CHICAGO -- Bill Rathje is an archeologist but not one to be found excavating ancient Mayan civilizations, Egyptian tombs or East Indian artifacts. He prefers to dig up more current, less glamorous ruins, what he calls "the pimples on Mother Nature's face."

A more accurate term for Rathje might be "garbologist" because he has been digging up garbage in landfills nationwide for three years.

Rathje (pronounced RATH-jay) says he has seen it all -- all of America's fast-food waste, disposable diapers, Styrofoam cups, plastic soda bottles, cans full of paint, broken furniture and assorted other oddments.

Conducting his Garbage Project, Rathje said, he has learned that people often mount campaigns against the least threatening environmental scourges and ignore more serious threats to landfills bursting at their clay-lined seams.

Rathje, a professor at the University of Arizona, recently addressed waste management companies and First Analysis Corp., a Chicago research firm that focuses on the environmental industry. He called plastics "the Great Satan" but said Americans should be more aware of materials such as paper and construction and demolition waste that take far too much valuable landfill space.

"Landfills close down not because they're too heavy but because there's too much volume," he said. Volume? The only man-made structure larger than Staten Island's Fresh Kills landfill is the Great Wall of China, Rathje said, and at 2.3 billion cubic feet and counting, the landfill will be bigger than the wall by 1991.

Despite what many people think, Rathje said, plastics have taken up no more than 12 to 13 percent of landfill space since 1975, although production of plastic packaging and products is booming. The difference is that plastics are becoming increasingly lighter, he said, noting that a plastic milk jug now weighs about 45 percent less than in the early 1970s. Plastic grocery bags, two-liter soft-drink containers, laundry detergent jugs and even glass are lighter. A glass bottle unearthed in a 1950s landfill often is whole and unbroken, whereas lighter weight glass in current landfills is in pieces, he said.

Diapers, which account for 1.8 percent of volume in landfills, are not the bacteria-producing waste that people suspect, Rathje said. Rather, newly added super-absorbent material contains all leachable toxic materials in landfills. "But since they're super absorbent, they're going to come in heavier and smellier anyway," he said.

Paper that filled 40 percent of landfill space in 1970 now fills 55 percent, and that percentage is growing. Newspapers, office wastepaper and especially telephone books are the culprits. Dig a trench in a landfill, Rathje said, and one can see phone books layered like a cake. Lacking light, air and space in a packed landfill, they do not deteriorate.

"Each two-volume set of Yellow Pages distributed in Phoenix last year, which will be thrown out this year, weighed 8.63 pounds, for a total of 6,000 tons of wastepaper, and that's only one city," Rathje said. "The phone companies even throw out their old books and put everything on microfilm."

Calculating exactly how much garbage Americans generate is an "imprecise exercise," and numbers may vary, said Marge Franklin, president of Franklin Associates Ltd., an environmental engineering and research firm in Prairie Village, Kan.

According to a Franklin Associates report this year for the Environmental Protection Agency, paper accounted for 34 percent and plastic 20 percent of landfill volume nationally in 1988, a slight difference from Rathje's figures, based on excavations at nine landfills nationwide.

"The difference is that one method is computed systematically, and Rathje's is empirical," said Sam Hartwell, a research associate at the Natural Resources Defense Council in New York. "Volumes may be over or underestimated because of many variables, but a more important finding of Rathje's is that, even though something like plastic and paper may be labeled biodegradable, they're really not once they get in a landfill because they can be dug up years later still intact."

To probe a landfill, Rathje uses a bucket auger with a 110-foot pole. At the pole's base is a bucket four feet high and three feet wide with steel teeth to grab a cookie-cutter portion of garbage. The first time Rathje used the device, he said, it bit through part of a car, engine and all.

The Garbage Project employs standard archeological procedure when the bucket dumps its first mouthful. The temperature is taken -- garbage usually is between 90 and 104 degrees Fahrenheit because of the depth -- and it is weighed. A sample is bagged and mailed to laboratories, universities and government agencies that study decomposition traits and bacteria.

The time when garbage was dumped usually can be ascertained quickly, Rathje noted, by checking the dates on about two dozen clean newspapers found in virtually every load. Other items are not so easily recognized.

On one dig, Rathje said, he thought he had gone "back on some 'Star Trek' time warp and was dealing with hand axes from North Africa about a million years ago." Analyzed, the two round, dark, rock-like objects were found to be kaiser rolls. Newspapers found nearby were dated 1952. The most abundant and intact food found in landfills, Rathje said, is the hot dog, adding, "There's something to say for all those preservatives."

Dennis Sabourin, vice president of Wellman Inc., a recycling company in New Jersey, said Rathje "brings perceptions about what kind of waste we're generating down to reality from firsthand knowledge, not mathematical calculations."

Rathje stressed that the best way to deal with garbage is not only to recycle but also to create markets for recycled products. "It does no good to put your papers out in the recycling bin," he said, "if there aren't enough $300 million recycling mills to handle it, as well as people who will create a demand for recycled products."

Until then, he said, "we won't be buried by our garbage, we'll just have to live on top of it."