastating quake of 31 B.C. described by the historian Josephus.

Accounts such as these are rarities, however, in the historical record. Geophysicists like Nur must turn to the archaeological world for more clues on these destructive forces of the past. “We try to interpret archaeological evidence in terms of earthquake damage as opposed to the other common explanations, which are war and time,” Nur says.

Nur is trying to help archaeologists think about the nature of the ruins they uncover. “Most of them have never taken a geology course; they don’t know anything about earthquakes. And so it was kind of a revelation for many of them.”

In November, a team of archaeologists and geophysicists climbed into a cave in the Dead Sea region, where they found ancient papyrus scrolls, coins and arrowheads, probably from about A.D. 130. Photo by Amos Frumkin, Hebrew University.

At the same time, Nur wants to use archaeological findings to better understand the spatial and temporal distribution as well as the magnitude range of past earthquakes. For this, he is turning to caves, hoping to discover evidence of past earthquakes through buried remains that will allow him to reconstruct a seismic past for the Eastern Mediterranean. “There are very few places in the world where human history is long enough and the archaeological finds are abundant enough.”

The excursion of paleoseismology into caves is a relatively new field, says Elisa Kagan of the Geological Survey of Israel. A seismologist herself, Kagan uses stalagmites, stalactites and fallen rocks to date Israeli caves going back 200,000 years, which she also believes collapsed from large earthquakes.

“Short records are not enough. Archaeology brings us further back in history and then geology brings us even further back,” she says. “The importance, of course, of all these types of work is to understand earthquake patterns because they are more complicated than what can be understood from the history alone.”

In the rubble and ruin of some caves in the Dead Sea region, Nur wants to find the missing pieces of a puzzle that began almost a half century ago. “I was looking at historical earthquakes and their effect on archaeology for many years when it became apparent to us that the Dead Sea Scrolls, which were found about 45 years ago or so, were all found in caves under rubble,” Nur recalls. The Dead Sea Scrolls are believed to hold great clues about the way of life for a small Jewish sect of people called the Essenes as well as about the emergence of early Christianity.

He and his colleagues believe that over time several earthquakes, including the 31 B.C. earthquake, may have buried older scrolls and some of the scroll writers. This hypothesis has led him to the caves themselves — places he never imagined visiting when he started off studying earthquake prediction at the Massachusetts Institute of Technology more than 30 years ago.

In 1996, he and colleagues climbed up into the Cave of Letters, one of many caves that sit in limestone cliffs overlooking the Dead Sea. The Dead Sea is a pull-apart basin, a deep depression 400 meters below sea level, created by the Dead Sea Transform fault. “So the caves are on the margin of this pull-apart basin, right smack on the fault,” Nur explains. Based on the extent of damage revealed by archaeological work in the caves, Nur’s team also can estimate the maximum earthquake magnitude possible on the Dead Sea Transform fault.

Archaeologists from Hebrew University in Jerusalem unearth a papyrus document found in a small cliffside cave in the Judean Desert, as part of a cave survey. The documents could tell researchers about a time period which saw a Jewish rebellion against the Romans in the second century. Through the surveying work, geophysicists hope to find older artifacts in order to reconstruct a 31 B.C. earthquake event that may have buried the writers of the Dead Sea Scrolls. Photo by Amos Frumkin, Hebrew University.

Specifically on this expedition, they were searching for a crushed skeleton an Israeli archaeologist claimed to have seen during a 1953 Dead Sea Scrolls expedition. As datable organic remains, the skeleton is unique from other, non-organic archaeological evidence. “If these ceilings didn’t fall on something organic, they may not be able to date them [collapsed ceilings],” Kagan explains. “Otherwise, maybe the archaeology is 2,000 years old and the ceiling fell yesterday.” If found and dated to before 31 B.C., the crushed skeleton could suggest that the 31 B.C. earthquake buried the scroll writers.

The cave ended up being too large and difficult to excavate. “The entrance to the cave was about a square foot … the floor was littered with boulders about 20 feet high and 20 feet across. It was pitch dark, no daylight ever; there were bats and bat manure. Even if you were not a claustrophobic you would become one,” he recalls.

