Team compiling 3-D map of what's under Illinois

MONTICELLO, Ill. -- As the small plane passes overhead, everything comes to a halt until the noise, not especially loud to the ear, fades into the distance and Tony Swierczek can resume mapping the underground by slapping a metal plate with a sledgehammer.

The plate is connected to a board stuck under the left rear tire of a sport utility vehicle that has a line of electrical cord and flat, book-sized devices strung out behind it, like a string of cans attached to the car of a newlywed couple.

The devices are sensors to pick up the sound waves that moved through the ground near Monticello and Allerton Park recently every time Swierczek, an Illinois State University student from Belleville, rapped the plate with the hammer.

Called "geophones," they're sensitive enough to pick up the airplane as well, or even someone walking nearby, which is why things stop when the plane passes so as not to confuse the portable computer that interprets the signals the sensors send back.

This is how the University of Illinois-based State Geological Survey looks for water, natural gas pockets and other underground features these days, and how survey officials hope they're laying groundwork to continue and expand a project to map the state's subsurface in three dimensions.

"This is one way of starting to interest people in this and to train them," said Bill Shilts, chief of the survey.

The students get paid and -- perhaps even more important -- get training and field experience using technology that is beginning to spread throughout geological work.

"Overall, it's really neat to get some hands-on experience," said Scott Perkins, an ISU senior from Peoria working with Larson. "Hopefully, it'll come in handy."