About the Cover

Sightings of rocks perched atop thin ice pedestals on a frozen lake are relatively rare. Known as Zen stones, they require the temperature to remain below freezing and the ice surface free of snow for several weeks. The winter climate at Russia’s Lake Baikal, where this photo was taken, meets both conditions. The sublimation of surface ice occurs at a rate determined by the temperature, humidity, and amount of sunlight it receives. To learn more, see the Quick Study by Nicolas Taberlet on page 62 . (Image by iStock.com/MikhailZykov.)