UT prof unearths clues about climate in caves Geology professor and his students get muddy while collecting calcite in Georgetown cave.
By Asher Price AMERICAN-STATESMAN STAFF Tuesday, July 08, 2008 If a stalactite hanging from a cave ceiling looks to the layman like an icicle, it's not a far-off comparison. In the eyes of University of Texas geology professor Jay Banner, stalactites, and their up-from-the-ground cousins stalagmites — both mineral formations left behind by dripping or seeping water — amount to a frozen record of climate, rainfall and atmosphere changes over the past 70,000 years. As scientists around the world work to measure the speed at which the Earth is warming and the variations in the greenhouse gas carbon dioxide, the answers may turn up in the caverns that lie beneath Central Texas. These underground spaces, in short, are a kind of thermometer for aboveground ones. With elbow pads and kneepads, helmet and headlamp, Banner has made at least 100 trips through mud and over rock beneath Texas to uncover clues about the past, and about the future of the state's aquifers. Banner, 51 who has a salt-and-pepper beard, grew up in Queens, New York, and still carries with him a kind of streetwise, corny humor. He defines speleothem, the collective term for underground rock formations, thusly: " 'Speleo,' which means in Greek 'cave,' and '-them,' which means 'them things,' " he says. "Together it means 'them things you find in a cave.' " (-Them does not, in fact, mean 'them things.' ") On a trip this month to Inner Space Cavern in Georgetown, where he does some field work, he explained to students that 100 million years ago, when the caves that make up the Edwards Aquifer first began forming by water dissolving underground limestone, the banks of the sea would have run about through Central Texas. "Your trip to spring break would have been much shorter, starting right outside your door, and you wouldn't have had to drive all the way down to South Padre," he said. "The bad news is that finding someone of the same species and of the opposite gender — which is the goal of spring break — would have been much harder." For a decade or so he has been studying the deposits of minerals called calcites that are left behind by the drip, drip, drip that trickles through soil and into the caves. With a battery-operated drill topped by a diamond-tipped, stainless steel bit, he and his research assistants have taken speleothem samples to bring back to their labs. Using an isotope dating system, they can seize on the age of the formations, and they analyze the mineral makeup of deposits left behind. "We can form a baseline level for the climate system before humans started doing things that supposedly change the climate," he said. He says that the historic growth rates of the formations correspond with soil moisture — the more water in the soil, the faster the growth of the formations — which in turn is driven by temperature variation. He had his first cave experience while still a graduate student at the State University of New York Stony Brook, when he went caving in West Virginia with friends. Then, in the early 1990s, while doing groundwater work in a limestone aquifer in Barbados, he became interested in what he saw as an understudied field. The tendency among spelunkers is to label rock formations with a method not unlike describing clouds on a lazy afternoon: A wavy ceiling at Inner Space Cavern is known as an upside-down lemon meringue; a stack of stone is known as Texas' largest ice cream sandwich; a butterscotch-colored stalagmite is Buddha enjoying a massive sundae. But the seemingly random underground rock formations have a pattern. They follow, for instance, fissures created by long-ago movement of tectonic plates. And Banner is hoping to chart the future of the formations, as well as the caves and aquifers generally, as he collects more data on their composition over the millenia. In many ways, the cavern is not just a frozen record of a long-ago climate. It is literally a graveyard of the past. The remains of armadillos the size of Volkswagen Beetles, saber-tooth tigers and mammoths have turned up here. "It's kind of like an adventure, even though it's scientific research," said Esther Mandelbaum, a 22-year-old geology major who helps Banner collect calcite samples at Inner Space Cavern. After a long morning of collecting water, air and mineral samples, while being careful not to touch the formations themselves, Banner led his students to a cave known simply as the mud room. "It's OK to throw mud at each other, just not at the walls or the ceilings," Banner told the students, who immediately obliged. [email protected]; 445-3643 Jay Banner Occupation:Professor and Dave P. Carlton Centennial Fellow in Geology. Director, Environmental Science Institute at the University of Texas. Joined the University of Texas faculty in 1990. Education:Ph.D. in earth sciences, State University of New York Stony Brook, 1986; M.S. in earth sciences, State University of New York Stony Brook, 1981; B.A. in Geology, University of Pennsylvania, 1978