Unable to find the crushed skeleton, they decided to turn to smaller caves nearby. Since then, in a collaboration of Stanford University with Hebrew University and Bar-Ilan University in Israel, a team of geologists and archaeologists has entered about 200 caves in the region. In November, the research group announced that they found in one of the caves ancient papyrus scrolls, coins and arrowheads, probably from about A.D. 130. Nur believes that much more remains to be found. He eagerly awaits his next cave expedition this month, hoping to find material old enough to prove their earthquake hypothesis. “Just call this Indiana Jones and the Dead Sea Scrolls.”

Lisa M. Pinsker

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Adventures in cave exploration

The stench of hydrogen sulfide gas emanates from the mouth of Cueva de Villa Luz, in Mexico, an indication of the cave’s formidable environment. A person who spends too much time inside the limestone labyrinth could die from the fumes. Geologist Louise Hose is no stranger to the smell, but ever since her first visit to the cave in 1996, she and her caving companions don gas masks and gas monitors while wading through the cave’s warm, white mineral streams to investigate its dark interior.

Every year, nearby villagers perform a traditional ceremony of asking the Zoque gods permission to enter the cave and harvest its unique bounty of fish. They quickly collect basketfuls of the sardine-sized mollies for food from a stream inside the cave’s main entrance. Two years ago, Hose witnessed a harvest that yielded 45 pounds of fish. In any other cave, this practice would collapse such a rare commodity, she says, one of the many distinctions that make Cueva de Villa Luz her favorite.

The secret behind the cave’s plentiful source of fish is sulfuric oxidizing bacteria that not only feed the fish, but also hang from the walls and ceilings generating gelatinous, slug-like and stalactite-dripping sulfuric acid Hose and her colleagues call “snottites.” Drop by drop, they create the cave’s cavernous hallways and crag-like tunnels. “When I first heard about colonies of microbes living in the cave, I assumed they were little things in a corner, not this dramatic feature carving out the entire cave,” Hose says. What makes the environmental conditions just right for the bacteria to take such an active role in the cave’s formation and whether the bacteria have pharmaceutical benefits are just two of the questions Hose hopes student geomicrobiologists following in her footsteps will answer.

Louise Hose takes a swim to check out a passage in a water-filled cave in Tabasco, Mexico. Photo by James Pisarowicz.

“Right now the whole geomicrobiology area is pretty exciting. Most of us 10 years ago getting our degrees didn’t consider it as a career,” she says. “Now a large number of institutes are looking to add geomicrobiology to their list. A degree program that focuses on mineralogy, geochemistry and microbiology is a winning combination right now. Students with that kind of training could go into pharmaceutical work, groundwater remediation or studying things as diverse as how caves form or what kind of life survives in volcanoes. It is esoteric, but we are finding life in places we never dreamed of before.”

Hose grew up in the Los Angeles area and teamed up with other cavers while she was an undergraduate at California State University (CSU) to explore caverns in the Sierras and the Mojave Desert. “I quickly became interested in geology but the faculty discouraged me, as a woman, from pursuing it as a career.” This was 1971. She moved to Arizona where she obtained her bachelor’s degree in secondary education and spent three years as the athletic coach and P.E. instructor that students also came to for questions about physical science. When she returned to CSU in Los Angeles for a master’s degree in geology the atmosphere had changed dramatically. “In 1973 and 1974 the federal government put pressure on oil and mining companies to hire women,” Hose explains.

Her graduate studies took her to a karst area in Tamaulipas, Mexico, the site of the Western Hemisphere’s deepest explored cave at that time. In 1990, Hose received her Ph.D. from Louisiana State University in Baton Rouge for her work on the Barberton Greenstone Belt in South Africa. She has worked as a contract geologic consultant and writer helping with television documentaries, conducting forensic studies and geologic investigations. Until recently, she also taught geology at Chapman University in Orange, Calif. In 1999, National Geographic Adventure featured Hose in their Explorers for the Millennium issue and in 2000, Outside Magazine named her one of 25 All-Star Athletes and Adventurers.

In December, Hose started as director of the National Park Service’s National Cave and Karst Research Institute, based in Carlsbad, N.M. She is in charge of promoting education and directing resources to help fund research in cave and karst communities. “Microbial studies are particularly fascinating, but also we will be working on groundwater contamination and pollution, subsidence and general engineering and education so folks living in a karst region can better understand the nature of the area they live in,” she says.


Christina Reed


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