lakes smaller than 100,000 square feet aren’t big enough to create a network of cracks.

As the cracks in the ice spread, listeners may be able to hear that the sound starts in one place and moves fast. When the vibrations are carried into the air, it sounds as if the ice is singing — a bit like standing near a railroad as a train approaches.

The cracks that produce the singing originate for several reasons; common among them is tension, which builds up in the ice and causes it to crack. Movement of the Earth’s tectonic plates similarly builds up tension in the crust, which is sometimes released in an earthquake.

The cause of the tension may be atmospheric pressure changes; the ice must follow suit, and because the ice is stiff, it adjusts by cracking. The cracks can also be caused by considerable air temperature variation. Cold ice takes up less space than warmer ice, so falling temperatures make the ice contract and crack. In very large lakes, there may also be enough of a tide to cause the formation of cracks.