Scientist Uses Tombstones to Track Environmental Changes
for National Geographic News
|November 27, 2001|
Tom Meierding has always been fascinated by graveyards. Over the last 25
years, he's visited more than 700 cemeteries and measured about 15,000
tombstones to see what kind of environmental secrets they might
Meierding is a geomorphologist at the University of
Delaware. He uses the tombstone data to determine past environmental
conditions and compare them with modern pollution
levelsinformation that's useful to art conservationists, policy
makers, urban planners, and others.
"Cemeteries have been among the most durable of cultural landscapes, preserved even in cities where competition for land is intense," he said. "If you know the scientific basis for environmental degradation, you can fight it more effectively."
His tombstone studies showed, for example, that much of the degradation to stones, monuments, and buildings in the Northeast United States is the result of environmental factors of 70 years ago. The assumption had been that the destruction was caused by the more recent effects of acid rain.
Rocks of Ages
Geomorphologists study the rates at which landforms develop and change, and the human and natural forces that affect that change, such as ice, wind, rain, waves, climate, and gravity.
Two decades ago, Meierding realized that "no one had quantified the weathering rate of rocks in rainy versus dry weather."
Baseline weathering rates enable scientists to determine whether rocks in a given area are weathering as a result of normal processes or at an accelerated rate as a result of environmental or other unusual conditions.
"The problem with studying weathering in nature is that you have no date on the rocks, no way to know if they've been moved, or how long they've been in a place," said Meierding.
Marble tombstones, on the other hand, offer an ideal testing medium because they are usually engraved with dates.
"I was planning to take a cross-country trip to visit my parents," he said, "and I decided to stop at cemeteries along the way."
Science is frequently a matter of trial and error.
Meierding's original hypothesis was that greater weathering would occur in rainy areas than in dry places. On his first cross-country swing, that is indeed what he found. But further study showed that his assumptions were incorrect.
"How I found out I was wrong in my hypothesis was by measuring stones in Hawaii. They have as much as three times the amount of rain as on the mainland, yet the stones were in perfect condition," he said.
Meierding measured a minimum of 30 stones in each cemetery. He developed a scale, based on the legibility of the carving on the stones and differences in their thickness between the top and bottom, to assess their condition.
He was then able to develop a number-based rating for each cemetery that described the overall condition of the tombstonesfrom excellent to seriously deteriorating.
"These are real quick and dirty measurements," he said. "It's the sheer volume of measurements that makes the data useful."
When he mapped his findings, he found that the most serious degradation had occurred in areas where there was heavy coal burning 60 to 70 years ago.
"A lot of the damage that was assumed to be relatively recent actually occurred in the 1930s, when industrial sites were located in the cities," he said. In rural areas, "the map exactly matched the high-sulfur coal fields."
Geography Meets Geology
Looking at things from a geographical perspective can provide a global view of the problem. Meierding's work with the university's art conservation department is a case in point.
"Art conservationists may look at a building or a sculpture and see that it is sustaining damage, but because they're looking at just one small sample, they have no way of identifying the source of the destruction," Meierding explained. "That makes it difficult to know what preservation techniques might be most effective."
Not all air pollution is the same. Brownstone buildings in New York City and Philadelphia are deteriorating as a result of their exposure to air pollution from the burning of high-sulfur coal. In Los Angeles, on the other hand, buildings exposed to high levels of smog don't suffer a similar fate because the air pollution is primarily made up of nitrous dioxide, rather than sulfur dioxide.
Tombstone-based research also can be useful in pinpointing some issues of environmental concern that merit in-depth study.
"In the 1980s, the government gave out a lot of moneyin the hundreds of millions, I thinkto study the effects of acid rain," Meierding said. "If they had been able to map some of the effects of air pollution first, they would have been much better able to target the research dollars."
Fortunately, the deterioration of historic buildings, monuments, and cemetery stones has slowed dramatically since World War II, in part because of clean air legislation, he said.
"Mapping also tells you what you can ignore," he said.
When he was studying cemeteries in mountain ghost towns, he visited a cemetery in Leadville, Colorado, where the old gravestones were in very bad shape. "I thought it was the effects of frost, until I mapped the findings," he said. There were many other towns at the same elevation with no damage, so frost could be eliminated as the cause.
"It turned out," Meierding said, "that at one point in time, Leadville had been the smelter capital of the West, processing gold, silver, and other ores mined during the Gold Rush era." Pollution from the smelting process had accelerated deterioration of the tombstones.
The importance of research such this, said Meierding, is simple: "You can't deal with the effects of pollution if you don't know the cause."
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