Idaho National Laboratory engineer Phillip West holds a curious metallic device about as wide as a steering wheel. It looks a bit like a flat, stoic face, with two large circular holes for eyes, protruding cylindrical ears and a long, disc-ended snout.
"Are we ready?" he asks, then kneels and nestles the snout gently into the dirt. West flips a switch on one of the machine's handles, and for the next eight seconds a rising tide of sound waves, strong enough to shake your shoes, floods the earth underfoot.
West's machine, which he calls the Look-Ahead Sensor, or LAS, is probing for tunnels, caves or other subterranean voids. This run, performed behind an INL office building in Idaho Falls, finds nothing out of the ordinary. But take the LAS to the right spot, such as certain stretches of the United States' southern border, and it would probably turn up something interesting.