Book 30, Question 23
How do scientists find shipwrecks at the bottom of a lake?
Scientists tow a device called side-scan sonar behind a boat.
It sends fan-shaped pulses of sound to the sides and listens for echoes, building a picture like a black-and-white photo of the lake bottom. Shipwrecks show up as sharp shapes with shadows. Cold, fresh water preserves wrecks well, and more than a thousand ships have been lost in the Great Lakes. The Edmund Fitzgerald lies in Lake Superior.