A Mammoth Find in Arizona

Sterling Nesbitt got the thrill of his life recently. Sterling, a collector of crinoid stems, sea urchins, and other small fossils for seven years - ever since he was eight years old - gained some valuable, firsthand experience at a really big excavation.

He and dozens of other Phoenix-area volunteers helped to unearth bones believed to be those of Columbian mammoths. The fossils were found in nearby Chandler, Ariz.

The mammoths grew to be from 10 to 12 feet tall at the shoulder and weighed from six to eight tons when fully grown. They migrated to North America from Asia 1.5 million years ago, during the Ice Age. They died out 10,000 years ago. Prehistoric humans hunted mammoths for food, and mammoth bones and fossil remains are fairly common.

Pieces of ribs that were dug up from the Chandler site and pieced back together stretched almost five feet long.

"It was really neat," says Sterling, who lives in Mesa, Ariz. "It was the first time I had excavated bones. It gave me a feel for what it would be like in the field if I go into paleontology as a career.''

Paleontology (pay-lee-un-TOL-uh-jee), the study of fossils and ancient life forms, is a hobby that most students can take up with relatively little equipment.

But before you go out into the yard and start digging, be aware that not all ground or every rock is a good place to find fossils. One reason is that fossils are formed in areas where there once was water: rivers, lakes, swamps, and oceans. There, mud or sand can bury an animal that has died so that it isn't disturbed and won't decay.

Set in stone

Millions of years later, the many layers of sand or mud (called sediment) have hardened into stone. Meanwhile, the animal's remains have been replaced by minerals in the rock. They have become rock, or been petrified.

Fossils of clams, snails, corals, and other ocean-dwelling creatures are commonly found in the midwestern United States. Millions of years ago, that region was a a warm shallow sea. The Midwest is also where Brad Archer, curator of Arizona State University's museum of geology, got his start in paleontology, in his native Wisconsin.

Mr. Archer led the team of excavators at the Chandler dig.

"Once you find your own fossil, you get hooked," Archer says, recalling his first field trip as a student at the University of Wisconsin. "The more you find, the more you want to learn about it," he says. "The more you learn about it, the more places you want to go."

The fossils from the mammoth excavation are currently under Archer's care at the ASU museum, where they are being cleaned and prepared for display.

Finding bones by accident

A sewer-line inspector was the first one to notice the mammoth bones. They were at the bottom of a trench that was eight feet deep.

The sewer line was part of a new-home development. Work on the excavation had to be done quickly so that the building could proceed.

In early July, in temperatures that topped 100 degrees F., Archer and his volunteers began to excavate. They spent 11 days unearthing the fossils. Twice, the developer gave the paleontologists an extension, saying it was OK to dig a little longer.

Archer and his team found two partial tusks, the seven-foot-long bones of the left and right front legs, even an ancient tortoise. Two, possibly three, mammoths were at the site.

The find also gave clues about what Arizona was like before it became desert. All the fossil animals found ate grass, suggesting that the land once received more rainfall and perhaps was cooler, too, Archer says.

For young adults interested in finding out more about fossils, Archer suggests finding a course offered by a local museum, club, or university.

"When you learn about them, you'll have the incentive to go out and learn more about them," he says.

Find Out More About Fossils

Contact the 'historical geology' department at a nearby college or university for suggestions on where to go to find fossils locally.

BOOKS

Be sure to ask your local librarian for other book titles and places to look.

* 'The Fossil Book,' by Carroll Lane Fenton and Mildred Adams Fenton (Dover Publications, 1996). This widely used reference covers everything from the smallest fossil up to the largest dinosaurs. Available in paperback.

* 'The Audubon Society Field Guide to North American Fossils,' by Ida Thompson (Knopf, 1982). Pocket-sized book with photos, geologic maps, and other useful information for the paleontologist in the field.

WEB SITES

* The National Museum of Natural History's Kids Guide. Here, you can find such topics as 'Digging into the Past' and 'Where Dinosaurs Still Rule!': web2.si.edu/resource/tours/kidsguide/nmnh/start.htm

* The Paleontological Society's home page. Not for the novice, but teachers may find some useful information here. uic.edu/orgs/paleo/homepage.html