National Geographic : 1987 Jan
Ice as artist endlessly improvises: Rapidly frozen by plummeting temperatures, a beaver pond, below, traps gas bubbles rising from decaying vegetation. A fallen grass sprig locked in clear ice blossoms with a feathery crystal, below right, created by escaping water vapor. Seeping through cracks in a dying plant stem, watery sap spreads an icy tutu, far right. Capped columns, right, are among the rare shapes snow crystals assume as they interlock and fall to earth, their form influenced by temperature, humidity, and speed of descent.